Technical Abstract Summaries
Technical Abstract Summaries
Conferences and Courses: 7–11 March 2010
Exhibition: 9–10 March 2010
Town and Country Resort & Convention Center, San Diego, California, USA
Technical Conferences
Sponsored by
7642 Electroactive Polymer Actuators and
Devices (EAPAD) XII (Bar-Cohen) . . . . . . . . 1-28
Co-sponsored by
American Society of
Mechanical Engineers
7643 Active and Passive Smart Structures
and Integrated Systems IV
(Ghasemi-Nejhad) . . . . . . . . . . . . . . . . . . . . 29-60
7644 Behavior and Mechanics of Multifunctional
Materials and Composites IV (Ounaies) . . 61-82
Cooperating Organizations
Intelligent Materials Forum (Japan)
Jet Propulsion Lab.
National Science Foundation
7645 Industrial and Commercial Applications
of Smart Structures Technologies IV
(McMickell). . . . . . . . . . . . . . . . . . . . . . . . . . 83-90
7646 Nano-, Bio-, Info-Tech Sensors and
Systems (Varadan) . . . . . . . . . . . . . . . . . . 91-103
7647 Sensors and Smart Structures Technologies
for Civil, Mechanical, and Aerospace
Systems (Tomizuka). . . . . . . . . . . . . . . . 104-144
7648 Smart Sensor Phenomena, Technology,
Networks, and Systems III (Peters). . . . 145-155
7649 Nondestructive Characterization for
Composite Materials, Aerospace Engineering,
Civil Infrastructure, and Homeland
Security IV (Shull) . . . . . . . . . . . . . . . . . . 156-172
7650 Health Monitoring of Structural and
Biological Systems IV (Kundu) . . . . . . . 173-201
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1
Executive Committee
Yoseph Bar-Cohen,
Jet Propulsion Lab.
Sang Choi,
NASA Langley Research Ctr.
Aaron A. Diaz,
Pacific Northwest National Lab.
Wolfgang Ecke,
Institut für Physikalische
Hochtechnologie e.V.
Mohammad Elahinia,
The Univ. of Toledo
Kevin Farinholt,
Los Alamos National Lab.
Mehrdad N. Ghasemi-Nejhad,
Univ. of Hawai’i at Manoa
Victor Giurgiutiu,
Univ. of South Carolina
Kumar V. Jata,
Air Force Research Lab.
Jaehwan Kim,
Inha Univ.
Tribikram Kundu,
The Univ. of Arizona
Jinsong Leng,
Harbin Institute of Technology
Donald J. Leo,
Virginia Polytechnic Institute
and State Univ.
Jiangyu Li,
Univ. of Washington
Jerome Lynch,
Univ. of Michigan
Theodore Matikas,
Univ. of Ioannina
Norbert Meyendorf,
Fraunhofer-Institut für
Zerstörungsfreie Prüfverfahren
and Univ. of Dayton
M. Brett McMickell,
Honeywell, Inc.
Zoubeida Ounaies,
Texas A&M Univ.
Kara J. Peters,
North Carolina State Univ.
Peter J. Shull,
The Pennsylvania State Univ.
Henry Sodano,
Arizona State Univ.
Kyo D. Song,
Norfolk State Univ.
Masayoshi Tomizuka,
Univ. of California, Berkeley
Vijay K. Varadan,
Univ. of Arkansas
Norman Wereley,
Univ. of Maryland, College Park
H. Felix Wu,
National Institute of Standards
and Technology
Chung-Bang Yun,
Korea Advanced Institute of Science
and Technology
2
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Conferences and Courses: 7–11 March 2010
Exhibition: 9–10 March 2010
Town and Country Resort & Convention Center, San Diego, California, USA
Symposium Chairs
Symposium Cochairs
Donald J. Leo, Virginia
Polytechnic Institute and
State Univ.
Norbert Meyendorf,
Fraunhofer-Institut für
Zerstörungsfreie Prüfverfahren
and Univ. of Dayton
Kara J. Peters, North
Carolina State Univ.
Norman Wereley, Univ. of
Maryland, College Park
Promotional Partners
IOP Publishing
Photonics Media
SPIE would like to express its deepest appreciation to the symposium chairs, conference chairs,
program committees, and session chairs who have so generously given their time and advice to
make this symposium possible.
The symposium, like our other conferences and activities, would not be possible without the
dedicated contribution of our participants and members. This program is based on commitments
received up to the time of publication and is subject to change without notice.
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
Monday-Thursday 8-11 March 2010
Part of Proceedings of SPIE Vol. 7642 Electroactive Polymer Actuators and Devices (EAPAD) 2010
are measured for several types of applied potential such as the
step input, sine wave, and square wave. An important feature of the
DAP manufacturing technique is the ability to control and vary the
architecture of the electrode in an IPT. The electrode architecture
is proved to be critical to the performance of the IPT, hence by
increasing its thickness the performance of the IPT will increase almost
proportionally. Ruthenium Dioxide, Platinum, and Single Walled Carbon
Nanotubes are among the several materials studied in the electrodes of
an IPT. Alos presented in this paper is a model depicting the electrode
as an active area, while the middle membrane of an IPT as a passive
area. The active areas model is experimentally verified in bending
and extension modes. Furthermore, presented in this paper are the
morphological studies performed by Bennett and Leo and compared to
the experimental data of the electromechanical characterization of the
ionic liquid based IPTs. In this study the authors varied the types and
concentration of ionic liquids, and they concluded that the ionic liquids
are disrupting the morphology of the ionic polymer. Finally a reliability
study of the dry actuators that demonstrates good performance up to
1 million is presented. This reliability study showed that the limitation
is not due to the ionic liquid but the adherence of the electrodes to the
membrane.
7642-01, Session 1
Biomimetics: lessons from nature
B. Bhushan, The Ohio State Univ. (United States)
Nature has developed materials, objects, and processes which function
from the macroscale to the nanoscale. These have gone through
evolution over 3.8 billion years. The emerging field of biomimetics
allows one to mimic biology or nature to develop nanomaterials,
nanodevices, and processes1. Properties of biological materials and
surfaces result from a complex interplay between surface morphology
and physical and chemical properties. Hierarchical structures with
dimensions of features ranging from macroscale to the nanoscale
are extremely common in nature to provide properties of interest.
Molecular scale devices, superhydrophobicity, self-cleaning, drag
reduction in fluid flow, energy conversion and conservation, high
adhesion, reversible adhesion, aerodynamic lift, materials and fibers
with high mechanical strength, biological self-assembly, anti-reflection,
structural coloration, thermal insulation, self-healing, and sensory aid
mechanisms are some of the examples found in nature which are of
commercial interest. This talk will provide a broad overview of various
objects and processes of interest found in nature and applications
under development or available in the marketplace. The recent research
on superhydrophobicity, self-cleaning, low adhesion/stiction, and drag
reduction in fluid flow2,3 will be highlighted.
7642-03, Session 1
Carbon nanotube yarn as a microscale
rotational actuator
1Bhushan, B., “Biomimetics: Lessons from Nature -An Overview,” Phil
Trans. R. Soc. A (in press).
2Nosonovsky, M. and Bhushan, B., Multiscale Dissipative Mechanisms
and Hierarchical Surfaces: Friction, Superhydrophobicity, and
Biomimetics, Springer, Heidelberg, Germany, 2008.
J. Foroughi, Univ. of Wollongong (Australia); T. Mirfakhrai, The
Univ. of British Columbia (Canada); R. H. Baughman, S. Fang, M.
E. Kozlov, The Univ. of Texas at Dallas (United States); J. D. W.
Madden, The Univ. of British Columbia (Canada); G. M. Spinks, G.
G. Wallace, Univ. of Wollongong (Australia)
3Bhushan, B. Jung, Y. C. and Koch, K., “Micro-, Nano-, and
Hierarchical Structures for Superhydrophobicity, Self-Cleaning and Low
Adhesion”, Phil. Trans. R. Soc. A (in press).
Actuator materials capable of producing a rotational motion are rare
and, yet, rotary systems are extensively utilized in mechanical systems
like electric motors, pumps, turbines and compressors. Rotating
elements of such machines can be rather complex and, therefore,
difficult to miniaturize. Rotating action at the microscale, or even
nanoscale, would benefit from the direct generation of torsion from
an actuator material. We have discovered that the electrochemical
charging of helically wound multiwall carbon nanotubes in the form of
a twisted yarn generates such rotational action. Large scale rotations
are produced from small voltage stimuli. The rotation angles are orders
of magnitude larger than piezoelectric or shape memory alloy torsional
actuators. The torsional strain, torque, speed and lifetime have been
evaluated under various electrochemical conditions to provide insight
into the actuation mechanism and performance. Finally, the rotating
motion has been coupled to a mixer for use in a prototype microfluidic
system.
7642-02, Session 1
Ionic liquid-based ionic polymer
transducers: a review
D. J. Leo, Virginia Polytechnic Institute and State Univ. (United
States); B. J. Akle, Lebanese American Univ. (Lebanon); A. J.
Duncan, Virginia Polytechnic Institute and State Univ. (United
States)
Ionic polymer transducers (IPT) are large strain low voltage ElectroActive Polymer (EAP) actuator. These ionic transducers made of an
ionic polymer membrane in which the cation is free to move while
the anion is covalently attached to the polymer backbone. The
membrane is sandwiched between two high surface area electrodes
toward which the cations migrate upon the application of an electric
field. The redistribution of ions is agreed upon for being the reason
for the electromechanical actuation. Traditionally IPTs requires water
to dissolve and mobilize the free cations inside the ionic polymer
membrane. Although some researchers attempted to package
the water hydrated IPT and use it in air, the use of these actuators
remained limited to underwater applications. To overcome this issue,
Bennett and Leo (200x) hydrated the IPTs with vapor free ionic
liquids. These liquids are special types of salts that are molten at
room temperature and exhibit immeasurable vapor pressure. When
saturated with ionic liquids, IPTs perform millions of cycles in air
without significant degradation in performance. In this paper we will
review the manufacturing techniques, the actuation performance,
the mathematical modeling efforts, and the reliability of these dry
Electroactive actuators. A special manufacturing technique denoted
the Direct Assembly Process (DAP) is developed to manufacture these
dry actuators. Several variants of this manufacturing technique are
presented and the performance of the resulting actuators is compared.
Actuation performance is characterized in both bending mode and
in extensional mode. The free displacement and the blocked force
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7642-04, Session 2
Refreshable Braille displays using
electroactive polymer (EAP) actuators
Y. Bar-Cohen, Jet Propulsion Lab. (United States)
The ability to read Braille text using a refreshable display helps vision
impaired persons benefit from the growing advances in computer
technology. The development of such displays in a full screen form is
great challenge due to the need to pack many actuators in a small area
without interferences. In recent years, various displays using actuators
such as piezoelectric stacks have become available in commercial form
but most of them are limited to one line. In recent years, researchers
in the field of electroactive polymers (EAP) investigated methods of
using these materials to form full screen displays. On the broader level
efforts are sought to develop haptic and tactile interfaces/displays
as tools for interaction with and/or thru computers. The applications
include teleoperators and simulators, computer interfaces and video
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
stretched in the machine direction to a thickness of 6 μm and formed
into roll actuators using an automated manufacturing process. The film
was first wrapped once around a 4 sided paddle along the machine
direction. Individually controlled vacuum on each side of the paddle
held the film along the edges. Conductive polymer was then sprayed
on the PVDF Perpendicular to the Machine Direction (PMD) to act as
a ground electrode. A second film layer was wound on and sprayed to
provide the positive electrode. The double-layer electroded film was
cut along the edges of the paddle using a knife. A heated, rotating
mandrel contacted the film and rolled up the actuator in the PMD to
produce a multi-layer tubular cylinder actuator (Length 5cm; ID 1.5mm;
OD 2mm). The actuators were experimentally tested for displacement
and blocking force.
games (e.g., joysticks and Wii), robotics, tactile displays, surgical forcefeedback devices, and many others. In order to take advantage of the
unique possibilities that EAP can provide this subject is was chosen
for highlight as a special session in the 2010 EAPAD Conference and
abstracts as well as demos for the EAP-in-Action Session will be
sought. This manuscript reviews the state of the art in EAP based
refreshable Braille displays.
7642-05, Session 2
EAP actuators aid the quest for the ‘Holy
Braille’ of tactile displays
N. H. Runyan, National Braille Press (United States) and Personal
Data Systems, Inc. (United States); D. B. Blazie, National Braille
Press (United States) and Blazie Engineering, Inc. (United States)
7642-07, Session 2
The Boston-based National Braille Press has recently established a
Center for Braille Innovation (CBI), whose mission is to research and
develop affordable braille literacy products. The primary focus has
been to facilitate the development of dramatically lower cost electronic
braille display devices, and the much-sought-after “Holy Braille” of a
full-page braille display.
N. H. Di Spigna, P. Chakraborti, D. A. Winick, P. Yang, T. K. Ghosh,
P. D. Franzon, North Carolina State Univ. (United States)
The integration of novel EAP-based Braille
cells for use in a refreshable tactile display
The continued development of the hydraulic and latching Braille cell
is presented. The effects that the material properties of the sealing
membrane and the shape of the lithographically defined bimorph
electrodes have on the polyvinylidene fluoride (PVDF) bimorph tip
displacement and the hydraulic operation of the cell have been
analyzed. A custom automated characterization program has
been developed to enable rapid and systematic data extraction of
the bimorph actuation. Testing of a prototype cell, along with the
challenges involved in its component interactions and fabrication, are
discussed. In addition, further development of the dielectric elastomer
fiber actuator has been investigated. The insertion of a spring core
under compression inside the prestrained electroactive polymer (EAP)
tube has been added to enhance the Braille cell properties. The effect
that this inner spring has on the axial strain and blocking force of a
prototype cell has been evaluated. The application of the two novel
cell designs in meeting the requirements of a full-page, portable,
refreshable Braille display is discussed.
In the spirit of that mission, we discuss the needs and requirements for
new tactile display devices to help improve the extremely low literacy
rate of blind students and to reduce the high unemployment among
non-braille readers who are visually impaired.
The report also discusses the needs and requirements of tactile graphic
image displays, optical-tactile print converters for reading systems,
“full” vision substitution arrays for “seeing-by-feel”, tactile virtual reality
systems, and compact tactile displays for watches, calculators, cell
phones, and other small devices.
The NBP specs include braille dot dimensions, spacing, displacement,
lifting force, and response time requirements. In addition to
summarizing the technical requirements and specifications for braille
and other tactile displays, the NBP web site and other sources of tactile
display specifications will be referenced.
We discuss human factors issues, such as why multiplexing with only a
single braille character display is not acceptable for most applications.
Several of the common and repeated pitfalls and assumptions that
have led many previous tactile display developments astray are
reviewed, in hopes that knowledge of these pitfalls will help developers
avoid similar, misguided approaches. Our report reviews some of the
major design limitations that caused many braille display developments
to fail.
7642-08, Session 2
Compact electroactive polymer actuators
suitable for Braille display
L. J. Gorny, M. Lin, S. Liu, Q. M. Zhang, The Pennsylvania State
Univ. (United States)
The CBI’s prior art listing of tactile display projects is briefly reviewed
and referenced, including some of the most notable past and current
projects utilizing solenoids, wax expansion, bimetallic expansion,
shape memory alloys, and both moving elastomer and plastic belt loop
displays.
The small strain level and brittle nature of piezoceramic actuators
used in the present commercial Braille display make it a challenge to
develop full page and graphic Braille display with compact size and
affordable price. On the other hand, recently developed electrostrictive
P(VDF-TrFE-CFE) terpolymer with the large strain (~5%), fast actuation
speed, and relatively high elastic modulus possesses great potential
for compact Braille actuators suitable for full page and graphic Braille
displays. This talk presents recent work in developing electrostrictive
PVDF terpolymer based Braille actuators which exhibit tip displacement
of 1 mm and force level more than 0.5 N with very compact size. In
order to further improve the Braille actuator performance, a new class
of terpolymer blends was developed recently which shows more
than twice the elastic energy density of the original electrostrictive
terpolymer. To match the requirement of 200 volts operation voltage,
used in the commercial Braille display with piezoceramic bending
actuators, a terpolymer film roll-to-roll zone drawing machine
was designed and developed. Making use of this machine, the
electrostrictive polymer films of 2 um thick has been produced with
high quality. As a result, the newly developed electrostrictive Braille
actuators can be operated under 200 volts, meeting the commercial
Braille display requirement.
Associated with our presentation, there will be a significant exhibit of
a wide variety of braille and tactile display devices, which should offer
attendees a rare opportunity to literally get a hands-on feel for tactile
display technologies and see what’s under their hoods.
Finally, we summarize the results of our investigations into tactile
display prior and current art, and list what appear to be the remaining
challenges to developing practical tactile displays employing EAP
actuator materials.
7642-06, Session 2
PVDF actuators for Braille displays
T. Levard, P. J. Diglio, C. D. Rahn, L. J. Gorny, Q. M. Zhang, The
Pennsylvania State Univ. (United States)
Multi-line refreshable Braille displays have generated research interest
because they allow blind people to interface with computers. This
paper addresses the challenge of producing miniature and reliable
actuators that generate the required 0.5 mm displacement and 100 mN
force in a low profile and 2 mm diameter form factor. PVDF films were
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
In particular, the paper describes both millimeter-scale arrays and
centimeter-scale single units of actuators, currently being developed
as soft, light, acoustically silent and cheap devices for two types
of applications: tactile displays and cutaneous stimulators. In both
cases, the most significant advantages of the proposed technology
are represented by high versatility for design (due to the fluid based
transmission mechanism), tailorable stiffness perceived by the user
(obtained by adjusting the internal fluid pressure), and suitable
electrical safety (enabled by both a passive interface with the user
and the insulating internal fluid). Millimeter-scale prototypes have
been fabricated so as to show a resonance frequency in the range
250-300 Hz, which represents the range wherein Pacinian cutaneous
mechanoreceptors exhibit maximum sensitivity; this provides an
optimum condition to eventually code tactile information dynamically,
either in combination or as an alternative to static driving.
7642-09, Session 4
Bistable electroactive polymers (BSEP)
Q. Pei, Univ. of California, Los Angeles (United States)
Bistable electroactive polymers (BSEP)
Zhibin Yu, Paul Brochu, Xiaofan Niu, Wei Yuan, Huafeng Li, Qibing Pei
Department of Materials Science and Engineering, University of
California, Los Angeles, CA 90095, USA
The ability to produce reversible, large-strain, bistable actuation has
been the Holy Grail in the pursuit of smart materials and structures.
Conducting polymers are bistable, but the achievable strain is small.
Large deformations have been achieved in dielectrical elastomers at
the sacrifice of mechanical strength. The gel or gel-like soft polymers
generally have elastic moduli around or less than 10 MPa. The
deformed polymer relaxes to its original shape once the applied electric
field is removed. We report new, bistable electroactive polymers (BSEP)
that are capable of electrically actuated strains greater than 200%. We
will discuss the various applications enabled by the BSEP including
Braille displays that can quickly refresh and maintain the displayed
contents without a bias voltage.
7642-12, Session 4
Flexible tactile sensor for robot fingertip
H. R. Choi, D. S. Kim, H. C. Nguyen, S. M. Jin, H. L. V. Nguyen, K.
J. An, H. P. Vuong, J. C. Koo, J. Nam, Y. K. Lee, Sungkyunkwan
Univ. (Korea, Republic of)
7642-10, Session 4
Tactile perception is one of the most important things for object
manipulation in unknown environments. Currently, there are many
kinds of tactile sensors which are developed using flexible PCB,
PDMS etc. However they actually are not soft enough for 3D shaped
applications like a robot hand because of their low flexibility. So in this
paper we proposed the novel tactile sensor using dielectric elastomer
which has high flexibility and strechability as a base material. Since
the dielectric elastomer is conformable, it can be easily covered onto
the curved robot fingertip surface. When pressure is applied to the
sensor, the dielectric elastomer gets compressed, and the capacitance
between top and bottom electrodes changes as they get closer. The
developed tactile sensor consists of two conductive layers separated
by a soft dielectric elastomer. We use flexible conductive silicone for
each conductive layer. The inner conductive layer configured with
multi-cells in order to detect both contact force and position and the
outer conductive layer is regarded as a common ground to reduce the
electrical noise coming from the environment. There are, in addition,
two thin protection layers on top and bottom surface. In the proposed
design, capacitive tactile sensor have been implemented using
commercially available capacitance to digital converter integrated
circuits(CDC), commonly used for example in cell phones. The CDC
detects the variation of a capacitance and the measurements are
sent to a microcontroller using inter integrated circuit(I2C) buses. A
Microcontroller will send the tactile data to a host using a CAN bus.
Vibrotactile display for mobile applications
based on dielectric elastomer stack
actuators
M. Matysek, P. Lotz, K. Flittner, H. F. Schlaak, Technische Univ.
Darmstadt (Germany)
Dielectric elastomer stack actuators (DESA) offer the possibility to build
actuator arrays at very high density. Depending on the film thickness
the actuator’s driving voltage can be defined. We recently published
details of or multilayer technology to reduce the driving voltage below
500V. In this paper we present the development of a vibrotactile display
based on this technology which is used to present several operating
conditions of a machine as haptic information to a human finger. As an
example the design of a MP3-player interface is introduced. To build up
an intuitive and user friendly interface several aspects of human haptic
perception have to be considered. Using the results of preliminary user
tests the interface is designed and an appropriate actuator layout has
been derived. The control of the actuators is important because there
are many possibilities to present different information with a single
actuator, e.g. by encoding the information in frequency, amplitude or
pulses. The realized system allows an almost free configuration of the
information encoding.
A built up demonstrator is used to investigate the concept of our
display by further user tests. The high recognition rate of more than
90% validates the concept.
7642-13, Session 4
Active polymers based high-resolution
tactile display
Finally the energy consumption of the device is determined. The
required real power is less than 0.3mW while the reactive power is
almost 100 times higher. Voltage and current of the actuator are 89.5°
out of phase, thus, the actuator represents a nearly purely reactive
load. Actuator design parameters affecting the power consumption are
determined.
A. Richter, G. Paschew, K. Arndt, Technische Univ. Dresden
(Germany)
Here, we introduce a high-resolution tactile display (1). We present
our artificial skin based on temperature sensitive “Smart Hydrogels”
which displays both visual and palpable information. Each of the single
actuators is controlled by a computer using an opto-electronical or a
resistive interface and thereby generating a high resolution temperature
field. The device containing an artificial skin consists of 4,225
individually controlled actuator pixels at a density of 300 actuators per
cm². An actuator pixel changes the color from transparent to opaque,
the altitude and the elasticity. Therefore the display is able to generate
artificial impressions about contours, textures, profiles and the softness
of a surface. The palpable impressions can be varied depending on
the design of the device such as the layers surrounding the actuators
or the actuator size, the resolution and the alignment. Due to its
color change the polymer display provides also visual monochrome
functionality. The artificial skin would allow physical-auditory interaction
to improve the communication of visually impaired persons with
electronic media. If the artificial skin is combined with image-based
diagnostics then new features will be provided in teleoperations. The
7642-11, Session 4
Hydrostatically coupled dielectric elastomer
actuators for tactile displays and cutaneous
stimulators
F. Carpi, G. Frediani, S. Tarantino, D. De Rossi, Univ. of Pisa (Italy)
Hydrostatic coupling has been recently reported as a means to
improve versatility and safety of dielectric elastomer (DE) actuators.
Hydrostatically coupled DE actuators rely on an incompressible fluid
that mechanically couples a DE-based active part to a passive part
interfaced to the load. In this paper, we present ongoing development
of bubble-like versions of such transducers, made of silicone and oil.
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
palpable recognition of objects inside the body without the necessity
to open it would improve diagnoses and allow preliminary simulation
of surgical operations. Introducing tactile information within minimally
invasive robotic surgery (MIRS) would combine the advantages of
conventional open surgery, which is in particular the tactile recognition
of the operation field, with that of the MIRS, e.g. for reduction of the
operative trauma for the patient.
7642-16, Session 5
Materials science on the nano-scale for
improvements in actuation properties of
dielectric elastomer actuators
G. Kofod, H. Stoyanov, M. Kollosche, S. Risse, H. Ragusch, D. N.
McCarthy, Univ. Potsdam (Germany)
1) Richter, A.; Paschew, G. Adv. Mater. in press, DOI: 10.1002/
adma.200802737.
Three properties of the elastic medium in a dielectric elastomer
actuator affect the actuation properties directly: dielectric constant,
electric breakdown strength, and mechanical stiffness. The dielectric
constant of a given elastomer can be improved by mixing it with other
components with a higher dielectric constant, which can be classified
as insulating or conducting. Insulating particles are commonly
metaloxides, we present our results on nanoparticulate TiO2 and
BaTiO3. We demonstrate how the permittivity may increase faster
than expected due to the high surface of the nanoparticles, but that
such composites are also very sensitive to air humidity, giving rise a
high apparent value of the low-frequency permittivity, but with drastic
effect on electrical loss. A chemical coating is shown to lead to strong
improvements.
7642-14, Session 4
EAP arrays of single-cell stretching devices
for tissue engineering applications
S. Akbari, M. Niklaus, H. R. Shea, Ecole Polytechnique Fédérale de
Lausanne (Switzerland)
Mechanical stimuli are critical for the development and maintenance
of most tissues such as muscles, cartilage, bones and blood vessels.
Commercially available cell stretching devices apply strain over areas
greater than one cm^2, and can only measure the average response
of large colonies of cells. We present here an array of 128 EAP
micro-actuators which impose unidirectional strain on single cells,
thus enabling for the first time, experiments on the cytomechanics of
individual cells.
Also, we show studies on conducting nanoparticles. Especially,
we demonstrate how “simple” percolation causes detrimental side
effects, leading to overall reduction in actuation. Careful distribution
of nanoparticulate metal in mesoporous silica-spheres leads to
useful increases in permittivity, but the mechanical properties are
not technologically useful. A “molecular composite” approach, in
which the conducting nanoparticles are docked chemically to the
backbone appears valuable. The achieved improvements seem to
be all connected to avoiding a random distribution of the conducting
entity, and instead achieving a constant nearest neighbour separation.
A shielding of each conducting entity should also be encompassed.
In combination, this leads to improved permittivity while leaving the
breakdown strength and the stiffness unaffected, in all causing an
activation of the polymer material towards actuation.
The 100x100 μm^2 dielectric elastomer actuators consist of 30
μm thick pre-stretched PDMS film (Sylgard 186) bonded onto a
support frame in which 50 μm deep and 100 μm wide channels are
patterned. Compliant gold electrodes are deposited by low-energy
ion implantations, as this technique allows making electrodes that
support large strain (175%) with minimal stiffening of the elastomer.
50 μm to 200 μm wide gold lines, orthogonal to the channels, are
patterned under the membrane, and a continuous implanted electrode
is deposited on the membrane. There is one actuator at the intersection
of each channel and line, on which a cell can be attached.
Our current device with 128 actuators on a 4 cm^2 chip is driven
by 4 independent control voltages, allowing different frequencies
and amplitudes to be applied to sections of the array to permit
simultaneous observation of cell behavior under various dynamic and
static mechanical strains. We are currently calibrating strain versus the
applied voltage, frequency and geometry. FEM simulations predict a
20% strain at 3.5 kV, easily covering biologically relevant levels.
7642-17, Session 5
Challenges in microfabrication of DEAs
B. Balakrisnan, E. Smela, Univ. of Maryland, College Park (United
States)
DEAs (dielectric elastomer actuators) have been demonstrated for
meso- and macro-scale applications, but only a few devices have been
shown at the micro-scale. The most commonly demonstrated microscale DEAs are diaphragms that bulge out of the plane of the wafer.
Microscale devices would have many useful applications, including
micro-robotics, micro-pumps, and micro-optical systems. In addition,
an advantage of the micro-scale devices is that since the layers are
thinner, the required driving voltages are reduced from kilovolts to tens
or hundreds of volts. However, fabrication of micro-scale DEAs remains
challenging. This is due in part to the fact that the vast majority of
macro-scale materials and/or fabrication methods cannot be adapted
to the micro-scale. On the micro-scale, the DEAs must be patternable,
as well as compatible with other materials used during fabrication,
such as sacrificial layers. Another practical issue in fabricating microscale devices is making connections to the top electrodes. It would
also be desirable for the fabrication to be compatible with CMOS
(complementary metal-oxide-semiconductor) driver circuits and other
MEMS (micro-electro-mechanical systems). This article addresses the
progress that has been made, as well as the challenges, in making
MEMS-based DEAs. It also highlights the key areas in which additional
research needs to be pursued.
7642-15, Session 4
Artificial muscle actuators for haptic
displays: system design to match the
dynamics and tactile sensitivity of the
human fingerpad
S. J. Biggs, R. N. Hitchcock, Artificial Muscle, Inc. (United States)
Electroactive Polymer Artificial Muscles (EPAM) based on dielectric
elastomers have the bandwidth and the energy density required to
make haptic displays that are both responsive and compact. Recent
work at Artificial Muscle has been directed toward the development of
thin, high-fidelity haptic displays. The litmus test in many applications,
for example touch screens, is the brief tactile “click” that confirms
keypress. As such, the parameter of interest is the transient response
of the system (actuator + display + fingertip). To design for a good
click, it is useful to know the inertial, damping, and spring loads of
these system components under transient conditions. Here we report
on the dynamic properties of our dielectric elastomer actuators, as
well as the dynamic properties of human fingerpads subjected to brief
“click” transients. Effects of button-press force, transient amplitude and
click duration are reported for a variety of users. Transient response for
clicks, and steady-state response for longer effects such as music and
games are compared.
7642-19, Session 5
Dielectric elastomer actuators: enhanced
performance by systematic improvement of
materials properties
M. Molberg, EMPA (Switzerland) and Ecole Polytechnique Fédérale
6
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
For this test an up-scaled set-up was used. By variation of different
parameter settings the transferability of the results to smaller
dimensions has been shown within a limited range. Those practical
results support the theoretical conclusions.
de Lausanne (Switzerland); Y. Leterrier, Ecole Polytechnique
Fédérale de Lausanne (Switzerland); C. J. G. Plummer, C. I. E.
Löwe, D. M. Opris, EMPA (Switzerland); J. E. Månson, Ecole
Polytechnique Fédérale de Lausanne (Switzerland)
It should be noted, that the presented investigations consider exclusive
the static behaviour of a DEA-setup with rigid electrodes. Further
investigations will focus on the applicability to dynamic operation
modes.
Dielectric elastomer actuators (DEAs) have attracted increasing
attention over the last few years owing to their outstanding properties,
e.g. their large actuation strains, high energy density, and pliability,
which have opened up a wide spectrum of potential applications in
fields ranging from microengineering to medical prosthetics. There
is consequently a huge demand for new elastomer materials with
improved properties to enhance the performance of DEA and to
overcome the limitations associated with currently available materials,
such as the need for high activation voltages and poor long-term
stability. In recent work, we have investigated different dielectric
and mechanical characterization methods for the determination
of materials parameters that describe the actuation behaviour of
dielectric elastomers. Three different elastomers were considered: an
acrylic adhesive (VHB), a silicone rubber (PDMS) and a thermoplastic
elastomer. The frequency dependence of the actuation performance
of these materials was found to be dominated by the mechanical
response rather than the dielectric properties, which remained relatively
constant in the frequency range investigated. Such results nevertheless
indicate that the overall performance may be improved by increasing
the dielectric constant, which has led us also to consider composite
elastomeric dielectrics based on the thermoplastic elastomer or
PDMS and conductive polyaniline or ceramic (PZT) powder fillers. The
potential of such materials as well as strategies to counter the adverse
effects of increased conductivity and elastic modulus will be discussed.
7642-20, Session 6
Optimized on dielectric elastomer actuator
based on acrylonitrile butadiene rubber
H. R. Choi, K. J. An, H. C. Nguyen, D. S. Kim, H. L. V. Nguyen, H.
P. Vuong, J. C. Koo, J. Nam, Y. Lee, Sungkyunkwan Univ. (Korea,
Republic of)
For many years, electroactive polymers (EAP) are popularly studied
as alternate of the traditional electromagnetic actuators. They have
characteristics as compliant, versatile, low density, and low cost.
Specially, Dielectric elastomer has high capacity of actuation as
human-muscle because of large deformation and large force. In
this paper, we optimized the effects of additives and vulcanization
conditions on the performance of a dielectric elastomer actuator.
Previously, Synthetic elastomer based on Acrylonitrile Butadiene
Rubber (NBR) was a material classified as a dielectric elastomer that
can have its characteristics modified according to the requirements.
In this paper, we make an experiment about mechanical properties
(Young modulus, stress relaxation), electric properties (dielectric
constant, dielectric loss, breakdown voltage), and electric-mechanical
properties (deformation of actuator). In the first experiment, this paper
compares with two kinds of NBRs on the overall performances of
the synthetic elastomer. We are carried out better NBR by analyzed
results of experiments. Based on the results of the first experiment,
Synthetic elastomer using selected NBR is optimized by DOE (Design
of Experiments). We use table of orthogonal arrays that four factors
were examined at three levels. Factors are composed of additives
such as dioctyl phthalate (DOP), barium titanium dioxide (BaTiO3)
and vulcanization conditions such as dicumyl peroxide (DCP), crosslinking times. Experimental results are analyzed by ANOVA (Analysis of
variance). And the last, we accomplished 10% deformation and high
force for an actuator.
7642-99, Session 5
Dielectric elastomer bending tube actuators
with rigid electrode structures
F. Wehrheim, J. Meyer, Richard Wolf GmbH (Germany); H. F.
Schlaak, Technische Univ. Darmstadt (Germany)
The common approach for dielectric elastomer actuators (DEA) is
based on the assumption that compliant electrodes are a fundamental
design requirement. Focused on tube-like and thin-walled actuator
geometries those compliant electrodes cause an unwanted change of
the actuator diameter during actuation. Additional support-structures
could improve the radial stability but would decrease the total available
space.
By following the ambition of maximum functional integration the
concept of using a rigid electrode structure arises. This structure
realizes both, actuation and support characteristics. The cross
sectional shape of this actuator-tube is supported by common circular
reference electrodes, which can be either axial-parallel or axial-coilshaped.
7642-21, Session 6
The dynamic properties of tubular DEAP
actuators
R. Sarbran, A. Poole, K. P. Lorenzen, Danfoss PolyPower A/S
(Denmark)
The intended rigid electrode structure is based on a stacked DEA. As
motivation and focused application a number of pairs of electrodes
align axial-parallel within the wall of an elastic tube. The volume
between the electrodes is occupied by an elastic dielectric. The axial
adjoining alignment of the different actuator-axis’ is expected to restrict
the extension of the dielectric in x-direction (tangential). The dielectric
should extend only in one direction.
Tubular actuators fabricated from dielectric electro-active polymers
(DEAP) have been developed and optimized with focus on high volume
roll to roll automated manufacturing techniques and processes.
This paper will expand upon the established static performance
characteristics of these actuators to include their response to time
varying electrical stimuli, reporting the resulting dynamic mechanical
and electrical behaviour. By measuring the mechanical outputs of
the actuators such as force and stroke, produced by time varying
electrical stimuli with different waveforms, the resonances as well as
response time and electromechanical efficiency of the actuators can
be obtained. Furthermore, to facilitate integration of the product into
electromechanical systems, an electrical model of the actuating device
is also presented. This measured and reported dynamic profile of the
actuators can be used for implementing the DEAP actuators inside
electrical and mechanical devices. Knowing the dynamic behaviour is
fundamental to utilizing these devices in, for example, closed looped
control systems. The techniques used to measure time dependent
responses are established as a methodology and are used to provide
consistent characterization of the behaviour of actuators.
By attraction of adjoining electrodes, the dielectric volume between
those electrodes reduces. Because the original volume is expected to
be non-compressible, the displaced dielectric is assumed to have the
cross sectional shape of a circular segment. This shape is represented
by the overlap sh, the area A2 and the volume V2. The overlap sh gives
an applicable indicator for geometrical limitations and has been used to
extract the first design rules regarding the electrode size x0·h0 and the
aspect-ratio h0/y0.
Considering the strain in any direction the mechanical efficiency mech
has been formulated. In combination with the relative displacement shrel further design aspects could be extracted by using this additional
indicator.
With reference to DIN ISO 7743 a test for determination of the
compressive stress-strain-characteristics has been applied.
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
A number of McKibben-type actuators were fabricated and tested for
electrode continuity, elastomer dielectric properties, fiber-elastomer
composite material mechanical properties, and actuator performance
under an applied electrical and stress field. Actuator results are
presented in terms of blocked stress and free strain with performance
of actual specimens compared to analytical predictions.
7642-22, Session 6
Radially-expanding mechanism for dielectric
elastomer actuators
A. T. Conn, J. M. Rossiter, Univ. of Bristol (United Kingdom)
Dielectric elastomer actuators (DEAs) offer numerous benefits as
high displacement smart material actuators. The output of a DEA film
is typically characterised by a large area expansion and a smaller
transverse displacement. Consequently, their application is often
limited by difficulties in resolving area expansion strain into a usable
output. DEAs also require pre-strain in order to achieve optimal
performance.
7642-24, Session 6
Graphite/PDMS stretchable electrodes for
dielectric elastomer actuators
M. P. Kujawski, J. Pearse, E. Smela, Univ. of Maryland, College
Park (United States)
In this paper, Hoberman’s radially-expanding mechanism is used to
form a novel DEA structure. The mechanism is composed of a number
of repeating angular scissor-links which resolve DEA area strain into
a uniaxial displacement and have intrinsic pre-straining capabilities.
This allows the Hoberman mechanism to be exploited as an actuator.
Additionally the structure can be used as a device for pre-straining
dielectric elastomer films. The mechanism’s performance as both
a DEA and a pre-strain device is investigated through kinematic
optimisation and stress/strain distribution analysis via photoelasticity
and finite element modelling. These analyses show that there is a
design trade-off between biaxial strain uniformity of the DEA layer and
the mechanism’s mass and frictional losses.
Dielectric elastomer actuators (DEAs), consisting of an elastomer
sandwiched between two electrodes and having large in-plane
expansion upon the application of a voltage, require electrodes that
are compliant. Currently, the most commonly used electrode material
is carbon grease. However, carbon grease smears easily and is difficult
to pattern, so an alternative material is required. This paper outlines the
fabrication and performance of a novel graphite/ polydimethylsiloxane
(PDMS) composite electrode material. This new material has a Young’s
modulus of only 0.43 MPa, has conductivities as high as 0.02 S/cm,
and is capable of reaching strains as large as 50% before failure.
Unlike other composite electrode materials, the elastic modulus of the
graphite/PDMS increases only slightly at the loadings required to make
the material sufficiently conductive for DEAs. Under repeated strain
cycles, the modulus remains constant, and the conductivity actually
increases. Furthermore, the graphite/PDMS composite is patternable
and will not rub off. DEAs were fabricated from PDMS using these
electrodes, and the strains were comparable to those in PDMS devices
made using carbon grease. This material may also find applications in
areas such as flexible electronics, robotics, strain gauges, and sensors.
The development of prototype actuators using this mechanism is
described along with the results of experimental tests. These tests
demonstrate that the prototype actuators resolve area expansion strain
into a uniaxial displacement (which can be linear or rotary) at the cost
of mechanical losses. The performance of the mechanism is compared
with existing linkages such as the bowtie configuration and potential
novel applications are discussed.
7642-23, Session 6
7642-25, Session 6
Processing, microstructure, and properties
of a fiber-reinforced dielectric elastomer
actuator
Effects of conductive particles on the
actuating behavior of dielectric elastomer
actuator
B. K. Stewart, NASA Langley Research Ctr. (United States); K. V.
Logan, Virginia Polytechnic Institute and State Univ. (United States)
Z. Zhang, Y. Liu, J. Leng, Harbin Institute of Technology (China)
Dielectric elastomer actuators are often characterized by large free
strain, and equally low blocked stress output. One hypothesis would
be that the addition of fiber reinforcement would increase the blocked
force output at the expense of free strain. Numerical values to quantify
the resulting tradeoff could potentially benefit dielectric elastomer
research and lead to a host of useful materials and devices.
Dielectric elastomer, also known as electroactive polymer artificial
muscle, has shown considerable promise for a variety of actuator
applications. However, the need for high actuating electric field of the
dielectric elastomer actuator greatly limits its practical applications. A
reduction of the actuating electric field may be achieved according to
develop elastomers with high permittivity. The effects of conductive
particles on the actuating behavior of silicone rubber-based dielectric
elastomer are studied in this work. Three different materials, which
are carbon nanotube, short fiber, and carbon black, respectively,
are used to increase the overall permittivity of the composites.
These composites are characterized by dielectric spectroscopy,
scanning electron microscopy, tensile mechanical analysis, and
electromechanical transduction tests. The effect of variation in filler
loadings on the complex and real parts of permittivity are distinctly
visible, which has been explained on the basis of interfacial polarization
of fillers in a heterogeneous medium. The phenomenon of percolation
was discussed based on the measured changes in permittivity and
morphology of composites at different concentrations of these
particles.
One candidate for a fiber-reinforced device is the McKibben-style
actuator. Based upon the work of Rivlin in characterizing the effect
of “inextensible fibers” on passive elastomers, the concept has been
recently been expanded to include effects of an applied electric
field on the McKibben structure. Recent analyses by McKay and
Goulbourne predict axial strains in the vicinity of 5% for fiber-reinforced
cylindrical dielectric elastomer actuators. By means of finite element
analyses, McKay predicted increased axial displacement with reduced
elastomer layer thickness. McKay’s analysis also predicted a change
from an axially elongating actuator to an axially constricting actuator
depending upon fiber orientation. In addition to axial performance
predictions, the reduction of elastomer thickness results in a profound
reduction of operating voltage of dielectric elastomer devices. The
analyses predict that many potential advantages can be achieved by
control of film thickness and fiber angle in a fiber-reinforced cylindrical
actuator. While the analyses show promise, use of commercially
available material forms, such as polyacrylate film products, limits the
ability of researchers to produce devices capable of testing analytical
predictions.
7642-26, Session 6
Thermodynamic design model for dielectric
elastomer actuators
A multistep process has been developed using uncured elastomer
precursor materials and tow placement strategies to produce
cylindrical actuators with precise control over elastomer thickness,
fiber orientation and fiber fraction. Elastomer thickness reductions of as
much as 80% over commercially available films have been obtained.
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J. Lucking Bigué, S. Proulx, P. Chouinard, J. Plante, Univ. de
Sherbrooke (Canada)
Dielectric Elastomer Actuators (DEAs) are a promising actuation
technology for small mobile robotics due to their high force-to-weight
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
ratio, high energy density (per volume) and potential for high energy
conversion efficiency. Nonetheless, designing such systems requires a
good understanding of the actuators’ thermodynamic performances in
order to optimize energy usage for a given actuator weight and volume.
This paper proposes a design model of DEAs’ thermodynamics, DEAs
that are controlled under three different modes of operation: constant
voltage, constant electrical field and constant charge. Accompanied
by a thorough experimental validation, this analysis is useful for design
work involving energy-related calculations, since it explains how
DEA performance is affected by the three modes of operation and by
material dependant loss mechanisms.
7642-96, Poster Session
Electric field modelling of DEAP material
with compliant metal electrodes
P. Wang, R. W. Jones, B. Lassen, Univ. of Southern Denmark
(Denmark)
Electrical breakdown is the main failure mode for DEAP materials. The
phenomenon occurs when the electric field in a material becomes
greater than its dielectric strength and the insulating barrier properties
are exceeded.
A thermodynamic analysis of a uniform DEA is conducted assuming
no losses. Fundamental equations are derived for actuator mechanical
work, energy consumption and efficiency for each of the three modes
of operation. The analysis reveals that DEAs use stored energy in
the form of electric charges, much like internal combustion engines
do in the form of compressed gasses. This work indicates that
the constant voltage and constant charge modes have opposite
performance characteristics. In fact, constant voltage mode involves
high mechanical work but low efficiency, while constant charge mode is
associated with low mechanical work and high efficiency. The constant
electrical field mode results in an average performance, positioned
between the performances of the other two modes. The effect of
energy recovery on DEA efficiency is also theoretically addressed as
it appears physically impractical, due to heavy system weights and
limited performance gains.
The electrodes, ideally, must be highly compliant, from both an
electrical and mechanical perspective. Compliant metal electrode
technology, derived from micro-machining and screen printing,
achieves compliance by using a corrugated profile. Increases in the
electric field distribution due to the profile(s), when compared with a
parallel plate type compliant electrode, might possibly cause a greater
incidence of electrical breakdown.
In this contribution, the electric field and surface charge density
characteristics of compliant metal electrode-based DEAP material
are investigated. A mathematical model of the electric behaviour in
the complaint conductor and dielectric are initially developed using
classical electrodynamics theory. This model is then implemented in
a finite element simulation package, COMSOL. Initially a comparison
is carried out between the electric field and surface charge density
characteristics of a compliant parallel plate type material with a
complaint metal electrode-based material with sinusoidal corrugations.
The possible affects that impurities in the elastomer might have on
the electric field behaviour are then examined. Only two defects are
addressed here - penetration of the metal electrode into the body of
the elastomer and air bubbles in the body of the elastomer.
Performance predictions of the thermodynamic analysis are completed
with a broad range of experimental data obtained from oblong-shaped
DEAs, made in both VHB 4905 acrylic and Nusil CF19-2186 silicone.
A work-cycle test bench was implemented to achieve complete
performance mapping of the constant voltage and constant charge
processes. Similar to motor efficiency maps, actuators at different
nominal voltages, actuator extensions and speeds are tested, and
overall energy conversion efficiencies are established. The experimental
performance trends are corroborated by the thermodynamic analysis
and the differences are explained by material-dependant electrical
and mechanical losses, the magnitudes of which are evaluated
experimentally. Finally, the design model is demonstrated through the
preliminary design of a DEA rotary motor.
7642-97, Poster Session
Active vibration control of periodic
disturbances using a DEAP damper
Results show the design model to be an interesting tool for actuator
preliminary design. The model also provides quantitative values of
actuator loss mechanisms, which help minimize energy consumption
in geometric design purposes. This work should be of interest to the
entire DEA community as it is a first cut DEA design tool.
R. Sarban, Danfoss PolyPower A/S (Denmark); R. W. Jones, Univ.
of Southern Denmark (Denmark); B. Mace, Univ. of Southampton
(United Kingdom)
Tubular dielectric electro-active polymer-based actuators have many
possible applications. The use of such a device to provide active
vibration control, either by itself or as a complimentry approach to
passive damping, potentially has a wide market.
7642-65, Poster Session
In this contribution a DEAP core-free tubular actuator will be examined
for its ability to carry out the active vibration control of periodic
vibratory disturbances. A potential problem with the use of any DEAP
devices to damp periodic vibrations, not just the actuator used here,
is that for periodic input voltages the mechanical output of the DEAP
actuator will be the square of the periodic input. This will result in an
output with several harmonics. Therefore from a vibration damping
perspective not only does the first harmonic of the periodic disturbance
need to be controlled but also subsequent harmonics to achieve the
‘best’ vibration damping performance across a range of frequencies.
Novel cellulosic gel preparation for using in
electro-responsive applications
A. Sirivat, W. Kunchornsup, Chulalongkorn Univ. (Thailand)
Celluloses used in the field of electro-responsive applications
are known as the “Electroactive-paper (EAPap)”. In this work,
physical and chemical cellulose gels are prepared and studied for
the effects of crosslinking ratio (CR) and ageing time (tag) on the
mechanical properties of the cellulose gels. An ionic liquid,1-butyl3-methylimidazolium chloride (BMIMCl), was used as an effective
cellulose solvent for EAPap. The crosslinking reaction conversion
increases with increasing CR and tag. The crosslinking reaction
products are ketone linkages and water molecules as by product. The
difference in optical properties is observed and is related to the relative
amount of ketone linkage as confirmed by FTIR-ATR. By-product
water molecules exhibit plasticizing effects which decrease the storage
modulus (G’) after 1 aging day The outward migration of the by-product
water molecules causes slightly increasing of G’ after 15 aging day due
to a closer packing. In addition, by-product water molecules create
cellulose aggregations and increase disordered region that contributes
to the increase in electrical conductivity based on the ion migration.
In addition, electromechanical properties of our cellulose gels will be
shown and compared with other electroactive material systems.
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First of all the dynamic characteristics of the core-free tubular actuator
used are introduced. The dynamic characteristics provide an indication
of the frequency range over which active vibration control might
be successful in damping vibrations. Feedforward active vibration
control is considered here and it is initially shown that a d.c. offset
of the controlled voltage signal can be used to improve the damping
characteristics of the device. Two approaches to remove the vibrations
due to higher harmonics are examined - (a)linearization of the control
signal, and (b) dedicated individual feedforward controllers for each
harmonic.
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9
Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
0.2wt% MWCNT contents had the highest value of piezoelectricity. the
rheological properties were also presented in order to understand the
dynamic behaviors of the composites
7642-98, Poster Session
Ultra high electrostriction behavior of
electroactive thermoplastic elastomer gels
by in-situ tracing microstructural change
during electromechanical actuation
7642-102, Poster Session
Electrically driven PEDOT/PSS actuators
C. M. Koo, S. M. Hong, Korea Institute of Science and Technology
(Korea, Republic of)
H. Okuzaki, Univ. of Yamanashi (Japan); T. Ito, Takano Co. Ltd.
(Japan); K. Hosaka, Univ. of Yamanashi (Japan)
Althought the dielectric elastomers have been able to actuate
electrostrictively more than 50% driven mainly by a Maxwell stress
effect and by the electrostrictive effect, relatively high applied electric
fields (>50V/mm) is the biggest challenge for the real applications. The
most efforts for reducing the operational voltage have been focused on
increasing a dielectric constant and decreasing a compressive modulus
because both are known to be key parameters in the Maxwell stress
effect of the dielectric elastomer.In this work, we illustrate a different
example where the electrostrictive effect dominates the actuation of
the dielectric elastomer resulting in a high electrostriction coefficient
as well as in a high electrostrictive strain at relative low operational
voltage.
Free-standing films made of poly(3,4-ethylenedioxythiophene)
doped with poly(4-styrenesulfonate) (PEDOT/PSS) were prepared by
casting water dispersion of its colloidal particles. Morphology, water
vapor sorption, and electro-active polymer actuating behavior of the
resulting films were investigated by means of atomic force microscopy
(AFM), sorption isotherm, thermal mechanical analysis (TMA), and
electromechanical analysis. It was found that the PEDOT/PSS film
sorbed 60% of moisture at relative water vapor pressure of 0.95. Upon
application of 10 V, the film underwent contraction of 2.4% in air at
50% relative humidity (RH) which significantly increased to 4.5% at
90% RH. The principle lay in desorption of water vapor sorbed in the
film due to Joule heating, where electric field was capable of controlling
the equilibrium of water vapor sorption. The film generated contractile
stress as high as 17 MPa under isometric condition and work capacity
attained 174 kJ m-3, where Young’s modulus of the film increased from
1.8 GPa to 2.6 GPa by application of 6 V at 50% RH.
7642-100, Poster Session
Development of high strain electro-active
polymer actuators via optimization of
the pore size of the conductor network
composite layer
7642-103, Poster Session
Effect of strain on the electrical conductivity
of a styrene-butadiene rubber
R. Montazami, Virginia Polytechnic Institute and State Univ. (United
States); S. Liu, The Pennsylvania State Univ. (United States); V.
Jain, Virginia Polytechnic Institute and State Univ. (United States);
Y. Liu, M. Lin, Q. M. Zhang, The Pennsylvania State Univ. (United
States); J. R. Heflin, Virginia Polytechnic Institute and State Univ.
(United States)
Y. H. Kim, J. Y. Lim, J. Y. Kim, G. Lee, A. N. Gent, C. Nah, Chonbuk
National Univ. (Korea, Republic of)
When the carbon black-filled rubbers are stretched, the electrical
resistivity increases at lower extension ranges, and then it decreases
with further extension. This complex behavior is attributed to the
morphology changes of carbon blacks during extension, i.e., breaking
and forming conducting paths.
For electro-active polymer actuator devices (EAPADs), the porosity
of the conductor network composite (CNC) is critically important as it
influences the mobility of the ions within the device and thus effects
the actuation speed and the efficiency (i.e. strain) of the actuator.
We have employed the layer-by-layer (LbL) assembly technique to
incorporate spherical metal nanoparticles into the CNC layer. The
size and geometry of the metal nanoparticles controls the pore size
of the CNC layer. In this work, the electromechanical response of
EAPADs is studied as a function of the size of the incorporated metal
nanoparticles. Significant improvements in the actuation speed and
strain were observed upon incorporation of larger metal nanoparticles
in the CNC layer, verifying that optimization of the size of the metal
nanoparticles leads to improvements in the efficiency of the EAPADs.
We have studied samples containing different size metal nanoparticles
and have observed that a large enough pore size facilitates improved
motion of the ions from one electrode to another; which leads to
a faster actuation speed and higher strain. For example, under
application of an electric field (4 V), samples containing ~220nm
diameter nanoparticles exhibited higher strain (12.4%) than samples
containing ~3nm diameter nanoparticles (6.9%).
In this study, highly conductive carbon blacks were selected and they
were compounded into a specially-designed styrene-butadiene rubber
(HSBR) with Tg of 38ºC. The loading level was of 5phr, 10phr, 15phr,
and 20phr, respectively. The electrical resistance was measured for all
compounds at room temperature, 40ºC, and 80ºC. And the resistivity
was also monitored with tensile straining. The electrical conductivity
increased as the content of carbon blacks and temperature were
increased. The resistivity increased with tensile loading, and it further
increased during unloading.
7642-104, Poster Session
Integration of dielectric elastomer stack
actuators into micro systems
K. Flittner, M. Schlosser, M. Matysek, P. Lotz, H. F. Schlaak,
Technische Univ. Darmstadt (Germany)
7642-101, Poster Session
Using dielectric elastomer stack actuators the electrical contact to
each conducting layer is a major concern. In order to integrate these
actuators inside micro systems e.g. microfluidic systems compatibility
to micro fabrication processes is required. The contact resistance and
number of connected layers influence the overall actuator performance
directly. Less active electrodes decrease the generated electrostatic
pressure of the actuator. High contact resistance negatively impacts
the dynamic actuator behavior.
Preparation and characterizations of PVDF/
MWCNT nanocomposites
S. M. Hong, Korea Institute of Science and Technology (Korea,
Republic of)
We investigated the interrelationships among the crystal structures
and the physical /ferroelectri/piezoelectric/rheological properties of
a thermoplastic composite based on poly(vinylidene fluoride)(PVDF)/
multiwall carbon nanotubes(MWCNT). Beta-form crystal increased with
CNT contents, passing through a peak, and decreased. the structural
changes depended on the CNT contents. the PVDF/MWCNT with
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Conventional interconnection processes like pulling copper wires
through the feeding lines, the contact ratio is in the range of 60%
to 90%, depending on the film thickness of the dielectric layer.
Furthermore, this process is not compatible to standard micro
fabrication technologies. Therefore, a new connecting process is
developed to achieve a high contact ratio and a low contact resistance.
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
geometry, the desired voltage-controllable deformation of the grating
can be optimized via manufacturing parameters, both in material
preparation and in grating implementation. A full characterization of the
deformation of the grating shape is required, both regarding the grating
pitch and the depth modulation and surface structural distortion, since
these effects could lead to decreasing diffraction efficiency and lower
beam quality. With properly chosen manufacturing parameters, a shift
in a 1μm grating period of up to 10% can be found. A model based on
independently measured material parameters is shown to describe the
optical behavior.
In this paper we evaluate a process based on electroplating for
connecting dielectric elastomer stack actuators and present a
measurement system to characterize the number of connected layers.
The performance of an electroplated contact is defined by the number
of connected layers and the contact resistance between electroplated
copper studs and graphite electrodes. It depends on different
parameters like the cross sectional area of the electrode layers for
connection and therefore on the layer thickness. Using multiple small
contacts instead of a single large one the performance of the contact
can also be positively influenced.
The full paper will include detailed information about the electroplating
process, measurement setup and measurement results.
7642-108, Poster Session
Modeling ionic polymer diluent response in
sensing
7642-106, Poster Session
Dependence on boundary conditions for the
actuation characteristics of the dielectric
elastomer actuators
U. Zangrilli, L. M. Weiland, Univ. of Pittsburgh (United States)
An ionic polymer transducer (IPT) may be employed as either an
actuator or sensor, where the bending mode of transduction has
frequently been studied. However, the electromechanical response
is not symmetric; the voltage signal required to induce a given tip
displacement in actuation is higher than that generated for the same
deformation in sensing by an order of magnitude or more. Thus,
the physical mechanisms responsible for actuation and sensing are
necessarily different. Because IPTs display sensing response for
any mode of deformation (bending, tension, compression, shear), it
is postulated that the mechanism of streaming potential dominates
sensing response. The source of the streaming potential is the flow of
entrained fluid and cations (electrolyte) with respect to the electrodes
expected for any mode of deformation. In this study flow is assumed
to be linear and Newtonian. Investigation will focus on the trends in
the final position of water molecules in response to IPT deformation.
Implications of these trends in relation to physical regions of the
polymer nanochannels will be explored.
M. Kollosche, H. Ragusch, G. Kofod, Univ. Potsdam (Germany)
One type of polymer actuators are the electric-field-actuated dielectric
elastomer actuators (DEA), which can be considered as soft rubber
capacitors. The actuation properties of electro-active polymers
are strongly dependent upon the properties of the constituent
materials and preparation methods. We present electro-mechanical
characterizations of dielectric elastomer actuators (DEA) prepared of
a thermoplastic tri-block copolymer, poly-styrene-ethylene-butadienestyrene (SEBS) with comparison to the commonly used VHB-4910
tape. This study focuses on the effects of the boundary conditions,
stiffness and voltage ramp on the breakdown properties of different
SEBS materials, and compares with similar measurements on VHB4910. Experiments were carried out on SEBS Dryflex 500120, 500040
and Dryflex 500000, provided by Elastoteknik AB (Sweden) as a dry
granulate solid. The solid elastomer was dissolved in a suitable solvent
and dropcast into the desired shape. A very strong dependence of the
electromechanical properties upon the voltage ramp was observed,
which is explained by visco-elastic influences. Measurements of
the electromechanical properties of SEBS DEAs under conditions
of constant strain and constant force are performed. These
measurements show an actuation strain of around 10%. SEBS was
thus found to have a number of advantages. The physical cross-linking
allows for a multitude of processing options, and generally simplifies
casting-based processes in comparison to chemically cross-linked
elastomer systems. Further, the reduced visco-elasticity compared to
VHB 4910 should result in actuator structures of improved conversion
efficiency.
7642-109, Poster Session
Photo/electro-responsive materials based
on spiropyran dyes, terthiophene, PEDOT,
and thiophene hybrid materials
M. Zanoni, Dublin City Univ. (Ireland); R. Breukers, Univ. of
Wollongong (Australia); R. H. Byrne, Dublin City Univ. (Ireland); G.
G. Wallace, Univ. of Wollongong (Australia); D. L. Officer, Univ. of
Wollongong (Italy); D. Diamond, Dublin City Univ. (Ireland)
Thiophene derivatives are ideal building blocks for many synthetically
processes for their widely studied conductive properties and for
their ease of characterisation. Considering this, and our extensive
experience with spiropyran derivatives, the idea to integrate the
attractive properties of these two interesting molecular families within
the same structure was proposed. Polythiophenes bearing covalently
attached receptor sites are particularly interesting to us as they have
properties that make them particularly desirable as chemical sensors
[1, 2]. Using electrochemical and chemical synthesis pathways [3, 4],
it is possible to produce and to characterize a family of new materials
qualified by similar physico-chemical properties and in particular,
conductivity.
7642-107, Poster Session
Novel approach to tunable diffractive
transmission gratings based on dielectric
elastomer actuators
M. Kollosche, Univ. Potsdam (Germany); S. Döring, FraunhoferInstitut für Angewandte Polymerforschung (Germany); G. Kofod,
Univ. Potsdam (Germany); J. Stumpe, Fraunhofer-Institut für
Angewandte Polymerforschung (Germany)
The new composite monomers constituted by the spiro-group and
the thiophenic function, were prepared by a new coupling process
developed in our laboratory. The subunits were then polymerized by
electrochemical synthesis on the ITO layers and by vapour phase
polymerization (VPP) [3] on the other materials. The electrochemicallyfunctionalized surface was the well-known Indium tin oxide (ITO)
layer; it was then followed by a poly-N-isopropylacrylamide
(PNIPPA) structure, self-polymerized by a 254nm UV light source
and subsequently treated in a special chamber prepared for the VPP
technique that allowed the insertion of the combined polymers into it.
The physico-chemical properties of the new materials were studied
under a range of different conditions, using different buffer solutions,
different ions (Co2+, Cu2+ and Ni2+) and various light sources (LED,
UV, visible light), in order to analyze all the features in as much detail
Dielectric elastomer actuators (DEA) made of thermoplastic tri-block
copolymer poly-styrene-ethylene-butadiene-styrene (SEBS) and of
the commonly used VHB-4910 tape were studied for voltage-tunable
optical transmission grating applications. Compared to ready-to-use
VHB tape, the dry granulate SEBS (Dryflex, Elastoteknik AB, Sweden)
must be dissolved in a suitable solvent and dropcast into the desired
shape. For DEA manufacturing, the material was pre-stretched, fixed
to a stiff frame and covered with appropriate stretchable electrodes.
Experiments are performed to implement master grating structures on
DEA films via different nano imprint techniques, e.g. hot embossing.
The master structures were produced by a holographic method
which writes sinusoidal surface relief gratings into photoactive films
of azobenzene polymers. Since the actuation strain of the DEA
strongly depends on the boundary conditions, e.g. pre-stretch and
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
pressure into actuation pressure in the direction of compliance. Results
of analysis of visco-elastic properties of fabricated laminates are
presented in the form of hysteresis loss diagrams and stress-relaxation
measurements.
as possible. Subsequently the new functionalized polymers will be
investigated for binding behaviour with a number of biological entities,
such as amino acids, small peptides and proteins [5].
To analyze the binding properties of the new materials FT-IR and
Raman analysis techniques were used. Furthermore complexation
and releasing properties were studied under electrochemical and
photochemical excitation [6].
7642-111, Poster Session
Several applications of these new materials can be proposed on the
basis of their switchable photochromic properties; first of all in the field
of the sensors and in second instance in the field of the smart materials
where binding with guest species can be turned on/off photonically,
and physical properties such as conductivity modulated using light.
Scavenging energy from human motion with
tubular dielectric polymer
C. Jean-Mistral, Commissariat à l’Énergie Atomique (France); S.
Basrour, TIMA Lab. (France)
ACKNOWLEDGEMENTS
5. S. Hammes-Schiffer, A. V.Soudakov. Proton-coupled electron
transfer in solution, Proteins and electrochemistry. Journal of Physical
Chemistry B, 2008, 14108-14123.
Scavenging energy from human motion is a challenge to supply low
consumption systems for sport or medical applications. A promising
solution is to use dielectric polymers to scavenge the mechanical
energy during walk. Indeed, the high energy density of dielectric
polymers, i.e. few J.g-1, is favourable to the miniaturization and the
integration of micro power generators. In this paper, we present a new
design of scavenger which is the first step toward an integration of
dielectric generators into textiles. Indeed, our scavenger is composed
of N tubular dielectric polymers attached to the fibber of a kneepad.
This structure is localized in front of the knee where the maximum of
strain is observed. Commercial silicone poly(dimethylsiloxane) Detakta
1505 tubes are used to create the generator. Compliant electrodes are
realized with a silver grease Circuit Work 7100. This grease is hand
brushed on and into the dielectric tube to create a variable capacitor.
As dielectric polymers are passive materials, scavenging energy need
the realization of energetic cycles with a poling voltage. Thus, energetic
cycles under a poling voltage less than 1500V have been realized.
These tests validate the analytic modelling presented in this paper.
Finally, for an energetic cycle at constant charge Q, one relaxed tube
is able to scavenge up to 29μJ with a poling voltage of 1000V. Thus,
on the available area in the front of the knee, i.e. 10cm², 6 tubes can
harvest 174μJ at 1Hz, enough to supply a low consumption system.
Tests on pre-stressed structures are under development.
6. J. Hirst, Elucidating the mechanisms of coupled electron transfer
and catalytic reactions by protein film voltammetry. Biochemical et
Biophysica acta, 1757, 2006, 225-239.
7642-112, Poster Session
The authors would like to acknowledge support for this research by
Science Foundation Ireland under CLARITY (Centre for Sensor Web
Technologies) grant 07/CE/I1147.
REFERENCES
1. D. F. Li, H. J. Wang, J. X. Fu, W. Wang, X. S. Jia, J. Y. Wang,
Preparation of a hydrophobic Polythiophene film to improve protein
absorption and proliferation of PC 12 cells. Journal of Physical
Chemistry B, 2008: p. 16290-16299.
2. S. Gambhir, K. Wagner, D. L. Officer, Towards functionalised
terthiophene-based polymers. Synthetic Metals 154, 2005: 117-120.
3. P. M. Bayley, B. Winther-Jensen, D. R. MacFarlane, N. M.
Rocher, M. Forsyth, Enhanced properties in chemically polymerized
poly(terthiophene) using vapour phase techniques. Reactive &
Functional Polymers 68, 2008, 1119-1126.
4. T. Y. Kim, C. M. Park, J. E. Kim, K. S. Sush, Electronic chemical
and structural change induced by organic solvents in tosylate-doped
poly(3,4-ethylendioxythiophene) (PEDOT-OTs). Synthetic Metals 149,
2005, 169-174.
Understanding the role of surface
and intermediate layer impedance in
mechanoelectric property of IPMC
7642-110, Poster Session
Electro-mechanical properties of novel
large strain PolyPower film and laminate
components for DEAP actuator and sensor
applications
K. J. Kim, R. Tiwari, Univ. of Nevada, Reno (United States)
Despite of large amount of research being reported on IPMCs
there is still a need to understand the mechanoelectric response.
Understanding the mechanoelectric behavior may help in design and
development of the polymer and enhance its applicability as well. Since
IPMC manufactured through electroless deposition have three distinct
layers: electrode, intermediate and polymer, the behavior of the material
is governed by the physics of each layer and the coupling between
them. Though the layers are distinct, the measurements to understand
the role played by individual layer are not plausible. In this paper
we tend to study the role of surface non-linearity due to distributed
impedance and intermediate layer impedance due to the metal
dispersed in the polymer. The model is developed incorporating these
impedances to predict the mechanoelectric behavior of IPMC. The
predictions are validated through series of electrochemical analysis.
Based on the model and experimental results we can conclude that
increasing the overall capacitance and decreasing surface impedance
results in improved mechanoelectric property of IPMC.
M. Benslimane, H. Kiil, M. J. Tryson, Danfoss PolyPower A/S
(Denmark)
A novel large strain PolyPower® compliant electrode has been
manufactured and tested. The new electrode design is based on the
anisotropic corrugated electrode principle with a corrugation profile
designed to enable up to 100 percent linear strain of PolyPower
compliant electrodes. Specifically, corrugations height-to-period ratio
in the 1.1 range allows stretching the thin metal electrode more than
100 percent without inducing any substantial damage to it. Based
upon this new design, PolyPower films and laminates are large scale
manufactured and used to fabricate PolyPower InLastor actuators and
sensors capable of withstanding large strain conditions. The metal
electrode is applied onto the corrugated surface of silicone elastomer
film.
Experimental measurements made with single and multi-layer dielectric
electro-active polymer (DEAP) PolyPower laminates will be presented.
Electrical and mechanical properties of the electrode will be discussed.
Stress and capacitance measurements as a function of strain and
corrugations height-to-period ratio are used as a basis to analyze
the properties of the laminates. It can be shown that the degree of
anisotropy of compliant electrode affects the stress and capacitance
dependence as a function of axial strain in the compliance direction.
The degree of anisotropy of the electrode depends very much on
the thickness of the coatings applied to the corrugated surface of
elastomer film. This degree determines the conversion ratio of Maxwell
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7642-114, Poster Session
Electromechanical properties of siliconePZT (lead-zirconate-titanate) composite
N. Gharavi, M. Razzaghi Kashani, A. Moradi, Tarbiat Modares Univ.
(Iran, Islamic Republic of)
Dielectric elastomer composites are widely used electromechanical
actuators. Compounding of dielectric elastomers with electroceramics
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
array of about 90 covered reservoirs is required for six months of
continuous operation (if a fresh biosensor is activated every 48 hours).
Such an array can be created on a chip of only several cm2 since
each protected cavity is only 200 microns in diameter. We will discuss
various platform designs, validation, sensor immobilization, and initial
test results.
helps to decrease the required electric field. In this work, silicone
rubber was compounded with Lead- Zirconate-Titanate (PZT)
electroceramic powder by the help of a silane coupling agent for better
compatibility between organic ceramic and inorganic polymer. Modified
PZT was added to silicone rubber with variable amount to study the
effect of ceramic concentration on composites properties. Morphology
of the composites was characterized by scanning electron microscopy,
mechanical properties of the samples were studied by uniaxial tension
tests, and their dielectric properties were compared through dielectric
measurements. The results showed that at about 10 wt% of PZT
loading dielectric permittivity is higher for this composite compared to
those for composites with lower or even higher loading of PZT.
We also fabricate and utilize PPy/Au microactuators for micromixing.
Mixing and homogenization of solutions is critical in analytical and
diagnostic applications that use microfluidics - such as “Lab on a
Chip” (LOC) technology. One of the limitations for mixing fluids in small
volumes is the absence of turbulent flow (so-called low Re regime).
In such regime the fluid behaves as an essentially viscous substance
- i.e. mixing of two adjacent layers in the fluid is limited to diffusion
only - there is very limited advection. Typical approach employed in
many LOC platforms is passive mixing - two fluid streams (intended
for mixing) are allowed to collide, to move through some “obstacle
course” in microchannels, or to flow side-by-side - operations that are
designed to reduce an effective diffusion distance in the fluids and to
facilitate mixing. Such passive mixing typically requires long channel
length which is problematic for microchips where size limitations
are important. Our alternative approach is to use PPy/Au active
micromixers. We will present promising initial results that demonstrate
feasibility of micromixing in a droplet of fluid.
7642-115, Poster Session
High-resolution tactile display operated
by an integrated ‘smart hydrogel’ actuator
array
G. Paschew, A. Richter, K. Arndt, Technische Univ. Dresden
(Germany)
Within the last thirty years microelectronics significantly changed our
life and work. Certainly it is consequent to ask about the potential of
microelectromechanical systems (MEMS) containing thousands of
components. Here, we introduce a high-resolution tactile display based
on the integration of 4,225 actuators with a density of 300 actuators
per cm² into an array displaying both visual and palpable information.
The actuators are fabricated simultaniously by UV-patterning. Active
polymeres called “Smart Hydrogels” are used as actuators which
are sensitive to changes in the temperature. The high resolution
temperature field is generated by an optical- or resistive interface that
is controlled by a computer. An actuator pixel changes the color from
transparent to opaque providing a visual monochrome functionality. It
changes as well the altitude and the elasticity. Therefore the display is
able to generate artificial impressions about contours, textures, profiles
and the softness of a surface. This surely is a basic feature necessary
for future haptic applications.
7642-117, Poster Session
Tunable stiffness and damping modules
using dielectric elastomers
S. Dastoor, M. Cutkosky, Stanford Univ. (United States)
The passive compliance and damping inherent in dielectric
electroactive polymers (EAPs) are an important aspect of their
potential as muscle-like actuators. The ability to actively tune
these parameters is useful in a variety of situations, from dynamic
locomotion of legged robots to adjustable suspension elements to
human- safe robot designs. Previous work on tunable elements has
relied on complex mechanical systems or fluid suspensions, neither
of which are ideal for compact or lightweight platforms. Our research
presents an electrically-variable stiffness and damping module based
on an EAP actuator. This module is based on a novel actuator design
using a pre-strained commercially available VHB acrylic film (3M),
a deposited carbon-based electrode, and multi-material support
structures. The manufacturing process for these structures and the
entire modules, from material preparation to final assembly, was
developed and fine-tuned for robust, reliable performance. In addition,
control electronics were modeled and developed to adjust these
passive parameters. Modeling of these modules is compared to data
obtained from a custom-built dynamic mechanical analyzer that is
used for experimental testing and characterization of the modules,
including their effective range of stiffness and damping values. Finally,
their feasibility for use in the suspension of a perching unmanned aerial
vehicle (UAV) as a proof-of-concept platform is examined.
7642-116, Poster Session
Utilization of electroactive polymer
actuators in micromixing and in extendedlife biosensor applications
V. Ho, Univ. of California, Irvine (United States); X. Casadevall i
Solvas, Imperial College, London (United Kingdom); D. Scott,
Univ. of Kentucky (United States); L. S. Dolci, Univ. degli Studi
di Bologna (Italy); L. Kulinsky, Univ. of California, Irvine (United
States); S. Daunert, Univ. of Kentucky (United States); M. J.
Madou, Univ. of California, Irvine (United States)
Polypyrrole (PPy)-based microactuators hold a promise for a wide
variety of engineering applications from robotics and microassembly
to biosensors and drug delivery systems. The main advantages of
using PPy/Au actuator structures (vs competing solid-state actuator
technologies) include ease of fabrication, low actuation energy, and
large motion range of microactuators. We present advances in two
areas of application - in the extended-life biosensor platform and in
micromixers.
7642-118, Poster Session
Optimization on the structure of micropumps driving by IPMC
H. Ding, Q. He, M. Yu, D. Guo, Z. Dai, Nanjing Univ. of Aeronautics
and Astronautics (China)
For some patients it’s extremely important to have a continuous
monitoring of their physiological levels (for example, glucose levels
in diabetic patients). Enzymatic biosensors typically can work for
several days before they deteriorate and should be replaced by fresh
biosensors. Our approach is to use an array of biosensors protected in
cavities covered by individually-addressed PPy/Au valves. Protected
biosensors do not deteriorate and can be stored for many months.
The biosensors are opened sequentially - once the working biosensor
starts to deteriorate, the fresh biosensor can be activated on-demand
by opening the corresponding protected cavity. The microvalve lids
are opened by the application of 1V bias. Thus, in-vivo biosensor
platform operation can be extended from days to months - the platform
lifetime is only limited by the number of biosensors in the array. An
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Four different designs of micro-pumps driving by IPMC, disc, S,
strip, and sector shapes, were designed. A series of IPMC-based
strip actuators were prepared, their actuation displacements were
measured by a laser displacement sensor, and the related bending
moments were calculated. Under ANSYS software, some parameters
of a pump such as withdrawal volume and working pressure were
simulated by changing the radius, thickness, and shape of IPMC
diaphragm and driven voltage. Results present that, comparing with
the other three kinds of diaphragms, the sector-shaped one produces
a larger withdrawal volume ;with the increasing of diaphragm radius,
the withdrawal volume increases; with the increasing of diaphragm
thickness, the working pressure increases; with the proper increasing
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
of voltage, both the withdrawal volume and the working pressure
effectively increase.
7642-28, Session 7a
Experiments with self-sensing IPMC
actuating device
7642-119, Poster Session
K. Kruusamäe, Univ. of Tartu (Estonia); P. Brunetto, S. Graziani,
Univ. degli Studi di Catania (Italy); A. Punning, A. Aabloo, Univ. of
Tartu (Estonia)
The area of allowable states in MooneyRivlin type dielectric elastomer generators
In earlier work we proposed the realization of a self-sensing IPMC by
patterning its surface in a way that separates the actuator and the
sensor parts. More specifically it is possible to measure the change in
resistance of a part of the surface electrodes and this information can
be used as feedback for the actuator part which, for example, may lead
to closed-loop control of the IPMC actuator. In this paper experimental
results about electrical properties (e.g. impedance and capacitance) of
the surface of the sensing part are presented. We present dynamical
variations of capacitance and impedance of IPMC sensor. Paper at
hand compares different methods for separating sensor and actuator
parts and introduces some results to verify preliminary electromechanical model.
S. Sun, L. Liu, Y. liu, J. Leng, Harbin Institute of Technology (China)
Dielectric elastomer(DE) could be used to design and fabricate
generator, which has been verified by experiments. The function
principle of DE generator is contrary to the one of DE actuator.
By imposing a low volt to the dielectric elastomer membrane to
produce pre electric particles on the two facing surfaces. Then apply
mechanical force to the sides of the membrane to produce pre-stretch.
As the result of pre-stretch, the thickness of the membrane becomes
thinner and the capacitance increases, mechanical energy is converted
to elastic energy. After the mechanical force is canceled, because of
elasticity the thickness of membrane increases while the capacitance
decreases, elastic energy is converted to electrical energy, there by
a cycle of conversion from elastic to electric energy is accomplished.
Researchers have always been expecting to find a model that can
well predict and evaluate the performance of dielectric elastomer
generator. Suo et al. proposes the typical failure model of neo-Hooken
type dielectric elastomer generator and calculates the maximal energy
converted in a mechanical and electrical cycle. In this paper, we
demonstrate the area of allowable states of various Mooney-Rivlin type
dielectric elastomer generators, which can be employed to direct the
design and fabrication of Mooney-Rivlin silicone generator, and the
results seem to support Suo’s theory.
7642-29, Session 7a
Conducting polymers as simultaneous
sensor-actuators
T. Fernandez-Otero, G. Vazquez, L. Valero, Univ. Politécnica de
Cartagena (Spain)
The electrochemical reaction for the oxidation/reduction of any
prevailing anion (A-) interchange-conducting polymer (CP), can be
written as:
7642-121, Poster Session
[CPa+( A-)]s + n(A-)aq+ mH2O ↔ [(CP(n+a)+)(A-)n+a (H2O)m]gel + (n
e-)metal
EAP generators
The reaction includes all the electrochemical properties and
electrochemical applications of those non-stoichiometric and reactive
materials. The progressive change of volume between [CPa+( A-)]s and
[(CP(n+a)+)(A-)n+a (H2O)m]gel taking place under flow of a constant
current originates the development of artificial muscles. The muscle
potential shift during any actuation must be influenced by any chemical
or physical variable acting on the chemical reaction. As expected the
evolution for any device (bilayer, triple layer or complex design), the
muscle potential changes if we modify: the electrolyte concentrations,
the temperature, the weight of objects attached to the bottom of the
muscle, or the current flowing through the device. Lineal evolutions are
obtained for the electrical energy consumed by the artificial muscle to
cross over a constant angle as a function of the studied experimental
variable. Both signals, the actuating current and the muscle potential
response, are included by the same two connecting wires, opening
a new paradigm for electrochemical devices. Those results underline
the simultaneous sensing and actuating capabilities of the device. If a
muscle moves freely meeting, touching, and pushing an obstacle the
muscle potential steps, proportionally to the mechanical resistance
of the obstacle, at the touching moment: this is a tactile muscle. The
tactile muscle mimics natural muscles: it is constituted by a reactive
material including organic polymers and water, and involves electric
currents, chemical reactions, conformational movements in chains,
ionic and aqueous interchanges. The driven electrochemical reaction
includes, simultaneously, actuating and sensing properties.
G. Kang, Korea Advanced Institute of Science and Technology
(Korea, Republic of)
In these days the micro power generators (MPG) are researched
frequently. MPG generally divided for Piezo generators,
electromagnetic and EAP (Electrically activated polymer) generators.
Among them, EAP has the unique characteristics of flexible, versatile,
silent and light. Research for EAP Generator has just started, so
analysis of EAP Generator is still rare. We presented the circuit for
harvesting of the electric energy, using a sequence of the charger`s
flow and the equivalent voltage-capacitor model. After that we verified
that EAP material has large specific energy density than other smart
materials. We simulated the state of electric energy with Smartspice of
Silvaco company. And we committed the basic experiment for knowing
tendency of rising voltage and verification of energy generation.
7642-27, Session 7a
IPMC: recent progress in modeling,
manufacturing, and new applications
K. J. Kim, Univ. of Nevada, Reno (United States)
Ionic Polymer-Metal Composites is a smart polymer-based actuator
and sensor that was introduced more than fifteen (15) years ago.
Since then significant progresses have been made to understand the
coupling mechanisms of electromechanical and mechanoelectrical
couplings. More recently the focus was on controls and manufacturing
of IPMCs for various applications. In this paper we present the recent
progress in modeling, manufacturing including scale-ups, and new
applications made by the researchers at University of Nevada, Reno.
7642-30, Session 7a
MEMS-based fabrication of multiple-degreeof-freedom ionic polymer-metal composite
actuators
Z. Chen, X. Tan, Michigan State Univ. (United States)
Ionic polymer-metal composites (IPMCs) are soft actuation materials
with promising applications in robotics and biomedical devices. In this
paper, a MEMS-based approach is presented for monolithic, batchfabrication of multiple-degree-of-freedom (MDOF) IPMC actuators
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
well understood. Radionuclide-labeled experiments were conducted
to follow the movement of electrolytes and water in these contractile
EAPs when activated. One of the biggest challenges in developing
these actuators was the electrode-EAP interface because of the
pronounced movement of the EAP. Plasma treatments of metal
electrodes significantly improved the attachment of the embedded
electrodes to the EAP material, which allowed for the embedded
electrodes and the EAP material of the actuator to work and move as
a unit.
that are capable of complex deformation. Such an actuator consists
of multiple, individually controlled IPMC regions that are mechanically
coupled through compliant, passive regions.
The developed fabrication process involves plasma etching, ionexchange, lithography, physical vapor deposition (PVD), and
electroless plating steps. Reactive ion etching (RIE) with oxygen and
argon plasmas is used to selectively thin down the passive area of
Nafion membrane with a patterned aluminum mask. An ion-exchange
process is introduced to stiffen the Nafion. We have discovered that
impregnating Nafion with platinum ions through ion-exchange can
also increase its stiffness, and reduce its swellability in water and in
acetone. This has proven critical in successful photolithography-based
patterning in that it ensures good adhesion of photoresist to the Nafion
film. A positive photoresist, AZ 9260, is used in photolithography to
create thick patterns which are used as the mask in the electroless
plating process to selectively grow platinum electrodes in IPMC
regions.
7642-33, Session 7b
Asymptotically accurate non-linear analysis
of electro-elastomer structures
R. G. Burela, D. Harursampath, Indian Institute of Science (India)
A characterization system consisting of a CCD camera and image
processing software has been set up to quantify the deformations
generated by the fabricated samples. We have verified that, by
controlling the phase differences between the voltage signals
applied to the IPMC regions, the samples can produce sophisticated
deformation modes, including bending, twisting, and cupping, which
show the promise of the fabricated MDOF actuators in robotic fish and
many other applications.
Electroactive materials exhibit mechanical deformation in the presence
of an electric field. This group of materials includes polymer gels,
piezoelectrics, electrostrictives, dielectric elastomers, and others.
They find potential applications as actuators and sensors. The
current study is carried out for a special class of elastomer polymer
membrane under structural applications wherein the maximum strains
are of the order of 30%. Electro-elastomers respond quickly and
efficiently at moderate strains. They also offer considerable actuation
pressures and high specific energy densities. Applications include
micro-robots, sound generators, displays, artificial blood pumps,
prosthetic devices, endoscopic surgery, adaptive structures, valves,
inflatable structures. The focus of this work is on the development
of asymptotically accurate nonlinear theory for electro-elastomerbased membrane structures. The problem is both geometrically and
materially nonlinear. The geometric nonlinearity is handled by allowing
for finite deformations and the material nonlinearity is incorporated
through hyperelastic material model. Electrical effect is derived through
Maxwell-Faraday electrostatics. The development, based on the
Variational Asymptotic Method (VAM) first proposed by Berdichevskii
[1979], with moderate strains and very small thickness-to-wavelength
ratio as small parameters, begins with three-dimensional nonlinear
electro-elasticity and mathematically splits the analysis into a onedimensional through-the-thickness analysis and a two-dimensional
membrane analysis. The through-the-thickness analysis provides
warping functions, constitutive relation between the generalized two
dimensional strain and stress tensors and the electric field for the
membrane analysis and a set of recovery relations to approximately
express the three-dimensional mechanical fields (displacement, strain
and stress) and electrical field in terms of two-dimensional variables
determined from solving the equations of the membrane analysis.
VAM can be implemented analytically or numerically, depending on the
complexity. Thus VAM enables one to analyze the variational problem
in a mathematically rigorous and yet computationally efficient manner
without making any ad-hoc assumptions. Electroactive elastomers
consist of nonlinear elastic, electroactive material coated on either side
by compliant electrodes. On applying sufficient voltage across these
electrodes, the material becomes polarized with microscopic dipoles
distributed throughout the body. In this way, the material responds to
the external electric field with an induced electric field opposing the
external field. Energy is stored in this induced field and interacts with
the mechanical energy such that the total energy is minimized when
the system is in equilibrium. The ‘stress’ developed in the material
due to the induced field is called the Maxwell stress. To simplify the
analysis and provide certain insights, mechanical and electric effects
were studied independently first, then they were rigorously coupled.
Hence, this work consists of three broad sections. First section deals
with the nonlinear mechanical response (in-plane and out-of-plane
deformation) of hyperelastic membrane structures under mechanical
loads. Dimensionally reduced effective material properties are
obtained. Second section deals with response under the electric field
and effective dielectric coefficients are obtained. Third section deals
with the fully coupled analysis of electro-elastomers and effective
piezoelectric coefficients are obtained as a function of the piezoelectric
coefficients of the membrane variables. The analytical results obtained
are then used to study the actuation of inflatable structures made of
electro-elastomers and to predict their response under simultaneous
dynamic electric and mechanical force fields.
7642-31, Session 7a
Effects of anisotropic surface texture on
the performance of ionic polymer-metal
composite
Q. He, H. Ding, M. Yu, D. Guo, Z. Dai, Nanjing Univ. of Aeronautics
and Astronautics (China)
Ionic polymer metal composite (IPMC), as one of the electrically
activated polymers (EAP), has been widely used as artificial actuator
because the advantages of large deformation, low driving voltage, low
noise, lightweight and flexibility. However, relative lower output-force
than that generated by other smart materials limit the wide applications
of IPMC. Here we report our studies of the effects of surface texturing
on the performance of IPMC. The Nafion membrane was prepared by
casting of liquid solution, and then was roughed through sandblasting
and polishing procedure, resulting in isotropic and anisotropic surface
texture respectively. The microstructure of the polymer surface and
metal electrode were analyzed and compared. Effects of the surface
texture on the displacement and the output force were experimentally
studied under various voltages and frequencies. Results showed that
the output force of the IPMC with anisotropic surface roughening is
clearly higher than that of IPMC with isotropic surface. The output force
generated by IPMC with anisotropic surface could be up to 65mN,
which was 3 times higher than that generated by IPMC with isotropic
surface and the force is enough for the driving of artificial gecko toes.
The study show that the anisotropic surface texture is an effective
method to improve the performance of IPMC.
7642-32, Session 7a
Considerations for contractile electroactive
polymeric materials and actuators
L. Rasmussen, D. Schramm, Ras Labs, LLC (United States); L. D.
Meixler, C. A. Gentile, G. Ascione, C. Tilson, K. Pagdon, Princeton
Plasma Physics Lab. (United States)
Ras Labs produces electroactive polymer (EAP) based materials
and actuators that bend, swell, ripple and now contract (new
development) with low electric input. In addition, Ras Labs can
produce EAP materials that quickly contract and then expand,
repeatedly, by reversing the polarity of the electric input. These recent
developments are important attributes in the field of electroactivity
because of the ability of contraction and contraction-expansion to
produce biomimetric motion. The mechanism of contraction is not
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
in extreme cases the sudden discharge of energy during breakdown
can present a serious fire risk. The breakdown strength of DEA however
is heavily dependent on the presence of microscopic defects in the
membrane giving its overall breakdown strength inherent variability.
The practical consequence is that DEA normally have to be operated
far below their maximum performance in order to achieve consistent
reliability.
7642-34, Session 7b
Modeling approaches for electroactive
polymers
W. Kaal, S. Herold, T. Melz, Fraunhofer-Institut für Betriebsfestigkeit
und Systemzuverlässigkeit (Germany)
Predicting when DEA are about to suffer breakdown based on
feedback will enable significant increases in effective DEA performance
without sacrificing reliability. It has been previously suggested that
changes in the leakage current can be a harbinger of dielectric
breakdown. Leakage current exhibits a sharp increase during
breakdown, but up to now it has not been possible to distinguish
leakage current from other current flows in situ.
EAP materials respond to external electrical stimulation with high
deformations and can therefore outperform other smart materials in
some applications. They can be used to design actuators which are
capable of much higher displacements, e.g. compared to piezoelectric
actuators. They can also be utilized to build generators for energy
harvesting applications. Imposing large deformations will lead to great
changes in capacitance, which can be exploited to convert mechanical
to electrical energy with appropriate switching circuits.
In this paper the relationship between electric field and leakage current
is investigated for simple VHB4905-based DEA. Particular emphasis
is placed on the behaviour of leakage current during breakdown
conditions and its potential as part of a “pain” parameter for predicting
breakdown in a timely manner. This data is used to test an enhanced
version of a Pulse Width Modulation based dynamic capacitive selfsensing system for DEA based on the authors’ previous work that
enables leakage current to be differentiated from both charging current
and the current due to a changing capacitance.
However, up to now applications based on electroactive polymers have
hardly ever exceeded laboratory scale; nevertheless the potential for
these materials is enormous. In order to properly design and optimize
robust and efficient systems reliable models are required. There are
many different physical effects that need to be taken into account like
the nonlinear coupling between mechanics and electrics, the nonlinear
material behavior at large deformations and some time-varying effects,
only to name a few. Nonetheless, up to now there have been only a
few works about modeling of dielectric elastomers. Therefore a finite
element model with multiphysical elements is developed and presented
in this paper. It can give helpful instructions for the design and
fabrication process of EAP-systems. The model can also be reduced in
order to implement it in larger models for the simulation of the overall
active system.
7642-37, Session 7b
Modeling of non ideal dielectric elastomer
stack actuators
P. Lotz, M. Matysek, K. Flittner, H. F. Schlaak, Technische Univ.
Darmstadt (Germany)
7642-35, Session 7b
To design actuators for specific applications it is necessary to describe
the performance of the actuators precisely. Hence, an accurate model
is essential dimensioning dielectric elastomer stack actuators.
Evaluation of electrostriction in dielectric
elastomer actuation and instability
In this paper we discuss the electrical and mechanical modeling of
such multilayer systems, the measurement of model parameters and
we will show a comparison between model and real actuators.
B. Li, Xi’an Jiaotong Univ. (China)
This paper presents the study of the electro-stress, especially the
electrostriction, in dielectric elastomer (DE) undergoing voltage-induced
large deformation.
The basic simplified equation of dielectric elastomer actuators
p=ε·E²
The electrostriction is investigated and evaluated by the free energy
model when the dielectric permittivity did not remain constant in DE
actuation. Unlike previous research on the parallel capacitor dielectric
subject to voltage of 1-2V with a broad frequency band, in this paper,
we study the situation when DE dielectric constant is strongly affected
at different expansion levels when a high constant voltage is applied.
The electrostrictive coefficients are obtained from experimental data
collected in dielectric constant measurement under 3kV DC voltage.
By using General Hook law, we study the relation of electric fields and
the DE stretch rate with/without electrostriction and the computational
results fits the experimental data more accurately (improved error of
1.75% vs. 4.76% ) when the electrostriction is involved. The instability
in DE actuation is explored, and two different results are presented. If
the electrostriction is neglected, the free energy model failed to predict
the electromechanical instability, and correct prediction is verified by
taking electrostrictive effect into instability consideration.
describes the electrostatic pressure causing the deformation of the
actuator. However, describing a stack actuator needs to consider
several important conditions like the number of connected electrodes
within the stack or other surrounding passive material.
The result suggests that the electrostriction would become pronounced
at DE large deformation and the electrostrictive effect should be taken
into account in the study of DE actuation stretch and the control of
instability.
The dynamic characteristics depend on the mechanical behavior of the
stack and electrical parameters as well. Finally, we show the correlation
of actuator layout parameters, driving voltage conditions (amplitude
and frequency) and fabrication parameters of the stack, as well.
Measurement data are shown validating the presented model.
We developed a model which allows concluding the number of
connected layers and the resistances of the graphite electrodesafter
measuring the frequency dependent impedance of the actuators. These
parameters are used to describe the dynamic actuation. Hence, the
actuator layout can be optimized, maximizing the electrostatic pressure
for the required bandwidth. Depending on the film thickness of the
dielectric layers 60% to 90% of the layers are typically connected,
contacting thinner layers is obviously more challenging.
Using the extracted electrical parameters and mechanical setup of the
stack the static deflection characteristics of different actuators can be
predicted precisely.
7642-36, Session 7b
7642-38, Session 7b
Leakage current as a predictor of failure in
dielectric elastomer actuators
Dielectric elastomer bimorphs using
electrolessly-deposited silver electrodes
T. A. Gisby, I. A. Anderson, S. Q. Xie, The Univ. of Auckland (New
Zealand); E. P. Calius, Industrial Research Ltd. (New Zealand)
C. Goh, G. Lau, Nanyang Technological Univ. (Singapore)
Continuous metallic thin films, which are widely used for microelectronic circuits, are seldom used as the electrodes for dielectric
elastomer actuators (DEA) because they limit the lateral strain of
Dielectric breakdown often leads to catastrophic failure in Dielectric
Elastomer Actuator(s) (DEA). The resultant damage to the dielectric
membrane effectively renders the DEA useless for future actuation, and
16
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
depends on the capacity change, while the DBS affects the possible
amount of charges on the dielectric polymer, which are the basis for
an energy gain. To analyze the design of EAP-generators at first and to
optimize material parameters of suitable EAP-generators afterwards,
a validate simulation model regarding material properties on the one
hand and geometric properties on the other hand is necessary. Further
on, the simulation model is also used to optimize the Energy Harvesting
Cycle. The EAP-generator used for the simulation model consists of a
polymer (i.e. polyurethane) between two flexible conducting electrodes,
integrated into an experimental case. For the parameterization of
the EAP-generator model it is characterized in a test bench, which
is designed to strain the device in one lateral direction using a linear
electric motor.
elastomer. Metalized DEA is not suitable for in-plane actuation.
However, in this paper, we demonstrated a multi-layered bimorph
design capable of a large out-of-plane actuation stroke even though
using metalized elastomeric layers. This metalized elastomer exhibits
a high breakdown voltage in comparison to the elastomer with grease
electrodes.
The electroless deposition method was commonly used for silvering
a mirror. The same method is used here to electrolessly deposit
compliant silver electrodes onto a VHB tape (F-9469 PC). This process
results in a shinny and highly conductive silver film, which is 200nm
thick. In general, a resistance of 10-50 ohm is measured with probes
positioned at 5 mm apart. The high conductivity ensures a fast
response.
A silvered DEA bimorph is made of 3 active layers of silvered VHB on
a polydimethylsiloxane (PDMS) layer. The silvered VHB layer is made
of a 0.13mm-thick tape, cut into a size of 20 mm x 10 mm and with
a silvered area of 16 mm x 6 mm. A tip displacement of 6 mm, with a
deflection angle of around 27.5°, was observed for the DEA bimorph
activated at 3000V. Electrical breakdown voltage of the silvered VHB is
3500 kV, which is higher than 2000V of a VHB tape coated with silver
grease. The silvered VHB layer is found to be able to self healed after
the electrical breakdown.
7642-41, Session 8a
Nanotube yarns as high stress actuators
and sensors
J. D. W. Madden, The Univ. of British Columbia (Canada); G. M.
Spinks, J. Foroughi, Univ. of Wollongong (Australia); T. Mirfakhrai,
The Univ. of British Columbia (Canada); R. H. Baughman, The
Univ. of Texas at Dallas (United States); G. G. Wallace, Univ. of
Wollongong (Australia)
7642-39, Session 7b
The high stiffness and tensile strength of carbon nanotube yarns
enables sensing and actuation at loads that are impractical in
electroactive polymers. Operation at several hundred megapascals
is observed, with strains of 0.6 %, and little creep. Ionic liquids are
employed to minimize creep. The mechanisms of actuation and of
sensing are related to the electrochemical charging of the yarns and
to yarn mechanics. A model that describes the electromechanical
coupling is presented. The model shows that actuation strain is
related to effective ion size, and is dependent on capacitance of the
nanotubes. The main fit parameter in the models is the radial modulus
of the yarns, for which only crude measurements using AFM are
available.
Self-priming circuit design for dielectric
elastomer generators
T. G. McKay, B. M. O’Brien, The Univ. of Auckland (New Zealand);
E. P. Calius, Industrial Research Ltd. (New Zealand); I. A. Anderson,
The Univ. of Auckland (New Zealand)
Dielectric Elastomer Generator(s) (DEG) are variable capacitor power
generators formed by hyper-elastic dielectric materials sandwiched
between flexible electrodes. Electrical energy can be produced from a
stretched, charged DEG by relaxing the mechanical deformation while
maintaining the amount of charge on its electrodes. This increases
the distance between opposite charges and packs like-charges more
densely, increasing the amount of electrical energy. The amount
of energy harvested from one cycle of this process has a limited
dependence on velocity, so DEG show promise for harvesting energy
from environmental sources providing variable frequency mechanical
deformations such as wind and ocean waves.
The interactions between yarn bundles are compared with those that
occur in electrostatically actuated dry nanotube sheets, where strains
of tens of percent or more are achieved at high frequencies. In these
materials the aniosotropic modulus is critical to achieving large strains.
7642-42, Session 8a
None of the components in a DEG system are ideal and an electrical
load drains charge, so charge is lost from the system. This means that
unless extra charge is periodically added to the system, the amount of
charge placed on the DEG will gradually drop. Batteries or capacitor
banks typically provide this, but they also have their energy depleted
over time and add bulk to the system. In this paper we present a selfpriming DEG system that is capable of utilizing some of the generated
energy to restore charge lost from the system, so no external priming
energy source is required provided there is enough mechanical energy
input. This paper will discuss how the self-priming circuit works, then
we present our ABAQUS FEA model, optimizing a hand pumped DEG
as a case study. Finally we fabricate our optimized DEG to verify that it
can self-prime and drive a load.
Conductive filler morphology effect on
performance of ionic polymer conductive
network composite actuators
S. Liu, Y. Liu, The Pennsylvania State Univ. (United States); H.
Cebeci, R. G. de Villoria, Massachusetts Institute of Technology
(United States); J. Lin, The Pennsylvania State Univ. (United
States); B. L. Wardle, Massachusetts Institute of Technology
(United States); Q. M. Zhang, The Pennsylvania State Univ. (United
States)
Several generations of ionic polymer metal composite (IPMC) actuators
have been developed. It has been discovered that the composite
electrodes which are composed of electronic conductor fillers and
ionic conductors, have great impact on performance of ionic polymer
actuators by affecting strain level, efficiency and speed. One of
important factors in composite electrodes is the shape of electronic
conductor fillers, which includes three kinds: particles, wires and
plates. RuO2 nanoparticles, vertically aligned carbon nanotube (CNT)
and exfoliated graphite nano platelets are used as conductor fillers for
different shapes, respectively. The rest parts in actuators are Nafion as
ionomer in composite/middle layers and room temperature ionic liquid
1-ethyl-3-methylimidazolium trifluoromethanesulfonate as electrolytes.
It is found that the aligned nano wires and plates show advantages
over random nano-particles. By using aligned CNT array and exfoliated
graphite platelets, the strain speed increases due to larger ionic
conductivity; the effective capacitance is increased due to larger
accessible area for ions and higher electronic conduction; the strain
increase from 3% to more than 10%. Furthermore, electromechanical
7642-120, Session 7b
Energy harvesting using electro active
polymers
J. Maas, C. Graf, Ostwestfalen-Lippe Univ. of Applied Sciences
(Germany); D. Schapeler, Bayer MaterialScience AG (Germany)
Due to the large amount of deformation Dielectric Polymers are
predestined for applications such as artificial muscles, speakers or
valves. Beside of this actuator function, Electro Active Polymers (EAP)
can also be used as generators to convert mechanical strain energy
into electrical energy by charge transfer using the polymer’s capacitive
behaviour. The requirements for these so called EAP-generators as
energy harvesting devices are a high dielectric break down stress (DBS)
and a large change of the capacity. The relative energy gain basically
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
efficiency is improved resulting from the anisotropic structure in aligned
CNT and exfoliated graphite platelet composite. The formal one clamps
strain in thickness direction and the latter one further clamps strain in
width direction.
7642-45, Session 8a
A study for thickness property of IPMCs
based on rules
C. Kim, H. Yang, Y. Park, N. Park, Yonsei Univ. (Korea, Republic of)
7642-43, Session 8a
Generally ionic polymer-metal composites (IPMCs) have been made
from commercially available perfluorinated ion-exchange polymer
membranes such as Nafion film. The membrane has a typical thickness
in the range of about 100~300 . Commonly, the thicker membrane
is used at the IPMC, the larger bending displacement could be got.
However, we can predict the fact not to continually increase the
displacement.
Ionic liquids in ionic polymer conductor
network composite actuators
Y. Liu, S. Liu, J. Lin, W. Liu, R. H. Colby, Q. M. Zhang, The
Pennsylvania State Univ. (United States)
In ionic polymer actuators the accumulation or depletion of excess
charges (ions) at the composite electrodes under an applied voltage will
generate strain in these regions. In order to increase the charge density
and population at the electrodes so that a large strain and high force
output can be realized, various ionomeric polymer/conductive network
composites (CNC) electrodes and electrolytes have been developed
to form ionomeric polymer/CNC actuators (IPCNC). IPCNC actuators
are attractive because it can be operated under a few volts. However,
IPCNC actuators suffer a low actuation speed, low efficiency (<3 %),
and low elastic energy density. The limiting factors of low actuation
speed and efficiency come both from the morphology of composite
electrodes and electrolytes. Since it is already shown that part of the
causes for low ion transport speed exist in the composite electrodes of
IPCNC actuator, in this study we will focus on the issues of designing
and using electrolytes which are ionic liquids (ILs). The issues include
ion size, activation energy, ion clusters, and etc. Comparison is done
by measuring capacitance, strain level and strain rate of actuators
with four ILs, plus using ab initio method to calculate ion size and
different ion pair status percentage. It is shown that by correctly
using combination of different cation and anion size, the speed and
efficiency could be dramatically improved. In addition, we will show the
preliminary results of using different ILs to couple different composite
electrodes with various morphologies for best performance.
In this study, we consider the relation between the bending
displacement and the thickness of the membrane through the various
experiments. We will establish a model to calculate the bending
displacement generated according to the change of the thickness and
propose the optimized condition of the thickness.
7642-46, Session 8b
Nanoporous carbon-based electrodes for
high strain ionomeric bending actuators
V. Palmre, Univ. of Tartu (Estonia); D. Brandell, Uppsala Univ.
(Sweden); U. Mäeorg, J. Torop, Univ. of Tartu (Estonia); O.
Volobujeva, Tallinn Univ. of Technology (Estonia); A. Punning, U.
Johanson, M. Kruusmaa, A. Aabloo, Univ. of Tartu (Estonia)
Ionic polymer metal composites (IPMCs) are electroactive material
devices that bend at low applied voltage (1-4 V). Inversely, a voltage
is generated when the materials are deformed,which makes them
useful both as sensors and actuators. In this paper, we propose two
new highly porous carbon materials as electrodes for IPMC actuators,
generating a high specific area, and compare their electromechanical
performance with recently reported RuO2 electrodes and conventional
IPMCs. Using a direct assembly process (DAP), we synthesize ionic
liquid (Emi-Tf) actuators with either carbide-derived carbon (CDC)
or coconut-shell-based activated carbon-based electrodes. The
carbon electrodes were applied onto ionic liquid-swollen Nafion
membranes using a direct assembly process. The study demonstrates
that actuators based on carbon electrodes derived from TiC have
the greatest peak-to-peak strain output, reaching up to 20.4 mε
(equivalent to >2%) at a 2 V actuation signal, exceeding that of the
RuO2 electrodes by more than 100%. The electrodes synthesized from
TiC-derived carbon also exhibit significantly higher maximum strain
rate. The differences between the materials are discussed in terms of
molecular interactions and mechanisms upon actuation in the different
electrodes.
7642-44, Session 8a
Experimental investigations on carbon
nanotube actuators defining the operation
point and its standard deviation
U. Kosidlo, R. Addinall, F. Tonner, I. Kolaric, C. Glanz, FraunhoferInstitut für Produktionstechnik und Automatisierung (Germany)
Carbon nanotube (CNT) actuators have been extensively investigated
from the perspective of materials, their composition, and system
construction as well as from three main performance features, which
are displacement, force and reaction time. However, up till now
none of CNT actuators has reached the stage of implementation
into products. It is due to the fact that even though from the point
of view of performance each property can reach satisfactory values,
their combination is much more difficult, as they are not proportional.
This relation of properties motivated the work to test and investigate
currently available CNT-polymer actuators to define their operation
point. Under this term one should understand a performance of
actuator where displacement, force and reaction time do not affect
each other. In other words, any change in one of the properties will
adversely affect at least one of the remaining ones.
7642-47, Session 8b
Dielectric elastomer actuators of silicone
rubber-titania composites obtained by
dielectrophoretic assembly of filler particles
M. Razzaghi-Kashani, S. Javadi, Tarbiat Modares Univ. (Iran,
Islamic Republic of)
The measurements are performed in out-of-plane mode on 2
cm diameter samples in low frequency range (0,01 - 1 Hz) under
application of low voltage (2 V).
High dielectric permittivity and low loss factor are desirable for
dielectric elastomer actuators to reduce the required electric voltage.
Structured Polymer composites may serve this purpose. Formation
of controlled morphology of fillers in polymeric composites may be
difficult to achieve by conventional methods such as mechanical
shear or chemical methods. Tunable structure of filler and
anisotropic properties in composites can be obtained by exploiting
dielectrophoretic assembly of fillers in a polymer composite by using
electric fields. In this study, different concentrations of TiO2 (Titania)
particles in silicone rubber matrix were assembled in a chain-like
structure by using an alternating electric field. Silicone rubber matrix
was vulcanized to transform the liquid to solid and maintain the filler
structure in the desired direction. Generation of chain structure of filler
Measurement curves of three main actuator properties are plotted
together against the frequency resulting in operation point as the
intersection point of those curves. Additionally the deviations
in actuator performance are assessed to reflect the actuators’
reproducibility and their production process stability by means of
standard deviation.
Knowledge about the relation between actuator properties together
with the value of operation point will allow better opposition of the
existing CNT actuator against its potential applications.
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
was verified by Scanning Electron Microscopy (SEM) and equilibrium
swelling. It was shown that dielectric permittivity of the oriented
composite is higher whereas its dielectric loss is lower in the orientation
(thickness) direction than those for the composites with random
distribution of filler. A critical concentration of filler was distinguished
as the percolation point at which the change in dielectric behavior
is exaggerated. The desired dielectric properties were achieved by
orienting filler in the thickness direction. Effect of filler structure on
enhancement of actuation force was quantified using an in-house
actuation set-up.
7642-50, Session 8b
Thermomechanical properties of multiwalled
carbon nanotube reinforced shape-memory
polymer nanocomposite
J. Zhong, J. G. Xian, H. Li, Harbin Institute of Technology (China)
In the present study, multiwalled carbon nanotubes (MWCNTs)
reinforced shape memory polymer (SMP) nanocomposites were
prepared with a high shear mixing process. The shape memory
effects, thermomechanical properties and electrical behaviors were
characterized to demonstrate the effect of the incorporation of the
MWCNTs. A well dispersion of the MWCNTs in the SMP were reached
with the current mixing process and brought in enhanced mechanical
properties, especially the modulus. The shape fixity and shape memory
recovery ratio can reach more than 98% for both plain SMP and
nanocomposites. The transition temperature for the shape memory of
the nanocomposites does not vary with the MWCNT content, while
the shape memory recovery rate decreases with the MWCNTs up to
2 wt.%. The testing on the repeatability and durability of the shape
memory effect indicates that the nanocomposites possess the same
shape memory effects as the plain SMP over 5 consecutive shape
memory cycles. In the transition temperature range, the addition of the
MWCNTs enhances the modulus of the SMP significantly, indicating the
increased recovery force. With the enhanced electrical conductivity of
the nanocomposite due to the incorporation of MWCNTs, the electroactive shape memory of the nanocomposites is realized.
7642-48, Session 8b
NOMS: nano opto-mechanical systems
E. M. Campo, H. Campanella, Ctr. Nacional de Microelectrónica
(Spain); J. Roig, Univ. Autònoma de Barcelona (Spain); M.
Omastová, I. Krupa, Polymer Institute (Slovakia); J. Esteve,
Univ. Autònoma de Barcelona (Spain); E. M. Terentjev, Univ. of
Cambridge (United Kingdom)
Nano-opto mechanical Systems (NOMS) based on the photoactuation
of optoactive polymer actuators and devices (OAPAD) is a much
sought-after technology. In this scheme, light sources promote
mechanical actuation of polymeric materials producing a variety of
nano-opto mechanical systems such as nano-grippers. The European
Union NOMS consortium is a multidisciplinary team assembled to build
a tactile tablet for the visually-impaired. The consortium is formed by
experts in materials, optics, microsystems, neuropsychology, as well as
end users, and commercial partners who will fabricate the first visual
aid tablet based on photoactuation technology.
7642-51, Session 8b
The purpose of this paper is to stir an interest in the field of
photoactuators; promoting OAPAD to mainstream R&D. To this
purpose, we will review the current state of the art on photoactuators
and address outstanding concerns towards microsystem integration.
Photoactive actuators could be a complement to Electroactive
Polymer Actuators and Devices (EAPAD). Indeed, the “wireless”
character of optical actuation could pose an advantage to electrical
actuation in some environments. Albeit, given the similarities of smart
materials presenting electro- and photo-actuation, advancements
of photactuators in microsystem integration are likely to produce
synergistic advancements in the integration of electroactuators and
vice versa. Ground-breaking OAPAD lay the ground of an incipient
field, likely to generate a strong impact in a variety of scientific arenas.
Ultimately, we envision optical actuation in multiple environments such
as intracellular motors, artificial muscles, and tactile displays for the
general public.
The constitutive relation of silicone rubber
soft active materials
L. Liu, S. Sun, Y. Liu, J. Leng, Harbin Institute of Technology (China)
Silicone rubber is a common dielectric elastomer material. Actuators
made from it show excellent activate properties including very large
strains (up to 380%), high elastic energy densities (up to 3.4 J/g), high
efficiency, high responsive speed, good reliability and durability, etc.
When voltage is applied on the compliant electrodes of the dielectric
elastomers silicone rubber, the polymer shrinks along the electric
field and expands in the transverse plane. In this paper, a theoretical
analysis is performed on the coupling effects of the mechanical and
electric fields. A nonlinear field theory of deformable dielectrics and
hyperelastic theory are adopted to analyze the electromechanical
field behavior of these actuators. Also the mechanical behavior of the
dielectric elastomer silicone rubber undergoing large free deformation
is studied. Finally, the constitutive model of a dielectric elastomer
silicone rubber composite under free deformation and restrained
deformation is derived.
7642-49, Session 8b
Self-assembled regular arrays of carbon
nanotube and the route toward actuation of
shape memory polymer
7642-52, Session 9a
Multi-scale mechanical modeling of
composite electroactive polymer tubular
actuators
H. Lu, Harbin Institute of Technology (China)
The synthesis of massive arrays of monodispersed carbon nanotubes
that are self-assembled on hydrophilic polycarbonate membrane
is reported. This approach involves individual carbon nanotube
manufacturing by non-ionic surfactant to aid in dispersion and
nanotubes self-assembled for three-dimensional orientation by
high press filtration. The inherent capability of carbon nanotube
and microstructure of well-packed arrays predominate excellent
conductive properties of massive arrays. These potential applications
of nanometer-sized sensor, probe and energy resistor have been
characterized in this study. Furthermore, the route toward application
of self-assembled regular arrays, as heat transmission intermedium,
has been carried out by activating shape-memory polymer. The
electrical conductivity of insulating polymer is significantly improved by
assembled carbon nanotubes, resulting in shape recovery behavior of
nanocomposite being driven by electrical resistive heating.
P. Wang, B. Lassen, R. W. Jones, Univ. of Southern Denmark
(Denmark)
Danfoss Polypower has developed a type of DEAP material that
combines a polymer thin film with a special compliant metal electrode
design that provides unidirectional motion. Based on this, a core-free
tubular actuator has been developed by rolling the DEAP thin film.
There are passive areas of material at both ends of the actuator. These
provide an area to attach the electrode connections and end caps as
well as stopping any short circuits along the edges.
The modeling of such systems are challenging due to their multi-scale
and multi-physics nature. In this work we focus on the multi-scale part
of the modeling problem only taking into account the electrostatic part
by including the Maxwell pressure.
Due to the multi-scale nature of the problem it is computationally
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
actuation and this effect should be minimized in order to achieve
optimum performance. The results of the proposed electrochemical
model are discussed in relation to the actuation mechanisms in an IPT
and suggestions are made for new transducers.
too expensive to directly implement the full three-dimensional (3D)
problem (Navier’s equations). This difficulty is overcome by reducing
the 3D model to two two-dimensional (2D) models easily handled
within the finite element framework. The passive areas degrade the
force characteristics of the actuator. This is taken into account by
considering the passive areas as springs. The models are compared
with experimental data obtained from a Danfoss PolyPower ‘InLastor’
actuator. We show that by taking into account the passive areas we
get good agreement between the model and the experiments, this not
being the case for a model which only takes into account the active
area.
7642-55, Session 9a
Optimal clamping conditions for linear strain
terpolymer actuators
L. J. Gorny, The Pennsylvania State Univ. (United States); B.
Zellers, Strategic Polymer Sciences, Inc. (United States); Q. M.
Zhang, The Pennsylvania State Univ. (United States)
7642-53, Session 9a
Three-dimensional numerical
implementation of a thermoelastic, finite
deformation constitutive model for shape
memory polymers
A recent study has been conducted using planar linear strain multilayer
electrostrictive P(VDF-TrFE) terpolymer actuators to optimize the
levels of strain achievable using a given actuator under various voltage
excitations. Clamping over a reduced section of the actuator’s width
is essential for devices that have aspect ratios (length to width) which
are small, as the outer un-electroded margin of the actuator produces
a clamping effect. It has been found that significant increases in both
the strain and the amount of force generated by the actuator can be
achieved by clamping over a fraction of the actuator’s width along the
top and bottom of the actuator. This phenomenon is explained using a
simple beam spring model to characterize device behavior numerically
and to provide a model for comparison to experimental results.
Experimental results presented verify the appropriateness of the simple
model and demonstrate the effectiveness of a reduced boundary
condition.
B. Volk, D. C. Lagoudas, D. J. Maitland, Texas A&M Univ. (United
States)
Shape memory polymers (SMPs) are a class of active materials
that, under an appropriate thermomechanical cycle, will recover a
thermodynamically stable applied strain. SMPs have been the focus
of many recent experimental and theoretical investigations, many of
which consider the SMP response due to infinitesimal deformations.
This paper focuses on the three-dimensional implementation of a finite
deformation constitutive model. The previously developed model is
based on the theory of nonlinear thermoelasticity, and accounts for
the coexisting active and frozen phases of the SMPs as well as the
transition between the two phases. The model is implemented as a
user material subroutine (UMAT) in ABAQUS.
7642-56, Session 9a
Thermo-chemo-electro-mechanical
modeling of polyelectrolyte gels
Upon implementing the model, the material properties in the model are
calibrated from finite deformation experimental data of polyurethane
(PU) SMPs. Tensile tests are performed on the PU specimens for
both constant strain and constant stress recovery scenarios. After
calibrating from a subset of the experimental results, the model is used
to predict the material response for the other thermomechanical load
paths. Furthermore, the three-dimensional implementation allows for
the modeling of complex geometries. Geometries of interest are based
on applications that include cardiovascular stents and hybrid SMASMP joints and composites.
T. Wallmersperger, K. Keller, B. H. Kröplin, Univ. Stuttgart
(Germany); M. Guenther, G. U. Gerlach, Technische Univ. Dresden
(Germany)
Polyelectrolyte gels show adaptive viscoelastic characteristics. In water
based solutions they have enormous swelling capabilities under the
influence of different possible stimulation types, such as chemical,
electrical or thermal stimulation.
In the present work a fully coupled 3-field formulation for
polyelectrolyte gels using the Finite Element Method (FEM) is applied.
This formulation consists of a chemical, electrical,
7642-54, Session 9a
and mechanical field equation. The mechanical field is coupled to the
chemo-electrical field by a prescribed strain stemming from an osmotic
pressure term. In experiments it has been proven that there is a large
dependency between the applied temperature and the actual swelling
degree of the gel. In the present research, the thermal stimulation is
investigated. First, only the actual temperature is considered in the
osmotic pressure term. Second,
A model of the nonlinear capacitance and
electrochemical behavior of ionic liquidionic polymer transducers
J. D. Davidson, N. C. Goulbourne, Univ. of Michigan (United States)
Ionic liquid-ionic polymer transducers (IL-IPTs) have received increasing
attention in recent years due to advantages over their water-based
counterparts. The negligible vapor pressure of an ionic liquid allows
for the transducer to operate in free air, opening up a wide range of
possible applications. In this work, a model of the electrochemical
behavior of IL-IPTs is proposed which accounts for the multiple mobile
ionic species in these devices and the nonlinearities due to the large
sizes of the ionic liquid ions and non-symmetry of the equilibrium
charge distribution. A numerical solution to the system of governing
PDE’s is obtained using the finite element method and the results
are used to describe the nonlinear capacitance of an IL-IPT. In recent
work, Kornyshev has shown that the electrochemical behavior of
a neat ionic liquid is distinctly different from a typical electrolyte
solution. Specifically, the double layer capacitance decreases with
the magnitude of the applied voltage. Here, it is shown that the
capacitance of an IL-IPT reaches a maximum at zero applied voltage
and then drops sharply as the applied voltage increases. Experimental
measurements of the capacitance/voltage relation of an IPT are taken
and a comparison is made with the proposed theory. The decrease
in capacitance with the applied voltage has a detrimental effect on
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additionally, temperature-dependant material parameters obtained from
experimental measurements are applied. The calibration of the derived
simulation results is performed with experimental results available in
literature.
7642-57, Session 9a
Electro-mechanical modeling of
interpenetrating polymer network reinforced
acrylic elastomer
A. Schmidt, EMPA (Switzerland); E. Mazza, ETH Zürich
(Switzerland); G. M. Kovacs, EMPA (Switzerland)
Interpenetrating polymer network reinforced acrylic elastomer (IPN) is
a very promising new material for dielectric elastomer actuators. IPN
achieves the performance of pre-strained acrylic elastomers without
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
high tensile stress, accompanying the creeping. The creeping or
anisotropic strain is induced by uniaxial stretching and/or slipping of
polymer chains along the stretch direction (partially due to breaking of
polymer chains). By release of the high tensile stress, the anisotropic
strain is relaxed to the original form by electrochemical cycling due
to the thermal fluctuation of polymer chains or elasticity. Namely the
training effect is essentially based on the electrochemical cycling
under high tensile stress, followed by release of the tensile stress. It
will also be mentioned that the training effects are also obtained in
electrodeposited polypyrrole film. The training effect of Polyaniline is
more pronounced than the case of polypyrrole. Detailed experimental
facts and the mechanisms will be reported.
the need of pre-strain. Thus it allows the design of free-standing
contractile dielectric actuators featuring very high actuation forces
and excellent reliability. This work presents the electro-mechanical
characterization of an acrylic IPN elastomer. We determined a timedependent 3D large strain model that is suitable for finite element
simulation of IPN actuators of general design. In order to characterize
the mechanical behavior of IPN an extensive experimental campaign
was carried out involving uniaxial and equibiaxial tension, relaxation
as well as membrane inflation experiments. Using image based
local deformation measurements as well as iterative finite element
calculations we determined constitutive model parameters that
describe the mechanical response for a wide range of strain and strain
rate. Our experimental observations reveal an important influence of
the material composition on mechanical behaviour. We propose a new
approach to rationalize the observed material composition dependence
and consider it in the model formulation. This modified model is
shown to provide an excellent fit of the multiaxial response of different
IPN membranes. The dielectric permittivity of IPN was characterized
for a range of biaxial strain states, and shown to decrease with
increasing planar strain. For electro-mechanical coupling, our model
uses the equation of Pelrine et al. modified by a strain dependent
permittivity. The predictive capabilities of the electromechanical model
are demonstrated based on observations from pre-strained circular
actuators.
7642-60, Session 9b
DNA hydrogel for bioinspired actuators
C. K. Lee, S. J. Kim, Hanyang Univ. (Korea, Republic of)
DNA hydrogels have a wide range of biomedical applications in tissue
engineering and drug delivery systems. There are two ways to create
DNA hydrogel structures: one is enzyme-catalyzed assembly of
synthetic DNA and the other is by crosslinking natural DNA chemically.
Here, we report a DNA hydrogel fiber without chemical crosslinking
or other gelling agents. A DNA hydrogel fiber without any covalent
crosslinks that is composed of knotted entanglements of DNA flexible
strands has been prepared using a wet spinning method employing an
ionic liquid as the DNA condensing agent and coagulation solvent. The
DNA fiber maintained a hydrogel form for about 3 months after soaking
in deionized water and a high swelling ratio of over 600% compared to
the dry state. The DNA hydrogel fibers may be exploited in a variety of
biomedical applications such as biocompatible composites, sensors
and artificial muscles.
7642-58, Session 9a
A theoretical modeling of mechanical and
electrical properties of enhanced dielectric
elastomers
S. Son, Virginia Polytechnic Institute and State Univ. (United
States); N. C. Goulbourne, Univ. of Michigan (United States)
In this paper, a theoretical model is derived to describe the effects of
additive on the electromechanical properties of dielectric elastomers
(DE). Additives such as silicone and copolymers have been infused
into a DE material such as 3M VHB 4910 resulting in improved
electromechanical properties. However, due to the challenges
experienced in tuning material properties for optimized actuation and
sensing response in a laboratory, a theoretical model that predicts bulk
properties of two phase materials would be of utmost value in pursuing
experimental outcomes in a systematic way.
7642-61, Session 9b
Optimisation of bio-inspired multi-segment
IPMC cilia
S. Sareh, A. T. Conn, J. M. Rossiter, Univ. of Bristol (United
Kingdom)
In nature, unidirectional fluid flows are often induced at micro-scales
by cilia and related organelles. A controllable unidirectional flow is
beneficial at these scales for a range of novel robotic and medical
applications, whether the flow is used for propulsion (e.g. swimming
robots) or mass transfer (e.g. prosthetic trachea). Ionic Polymer Metal
Composites (IPMCs) are innovative smart materials that can be used
directly as active propulsive surfaces rather than a traditional motor
and propeller. IPMC actuators with two segmented electrodes that
attempt to mimic the motion of cilia-like organelles have been realised.
In this paper the optimisation of these actuators towards producing
unidirectional flows is described.
A DE with an additive is considered as a heterogeneous material
consisting of two phases, a base matrix and inclusions, respectively.
Within a micromechanics framework, a multiple-inclusion method
(Eshelby or Mori-Tanaka) are used to determine the bulk properties of
the resultant material. In the first approach, it is assumed that all the
inclusions are geometrically identical and interactions between them
are neglected. The volume fraction and geometry of an additive are
used to compute the material properties. This approach is limited to the
case of low volume concentrations of the additive. For higher additive
concentrations, the second approach considers interactions between
the constituents so that it includes the effect of the surrounding matrix
and the other inclusion.
A parametric study of the kinematic and hydrodynamic effect of
modulating the drive signal has been conducted. As with eukaryotic
cilia and flagella found in mammals, the segmented IPMC actuator
can generate both flexural (asymmetric) and undulatory (symmetric)
motions from the same physical structure. The motion is controlled
by applying profiles of driving frequencies and phase differences.
Kinematic analysis using a camera and laser displacement sensor
has been used to measure and classify different motion types. The
hydrodynamic forces produced by each motion type have been
estimated using particle-tracking flow visualisation. This allows drive
signal profiles to be ranked in terms of the actuator power output and
fluid flow directionality. Using the results of the parametric study, the
IPMC motion is optimised towards producing unidirectional flow via a
repeatable, asymmetric cilia motion. Finally, the hydrodynamic effects
of scaling are discussed for cilia-like IPMC actuators.
In this paper, an enhanced DE is modeled using VHB 4905 with
additive. Theoretical calculations describing the effect of additives on
the electromechanical properties of DEs are presented. It is expected
that the theoretical model will provide guidelines for tuning the material
properties of DE.
7642-59, Session 9b
Training of artificial muscles based on
conducting polymers
K. Kaneto, H. Hashimoto, Kyushu Institute of Technology (Japan)
We demonstrate first time that artificial muscles based on
conducting polymers, polyaniline films can be strengthened in the
electrochemomechanical strain (ECMS) upon training. It has been
found in fact that the stroke of ECMS of polyaniline films increased
to 6.5% by training from that of initial strain of 4.8% before applying
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
7642-62, Session 9b
7642-64, Session 9b
Mechanical characterization of conducting
polymer actuated neural probes under
physiological settings
Fabrication of multiwalled carbon nanotube
polydimethylsiloxne nanocomposite polymer
flexible microelectrodes for microfluidics
and MEMS
E. D. Daneshvar, M. R. Abidian, Univ. of Michigan (United States);
E. Smela, Univ. of Maryland, College Park (United States); D. R.
Kipke, Univ. of Michigan (United States)
A. Khosla, B. L. Gray, Simon Fraser Univ. (Canada)
Over a last decade Polydimethylsiloxane (PDMS) has been the first
choice by researchers worldwide for rapid prototyping of lab on a
chip systems (LOC’s) because of its unique properties such as, it can
be easily micromolded and is an insulator, transparent, flexible and
biocompatible. One of the drawbacks of PDMS based LOC’s is that, it
is difficult to embed, pattern or integrate conductive tracks on PDMS
to because the adhesion between metals (eg. Gold, Silver, Platnium
etc.), intrinsically conducting polymers (eg. PDOT:PSS) and PDMS is
very week and often leads to micro-cracks resulting in failure of device.
The integration of conductive tracks or structures in PDMS based
LOC’s is extremely important for signal routing, interfacing to signal
processing electronics, and to power active devices. Hence there is
need to develop flexible electrically conducting polymer which not only
have a good adhesion to PDMS but is also are resistant to microcrack formation. The work improves on previous research in which
Multiwalled carbon nanotubes were manually mixed in PDMS matrix
and then ultrasonically agitated in agitated ultrasonically at 24 khz.
In this work we have employed shear mixing technique to sdisperse
MWCNT’s in PDMS matrix and for the first time present fabrication
of microelectrodes using our materials and processes. Multiwalled
Carbon Nanotubes with an outer diameter of 10nm and length of 30μm
were purchased from Cheap Tubes Inc, USA) and PDMS polymer
matrix which consists of base elastomer and curing agent (Sylgard 184
Elastomer Kit) was bought from Dow Corning, USA. The electrically
MWCNT -PDMS nanocomposite is prepared by shear mixing. The
resultant nanocomposite was successfully micromolded against a SU-8
master mold in to electrodes of 1000 μm x 100 μm with a height of 50
μm in size on a non conducting PDMS. The electrical resistivity of the
electrodes was calculated using four probe measurement and was
found to be equal to 89.2 at 2 weight percentage of MWCNT in PDMS
Matrix which is better than our previously reported value of 102.12 Ω/
cm at similar weight percentage.
Most implantable chronic neural probes have fixed electrode sites on
the shank of the probe. Neural probe shapes and insertion methods
have been shown to have considerable effects on the resulting
chronic reactive tissue response that encapsulates probes. We are
developing probes with controllable articulated electrode projections,
which are expected to provoke less reactive tissue response due to
the projections being minimally sized, as well as to permit a degree
of independence from the probe shank allowing the recording sites to
“float” within the brain. The objective of this study was to predict and
analyze the force-generating capability of conducting polymer bilayer
actuators to actuate electrode projections from the probe shank under
physiological settings.
Custom parylene beams 1 cm long having varying widths (100 - 1000
microns) and thicknesses (8 - 15 microns) were coated with Cr/Au.
Polypyrrole was potentiostatically polymerized onto the Au at 0.5 V in
a solution of 0.1 M pyrrole and 0.1 M dodecylbenzenesulfonate (DBS)
to varying thicknesses. Using cyclic voltammetry, the bilayer beams
were cycled between 0 and -1 V in artificial cerebral spinal fluid at
37C, as well as in aqueous NaDBS at room temperature as a control.
Video and scanning electron micrographs were taken and used to
quantify thicknesses and deflections. Force and strain were measured.
By integrating polypyrrole-based conducting polymer actuators, we
present a novel microfabricated neural electrode. We demonstrate that
by oxidizing and reducing the polymer layer, we can control electrode
projection deflection under physiological settings.
7642-63, Session 9b
Robust PID force control of IPMC actuators
S. Sano, S. Sato, Toyohashi Univ. of Technology (Japan); K. Takagi,
Nagoya Univ. (Japan) and RIKEN (Japan); N. Uchiyama, Toyohashi
Univ. of Technology (Japan); K. Asaka, National Institute of
Advanced Industrial Science and Technology (Japan)
7642-87, Session 9b
Anthropomorphic robotic face with servodriven muscle system: a comparative
analysis with EAP systems
Compared with the conventional actuators, the response of the IPMC
can be easily changed by environmental conditions such as humidity
or counter ions within the polymer. Therefore, the precise force control
of IPMCs is a challenging task and it is expected that the development
of robust or adaptive compensation methods for the uncertainty or the
variation of the model. From the point of view of a practical use, PID
(proportional, integral and derivative) control is the most commonly
used methods due to the simplicity. However, the performance may
degrade easily owing to the uncertainty, or the system may become
unstable, unless the PID gains are properly designed.
N. D. Thayer, S. Priya, Virginia Polytechnic Institute and State Univ.
(United States)
An expressive robotic face with muscle locations based on spatial point
tracking of a human face has been developed. Servo motors mounted
within the skull pull anchor wires that were attached on the inside of a
silicone skin that forms the outer face layer. The deformation of the skin
allows the face to display expressions. The basic expressions required
to aid normal conversations can be conveyed by this current generation
prototype. The skin possesses material properties very similar to
that of human skin and contributes to bio-mimetic appearance and
functionality. A two degree of freedom (DOF) set of eyes with pinhole
cameras mounted inside the head capable of blinking and pupil dilation
was also developed. The eyes can also be used for visual feedback.
We analyze the performance of the face using mathematical models
and compare the expressions achieved with that of a human face. This
research is being done with the aim to increase the quality of training
for medical students by simulating patient facial expression under
different medical situations. This paper will address the advantages and
disadvantages of the prototype with respect to electro-active polymer
based actuation in terms of motion, power consumption, precision and
control.
This paper discusses a simple robust PID tuning method for the force
control of IPMC actuators. As the first step, the system is modeled by
a linear time invariant system which represents the responses of the
electrical and the electro-mechanical systems.
The uncertainty is expressed by interval polynomials of the closed-loop
characteristic equation. The intervals of the uncertainty are determined
by an identification experiment. As the second step, the PID gain is
determined by a pole assignment to be satisfied the robust stability.
Using Kharitonov’s theorem, we show that only one polynomial is
required for the robust stability check of the model.
In the experimental verification, two IPMCs are used for the control
and the disturbance. The step response and the tracking control for
the sinusoidal input are examined with and without the disturbance.
Experimental results show the effectiveness of the force control
achieved by the proposed method.
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
to experimentally determine the temperature distribution along the
actuator in air and aqueous conditions. Analytical and finite element
heat transfer models were developed to compare with experimental
results. The models allowed optimization of actuator structure in terms
of energy efficiency by predicting the effect of design parameters
such as silicone thickness and SMA wire diameter. A feedback control
system was implemented by sensing temperature at the surface of
the SMA wires in order to match the Aurelia aurita cycle time and
therefore maximize propulsion efficiency. Current feedback control
allows the optimization of SMA power consumption and prevents their
overheating for a better actuation lifespan.
7642-66, Session 10a
Dielectric electro active polymers:
development of an industry
M. J. Tryson, Danfoss PolyPower A/S (United States); H. Kiil,
Danfoss PolyPower A/S (Denmark)
Dielectric electro active polymers hold much promise as a smart
material. Over the years devices have been developed that
demonstrate DEAP’s unique capabilities as an actuator, sensor, and
energy conversion. In recent years significant progress has been made
towards commercialization of this technology platform. The behaviour
of these devices has been widely modelled and models correlated
to real world devices. A wide network of international researchers
continues to extend the state of the art and equip engineers with the
skills and background to design DEAP into numerous applications. A
strong collaborative environment exists between research and industry,
consortia like organizations are being formed to maximize research.
DEAP is poised for an era of rapid acceleration of capabilities and
acceptance into mainstream products.
7642-69, Session 10b
Biomimetic control for DEA arrays
B. M. O’Brien, T. A. Gisby, S. Q. Xie, The Univ. of Auckland (New
Zealand); E. P. Calius, Industrial Research Ltd. (New Zealand); I. A.
Anderson, The Univ. of Auckland (New Zealand)
Arrays of actuators utilizing mechano-sensitive control strategies are
ubiquitous in nature across a variety of size scales. An example is the
Comb Jelly, whose longitudinal rows of ciliated paddles are controlled
in this manner, with each paddle triggering the next to generate a wave
of actuation that sweeps down the row. In a similar fashion, the beating
of the human heart is regulated by mechano-sensitive feedback loops
occurring from the cellular to whole organ level.
7642-67, Session 10a
A hybrid microbial dielectric elastomer
generator for autonomous robots
This control strategy is particularly powerful when used in Dielectric
Elastomer Actuator(s) (DEA) systems, as DEA can be rendered selfsensing and readily fabricated into arrays that are useful for a variety
of applications. Self-sensing feedback provides mechanical state
information that can be used to detect when a DEA is influenced by
one of its neighbors. We have previously shown that an array of DEA
bending actuators can be controlled to produce a wave of actuation
using a simple self-sensing state machine for each unit of the array.
I. A. Anderson, The Univ. of Auckland (New Zealand); I. Ieropoulos,
Bristol Robotics Lab. (United Kingdom); T. G. McKay, B. M.
O’Brien, The Univ. of Auckland (New Zealand); C. Melhuish, Bristol
Robotics Lab. (United Kingdom)
Dielectric elastomer generator (DEG) systems use elastomer
membranes coated with compliant electrodes. Energy can be
harvested when work is done on a DEG membrane through coupling
between mechanical strain actuated by an external source such as
wind and electrical charge: 1) wind deforms the membrane, 2) a bias
voltage charges the membrane, 3) the membrane is relaxed raising the
potential energy per charge, and 4) charge is drained to an electrical
load or storage capacitor. The system requires starting charge and
charge to compensate for losses due to leakage.
In this paper we show how the speed of this wave can be controlled
using multi-level biomimetic controllers. The controllers manipulate
global state machine variables such as sensitivity, charging or
discharging current and refractory period to regulate the speed of
the wave. The performance of different controllers was evaluated
experimentally by applying them to real DEA arrays.
A self-primer circuit can restore the leaked charge and the starting
charge can be supplied by another energy source such as microbes.
Consider the Ecobot robot that converts biomass, in the form of flies,
to electrical energy using microbial fuel cells (MFC). We have used the
Ecobot MFC system to supply starting charge at between 3 and 5 volts
to a DEG coupled to a self-primer circuit. The DEG membrane was
cyclically stretched producing charge that replenished leakage losses
and supplied excess charge for Ecobot’s storage capacitors.
It is expected that such controllers will have multiple applications
in robotics. Several applications, including flexible robotic hearts,
peristaltic pumps, conveyor systems, and propulsion systems will be
discussed.
Combining MFCs with DEGs has many advantages. The robot could
maintain energy stores should there be a temporary reduction in the
biomass intake or wind loading. There is no need for a heavy auxiliary
battery. The DEG activation can be controlled by a central processor,
and turned off when the wind stops. Finally, the high voltage charges
used in the DEG can also be used for trapping flies, thus assisting in
replenishing the MFC.
Control of twisting motion of a multielectrode IPMC actuator
7642-70, Session 10b
Y. Jung, S. Kim, K. J. Kim, K. K. Leang, Univ. of Nevada, Reno
(United States)
A novel multi-electrode ionic polymer-metal composite (IPMC) actuator
is proposed for applications requiring multiple degrees-of-freedom
motion, such as bending and twisting, for applications that include
highly-dexterous artificial fins for underwater systems and artificial
valves in biomedical devices. The multi-electrode pattern on the IPMC
is created using two techniques, masking and surface machining. The
twisting ability of a prototype actuator is evaluated and compared to an
electro-mechanical model developed using the finite element method.
The model is developed for optimizing the electrode pattern for
maximizing actuation performance, such as twisting motion. A digital
control system is proposed to control the multiple-electrodes on the
IPMC actuator to achieve bending and twisting motion. Experimental
results show achievable twisting up to 5 degrees for a 25 mm x 50
mm x 0.2 mm actuator. Technical design challenges and performance
limitations are discussed.
7642-68, Session 10b
Feedback control of BISMAC actuators
through active temperature sensing
A. Villanueva, S. Priya, Virginia Polytechnic Institute and State Univ.
(United States)
Bio-inspired shape memory alloy composite (BISMAC) actuators have
been developed for the propulsion system of unmanned undersea
vehicles (UUVs) mimicking the rowing mechanism utilized by jellyfish
with small fineness ratio. BISMAC actuators consisting of silicone,
spring steel and shape memory allow wires were shown to recreate the
bell deformation of Aurelia aurita jellyfish species. However, in order to
achieve a similar cycle time as the natural counterpart, it is important
to incorporate active temperature control. Initial tests were conducted
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
actuation has no effect. When the temperature is elevated above Tg
the material becomes soft and elastic, and dielectric actuation can
be exploited. We present preliminary results showing this zero-energy
fixity property. Applications are widespread in the fields of robotics
and engineering and include morphing wings that only need energy to
change shape and control valves that lock rigidly into position.
7642-71, Session 11a
Polypyrrole composite actuator synthesis,
characterization, and application for
Jellyfish unmanned underwater vehicle and
robotic face
7642-74, Session 11a
Y. T. Tadesse, J. Brennan, C. F. Smith, A. Villanueva, S. Priya,
Virginia Polytechnic Institute and State Univ. (United States)
Jamming as an enabling technology for soft
robotics
In this paper, we analyze the effect of geometry in conductive polymermetal composite actuators. The stripe actuator design consists of
gold coated polyvinylidene difluoride (PVDF) substrate membrane
with polypyrrole film grown potentiodynamically on top and bottom in
sandwich structure. For axial type actuator, a sacrificial core substrate
was used which can be dissolved after polymerization of Pyrrole.
Synthesis of all samples was done using cyclic voltametry technique.
Result indicate that axial type actuator consisting of 0.25 M Pyrrole,
0.10 M TBAP and 0.5 M KCl in aqueous solution exhibits strain up
to 6 % for applied potential of 6V DC after 80 sec stimulation time
and exhibits18 kPa blocking stress. Characterization of the actuator
was conducted to establish stress-strain and energy density - time
response relationships. Potential applications of conductive polymer
based actuator include biometric jellyfish and facial expressive robotic
head.
E. Steltz, A. Mozeika, iRobot Corp. (United States)
This paper presents a new architecture in soft robotics that utilizes
jamming of a granular medium. We describe a new concept of
actuation that modulates the direction and amount of work done by a
single central actuator using jamming “activators” to jam and unjam
components around the actuator. These ideas are demonstrated
in the Jamming Skin Enabled Locomotion (JSEL) prototype which
can morph its shape and achieve locomotion. Next, a new actuator
denoted a Jamming Modulated Unimorph (JMU) is presented as an
alternative to the JSEL topology to better aid navigating through small
holes. The JMU uses a central McKibben actuator and a discrete
number of jamming cells to turn the 1 DOF McKibben actuator into a
multi DOF bending actuator. Full characterization of the JMU actuator
is presented, followed by a concluding argument for jamming as an
enabling mechanism for soft robots in general, regardless of actuation
technology.
7642-72, Session 11a
Large planar dielectric elastomer actuators
for fish-like propulsion of an airship
7642-75, Session 11a
C. Jordi, S. A. Michel, EMPA (Switzerland); A. Bormann, C.
Gebhardt, Aeroix (Germany); G. M. Kovacs, EMPA (Switzerland)
Performance of multi-segment dielectric
elastomer machines
One of the great advantages of dielectric elastomers (DE) is their
scalability. Large planar DE are quite unique in the world of actuators.
An ideal application of such an actuator is the activation of inflatable
struc-tures. As research platform a model airship of 8 m in length was
constructed that can move its body and tail fin in a fish-like manner.
Unlike the propulsion with rotors, the fish-like movement is silent and
the airflow around the airship is not disturbed by the fast airflow after
the rotor. The bending actuation of the helium-filled hull is realized with
planar two-layered DE of 1.6 m2 on either side. The tail fin is moved by
four-layer planar DE of 0.3 m2 on either side. A design for actuators of
such dimensions was developed and the actua-tors were characterized
in terms of performance.
E. P. Calius, Industrial Research Ltd. (New Zealand); B. M. O’Brien,
T. A. Gisby, T. G. McKay, I. A. Anderson, The Univ. of Auckland
(New Zealand)
Dielectric Elastomer Actuators (DEA) have impressive performance
characteristics that equal or surpass biological muscle in several
respects. But raw performance is of limited utility without the ability
to steer motion and work along desired paths. Bio-engineering and
bio-robotics applications in particular often involve mimicking the
movements of live beings, and require creating devices capable of
many more degrees of freedom than in conventional mechanisms.
A simple linear actuator can be constructed by putting the DEA
membrane under tension and partitioning its electrodes into two
independently addressed segments. As these segments are actuated
in turn, one will grow larger while the other shrinks resulting in
displacement from the active towards the passive areas. By applying
this principle of electrode segmentation and sequential actuation in two
dimensions instead of only one it becomes possible to generate richer
movement patterns. In previous work we have used it to generate
orbital motions that drive a rotating shaft, thus creating a rotary motor.
7642-73, Session 11a
Dielectric elastomer actuators with zeroenergy fixity
J. M. Rossiter, Univ. of Bristol (United Kingdom); K. Takashima, T.
Mukai, RIKEN (Japan)
In this paper we present a generalization of the rotary motor concept
that leads to flat actuators capable of complex motions through phased
actuation of unequal segments. Mathematical models are developed
that provide insight into the relationships between the number and
geometry of the electrode segments and the amplitude and curvature
of motion. The design of segment shapes to obtain the desired twodimensional trajectory of a point is examined, and the limits of motion
available in multi-segment DEA are explored. Examples are given of
actuator segment optimization for square and elliptical trajectories.
Although dielectric elastomer actuators are becoming more powerful
and more versatile one disadvantage of DEAs is the need to
continuously supply electrical power in order to maintain an actuated
state. Previous solutions to this problem have involved the construction
of a bistable or multi-stable rigid mechanical structure or the addition
of some external locking mechanism. Such structures and mechanisms
add unwanted complexity and bulk. In this paper we present a
dielectric elastomer actuator that exhibits zero-energy fixity. That is, the
actuator can be switched into a rigid state where it requires no energy
to maintain its actuated shape. This is achieved without any additional
mechanical complexity. This actuator relies on changes to the elastic
properties of the elastomer material in response to a secondary
stimulus. The elastomer can be switched from a rigid glass-like state
to a soft elastic state as required. We present a dielectric elastomer
actuator that utilizes shape-memory polymer properties to achieve
such state switching. In this case control of the elastic properties is
achieved through temperature control. When the material is below its
glass transition temperature (Tg) it is in its rigid state and dielectric
24
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7642-76, Session 11b
Hydrogel-based piezoresistive biochemical
microsensors
M. Guenther, V. Schulz, G. U. Gerlach, Technische Univ. Dresden
(Germany); T. Wallmersperger, Univ. Stuttgart (Germany); F.
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
owing to the their unique advantages, such as large recoverable
deformation, lower manufacturing cost, easier pretreatment procedure
and lower recovery temperature. Our major researching efforts are
focused on the fundamentals and their applications of SMPs and their
composites. In this paper, the synthesis of SMPs is presented firstly,
with a detailed description of fabrication and processing method.
We also investigate the constitutive model of these thermosetting
SMPs. The characterization method and main parameters of shape
memory effect are described to determine the shape recovery
properties of SMPs. Then, different kinds of reinforcement are
embedded into SMPs to form smart composite materials, aiming to
improve their properties or strengthen the materials. Furthermore, in
order to realize the actuation of SMPs for a special application, the
investigation of actuations in multi ways are also performed, namely
electroactive SMPs, solution activated SMPs, and light-induced SMPs.
Finally, based on the unique properties of such materials, primary
applications are also studied, including shape memory polymer foam,
biodegradable SMPs, morphing wing and space deployable structures,
which provide meaningful guidance for further researching works in this
area.
Solzbacher, J. J. Magda, P. Tathireddy, G. Lin, M. P. Orthner, The
Univ. of Utah (United States)
This work is motivated by a demand for inexpensive, robust and
reliable biochemical sensors with high signal reproducibility and longterm-stable sensitivity, especially for medical applications. Microfabricated sensors can provide a continuous monitoring and on-line
control of analyte concentrations in ambient aqueous solutions. The
piezoresistive biochemical sensor containing a special biocompatible
polymer (hydrogel) with a sharp volume phase transition in the neutral
physiological pH range near 7.4 can detect a specific analyte, for
example, carbon dioxide or glucose. Thereby the hydrogel-based
biochemical sensors are useful for the diagnosis and monitoring
of diabetes and of pulmonary disease. The basic working principle
is as follows. A chemical reaction takes place due to the analyte
concentration change resulting in a pH change. The latter is detected
by means of pH-sensitive gel swelling leading to the deflection of
bending plate in piezoresistive pressure sensor. The measured kinetic
curves have been analysed by means of appropriate models and
some methods improving the properties of the biochemical sensors
have been proposed. The polymer film preparation conditions
and measurement conditions, which are necessary for high signal
reproducibility and high long-term stable sensor sensitivity, were
determined. The improvement of sensor properties such as response
time, sensitivity, stability and selectivity is discussed for both in vitro
and in vivo usages of the implantable sensors.
7642-79, Session 11b
Electromechanial characteristics of
actuators based on carbide-derived carbon
J. Torop, F. Kaasik, Univ. of Tartu (Estonia); T. Sugino, National
Institute of Advanced Industrial Science (Japan); A. Aabloo, Univ. of
Tartu (Estonia); K. Asaka, National Institute of Advanced Industrial
Science (Japan)
7642-77, Session 11b
Flexible strain sensor for air muscles using
polypyrrole coated rubber
An electromechanical transducer was prepared using non-ionic
polymer, ionic liquid and carbide-derived carbon (CDC). Recently
simple layer-by-layer casting method was discovered for actuator
production using bucky gel” mixture as a precursor of actuator
electrode layers. In this paper we investigate carbide-derived carbon as
new alternative candidate to carbon nanotubes to replace nanotubes in
electrode layer of transducer. At the initial stage of the study, the ratio
of nanoporous high surface TiC-derived carbon powder, 1-ethyl-3methylimidazolium tetrafluoroborate (EMIBF4) and polymer (PVdF(HFP))
was varied and each formed electrode was analyzed to find out an
optimal composition. The results revealed that the optimal component
ratio for electrodes is: 35 wt% PVdF(HFP), 35 wt% EMIBF4 and 30
wt% CDC. The assembled three layer transducers were characterized
by measuring blocking force, maximum strain, speed and their power
consumption and capacitance. The synthesized actuator showed very
good force and capacitive characteristics and it is preferable for slow
response applications compared to transducers based on carbon
nanotubes.
A. P. Tjahyono, K. C. Aw, J. Travas-Sejdic, K. Li, The Univ. of
Auckland (New Zealand)
Air muscle is an important advancement in the field of artificial
muscle. However, external sensors are still being used to indicate
its displacement or strain. Some of these external sensors are bulky,
expensive and impractical for real life applications. The integration
of a strain sensor into air muscles would ease the complexity of the
hardware system. This would contribute to the development of a
complete self-contained system where the actuator and sensor are
integrated.
A flexible strain sensor was developed by coating butyl-rubber with the
conducting polymer, polypyrrole (PPy) through chemical deposition.
Micropores in the rubber were increased using sulphuric acid before
PPy deposition to improve adhesion of PPy. PPyThis deposition makes
the rubber conductive and the electrical conductivity is determined
by the deposited PPy. This flexible strain sensor responses to the
strain experienced by the rubber through the changes in electrical
conductivity or resistance. Using a wheatstone bridge to determine
the electrical response, it was found that the electrical resistance
has a positive trend with the applied strain. In addition, the electrical
responses could reach to a strain of up to 30%.
7642-80, Session 11b
Liquid crystal elastomer composite with
optimum actuation amplitude
The ability to mount the sensor directly onto the air muscle allows for a
complete integration, creating a simple actuator and sensor system. As
the PPy was deposited chemically, it has no mechanical component,
eliminating wear and movement; hence increase in durability and less
maintenance. More importantly, it is inexpensive to manufacture and
light weight, making this sensor applicable for other applications to
measure displacement or strain.
Y. Y. Huang, Y. Ji, E. B. Terentjev, Univ. of Cambridge (United
Kingdom)
We have investigated a composite design of spontaneously actuating
liquid-crystal elastomer (LCE) and heating wires embedded into the
rubbery matrix. We focus on the bistable configuration of wires at a
critical angle to actuation direction, which theoretically provides a
second energy minimum for wires deforming within an incompressible
matrix. Experiments confirmed the practicality of the theory when wires
are embedded in a soft matrix such as an elastomer. Two stacking
designs were tested: the double layer composite with parallel wires
between the layers yields a shape change of 150%, whereas the triple
layer composite with wires wrapped around the middle layer gives
a change of 130%, with better durability. It is expected that better
actuation stroke could be achieved if main-chain LCE layers were
used, for which the intrinsic amplitude of thermal contraction can reach
several hundreds percent. We also critically evaluate the response time
and power efficiency of heat-stimulated LCE actuators. It is found that
heat capacity of LCE determines its performance limits for operations
7642-78, Session 11b
Multifunctional shape memory polymers
and their composites: fundamentals and
applications
J. Leng, Y. Liu, S. Du, Harbin Institute of Technology (China)
As a novel kind of smart materials, shape memory polymers (SMPs)
have been one of the most attractive subjects under intensive
investigation in the recent years. Various applications are also explored
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
at a fixed ambient (e.g. room) temperature. The combination of critical
angle geometry and resistive heating of embedded wires should yield
optimum strain achievable by a remote stimulus. It also opens up the
possibility of providing large actuation forces by making multi-layer
LCE composites.
7642-83, Session 12a
Active vibration control using DEAP
actuators
R. Sarban, Danfoss PolyPower A/S (Denmark); R. W. Jones, B.
Lassen, Univ. of Southern Denmark (Denmark)
7642-81, Session 12a
Dielectric electro-active polymer (DEAP) is a new type of smart
material, which when utilised as actuators, has the potential to be used
for effective actuation in different applications. DEAP has a range of
properties that place it somewhere between those of piezoceramics
and shape memory alloys (SMA’s).
Nonlinear force control of dielectric
electroactive polymer actuators
M. Y. Ozsecen, C. Mavroidis, Northeastern Univ. (United States)
Among others, active vibration control is one of the application
areas where the tubular type DEAP actuators have shown promising
performances.
Electroactive polymer (EAP) based actuators can provide compact
actuation solutions to engineering problems in many fields such as:
robotics, medical devices, power generation, actuators and sensors.
Their characteristics are advantageous over conventional types of
actuators due to their lower weight, faster response, higher power
density and quieter operation. When considered as actuators an
effective controller is necessary to get greater performance out of
EAPs, specifically when controlling the amount of force exerted for
an interaction between an object and a human. Applications that
use EAPs as haptic interfaces could benefit from various controllers.
To date little research has been conducted into the force control of
EAPs or their possible applications which utilize force control. This
paper presents a real-time nonlinear force controller for a Rolled type
Dielectric Electroactive Polymer (RDEAP). To increase the response
characteristics of the actuator, a control algorithm and non-linear
inverse model were derived using the actuator’s nonlinear behavior.
Experiments have been conducted to compare the response of P, PI
and PID controllers both with and without the feed forward non-linear
term. A PID controller with the inverse model as a feed forward term
has been found to give the fastest rising time (~40ms) and settling
time (~50ms). The force controller presented can enhance the safety
and performance of this unique family of actuators, allowing for more
advanced and efficient applications.
This work, first, introduce DEAP-based tubular actuators produced
by Danfoss PolyPower A/S. Static and dynamic characteristics of
the actuators are then investigated. Models, describing the static
and dynamic characteristics, are developed and compared with
experimental results. Different control strategies, used in active
vibration control, are investigated and the implications due to unique
characteristics of the DEAP actuators, in control design, are assessed.
Active vibration control for both tonal and broadband vibrations are
considered, and performance of various control strategy for each
vibration type is investigated. Experiments, using the designed
controllers and the DEAP-based actuators, for tonal and broadband
vibration are then carried out. The performance of the DEAP actuators,
in tonal and broadband vibration suppression, is illustrated.
7642-84, Session 12a
Hysteresis compensation for an open-loop
controlled tubular actuator
J. Oubaek, Danfoss PolyPower A/S (Denmark); R. W. Jones, Univ.
of Southern Denmark (Denmark); R. Sarban, Danfoss PolyPower
A/S (Denmark)
7642-82, Session 12a
The development of a precision control system for the DEAP tubular
actuator is a basic requirement for commercialisation of the technology.
For time-varying reference changes the performance of feedback
control, using a conventional proportional and integral (PI) controller,
is far from satisfactory with the underlying hysteresis of the powered
actuator and the 90 degrees phase lag from the PI controller combining
to create a delayed controlled response.
Closed loop control of a rotational joint
driven by two antagonistic dielectric
elastomer actuators
M. Randazzo, M. Fumagalli, G. Metta, G. Sandini, Italian Institute of
Technology (Italy)
Open-loop control, where the controller is based on an approximate
inverse of the actuator model, offers the potential of much improved
controlled tracking performance with time-varying reference signals.
This contribution examines open-loop control of a tubular actuator with
hysteresis compensation being integrated into the control scheme to
improve position tracking precision with periodic reference signals.
The hysteresis compensation approach used is based on the phaser
concept introduced by Cruz-Hernandez and Hayward. A phaser is an
ideal frequency domain operator that shifts a periodic input signal by a
constant phase-angle without changing the magnitude of the system
and this approach provides simple, yet effective, linear compensation
of hysteresis.An initial simulation study introduces the ideas behind
phaser-based hysteresis compensation. The approach is them applied
to a core-free tubular actuator with the hysteresis related phase lag
being determined for a range of periodic input voltages. The designed
phaser is then implemented into the real-time open-loop control system
and improved tracking of the reference signal demonstrated.
Dielectric elastomers are a subclass of electronic EAPs able to produce
large deformations (and thus mechanical work) when an external
electric field is applied.
While the intrinsic compliance of this kind of polymeric actuators
have been always addressed as major benefit respect to traditional
electromagnetic motors, unable to fully capture the capabilities and
mechanical properties of biological muscles, their polymeric nature
poses peculiar challenges in controlling a system which is subject to
nonlinearities, hysteresis and viscous creep behavior.
In this paper we explore the controllability properties of a simple
rotational joint driven by two dielectric elastomer actuators arranged in
an antagonistic configuration. A number of sensors are used to obtain
information about the state of controlled system: the angular position of
the joint is measured by an angular encoder, tension sensors are used
to monitor the tension of the two driving tendons and linear encoders
provide accurate measurements of the displacements generated by
the two actuators. Moreover, the capacitance of the two dielectric
elastomer actuators is estimated and used to obtain additional
information about the status of system.
7642-85, Session 12a
Using this feedback information, a control algorithm has been
implemented on a microcontroller unit in order to independently
activate the two actuators, allowing a closed loop control of both
the angular position of the joint (position control) and its stiffness
(impedance control).
Flexible enhanced energy density
composites for dielectric elastomer
actuators
A detailed description of the developed control strategy and its
performances under different load conditions are discussed in this
paper.
H. Stoyanov, M. Kollosche, D. N. McCarthy, G. Kofod, Univ.
Potsdam (Germany)
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
dexterity will allow future implementation for complex grasping tasks
and object manipulation. This paper focuses on the mechanical design
analysis and comparison with biological systems for the prototype
hand and forearm. This paper will address the advantages and
disadvantages of the prototype with respect to electro-active polymer
based actuation in terms of motion, power consumption, precision and
control.
Dielectric elastomer actuators deform due to voltage-induced Maxwellstress, which interacts with the mechanical properties of the material.
Such actuators are considered for many potential applications where
high actuation strain and moderate energy density comparable to
biological muscle are required. However, the high voltage commonly
required to drive them is a limitation, especially for biomedical
applications. The high driving voltage can be lowered by developing
materials with increased permittivity, while leaving the mechanical
properties unaffected. Here, an approach to lowering the driving
voltage is presented, which relies on a grafted nano-composite, in
which conducting nanoparticles are integrated directly into a flexible
matrix by chemical grafting. The conducting particles are π-conjugated
rod macromolecules, which are grafted chemically to a polymer
matrix flexible backbone. Dielectric spectroscopy, tensile mechanical
analysis, and electrical breakdown strength tests were performed to
fully characterize the electro-mechanical properties. Planar actuators
were prepared from the resulting composites and actuation properties
were tested in two different modes: constant force and constant strain.
With this approach, it was found that the mechanical properties of the
composites were mostly unaffected by the amount of nanoparticles,
while the permittivity was seen to increase from 2.0 to 15, before
percolation made further concentration increases impossible. Hence,
it could be demonstrated that the so-called “optimum load” was
independent from the permittivity (as expected), while the operating
voltage could be lowered, or higher strains could be observed at the
same voltage.
7642-89, Session 12b
Feasibility analysis of a dielectric elastomerbased ankle-foot orthotic
A. P. Mulgaonkar, M. O. Culjat, W. S. Grundfest, Q. Pei, Univ. of
California, Los Angeles (United States)
Several papers in the published literature have discussed using
dielectric elastomer-based actuators to provide active control of
the ankle-foot orthotics commonly used to treat the drop-foot gait
pathology commonly associated with brain/spinal cord trauma,
traumatic brain injury, multiple sclerosis, cerebral palsy, and stroke.
While dielectric elastomer actuators show promise in this application
due to their light weight and high power density compared to
traditional actuation methodologies, a working system has not been
demonstrated to date. In this paper we aim to rigorously demonstrate
the feasibility of such a system. Real-time kinematic gait analysis was
used to determine the necessary base-line torque about the anklejoint and validate existing models of ambulatory motion. Mechanical
and electrical analysis of a simple core-free rolled dielectric elastomer
actuator was performed to quantify actuation and charging time
constants to determine if these parameters are in line with natural gait.
Several different actuator positions and orientations based on anklephysiology were further explored through modeling with and scalemodel testing. All this data has been aggregated into a dynamic modelbased simulation of active gait assistance with a dielectric-elastomer
powered ankle-foot orthotic.
7642-86, Session 12a
Generation fuzzy rules and learning
algorithms for swimming fish robot using
IPMC actuators
J. H. Kim, C. Kim, H. Yang, J. Park, Yonsei Univ. (Korea, Republic
of)
Nowadays, Research concerned in the artificial life is devoted to
understanding life by attempting to abstract the fundamental dynamical
principles underlying biological phenomena, and recreating these
dynamics in other physical media including computers.
7642-90, Session 12b
Development of a deformable mirror based
on conductive polymer actuator arrays for
use in adaptive optics
In addition to providing new ways to study the biological phenomena
associated with biological life(B-life), artificial life(A-life) allows us
to extend our concepts to the larger domain of “life-as-it-couldbe”. Swimming fish robot has complicated behaviors and activities
to swim in the water. In addition, it is essential that swimming fish
robot compose of complex mechanical elements due to taking many
complex behaviors. So, we propose Ionic Polymer-Metal Composites
(IPMCs) to control swimming fish robot activities. We will acquire
good control Mechanical system by IPMCs on swimming fish robot
and artificial intelligence algorithms will be obtained by our suggested
environment learning algorithms for swimming fish robot.
A. D. Price, H. E. Naguib, F. Ben Amara, Univ. of Toronto (Canada)
Adaptive optical systems incorporate active components that
compensate for wavefront aberrations introduced by optical defects.
The increase in resolution is limited by the stroke of the adaptive
component’s underlying actuating mechanism and the differential
stroke of neighbouring actuators. This study first explores the design
and fabrication of a novel deformable mirror based on electroactive
polymers, and more specifically the conductive polymer polypyrrole. A
unique Vistec EBPG 5000+ electron beam lithography tool is employed
in combination with conventional potentiostatic electropolymerization
techniques to produce layered high-density nano-scale polypyrrole
actuator arrays. Evaluation of the conductive polymer based
deformable mirror is subsequently conducted using a wavefront
sensor and the mirror itself as the wavefront corrector. These results
indicate that the device delivers superior performance in terms of
combined stroke and time response when compared with conventional
alternatives such as piezoelectric mirrors or micromachined mirrors
utilizing electrostatic electrodes. As this performance was previously
unattainable, the implications of this technology are diverse and range
from more powerful astronomical telescopes to improved retinal
tissue diagnosis. Finally, this investigation serves to demonstrate the
successful implementation of electroactive polymers in a complex
engineering system.
7642-88, Session 12b
Design and implementation of dexterous
robotic hand for human controlled
interfaces: a comparative analysis with EAP
systems
N. D. Thayer, S. Priya, Virginia Polytechnic Institute and State Univ.
(United States)
An anthropomorphic robotic hand with 23 degrees of freedom
(DOF), dexterous enough to type on a standard keyboard, has been
developed. The design was inspired by human hand physiology.
The hand consists of 19 servo motors that drive tendons which run
from the forearm to the hand contribute to the system’s human-like
functionality and physical appearance. Antagonistic torsional springs
and a 4-bar mechanism were utilized to decrease the complexity of
control. A kinematic relationship between joint space and end effector
was established using Denavit-Hartenberg representation coupled with
LabView and Matlab to produce accurate typing motions. The high
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Conf. 7642: Electroactive Polymer Actuators and Devices (EAPAD) XII
focus by changing its focal distance with moving lens or focal plane.
the proposed optical system changes its lens thickness using a
annulary connected polymer actuator in order to get image focuses.
The proposed biomimetic lens system ensures high shock durability,
compact physical dimensions, fast actuations, simple manufacturing
process, and low production cost.
7642-91, Session 12b
A universal dielectric elastomer generator
for improved energy harvesting
P. Brochu, X. Niu, W. Yuan, Q. Pei, Univ. of California, Los Angeles
(United States)
7642-94, Session 12b
Dielectric elastomers are a promising transducer technology that
combines low cost, light weight, high fracture toughness, and
high energy density. Recent interest in dielectric elastomer energy
generators has spurred the development of several designs capable
of harvesting energy from a variety of sources from human to wave
energy. We have recently reported on a scalable universal dielectric
elastomer energy generator that is capable of generating 40 mJ per
cycle with an active volume of only 0.57 cm3 and a maximum efficiency
of 55%. We build on these results and use recent advances in dielectric
elastomer technology to demonstrate an improved generator design.
We explore the energy generating characteristics of the generator and
compare its performance to theoretical limits.
Active skin on steering wheel
H. L. V. Nguyen, H. C. Nguyen, D. S. Kim, K. J. An, H. P. Vuong, J.
C. Koo, Y. K. Lee, J. Nam, H. R. Choi, Sungkyunkwan Univ. (Korea,
Republic of)
Conventional technologies, at this time, can not extend to advanced
applications which can exploit haptic feel in the human-machine
interaction. While dielectric elastomer can be a feasible technology
with many good properties, such as soft, flexible, miniature, light
weight and high efficiency. So in our research we propose “Active
skin using dielectric elastomer”, which contains tactile stimulator
and tactile sensor integrated in a single unit. It can sense the contact
force (even the position) and transfer the touch feel to the skin such
as fingertips, and thus, can use as a haptic interface. Its configuration
includes some layers of tactile stimulator, one layer of tactile sensor,
and cover by protection layers on top and bottom surface. With large
number of cells, when we touch, the active skin can use to determine
the force and position at the same time. Independent control of each
cell also can give us various choices for surface display. Each cell is
designed as a spherical-cap shape to make best support structure
for sensing layer, and orient the displacement direction. The controller
of active skin uses microcontroller communicates with PC by CAN
communication. Microcontroller will receive command from PC and
control tactile stimulator part, it also receive sensing signal from tactile
sensor part and send back to computer. For example of application we
cover the active skin on steering wheel. So the action of steering wheel
and operation of active skin can interact with each other.
7642-92, Session 12b
Array of lenses with individually tunable
focal-length based on transparent ionimplanted EAP
M. Niklaus, H. R. Shea, Ecole Polytechnique Fédérale de Lausanne
(Switzerland)
We report the fabrication and characterization of 2x2 arrays of mmdiameter lenses, whose top surface is a transparent PDMS EAP
actuator, which, when actuated, allows the focal length to be tuned.
Arrays of lenses with individually tunable focal length are of interest for
laser trapping, beam steering, and imaging. Conventional EAP devices
(carbon electrodes) are not transparent, so the polymer actuator
cannot also be the lens. However electrodes fabricated by low-energy
ion implantation, in addition to allowing conduction at 175% strain
and changing minimally the stiffness of the soft elastomer, are more
than 50% transparent in the visible. We have developed a chip-scale
process to microfabricate arrays of lenses. The array consists of
a water-filled socket, on top of which a Pyrex chip is bonded. The
Pyrex chip has four through-holes, 1 to 3 mm in diameter, on which
a 30 micron thick PDMS (Sylgard 186) layer is bonded. The PDMS
layer is implanted on both sides to pattern the electrodes used for
EAP actuation with 50 μm resolution. Applying a voltage to one of the
lens-actuators leads to an area expansion and hence to a change in
radius of curvature, varying the focal length. The devices work in pairs:
the actuated device has a decreased focal length, while the fluidically
connected un-actuated device has an increased focal length. We report
tuning the focal length from 4 mm to 8 mm at 1.7 kV, and present
changes in optical transmission and membrane stiffness following
gamma and proton irradiation.
7642-95, Session 12b
Multilayered low voltage P(VDF-TrFE)
actuators built on flexible printed circuit
board for microrobot applications
E. N. Edqvist, Uppsala Univ. (Sweden)
A multilayered, low weight resonating locomotion module is presented
and tested as conveyer. The characterized module has four cantilevers,
of which three are used as legs. A lithographically patterned flexible
printed circuit board is used as a substrate on which a structure of
14 layers of spin coated poly(vinylidenefluoride-trifluoroethylene)
with alternating evaporated aluminium electrodes are deposited.
The multilayered electrodes are connected with conductive adhesive
after extensive P(VDF-TrFE) has been removed in an plasma etch. By
bending the three legs 60° out of the plane using a folding equipment
the two dimensional structure is transformed into a three dimensional
structure. Three locomotion modules are characterized by connecting
them with copper wires. Using the three modules in three different
setups the modules are tested with the legs downwards or upside
down against a glass plate. By changing the drive voltage and
frequency the minimum voltage required for motion is investigated.
Successful speed measurements were done already at 1.5 V and the
module was capable of forward, backward, right and left movements.
With wires attached to it, using a 40 V square wave signal at 18020 Hz,
it could move 150 mg, which is more than 37 times it own weight.
7642-93, Session 12b
Biomimetic small scale variable focal length
lens unit using electro-active polymer
actuators
B. Kim, H. L. V. Nguyen, M. Cho, Y. K. Lee, J. Nam, H. R. Choi, H.
Moon, J. C. Koo, Sungkyunkwan Univ. (Korea, Republic of)
Having a combination of a gel-like soft lens, ligaments, and the Ciliary
muscles, the human eyes are effectively working for various focal
lengths without a complicated group of lens. The simple and compact
but effective optical system should deserve numerous attentions from
various technical field especially portable information technology
device industry. Noting the limited physical space of those deivces,
demanding shock durability, and massive volume productivity, the
present paper proposes a biomimetic optical lens unit that is organized
with a circular silicone lens and an annular dielectric polymer actuator.
Unlike the traditional optical lens mechanism that normally acquires a
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Conf. 7643: Active and Passive Smart Structures and Integrated
Systems IV
Monday-Thursday 8-11 March 2010
Part of Proceedings of SPIE Vol. 7643 Active and Passive Smart Structures and Integrated Systems 2010
7643-01, Session 1a
7643-03, Session 1a
Study of a tuned vibration absorber using
piezoelectric patches with active shunt
circuits
Seismic performance of a novel 3D isolation
bearing
J. Jia, Harbin Institute of Technology (China); J. Ou, Harbin Institute
of Technology (China) and Dalian Univ. of Technology (China)
M. Fontaine, M. A. Wickersham, U. A. Korde, South Dakota School
of Mines and Technology (United States)
Tuned vibration absorbers (TVAs) have been extensively used to control
vibrations for almost 100 years. The concept of a TVA is very simple. A
small mass is attached to a parent structure through a spring. The TVA is
tuned to absorb energy and reduce the vibration amplitude at the parent
structure’s resonant frequency. A TVA can be used to damp a single
unwanted resonance or to provide broadband vibration control.
Smart structures represent an opportunity to re-examine TVAs. In this
study, a TVA is constructed from a piezoelectric patch and a shunt
circuit. A negative capacitance shunt can be tuned to dramatically alter
a piezoelectric’s stiffness and shift its resonant frequency. The patch
is harmonically excited at a frequency near a resonant frequency and
the shunt is tuned to match the patch’s impedance in a chosen mode,
shifting its natural frequency to match the forcing frequency while
applying optimal damping. The other modes are observed to determine
if impedance-matching a particular mode at a chosen frequency results
in broadband damping. The piezoelectric structure is also coupled with
a cantilevered aluminum beam. The coupled system is similar to a TVA.
In our investigations, the beam is excited at a resonant frequency and
the shunt circuit tuned to shift one of the patch’s resonances to match
the beam’s. We observe the extent to which energy from the resonating
beam is absorbed by the patch and optimally damped, resulting in
damping for the coupled system.
7643-02, Session 1a
Optimizing switching algorithm of
synchronized switch damping for multimodal
excitation
This abstract is intended to submit to:
Track 3: Passive and Active Vibration Isolation Systems
S. M. Schwarzendahl, X. Han, M. Neubauer, Leibniz Univ. Hannover
(Germany)
7643-04, Session 1a
Shunted piezoceramics can be used to dissipate vibration energy
of a host structure and therefore reduce vibration amplitudes. The
piezoceramic converts a portion of the mechanical energy into electric
energy which is then dissipated in an electric Network. One semi-active
control technique is the synchronized switch damping on inductance
(SSDI), which has a good damping performance and can adapt to a wide
range of excitation frequencies.
In the standard SSDI a switch is closed during maximum deformation for
one half of the electrical period time. This results in an inversion of the
electrical charge. For the rest of the half-period the switch is opened and
the charge remains constant. This results in a nearly rectangular voltage
signal, which is in antiphase with the deformation velocity. In case of
multimodal excitation, more sophisticated switching laws are developed
with aim to extract vibration energy from higher modes (i.e. ‘SSDImax’,
Richard 2009).
This paper describes a novel multimodal switching law for vibration
damping. An observer is designed to obtain an estimation of the first
two vibration modes, which are used to determine the switching times.
In simulations the increase in energy dissipation is evaluated and
compared to the standard SSDI and SSDImax techniques. With the new
switching algorithm an improvement in energy dissipation is observed.
The theoretical results are validated by measurements carried out on
a clamped-free beam. The location of the piezoceramics is chosen to
optimize the electro-mechanical coupling with the first vibration mode
of the beam. The modal observer is realized in a realtime environment.
Measurements show a good agreement with the theoretical results.
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Remarkable vertical seismic ground motions and its effect on many
modern engineering structures were observed in recent severe
earthquake events, but traditional and widely used base isolation
system only can effectively mitigate horizontal seismic responses. A
promising three-dimensional isolation bearing (3DIB), consisting of
laminated rubber bearing with lead core (LRB), combined coned disc
spring and steel damper of rhombic steel plate for vertical added
damping and stiffness (ADAS), was proposed to mitigate horizontal and
vertical structural seismic responses simultaneously and separately.
Validation of energy dissipation capacity was performed by numerical
simulation. The working mechanism and mechanical characteristics of
the novel 3DIB was deduced according to each component. Threegroup seismic ground motion records were selected to validate the
effectiveness of the proposed 3DIB on a continuous slab bridge,
including near-fault seismic records with and without pulse-type
character, and often-used seismic records in many time-history
dynamic analyses. Transient analysis was carried out for the continuous
bridge subjected to these three-group seismic ground motions to
validate the effectiveness of the proposed 3DIB. Numerical simulation
results of the rhombic steel plate revealed that this steel damper can be
dissipated hysteretic energy even in small displacement. The proposed
3DIB is essentially effective to mitigate vertical and horizontal structural
seismic response simultaneously and separately. Near-fault pulse-type
seismic motions maybe impose enormous horizontal displacement on
LRB, which will result in failure of the LRB. Parametric analyses showed
that the proper vertical damping ratio is around 20%. The proposed
3DIB is promising to be applied to industrial facilities and even some
civil engineering structures to actualize three-dimensional isolation.
·
Twist control of airfoils using a ‘reactive’
method
J. Runge, D. R. Osmont, ONERA (France); R. Ohayon,
Conservatoire National des Arts et Métiers (France)
Active twist control of airfoil by means of embedded actuators has
been widely studied during the last decade (N.A.S.A., University of
Maryland, D.L.R., ...) Here, we propose a method which is to our
knowledge new and which make it possible to control the twist
by modifications of the internal structure of the profile inducing
displacement of the shear center and therefore modifications of the
twist moment and torsion angle. This method is only operating if the
profile is submitted to an external force. This is why this method is
called “reactive”. In order to check experimentally the potential of the
proposed system, a first demonstrator has been designed for which
the structural modifications are done by hand. It is a generic cantilever
beam airfoil with span 500 mm, chord 100 mm and thickness 10
mm. The results obtained have shown that for a flexure-torsion load
simulating an aerodynamic force, the twist angle at the free end is:
0.09° when the system control is not active and can vary between the
ranges 0.35° and -0.17° when the system is active. These first results
show the potential of the method proposed. It is possible to induce
variations of the twist angle of the order of the static twist angle. In
order to improve these results and the method, a second structural
demonstrator has been designed making it possible to perform quasi
open loop control. The new results will be presented.
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Conf. 7643: Active and Passive Smart Structures and Integrated
Systems IV
The control strategy proposed proved to be able to handle the
nonlinearity of the actuator and of the power supply and to reject
external disturbances.
7643-05, Session 1b
Optimum design of bridges with
superelastic-friction base isolators against
near-field earthquakes
7643-07, Session 1b
O. E. Ozbulut, S. Hurlebaus, Texas A&M Univ. (United States)
Shape memory alloy post buckled
precompressed (SAPBP) actuator concepts
and theory
The seismic response of a multi-span continuous bridge isolated with
novel superelastic-friction base isolator (S-FBI) is investigated under
near-field earthquakes. The isolation system consists of a flat steelPTFE sliding bearing and a superelastic NiTi shape memory alloy (SMA)
device. Sliding bearings limit the maximum seismic forces transmitted
to the superstructure to a certain value that is a function of friction
coefficient of sliding interface. Superelastic SMA device provides
restoring capability to the isolation system together with additional
damping characteristics. The key design parameters of an S-FBI
system are friction coefficient of the sliding bearings, initial stiffness
and post-yield stiffness of SMA device and yielding displacement of
SMA device. The goal of this study is to obtain optimal values for each
design parameter by performing sensitivity analyses of the isolated
bridge.
R. M. Barrett, T. Sinn, The Univ. of Kansas (United States)
This paper explains a new arrangement of shape memory alloy (SMA)
actuators. SMA actuators are typically used either antagonistically
and/or arranged to move structural components with linearly varying
resistance levels, like springs. This generally means that large
percentages of strain energy are spent doing work on passive structure
(rather than performing the task at hand, like moving a flight control
surface or resisting airloads etc.). Post-Buckled Precompressed (PBP)
actuators on the other hand are arranged so that the active elements
do not waste energy fighting passive structural stiffnesses. Most (if not
all) of the PBP actuators of the past have used piezoceramic elements
and are highly prone to tensile failure on convex faces. Because SMA
actuators are far more tolerant of tensile stresses than piezoceramics,
a switch of actuator type is a natural progression of technology.
The paper opens with a short survey on the history of PBP beams
and plates. The paper then delves into actuation theory and gives a
detailed explanation of the experimental set up. A 6” x 10” test article
composed of a glass fiber/ steel composite sheet with SMA wires on
top and bottom was used to prove the concept. Substantial deflection
and moment generation capabilities were recorded over similarly sized
piezoelectrically actuated PBP plates. The paper shows tip rotations
on the order of 45° which is nearly triple the levels achieved by
piezoelectric PBP actuators. The paper concludes with a discussion of
both PBP-controlled and snap-thru dynamics as well as an assessment
of future applications.
First, a three-span continuous bridge is modeled as a two-degrees-offreedom with S-FBI system. A neuro-fuzzy model is used to capture
rate-dependent nonlinear behavior of SMA device. A time-dependent
method which employs wavelets to adjust accelerograms to match
a target response spectrum with minimum changes on the other
characteristics of ground motions is used to generate ground motions
used in simulations. Then, a set of nonlinear time history analyses of
the isolated bridge is performed. The variation of the peak response
quantities of the isolated bridge is shown as a function of design
parameters. The results show that the optimum design of the isolated
bridge with S-FBI system can be achieved by a judicious specification
of design parameters.
TRACK 5
7643-06, Session 1b
7643-08, Session 1b
Laguerre model based adaptive control of
antagonistic shape memory alloy (SMA)
actuator
Compressive and tensile deformation
behaviors of a Ti-Mo based shape memory
alloy
S. Kannan, Univ. Metz (France) and Arts et Metiers ParisTech-Metz
(France); C. Giraud-Audine, Univ. Metz (France) and Arts et Metiers
ParisTech -Metz (France); E. Patoor, Univ. Metz (France) and Arts et
Metiers ParisTech-Metz (France)
C. Xie, J. Song, X. Zhang, W. Zhou, Shanghai Jiao Tong Univ.
(China); M. H. Wu, Edwards Lifesciences LLC (United States)
Ni- free shape memory alloys are promising functional materials
for medical applications. A newly developed Ti-Mo based shape
memory alloy shows superelaticity after thermomechanical
treatment. However,the microstural evolution and precipitation
during thermomechanical processes are still not well understood. In
the present paper, compressive deformation behavior at a series of
temperatures of 298K - 973K and tensile deformation behavior of the
alloy after aging at 523K - 973K have been investigated systematically.
It is found that the compressive yield stress and ultimate compressive
strength change with the deformation temperature in thress stages.
The ultimate tensile strength and yield stress of aged samples also
change with the aging temperature following a non-linear relationship.
Microstructures of aged samples as well as effects of lattice softening
and aging-induced precipitates on the deformation behavior have been
investigated and discussed.
In this article Model Predictive Adaptive Control based on a Laguerre
parametrization is successfully tested on an Antagonistic Shape
Memory Alloy (SMA) actuator.
A usual way to handle the hysteresis is to use a phenomenological or
a constitutive model. However, the identification of parameters of the
material is a task difficult to realize online due to the nonlinearities of
such model.
To adress this problem, an alternative method based on a modified
Series-Parallel Model Reference Adaptive Control is used here. It relies
on a black box model using a linear parametrization of a Laguerre
filters, and the only measurement is the displacement of the actuator. A
Recursive Least Square (RLS) algorithm is used to identify the weights
of the filter that minimize the error between output of the closed loop
control system and the linear Laguerre filter (parallel adjustable system).
Using the certainty equivalence principle, a predictive controller gain is
tuned online (series adjustable system).
7643-125, Session 1b
The experimental setup used is a linear antagonistic SMA actuator
consisting of two prestressed NiTiNol wires moving a payload. Power
is supplied using two voltage amplifiers. The algorithms for online
identification and control were implemented using a dSPACE-1104
interface board.
Modeling and optimization of shape
memory-superelastic antagonistic beam
assembly
With appropriate tuning parameters the adaptive controller can track
different kinds of reference signals. Thermal disturbances added to the
either one of the SMA wires are correctly rejected.
30
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M. Tabesh, M. H. Elahinia, The Univ. of Toledo (United States)
NiTi shape memory alloys (SMA) are the most commonly studied and
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Conf. 7643: Active and Passive Smart Structures and Integrated
Systems IV
Further investigation has determined the input waveform of a person
walking at a range of speeds, whilst wearing a load carrying garment
intended for the inclusion of a piezoelectric transducer. This garment
was loaded with mass equivalent to that expected in normal usage.
The garment was modified by the inclusion of a load cell within one
of the supporting straps, which was sampled, and the resulting load
waveform stored and plotted. The waveform was then used as an input
for further testing of a PVDF film sample, with the goal of determining
the long term performance of the material. A film was tested on a large
electromagnetic actuator, especially designed and built for the purpose
of testing flexible transducer materials. In particular, the performance of
a film sample has been studied, indicating that degradation of electrical
energy output occurs with an increasing number of mechanical (stress)
cycles.
implemented SMAs. They gained researchers’ attention due to their
special properties of shape memory (SM) and superelasticity (SE). In
addition, the material is biocompatible (with mechanical properties
more comparable to bone than Ti-based compounds or Stainless
steel) and has a good resistance to wear and corrosion. The shape
memory effect is the recovery of large strains (up to 8%) created in the
material while in low temperature by raising the temperature to above
a specific level. That specific temperature (called Austenite finish Af)
can be manipulated via changing the composition of the material or
thermo-mechanical treatment to get a value around body temperature.
Superelasticity (SE), shape memory effects (SM), high damping
capacity, corrosion resistance and biocompatibility, are properties of
NiTi that makes the alloy ideal for biomedical devices
NiTi is used in orthopedic implants as compression staples/clamps
for the treatment of bone fracture and anterior fusion of the spine. It is
also employed in intramedullary nails that are used to apply controlled
force to the bone. Application of NiTi infixation bone plates or rod for
the treatment of scoliosis as well as all the aforementioned cases are
nowadays common.
7643-11, Session 2a
Novel two-stage piezoelectric-based
electrical energy generators for low and
variable speed rotary machinery
The development phase for such applications requires primary
modeling and simulation considering NiTi’s complicated
thermomechanical behavior. There are many models that can capture
the performance of shape memory alloys; among them the Tanaka
model (later extended by Brinson) was utilized in this study to
simulate the behavior of SMA; namely the shape memory effect and
superelasticity. In this work, the 1D model developed by Brinson was
modified to capture the shape memory effect, superelasticity and
hysteresis behavior, as well as partial transformation in both positive
and negative directions. This model was combined with the Euler
beam equation which, by approximation, considers 1D compression
and tension stress-strain relationships in different layers of a 3D beam
assembly cross-section.
R. T. Murray, J. S. Rastegar, Omnitek Partners, LLC (United States)
A novel class of two-stage piezoelectric-based electrical energy
generators is presented for rotary machinery in which the input speed
is low and varies significantly, even reversing. Applications include
wind mills, turbo-machinery for harvesting tidal flows, etc. Current
technology using magnet-and-coil rotary generators require gearing
or similar mechanisms to increase the input speed and make the
generation cycle efficient. Variable speed-control mechanisms are
also usually needed to achieve high mechanical to electrical energy
conversion efficiency.
The algorithm utilizes an iterative method to decide whether the
state of the material at every node is in linear elastic mode, i.e. pre or
post transformation, or in transformation mode to use cosine-form
transformation equations. The algorithm finally solves for the deflection
of an SMA beam.
Presented here are generators that do not require gearing or speed
control mechanisms, significantly reducing complexity and cost,
especially pertaining to maintenance and service. Additionally, these
new generators can expand the application of energy harvesting to
much slower input speeds than current technology allows.
a Shape memory-superelastic NiTi antagonistic beam assembly can be
used for enhancing the performance of pedicle screws in osteoporotic
bones. A pedicle screw is a particular type of bone screw designed
for implantation into a vertebral pedicle. The pedicle screw, which is
sometimes used as an adjunct to spinal fusion surgery, provides a
means of gripping a spinal segment. The major drawback of spinal
surgical treatment with pedicle screws is the lack of strength in
degraded osteoporotic bone. The antagonistic assembly consists of a
superelastic NiTi (with lower Af temperature) tubular beam and a shape
memory NiTi (with higher Af temperature) circular wire that serves as a
strength enhancement attachment for pedicle screws.
The primary novelty of this technology is the two-stage harvesting
system. The harvesting environment (e.g. wind) provides input to the
primary system, which is then used to successively excite a secondary
system of vibratory elements into resonance - like strumming a guitar.
The key advantage is that by having two decoupled systems, the
low-and-varying-speed input can be converted into constant and
much higher frequency vibrations. Energy is then harvested from the
secondary system’s vibrating elements with high efficiency using
piezoelectric elements or magnet-and-coil generators. These new
generators are uncomplicated, and can efficiently operate at widely
varying and even reversing input speeds.
Proper functionality of this application necessitates an optimization
routine to be performed so that the optimum configuration in terms
of several variables forming the assembly such as geometry and
dimensions can be defined. For the purpose of this study, an objective
design is pursued aiming at optimizing the dimensions and initial
configuration of the SMA wire-tubing assembly.
Conceptual designs are presented for a number of generators and
subsystems (e.g. for passing mechanical energy from the primary to
the secondary system). Additionally, analysis of a complete two-stage
energy harvesting system is discussed with predictions of performance
and efficiency.
This paper is being submitted for SSN03, Track 1: Energy Harvesting
Technologies
7643-09, Session 2a
Long term transducer performance for
human motion energy harvesting
7643-12, Session 2a
Energy-harvesting power sources for veryhigh-G gun-fired munitions
S. Behrens, S. A. McGarry, Commonwealth Scientific and Industrial
Research Organisation (Australia)
J. S. Rastegar, R. T. Murray, Omnitek Partners, LLC (United
States); C. M. Pereira, H. Nguyen, U.S. Army Armament Research,
Development and Engineering Ctr. (United States)
The use of a metallised PVDF film as a transducer for human motion
energy harvesting has been investigated. A transducer can be
placed between a load and the wearer of the load, to be activated
by differential movement between the two, as the wearer walks or
performs other duties. From preliminary testing of the film in tension,
the electrical energy outputs of the PVDF due to a range of sine
waveform mechanical load cases and frequencies, as well as electrical
parameters, was determined. This work was performed with the goal
of maximising output efficiency. Experimentation was conducted on
especially constructed laboratory hardware.
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Several novel classes of piezoelectric-based energy-harvesting power
sources are presented for very high-G gun-fired munitions (40,000 240,000 Gs). The power sources are designed to harvest energy from
the firing acceleration and in certain applications also from in-flight
vibrations. The harvested energy is converted to electrical energy for
powering onboard electronics, and can provide enough energy to
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31
Conf. 7643: Active and Passive Smart Structures and Integrated
Systems IV
materials, exhibiting unique thermo-mechanical behaviors, such as
shape memory effect and superelasticity, which enable their great
potentials in seismic engineering as energy dissipation devices. This
paper presents a study of the mechanical behaviors of superelastic
SMAs, specially emphasizing on the influence of strain rate under
various strain amplitudes. Cyclic tensile tests on superelastic NiTi
SMA wires with different diameters under quasi-static and dynamic
loadings were carried out to assess their dynamic behaviors. An
internal temperature variable which indicates the influence of loading
frequency under various strain amplitudes and different temperatures
was introduced to the Liang’s constitutive equation of SMA. Numerical
simulation results based on the proposed constitutive equations
and experimental results are in good agreement. The findings in this
paper will assist the future design of superelatic SMA-based energy
dissipation devices for seismic protection of structures.
eliminate the need for batteries in applications such as fuzing.
During the munitions firing, a spring-mass system undergoes
deformation, thereby storing mechanical potential energy in the elastic
element. After release, the spring-mass system is free to vibrate and
energy is harvested using piezoelectric materials. Two distinct classes
of systems are presented: First are systems where the spring-mass
elements are loaded and released directly by the firing acceleration.
Second are those which use intermediate mechanisms reacting to the
firing acceleration to load and release the spring-mass system.
Description and evaluation of various methods for loading and
releasing the spring-mass system in the high-impact environment, as
well as packaging for very-high-G survivability are discussed at length.
Also included are methods for using the devices as hybrid generatorsensors, how the devices intrinsically provide augmented safety, and
methods to increase the efficiency of such power sources for very
high-G applications.
Examples of a number of prototypes for complete high-G energy
harvesting systems are presented. These power sources have been
designed using extensive modeling, finite element analysis, and model
validation testing. The results of laboratory, air-gun and firing tests are
also presented.
7643-15, Session 2b
Shape memory effect and mechanical
properties of short fiber reinforced SMP
composite
This paper is being submitted for SSN03, Track 1: Energy Harvesting
Technologies
K. Yu, Y. Liu, J. Leng, Harbin Institute of Technology (China)
By adding random distributed short fiber into a shape memory polymer
(SMP) matrix, both the mechanical properties and the shape memory
behavior are improved significantly, overcoming the traditional defects
of SMP composite reinforced by long fiber and particles. In this paper,
the short fibers reinforced SMP were developed for the improvement of
the mechanical and thermal properties of styrene-based SMP bulk. The
specimens with different chopped fiber weight fractions were prepared,
and then their mechanical behavior and shape memory effect were
investigated. As a result, the resistance against mechanical and thermal
mechanical loads in the developed materials increased due to the role
of reinforcement fiber. For composite filled with short carbon fiber, not
only the actuation of SMP composite can be driven by low voltage, but
also its tensile, bending strength, glass transition temperature storage
modulus and thermal conductivity increased by a factor of filler content
of carbon fiber increased. The results show meaningful guidance for
further design and the performance evaluation of such composite
materials.
7643-13, Session 2a
Strength analysis of piezoceramic materials
for structural considerations in energy
harvesting for UAVs
S. R. Anton, A. Erturk, D. J. Inman, Virginia Polytechnic Institute
and State Univ. (United States)
The concept of energy harvesting in unmanned aerial vehicles (UAVs)
has received much attention in recent years. Piezoceramic patches
attached to the wings of an aircraft can be used to convert naturally
occurring wing vibrations into usable electrical energy. In an effort
to improve the efficiency of vibration energy harvesting systems, a
multifunctional approach to harvesting has recently been proposed by
the authors where a single device, known as a self-charging structure,
is capable of harvesting energy, storing that energy, and carrying
structural load. Self-charging structures consist of piezoceramic layers
for energy generation, thin-film battery layers for energy storage, and
a central substrate layer. In UAV applications, a critical element of the
self-charging structure concept is the ability of the device, particularly
the piezoceramic elements, to support aerodynamic loads. Bending
strengths of various piezoceramic materials, however, are not well
documented in the literature. The second part of this work presents
an experimental investigation of the bending strengths of several
monolithic piezoceramic materials including PZT-5A and PZT-5H,
commercially packaged devices using PZT-5A such as QuickPack and
Macro-Fiber Composite (MFC) piezoelectrics, as well as PMN-PT and
PMN-PZT single crystal piezoelectrics. A standard three-point bending
test is used to quantify the bending strength of each type of material
tested. Results of the testing are reported and can be used as a design
tool in the development of vibration energy harvesting systems in which
the active device is subject to bending loads.
7643-16, Session 2b
Experimental investigation of active rib
stitch knitted architecture for flow control
applications
B. Pascoe, J. M. Abel, J. E. Luntz, D. E. Brei, Univ. of Michigan
(United States)
For many years research has been conducted to investigate the
potential for actively controlling flow patterns around aircraft wings
mid-flight to optimize aerodynamic performance. By delaying
or preventing separation of the boundary layer around the wing,
improvements in air flow can be achieved which can enhance highlift capability, reduce drag, and increase maneuvering performance,
allowing for increased fuel economy and operation over diverse flight
conditions resulting in the ability to complete longer, more difficult
missions. Several methods of active flow control during transonic flight
have been investigated with great promise including synthetic jets and
micro flaps. Surface texturing, however, is an alternative method that
has the potential to provide a varied surface profile while maintaining
a continuous, smooth aerodynamic structure. The creation of contour
bumps has been computationally shown to reduce drag in transonic
flight by 24% under certain flight conditions but actively varying the
bump height mid-flight and creating longer gradual bumps have posed
technical difficulties. Active knits, which are a novel class of cellular
structural smart material actuator architectures created by continuous,
interlocked loops of stranded active material, are one unique approach
to provide this active surface texturing. All active knit stitch patterns
are created by a specific array of two basic loop structures - knit loops
7643-14, Session 2b
A one-dimensional rate-dependent
constitutive model for superelastic shape
memory alloys
H. Qian, Zhengzhou Univ. (China); H. Li, Dalian Univ. of Technology
(China); G. Song, Univ. of Houston (United States); H. Chen,
Zhengzhou Univ. (China); R. Wen, Hebei Univ. of Technology
(China)
Shape memory alloys (SMAs) are a relatively new class of functional
32
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and purl loops. One stitch pattern that displays potential to realize
flow control applications, among other applications requiring actuation
normal to a surface is the rib stitch. This stitch can be used to create
the necessary spanwise discrete periodic arrays for flow control
across the wing provided it can withstand aerodynamic forces while
supplying adequate actuation displacement for flow control. This paper
presents a preliminary experimental investigation into the potential
of using shape memory alloy (SMA) wire in a rib stitch knit textile for
actuation normal to a surface by examining the force-displacement
capabilities of the textile. A SMA rib stitch prototype was created and
tested to determine the performance and the pre-loaded single stroke
deployed actuation capability. Both experimental tests demonstrated
promising results, providing practical displacements under large
surface pressures comparable to normal-cruise aerodynamic wing
loads. The rib stitch active knit architecture may also be able to actuate
against higher surface pressures such as those required for flow control
as well as the increased wing loading incurred during takeoff, landing,
and other flight maneuvers through optimization of material (SMA or
another smart material), geometric (SMA wire diameter, course height,
wale width, number of courses, and number of wales) and architectural
(number of wales per rib) design parameters. Although this preliminary
experimental investigation looks at just one possible configuration
of design parameters, it demonstrates the ability to create novel,
three-dimensional, distributed actuation capable of providing surface
texturing under loads similar to aerodynamic forces at typical normalcruise conditions.
7643-18, Session 2b
Development, assembly, and validation of
an SMA-actuated two-joint nozzle and sixchannel power supply for use in a smart
inhaler system
S. J. Furst, R. Hangekar, S. S. Seelecke, North Carolina State Univ.
(United States)
The smart inhaler design concept recently developed at NC State
University has the potential to target the delivery of inhaled aerosol
medication to specified locations within the lung system. This targeted
delivery could help patients with pulmonary ailments by reducing the
exposure of healthy lung tissue to potentially harmful medications.
However, controlled delivery can only be accomplished if medication
is injected at a precise location in an inhaled stream of properly
conditioned laminar flow. In particular, the medication must be injected
into the inhaled flow using a small nozzle that can be positioned
without disturbing the flow. This paper outlines the procedure used to
assemble and control a key component of the smart inhaler: a shape
memory alloy (SMA) based dual-joint flexible nozzle that exploits the
sensing and actuating capabilities of thermally activated SMA wires.
A novel 6-channel power-supply is used to control input power and
measure the resistance across the SMA. Since a practical fabrication
process may result in SMA wires with different contact resistances, the
power supply employs an initialization procedure to self-calibrate and
provide normalized power distribution 6 SMA wires simultaneously.
Furthermore, a robust control scheme is used to ensure that a constant
current is provided to the wires. In validation tests, a LabVIEW-based
video positioning system was used to measure the deflection of the
nozzle tip and joint rotation. Results show that the carefully controlled
assembly of a stream-lined nozzle can produce a practical smart
structure, and joint rotation is predictable and repeatable when power
input is also controlled. Future work will assess the use of the SMAresistance measurement as position feedback and PID position control
power as a measurement of the convective cooling that results from
the moving airflow.
7643-17, Session 2b
Ferromagnetic shape memory flapper
Y. Ganor, Univ. of Minnesota (United States); O. Kanner, D. Shilo,
Technion-Israel Institute of Technology (Israel); R. D. James, Univ.
of Minnesota (United States)
Flapping mechanisms that generate propulsion for swimming and flying
are abundant in nature. One way of obtaining motion is by a transverse
movement of surfaces in media which forms lateral thrust, thus
propelling the body. Of a great interest are systems that can produce
propulsion at scales of millimeter down to a micron, or perhaps
smaller. Possible candidates for those tasks are active materials. These
materials are commonly applied as actuation devices in Micro Electro
Mechanical Systems (MEMS).
7643-19, Session 3a
Impedance matching for improving
piezoelectric energy harvesting systems
Among active materials, shape memory alloys offer the largest work
output per cycle accompanied by huge strains. Temperature change
induces a structural transformation from austenitic to martensitic
phase, thus producing large strains. These materials are attractive for
MEMS applications, but for the problem of small-scale autonomous
motion, the difficulty of supplying temperature pulses to a moving
vehicle seems hard to overcome. Moreover, the ability to generate
high gradients of temperature for this motion is limited by the heat
conduction of the alloy and its surroundings.
J. Liang, W. Liao, The Chinese Univ. of Hong Kong (Hong Kong,
China)
In a piezoelectric energy harvesting system, the dynamic behavior of
the mechanical structure as well as the energy flow within the system
vary with different harvesting interface circuits connected. Meanwhile,
the impedance matching is regarded as theoretical base for harvesting
efficiency en-hancement, and hopefully could provide guidance
for harvesting interface optimization. Most pre-vious literatures on
impedance matching for piezoelectric energy harvesting started their
analyses by assuming that harvesting interfaces, which are nonlinear
in nature, can be equalized to linear loads, and the load impedance
can be arbitrarily set, so that the output impedance of the piezoelectric
structure can surely be matched. Yet, after investigating the equivalent
impedances of the current existing harvesting interfaces, including
standard energy harvesting (SEH), parallel synchronized switching
harvesting on inductor (p-SSHI), and series synchronized switching
harvesting on inductor (s-SSHI), we found that, their ranges are in fact
limited. Therefore, to optimize the harvesting efficiency, constrained
matching instead of free matching should be adopted. In addition, we
also point out that previous literatures have been confusing for the
purpose of matching for energy harvesting. With the understanding on
energy flow within piezoelectric devices, we know that only a portion
of the extracted energy is able to be harvested, while the other is
dissipated throughout the harvesting process. So even the energy
extracted from the source is maximized by matching the impedance;
there is no guarantee that harvesting efficiency is surely improved. The
harvesting efficiency also depends on the ratio between harvested
energy and dissipated energy. These two issues discussed in this
In recent years, a sub class of shape memory alloys known as
ferromagnetic shape-memory (FSM) alloys has received much attention
because they can provide large strains and have fast responses to
external magnetic fields. Unlike temperature controlled shape memory
actuation, the ferromagnetic shape memory actuation can also be
induced by fast rearrangement of twin variants of the martensite. By
applying a magnetic field to the martensitic state, they can be made to
undergo large deformations, comparable to that produced by the best
shape memory materials.
A new method for propulsion using a Ni2MnGa ferromagnetic shape
memory flapper is introduced. We examine the magnetic field induced
strain of pure shear by means of a state of the art generator that
provides alternating magnetic fields of 7000Oe at frequencies of up to
100Hz. Preliminary measurements show shear deformation of about
5% and thrust forces in the mN range, which open new frontiers in
propulsion mechanisms.
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output is calculated for a mechanically excited system including an
equivalent electrical load (complex, linear impedance). To compute the
results harmonic analyses are preformed where harmonic excitation
and harmonic response are assumed. This type of analysis is used to
calculate the frequency response of the generator for different loads
and excitation parameters.
article paper are crucial. Without these considerationsing these, the
impedance matching method would beis far from ready to be applied
to improve the harvesting efficiency.
7643-20, Session 3a
To validate the finite element results the generators have been
manufactured and characterized experimentally. Analog to the
calculations the frequency response has been measured for various
loads. Further the vibration shape has been recorded using a scanning
laser vibrometer.
Broadband pipeline vibration energy
harvesting
A. M. Baz, Univ. of Maryland, College Park (United States); M. H.
Arafa, The American Univ. in Cairo (Egypt); W. N. Akl, Nile Univ.
(Egypt); K. Al-Hussain, Saudi Aramco (Saudi Arabia)
The experimental and theoretical results are discussed in detail
especially regarding the utilization of the proposed shapes for
broadband energy harvesting demands.
The quest to harvest energy from ambient vibration has received
considerable attention in recent years since sources of mechanical
vibration are abundant in many environments. Of particular interest
to the oil and gas industry is the use of pipeline vibrations to provide
renewable power to various remote electronic sensors that are
mounted on a pipeline for the purpose of structural health monitoring.
While a wealth of research has been focused on scavenging vibration
that is predominantly harmonic, less emphasis was granted to
applications where the vibration is broadband by nature, as in the case
at hand.
7643-22, Session 3a
Piezoelectric energy harvesting from flow
excitation: modeling and experiment
A. Erturk, Virginia Polytechnic Institute and State Univ. (United
States); W. G. R. Vieira, C. De Marqui, Jr., Univ. de São Paulo
(Brazil); D. J. Inman, Virginia Polytechnic Institute and State Univ.
(United States)
Pipelines conveying gas under pressure exhibit turbulence-induced
vibrations. The current work is concerned with extracting useful power
from pipelines operating well within their elastic stability region. Under
such conditions, the pipeline vibrations exist in small magnitudes and
are unlikely to cause structural failure, yet can be exploited to provide
useful energy for low-power electronic devices. Accordingly, emphasis
in the present work is placed on the development of an energy
harvesting technique employing the omnipresent and inevitable flowinduced vibrations in gas pipelines. To this end, the turbulence-induced
loads and ensuing structural response are estimated using Large Eddy
Simulation (LES) analysis, in conjunction with a finite element model
of the pipe under investigation. A piezoelectric resonator, tuned at one
of the structural vibration modes, was shown to be an efficient energy
harvesting platform. Simplified electrical circuits were employed for
signal conditioning to transform the piezoelectric output signals into a
more usable form. The phenomenon was simulated experientially on a
PVC pipe conveying compressed air that is regulated by an air blower.
The findings of the experiments are also confirmed by numerical
modeling to illustrate the viability of the proposed design.
Among the alternative transduction mechanisms for vibration-toelectric energy conversion, piezoelectric transduction has received
the most attention over the last decade. Typically, cantilevers with
piezoceramics are used as piezoelectric energy harvesters and the
source of excitation is assumed to be harmonic base motion [1,2].
Utilization of flow excitation has been mainly investigated by means
of windmill-type conventional devices, which cannot be embedded
into several engineering structures, such as aircraft wings. This paper
presents lumped-parameter and distributed-parameter piezo-aeroelastic models for energy harvesting from unsteady aerodynamic loads
due to flow excitation. Model predictions are compared against the
experimental results for the flutter case.
Energy harvesting from flow excitation and aeroelastic vibrations have
been investigated by a few authors. Power generation from vortex
excitation of a piezoelectric membrane behind a bluff body was
investigated by Allen and Smits [3] experimentally. A theoretical work
simulating energy harvesting from aeroelastic vibrations of a typical
section was presented by Bryant and Garcia [4]. A finite element piezoaero-elastic model was given by De Marqui et al [5] with simulation
results for energy harvesting from a generator wing. A complete work
covering both the theory and experiment for energy harvesting from
aeroelastic vibrations has not appeared in the literature. This paper
aims to provide both lumped-parameter and distributed-parameter
piezo-aero-elastic energy harvester models for power generation
from flow excitation. Experimental results are presented for model
verification.
7643-21, Session 3a
A novel approach for a piezoelectric
broadband vibration energy harvesting
generator
J. Twiefel, J. Wallaschek, Leibniz Univ. Hannover (Germany); S.
Priya, V. Bedekar, Virginia Polytechnic Institute and State Univ.
(United States)
Figure 1a shows a schematic of the well-known typical section under
flow excitation [6]. The governing equations of this system with
piezoelectric coupling can be given by where the mechanical degrees
of freedom are the pitch ( ) and plunge (h) displacements and the
aeroelastic loads (L and M) are obtained from the Theodorsen model
[7]. For the maximum electrical energy generation, the flutter case is
considered, which agrees with the harmonic motion assumption of the
unsteady aerodynamic model considered here.
In this study we report H-Shape and Y-Shape piezoelectric transducer
structures for harvesting the vibration energy over a broad frequency
range. The mechanism for broad band is based upon merging the
multiple vibration modes together by exciting complex shapes. The
design of H-shape transducer was inspired by tuning fork resonators
which are known to posses four distinct modes in close vicinity to each
other. Experimental and theoretical results are presented on preliminary
transducer design; analyzing their performance in terms of output
power and bandwidth (frequency range over which power reduces by
half).
Figure 1b displays the experimental setup representing a typical wing
section in front of a blower. This setup is used for verification of the
lumped-parameter piezo-aero-elastic model.
Figure 1. (a) Typical wing section with pitch and plunge degrees of
freedom and (b) the experimental setup representing a typical section
under flow excitation
The shape of the generators reminds in top view to the letters H and Y
respectively. In thickness direction they have a bimorph like structure
with a thin metal layer and a top and bottom piezoelectric layer, poled
in opposite direction. The electrodes cover the complete top and
bottom side. Both generators are mounted vertically in the center to
harvest primarily energy from vertical, vibrations.
Distributed-parameter modeling of a cantilever with piezoceramics
under flow excitation will also be given along with the experimental
results. An electromechanical bending-torsion formulation is employed
based on the thin beam theory by taking the aerodynamic loads from
the Theodorsen model [7].
Due to the complex shape, the systems behavior is investigated
theoretically by means of FEM (Ansys) Simulations; the electrical power
34
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flow excitation
References
piezoelectric patch pairs. These patches will be shunted with varying
selected impedances to allow for comparison of control ability. This
comparison includes an analysis of spatial RMS velocity, traveling
waveform shape, and wave power reduction through the patch array.
[1] Erturk, A., Hoffmann, J., and Inman, D.J., 2009, A
Piezomagnetoelastic Structure for Broadband Vibration Energy
Harvesting, Applied Physics Letters, 94, 254102 (3pp).
7643-26, Session 3b
Track 1: Energy Harvesting and Scavenging
[2] Erturk, A. and Inman, D.J., 2009, An Experimentally Validated
Bimorph Cantilever Model for Piezoelectric Energy Harvesting from
Base Excitations, Smart Materials and Structures, 18, 025009 (18pp).
[3] Allen J.J. and Smits A. J., 2001, Energy Harvesting EEL, Journal of
Fluid and Structures, 15, pp.1-12.
Active vibration control with optimized
modified acceleration feedback equipped
with adaptive line enhancer
[4] Bryant, M. and Garcia E., Development of an Aeroelastic Vibration
Power Harvester, Proceedings of SPIE 2009, 728812-1.
S. N. Mahmoodi, M. J. Craft, M. Ahmadian, Virginia Polytechnic
Institute and State Univ. (United States)
[5] De Marqui, Jr., C., Erturk, A., and Inman, D.J., 2009, PiezoAero-Elastically Coupled Modeling and Analysis of Electrical Power
Generation and Shunt Damping for a Cantilever Plate, Proceedings of
the 17th International Conference on Composite Materials, Edinburgh,
UK, 27-31 July.
The modified acceleration feedback (MAF) controller, an active vibration
control method that uses collocated piezoelectric actuator actuators
and sensors, is developed using an optimal controller. The control
mechanism consists of two main parts: 1) Frequency adaptation
mechanism that uses Adaptive Line Enhancer (ALE), and 2) optimal
controller. Frequency adaptation only tracks the frequency of vibrations
using ALE. The obtained frequency is then fed to MPPF compensators
and the optimal controller. This provides a unique feature for MAF, by
extending its domain of capabilities from controlling tonal vibrations to
broad band disturbances. The optimal controller mechanism consists
of a set of optimal gains for wide range of frequencies that is provided
based n the characteristics of the system. Based on the tracked
frequency, the optimal control system decides to use which set of
gains for the MAF controller. The gains are optimal for the frequencies
close to the tracked frequency. The numerical results show that the
frequency tracking method that is derived has worked quite well. In
addition, the frequency tracking is fast enough to be used in real-time
controller. The results also indicate that the MAF can provide significant
vibration reduction using the optimal controller.
[6] Hodges, D. H., and Pierce, G. A., 2002, Introduction to Structural
Dynamics and Aeroelasticity, Cambridge, Cambridge University Press.
[7] Theodorsen, T., 1934, General theory of aerodynamic instability and
the mechanism of flutter, NACA TR 496.
7643-23, Session 3a
Power-amplifying strategy in vibrationpowered energy harvesters
P. S. Ma, J. E. Kim, Y. Y. Kim, Seoul National Univ. (Korea, Republic
of)
A new cantilevered piezoelectric energy harvester of which the lumped
mass is connected to a harmonically oscillating base through an elastic
foundation is proposed for maximizing generated power and enlarging
its frequency bandwidth. The base motion is assumed to provide a
given acceleration level. Earlier, a similar energy harvester simulating
a dynamic vibration absorber was developed but the mechanism of
the present energy harvester is new because it incorporates a massspring system in addition to a conventional cantilevered piezoelectric
energy harvesting beam. Consequently, the proposed energy harvester
actually forms a two-degree-of-freedom system. After presenting
an overall mechanism of the developed energy harvester, it will be
theoretically shown that the output power can be indeed substantially
improved if the fundamental resonant frequencies of each of the two
systems in the proposed energy harvester are simultaneously tuned
as closely as possible to the input excitation frequency and also if the
mass ratio of a piezoelectric energy harvesting beam to a lumped mass
is adjusted below a certain value. The performance of the proposed
energy harvester will be first checked by numerical simulation using
ANSYS and then verified through several numerical experiments. It will
be also shown that the trade-off between the output power and the
output frequency bandwidth can be made by adjusting the mass ratio.
7643-27, Session 3b
Numerical and experimental investigation
for centrifugal loading effect on shunted
piezoelectric damping
J. B. Min, NASA Glenn Research Ctr. (United States)
Newer high-performance turbomachinery blade designs have
led to decreased blade damping and higher vibratory stresses.
Designing damping treatments for rotating blades in an extreme
engine environment is difficult. Several damping methods have
been investigated at NASA Glenn Research Center for use in aircraft
engines, including viscoelastic damping, impact damping, plasma
sprayed damping coatings, and high-damping high-temperature shape
memory alloy materials. The current effort seeks to investigate the
ability of shunted piezoelectric materials to damp vibrations of rotating
turbomachinery blades. While ample research has been performed on
the shunted piezoelectric material to control the structural vibration
damping, very little study has been done for rotational and temperature
effects. Experimental test and analysis are performed for both nonspinning and under centrifugal loading with the plate speciemens. The
finite element (FE) simulations are also performed using the ANSYS
Multiphysics code which can supports piezoelectric coupled-field
elements and electric circuit elements used for the resistor-inductor
circuit simulations. Passive and active resonant damping control test
results show that shunted piezoelectric damping control techniques
obtained in this study have a great potential to be able to reduce plate
vibrations under centrifugal loading at room temperature and under
vacuum conditions. The FE results also show a good correlation with
experimental test results. The validated numerical models and the
experimental test results obtained from this study will allow us to
extend our current effort for design and optimization of more complex
turbomachinery rotor blade systems.
7643-25, Session 3b
Periodic piezoelectric sensor-actuator array
for vibration suppression on a beam
B. S. Beck, K. A. Cunefare, Georgia Institute of Technology (United
States)
The use of piezoelectric patches for actuation as a vibration
control method has been widely investigated. Some of the uses for
piezoelectric actuators include velocity feedback, synthetic impedance
control, as well as a shunted sensor-actuator. Likewise, periodic
structures have been shown to be effective in allowing the dissipation
of traveling wave energy. The combination of these control procedures,
an active periodic piezoelectric array, allows for enhanced vibration
control. Presented here is the investigation of thin beam with 16
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Conf. 7643: Active and Passive Smart Structures and Integrated
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changing the distance between the outer magnets as the suspension
is dependant on this. These attributes will be discussed in detail in the
paper.
7643-28, Session 3b
Multimodal vibration control of a flexible
beam and plate using multilayered
piezoelectric film sensor/actuator
The paper will also detail the developed non-linear model of the system
and will compare results with measurements from the prototype.
Derivations of other parameters such as the systems mechanical
damping and electromagnetic coupling coefficient will also be
described. The paper will also compare the magnetically suspended
device’s performance against other vibration harvesting devices
reported in the literature using figure of merits such as power density
and system effectiveness.
T. Nishigaki, Kinki Univ. (Japan)
In the authors’ previous reports, it was shown that piezoelectric films
were able to be used as sensors and as actuators simultaneously for
free or forced vibration control of flexible thin structure without affecting
total weights and motion characteristics of the structures. In these
methods, piezoelectric film sensor and actuator were shaped using
the equivalent shaping functions and were collocated bonded on the
surfaces of the beam, the ring and the plate. Direct velocity feedback
control was successfully applied to increase damping effects to the
first vibrational mode. However, multimodal active vibration control
experiments using these high-polymer piezoelectric films were difficult
in several reasons. Included in these difficulties were the unstable
vibrations due to the electromagnetic interactions between the sensor
and the actuator, and the phase lag included in the transfer functions
of the controller in high frequency area. In order to overcome these
difficulties, it was proposed in this paper to shape piezoelectric sensor
and actuator using different shaping functions. At first, fundamental
equations were derived and vibration responses of the structure were
derived based on the modal coordinate systems. Then, it was shown
that by considering phase characteristics of the velocity feedback
controller in conjunctions with the polarity of the piezo films in higher
order modal frequencies, multimodal control will be implemented both
theoretically and experimentally. Finally, numerical and experimental
results for flexible beam and plate were shown. (TRACK 3: Passive and
Active Vibration Isolation Systems )
TRACK 1: Energy Harvesting and Scavenging
7643-31, Session 4a
Nonlinear vibrations of the piezoelectromagnetic structure for energy
harvesting
M. A. Karami, D. J. Inman, Virginia Polytechnic Institute and State
Univ. (United States)
A nonlinear energy harvesting structure is proposed to convert
ambient vibrations to the electric energy using the piezoelectric and
electromagnetic mechanisms. Harvesters potentially eliminate the
need to change batteries of standalone electric devices and are crucial
for hard to reach sensors, such as those used for structural health
monitoring. A typical vibrational energy harvesting device consists
of a spring (possibly a cantilever beam) connected to a mass. As the
base vibrates the spring deflects and the stress energy created in the
spring can be converted to electrical energy. There are two challenges
in design of vibrational energy harvesters. The first is the necessity to
have a low frequency structure. The frequency of the common ambient
vibrations is between 0.1 to 100 Hz. The challenge is to design a
structure which can sustain the vibrations while having a low natural
frequency. The second challenge is to have a broad band energy
harvester. The power outputs of conventional harvesters are orders
of magnitude higher if they are excited at their natural frequency but
this high power is only available over a few Hz window. The stochastic
nature of the ambient vibrations requires the harvester to be less
sensitive to the excitation frequency.
7643-30, Session 4a
A magnetically sprung vibration harvester
P. Constantinou, P. H. Mellor, P. D. Wilcox, Univ. of Bristol (United
Kingdom)
The requirement to monitor safety critical systems in remote and
harsh environments using Wireless Sensor Nodes (WSN) is becoming
more important. Traditionally, WSNs are supplied energy from
batteries, however these limit the WSN, due to their need for frequent
replacement or recharging. Ideally a WSN would be completely
autonomous such that its benefits can be exploited. To achieve this,
an alternative source of energy to batteries is required. Energy can be
supplied to the WSN by means of ‘harvesting’ otherwise unused energy
from the local environment into a useable form.
Fig. 1: Nonlinear Piezo-electromagnetic harvester
The proposed nonlinear multi physics energy harvester (depicted in
Fig. 1) is realized by placing a rare earth magnet at the tip of a bimorph.
Another permanent magnet is placed right bellow the beam in its
undeformed configuration. The same poles of the two magnets face
each other so that there is a repulsive force acting between the two.
The placement of magnets will introduce a nonlinear softening term to
the lateral force - displacement relation of the cantilever beam.
This paper will discuss the topology and properties of a magnetically
sprung vibration generator that can harness mechanical vibrations.
The topology comprises three annular permanent magnets arranged
laterally, with opposite magnetisation directions, along a shaft. The two
outer magnets are fixed to a frame and the central magnet, which is
free to move, is suspended between these, due to the repulsive forces
it experiences. The resultant experienced force acts as an equivalent
suspension that behaves like a hardening spring. When the frame is
excited the central magnet will pass through a co-axial coil inducing a
current if a load is connected.
The paper first formulates the nonlinear governing equation of the
beam deflection and the two electromechanical relations between the
voltages from the Piezo patch and the magnets and the tip velocity of
the beam. The identified three dimensional system is analyzed using
the method of multiple scales and the projection method to study the
bifurcations of the system. By decreasing the distance between the
magnets the nonlinear softening effect intensifies. At first the typical
vibration of a weekly nonlinear system is observed which translates
to more frequency bandwidth and the useful jump phenomenon. If
the nonlinear magnetic force is increased further, the structure goes
through a chaotic motion for moderate base excitations and it can
go through limit cycle oscillations if the amplitude of base excitation
is higher. The chaotic oscillations result in higher electrical energy
resulted from a given base excitation. Moreover, the chaotic vibrations
are way less sensitive to base excitation frequency and therefore a
nonlinear harvester with chaotic behavior has a wide bandwidth of
energy production. The analytical study performed, identifies the
thresholds of magnet distance and other parameters which result in
chaotic vibrations. The predictions facilitate the design of a nonlinear
harvester. Finally the experimental setup in Fig.2 is used to examine the
accuracy of the analytical predictions and to illustrate the usefulness of
The paper will present a complete model of the system focussing on
spring characteristic of the magnetic suspension. The non-linearity of
the suspension mechanism yields a non-linear response resulting in
a bi-stability and associated ‘jump’ phenomenon. This non-linearity
is validated against measurements. Due to the non-linear suspension
two measured load-power curves, corresponding to the upper and
lower bounds of the bi-stability result. Those predicted by the model,
correspond well with the measured values at the upper bound of the
bi-stability. The bi-stability phenomenon can be usefully exploited
in developing a vibration harvester with a broad resonant response.
This will be useful in an environment where there are either multiple
or varying dominant excitation frequencies. An additional property of
the system that can be exploited in such or unknown environments
is its ability to ‘tune’ its resonant response. This can be achieved by
36
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the need to include a non-standard part in their material inventory. For
wayside applications, although the use of solar panels are starting to
gain some attention they are yet to be widely used on railroad tracks
due to their high maintenance, dependability on geographical location
and daylight, and high cost-to-power efficiency. Some predict that we
are still decades away from having solar panels that can be used for
general use in a cost effective manner.
the proposed design in action.
Fig. 2: The experimental setup
7643-32, Session 4a
Self-contained active fluid mount
This paper will describe the work that we currently have underway for
exploring vibration-based electromechanical energy harvesting systems
that can be readily installed on railcars and at trackside. Such devices
are expected to remedy the short comings of the energy generators
that are currently available. Additionally, they will vastly improve
on the performance of the piezoelectric-based (PZT-based) energy
harvesting systems that have been investigated in the past. Although
PZT-based systems work well for many applications that require a
minimal amount of energy-such as, operating micro-electronics-they
have consistently proven to be too fragile for most rail operations and
not able to generate sufficient electricity for running most devices that
are of practical interest to the railroads. In contrast, vibration-based
systems are mechanical in nature, can be sized according to the
amount of energy that they are expected to generate, can tolerate the
demands of the railroad operation, and provide more Watts-per-dollar,
when compared to both PZT-based systems and the generator roller
bearings.
N. Vahdati, S. Heidari, Nanyang Technological Univ. (Singapore)
Active fluid mounts have not been as widely used as passive fluids
mounts in aerospace application due to a need for a source of power
and a controller and the need to bring this power and control signal to
the mount via wiring harness. In order to resolve these issues, a selfpowered self-contained active fluid mount is developed.
The proposed new design consists of a conventional passive fluid
mount, and two voice coils. The first voice coil, placed in the lower
chamber of the passive fluid mount, acts like an actuator and it
changes the volumetric stiffness of the bottom chamber to provide
a wide band notch frequency. And the second voice coil acts as
an energy harvesting device which is connected to the engine and
converts the engine vibrational energy to electrical energy.
The amplitude and phase of the induced current in the energy
harvesting device is modified through a passive electrical circuit and
applied to the voice coil actuator.
This active mount is modeled using bond graph modeling technique
and MATLAB. Dynamic stiffness, required current for the voice coil
actuator, and the induced current in the energy harvesting voice coil
are plotted. Realistic parameters were implemented into the MATLAB
model and it is shown that in a wide frequency range, the induced
current in the energy harvesting voice coil is larger than the required
current of the voice coil actuator. Therefore, the need for an external
source of power is eliminated.
7643-35, Session 4a
Optimal and sub-optimal power
management in broadband vibratory energy
harvesters with one-directional power flow
constraints
J. T. Scruggs, Duke Univ. (United States)
7643-33, Session 4a
TRACK 1: ENERGY HARVESTING AND SCAVENGING
In many applications of vibratory energy harvesting, the external
disturbance are most appropriately modeled as broadband stochastic
processes. Optimization of power generation from such disturbances
is a feedback control problem, and solvable via a LQG control theory.
However, attainment of this performance requires the power conversion
system which interfaces the transducers with energy storage to be
capable of bi-directional power flow, and there are many applications
where this is infeasible. One of the most common approaches to power
extraction with one-directional power flow constraints is to control the
power conversion system to create a purely resistive input impedance,
and then to optimize this effective resistance for maximal absorption.
This paper examines the optimization of broadband energy harvesting
controllers, subject to the constraint of one-directional power flow.
We show that as with the unconstrained control problem, it can be
framed as a “Quadratic-Gaussian” stochastic optimal control problem,
although its solution is nonlinear and does not have a closed-form.
This paper discusses the mathematics for obtaining the optimal power
extraction controller for this problem, which involves the stationary
solution to an associated Bellman-type partial differential equation.
Because the numerical solution to this PDE is computationally
prohibitive for harvester dynamics of even moderate complexity, a suboptimal control design technique is presented, which is comparatively
simple to compute and which exhibits analytically-computable lower
bounds on generated power Examples will focus on mW-scale
piezoelectric bimorph energy harvesting systems, inertially excited by
random vibration of the base mount.
The influence of power harvesting circuits
on energy harvesting performance
D. Quinn, The Univ. of Akron (United States); S. G. Burrow, D. K.
Barton, Univ. of Bristol (United Kingdom)
We consider the performance of a vibration based energy harvesting
with realistic topologies for the electrical circuit. Specifically we apply
a novel perturbation approach to describe the time-varying power
harvested in the system, including a rectifier in the circuitry. This
approach considers the full electromechanical coupling between the
mechanical and electrical components, including the amplitude and
phase of the mechanical response. The resulting analysis is able to
describe the behavior of the system as the mechanical response is
detuned from resonance by the electrical load. In addition, the charging
of the circuit over time is also captured by the analysis. Finally,
experimental results are compared against the analytical predictions to
verify the analytical approach.
7643-34, Session 4a
Effective energy harvesting devices for
railroad applications
M. Ahmadian, Virginia Polytechnic Institute and State Univ. (United
States)
7643-36, Session 4b
This paper presents the results of the design and development of a
new generation of energy harvesters for railroad applications. The
onboard and wayside applications of many smart devices that can
add to the efficiency of rail operation are often hindered by the lack of
availability of electrical power on railcars or at remote track locations.
Although ideas such as Timken’s Generator Roller Bearing exists,
the railroads have been slow in adopting them for various reasons,
including the cost premium over traditional tapered roller bearings and
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A dual adaptive tunable vibration absorber
using MREs for vehicle powertrain vibration
control
N. Hoang, N. Zhang, Univ. of Technology, Sydney (Australia); H. Du,
Univ. of Wollongong (Australia)
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37
Conf. 7643: Active and Passive Smart Structures and Integrated
Systems IV
This paper presents a dual Adaptive Tuned Vibration Absorber
(ATVA) which uses enhanced magnetorheological elastomers (MREs)
for torsional vibration control of a vehicle powertrain system in the
steady stage. The MRE used in this application is a soft MRE with
a significant MR effect (the increase in elastic modulus is up 100
times in a magnetic field flux intensity B up to 0.5 Tesla). Thus, each
single ATVA using the MRE can operate effectively in a much wider
working frequency range than a classic dynamic absorber does. In
this application, the dual ATVA is proposed rather than a single ATVA
because of two main reasons. The first one is that the effectiveness of
a single ATVA for the primary powertrain, which is modeled as a fourdegree-of-freedom system, depends on not only the ATVA parameters
such as inertia, stiffness and damping coefficients but also on the
powertrain vibration mode shapes. In other words, if a single ATVA is
installed at a fixed position in the powertrain, it may work effectively
only with one or few powertrain frequencies. That means this single
ATVA will not be able to deal with resonances happening at the other
powertrain frequencies although these frequencies are in its working
frequency range. The second reason is that a single ATVA cannot
deal with two or more resonances at the same time while vehicle’s
engine fluctuation torque is a multi-frequency excitation because of
the internal combustion engine features (that means the powertrain
is often subjected to a multi-harmonic fluctuation torque). This paper
also proposes a concept design of the dual ATVA. According to the
design, the MRE material plays a role as torsional springs, whose
stiffness and damping coefficients are controlled by magnetic circuits
attached to the dual ATVA. In addition, in this paper the MRE shear
modulus is approximated by a cubic polynomial of MRE magnetic
field flux intensity B. The proposed approximation is compared to the
experiment data of the soft MRE material and they are in agreement.
This approximation is convenient for tuning each single ATVA frequency
as well as analyzing the vibration of the combined system, which
consists of powertrain and the dual ATVA. The numerical simulations
of the combined system are used to validate the dual ATVA proposed
design. The simulation results showed that resonances happening
to powertrain natural frequencies can be deal with. By using the dual
ATVA, powertrain resonant frequencies are shifted away excitation
frequencies so that powertrain vibration response is significantly
suppressed. In addition, the effect of the dual ATVA parameters such as
inertia moment, stiffness and damping coefficients to its effectiveness
were examined. Furthermore, several location combinations of
single ATVAs are examined to find the best combination for the
powertrain system in this study. The dual ATVA will be a useful device
for powertrain vibration suppression. The effectiveness of the dual
ATVA for powertrain vibration during transient stage, when excitation
frequencies of fluctuation torque are not constant but vary with the
time, over a frequency range will be our next work.
terms of performance and safety.
In this research, a magnetorheological fluids based compact
multifunctional actuator for assistive knee braces is designed. With
MR fluids, the actuator possesses multiple functions as motor, clutch,
and brake while meeting the requirement of normal walking as well.
The objective of this paper is to design and control the multifunctional
actuator. Position control, speed control, force and acceleration control
are considered. The simplified modeling of the actuator with gearbox
as well as controller is presented and the control system is designed.
Controllers like PID control and impedance control are adopted in
the system. Experimental results show that the motion control of the
actuator can be well implemented.
In addition to the system motion control, each function of the actuator
is investigated. For motor function, the actuator could work well as
the servo system for controlling the position, speed, and force output.
In another operation as clutch, the actuator could adjust the torque
transferred from the rotor to outside and provide safety to prevent
the system from exceeding the restricted motion. Compared with
conventional electric motor, the force and acceleration control in brake
function is easier to be implemented for the multifunctional actuator. By
cooperating among all three functions, the actuator could also fulfill the
positioning task as a stepping motor.
To be applied for assistive knee braces, a normal human walking gait
is illustrated. According to the gait cycle, at the state of stance flexion
and extension, the actuator works as brake; at the state of pre-swing
and swing extension, the actuator works as motor and clutch; at
the state of swing flexion, the actuator works as clutch. To conduct
experiments, angle position and torque references are given for the
multifunctional actuator to track the desired motion. The results show
that the multifunctional actuator is promising for assistive knee braces.
7643-39, Session 4b
A compressible magnetorheological fluid
damper-liquid spring for controllable
suspension system
P. Raja, X. Wang, F. Gordaninejad, Univ. of Nevada, Reno (United
States)
In this feasibility study a small-scale prototype compressible magnetorheological fluid damper - liquid spring (CMRFD-LS) for a tracked
vehicle suspension system is designed, developed and tested. The
goal of this study is to develop a CMRFD-LS device which will have
a stiffness of 1.19 x 106N/m under a stroke of 10.16cm (4in) and a
considerable controllable dynamic damping force range under an
applied magnetic field. The proposed device consists of a cylinder
and piston-rod arrangement with an annular MR valve. The internal
pressures in the chambers on either side of the piston develop the
spring force, while the pressure difference across the MR valve
produces the damping force, when the fluid flows through the MR
valve. A fluid mechanics-based model is conducted to predict the
behavior of the damper device under sinusoidal input. The performance
of the device, filled with pure silicone oil and MR fluid, is studied under
oscillatory vibrations for various frequencies and applied magnetic
fields. The experimental results are in good agreement with the
theoretical predictions.
(Track 3: Passive and Active Vibration Isolation Systems)
7643-37, Session 4b
Design and control of multifunctional
actuators for assistive knee braces
H. Guo, W. Liao, The Chinese Univ. of Hong Kong (Hong Kong,
China)
(Track 4: Magneto Rheological Systems)
Assistive knee braces are a type of wearable equipment that can
enhance people’s strength and provide desired locomotion. It is
possible to use knee braces to assist elderly or disabled people
improving their mobility so as to solve many daily life problems, like
going up and down stairs and over obstacles. In addition to support
human body, smooth and comfortable locomotion is also desirable for
assistive knee braces. The actuation system should not only provide
desired torque, but also have the ability of agile and accurate control
in various conditions. To assist the wearer in various postures and
prevent knee braces from exceeding the restricted motion, actuators
should also function as brake/clutch with the feature of safety interlock.
Furthermore, power consumption in the actuation system is another
consideration in lengthening the working time of batteries after fully
charged. Therefore, well designed actuators with appropriate control
algorithm would be the key component of assistive knee braces in
38
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7643-40, Session 4b
Design and testing of a magnetorheological
damper to control both vibration and shock
loads for a vehicle crew seat
A. Becnel, W. Hu, Univ. of Maryland, College Park (United States);
G. J. Hiemenz, Techno-Sciences Inc. (United States); N. M.
Wereley, Univ. of Maryland, College Park (United States)
A magnetorheological shock absorber (MRSA) prototype was designed,
fabricated and tested to integrate semi-active shock and vibration
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Conf. 7643: Active and Passive Smart Structures and Integrated
Systems IV
mitigation technology into the existing EFV (Expeditionary Fighting
Vehicle) forward seating positions. The MRSA was designed so that it
could both isolate occupants from whole body vibration (WBV) during
normal operations, as well as reduce occupant lumbar loads during
extreme events such as rogue waves or ballistic/UNDEX shock events.
The MRSA consists of a piston with a flow-mode MR valve having an
annular cross-section, a magnetorheological (MR) fluid cylinder, and
a nitrogen accumulator. Piston motion forces MR fluid to flow through
an MR valve, where it can be activated by a magnetic field. Utilizing
Bingham-plastic (BP) constitutive fluid relationships and a steady
state fluid flow model, the MR valve was designed using magnetic
circuit analysis, and subsequently validated via electromagnetic finite
element analysis (FEA). The MRSA prototype was tested at low speeds
(vibration mode) and high speeds (shock mode) on a servohydraulic
testing machine as well as a rail-guided drop test stand, respectively.
A refined hydromechanical model was developed that includes
compressibility effects within the damper system and predicts the
time response under cyclic or impact loadings. This model was then
validated using the measured test data. Key design considerations for
the MRSA to accommodate both vibration and shock spectra using a
single MR device are presented.
7643-42, Session 4b
Structural considerations in designing
magnetorheological fluid mounts
T. M. Nguyen, Univ. of Minnesota (United States); C. Ciocanel,
Northern Arizona Univ. (United States); M. H. Elahinia, The Univ. of
Toledo (United States)
Modern vehicles have been increasingly equipped with advanced
technologies such as hybrid and cylinder-on-demand to enhance fuel
efficiency. These technologies also come with vibration problems due
to the switching between the power sources or the variation of the
number of active cylinders. The challenge has been addressed by a
large variety of vibration isolator designs ranging from passive to active.
Semi-active mounts have caught the attention thanks to their adaptive
nature with affordable price. Among the semi-active categories, the
magnetorheological fluid (MRF) mounts have been proven to be a
highly potential solution to modern vehicle vibration isolation. The
reasons are due to the responsive changes in characteristics of the
mount when a magnetic field is present without involving with any
moving components.
This study looked into several innovative designs of the MRF mounts.
The characters of the MRF mounts depends significantly on the
compliances of the rubber, the number and arrangement of the fluid
chambers and the number of the flow passages connecting each pair
of the chambers. These parameters provide the designers with various
options to design the mounts to function in changing conditions and
a wide range of frequencies. Different values of the aforementioned
parameters were selected to form specific designs with certain
characteristics. The magnetorheological effect plays the role of
proportionally controllable valves installed at the flow conduits. The
states of the MRF valves determine the stiffness and damping of the
semi-active mounts.
7643-41, Session 4b
Force characteristics of a modular squeezemode magneto-rheological element
M. J. Craft, M. Ahmadian, A. Farjoud, W. Burke, C. Nagode, Virginia
Polytechnic Institute and State Univ. (United States)
While few publications exist on the behavior of MR fluid in squeeze
mode, devices using squeeze mode may potentially take advantage of
the very large range of adjustment that squeeze mode offers. Based on
results obtained by modeling and testing MR fluid in a squeeze mode
rheometer, a novel compression-controlling device has been fabricated
and tested, which utilizes the squeeze mode of the MR fluid. The
device, consisting of a flexible cylindrical membrane fastened at each
end to a steel endplate (pole plate), was tested in a squeeze mode
rheometer and compared with simulated results.
The research is planned to include two phases: analytical modeling and
experimental validation. This paper summarized the procedure of the
first step, i.e. analytical study. The research was started by constructing
mathematical model for each design. The models were simulated in
MATLAB/Simulink© to show the design’s behavior. The advantages and
disadvantages were highlighted with considerations from the vibration
isolation perspectives. The categories used for the mount assessment
includes the structure, the performance and the cost. This study can be
used as a useful reference source for MRF mount designers.
While many commercial dampers exist today that utilize MR fluid,
these devices all typically operate with the fluid in shear or valve mode.
While these modes work well in damping applications, recent modeling
and testing with MR fluid in squeeze mode has revealed much higher
force ranges are obtainable. Given this, a controllable MR device was
designed, fabricated, and tested to take full advantage of the squeeze
mode operation.
No control algorithm was considered in this research in order to
emphasize the importance of the mount construction. The hydraulic
and magnetorheological (MR) effects are dominant in the mount, so the
elastomer is considered linear.
One significant problem concerning the design of this MR device,
known as an MR Pouch, was to find a flexible membrane material
that would not degrade or leak after extended periods of contact with
oil-based MR fluids. After significant effort, an affordable and practical
pouch material was fabricated for a prototype device. The flexible
membrane, consisting of a two-part silicone rubber was commercially
available and could be made into the required shape for use in the
rheometer.
7643-129, Session 4b
Simulated and experimental flow evaluation
for a magnetorheological fluid based
micropump
The MR Pouch design uses a novel approach for implementing
squeeze mode control. The MR fluid is completely self-contained and
does not require an external reservoir to compensate for the volume
change between the pole plates. Because the flexible membrane
compensates for volume changes, there is no need for dynamic seals
and associated surface finish treatments. Additionally, MR Pouches are
scalable depending on the application.
N. Bruno, A. Kipple, C. Ciocanel, Northern Arizona Univ. (United
States)
This paper presents simulated and experimental results for a
magnetorheological fluid based micropump. The pump is simulated
as a micro-electro-mechanical-system (MEMS) and the departure
from a classical Newtonian flow is considered. The development
of a magnetorheological fluid based micropump is motivated by
the elimination of the mechanical moving parts, usually required
to sustain the flow, by the bidirectional flow capability achieved by
simply switching direction of the electrical current passing through
electromagnets, and by the high level of controllability that leads
to a wide range of achievable micro-flowrates. In order to optimize
the pump output, several geometric configurations, together with
different materials selection, were simulated and the advantages
and disadvantages of each configuration are discussed. The optimal
configuration was replicated experimentally facilitating the comparison
of simulated and measured flowrates. To this end, the difference
Based on modeling refined for the initial squeeze mode rheometer
testing, a model of the MR pouch was developed. This model was
verified by comparison with data collected on a MTS load frame.
The results of the MR pouch were extremely promising for small
displacements, where the compression force could be varied from less
than 10lbs to greater that 1000lbs. The compression force required
was dependent on both the displacement (distance between the pole
plates) and the current going to the electromagnet. Additionally, the
magnetic field density, B, was also recorded during all of the tests to
correlate the change in magnetic field flux density in the fluid due to the
position of the pole plates.
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Conf. 7643: Active and Passive Smart Structures and Integrated
Systems IV
In addition to the model predictions, wind tunnel test results for a
prototype device will be presented and discussed.
between the simulated and experimental results is larger than 15%;
the reasons for this level of error are discussed in detail and potential
improvement solutions are suggested.
7643-45, Session 5
7643-43, Session 5
High efficient energy harvesting using piezo
macro fiber composites on vibrators with
optimized energy transfer
Self-powered smart blade: helicopter blade
power extraction and conditioning for
on-blade RF wireless embedded sensor
systems
T. P. Daue, J. Kunzmann, Smart Material Corp. (United States); A. J.
Schönecker, Fraunhofer Group (Germany)
A. Fang, M. J. Bryant, E. Garcia, Cornell Univ. (United States)
The paper focuses on evaluating how much power is available at the
trailing edge of a helicopter blade at various lengths of the span and
how the transformed energy can be manipulated into a stable power
source for a self-contained wireless embedded sensing system. A
novel aeroelastic piezo-electric energy harvester has been developed
by the Laboratory for Intelligent Machines (LIMS) group at Cornell
and it can be cantilevered off the trailing edge of a helicopter blade
where the induced airflow due to the rotational motion of the blade
excites the energy harvesting device. The current generated is passed
through conditioning circuitry ultimately powering a Texas Instruments
MSP430F2274 microcontroller, a MEMS accelerometer, and a CC2250
2.4 GHz RF wireless transceiver. A study of power consumption
compared to varying duty cycle lengths is also performed. The results
can be used to tune the design of the aeroelastic piezo-electric energy
harvesting device for maximum performance.
Harvesting energy from “waste” vibration present in the environment
has seen an increasing interest during the past years as part of the
general heightened awareness for alternative energy sources. Beside
of typical electro mechanical methods, ferro electric devices have
proven to be very effective to harvest energy for low power devices as
often found in portable electronics, sensor controlled and condition
monitoring systems due to the wide usable frequency range and
adaptability.
Due to their excellent properties like flexibility, anisotropy and long term
stability Macro Fiber Composites (MFC) fit most of the requirements
to meet the specifications of energy harvesting systems based on the
piezo electric effect. A test set up for the introduction of uniform strain
into the MFCs as well as an electrical impedance matching will be
presented based on a general consideration about energy transfer in
electric dipoles and a comparison between soft and hard piezo electric
materials (PZT). Test results outlining the differences between a PZT5A1 and a PZT-SP4 material particularly with respect to power output,
electrical mismatching and long term stability will be discussed.
7643-46, Session 5
Dynamic analysis of a structure integrated
with periodically arranged piezoelectric
transducers
Finally examples of MFC based energy harvesting systems from
different fields of application are presented, demonstrating the high
potential of the MFC technology for the generation of electrical energy
from mechanical vibrations. A short summary of the requirements for
the electrical and mechanical subsystem concludes the presentation to
help system engineers to design high performance energy harvesting
systems.
Y. Lu, J. Tang, Univ. of Connecticut (United States)
In various engineering applications piezoelectric transducers have been
used as actuators and/or sensors. When placed in a spatially periodic
pattern, multiple transducers may exhibit unique characteristics which
could benefit certain applications, e.g., enhanced sensitivity in damage
detection or increased energy conversion efficiency. In this paper, a
transfer-matrix-based modeling technique is adopted in the analysis
of a beam structure integrated with multiple, periodically arranged
piezoelectric transducers and shunt circuits. The beam is divided into a
number of elements, each represented by two state vectors at its both
ends. Vertical displacement, angle of rotation, moment and shear force
are included in the state vectors as variables. Based upon a chosen
beam theory, e.g. Euler-Bernoulli theory, the transfer matrix relating
adjacent state vectors can be derived by matrix manipulation. In
addition, the electro-mechanical interaction between the piezoelectric
transducers and the beam is also taken into account. The electric
charge collected by a transducer results in a mechanical moment
applying back to the beam. A point matrix is thus added to include the
effects of such feedback. The transfer-matrix-based modeling method
is validated by comparing its frequency response results with that
of a widely used modal method. Strong correlation can be observed
between the two. Since the transfer matrix by nature has the advantage
on describing the state propagation within the structure, the derived
method thus could facilitates analysis involving local dynamics. As
an example we apply it to the case of energy harvesting from beam
vibration by periodically arranged piezoelectric transducers together
with shunt circuits. Our analysis shows the specific configuration in
both electrical and mechanical phases leads to typical characteristics
of periodic structure. By adjusting electrical components we can further
tune the energy harvesting process.
TRACK 1: Energy Harvesting and Scavenging
7643-44, Session 5
Self-powered smart blade, part 1: helicopter
blade energy harvesting
M. J. Bryant, A. Fang, E. Garcia, Cornell Univ. (United States)
A piezoelectric energy harvester driven by aeroelastic flutter vibrations
has been designed to power embedded wireless sensors in a
helicopter rotor. The nature of the rotor application makes using
traditional hardwired sensing techniques difficult because slip ring
systems are required to power and receive data from the sensors
through the spinning hub. These difficulties make the rotor application
well suited to a wireless sensing scheme that derives it power entirely
from the operational environment.
The aeroelastic energy harvester consists of a piezoelectric beam
cantilevered from the trailing edge of the rotor with a small plate
attached to the tip of the beam by a flexible joint. Above a critical flow
speed, a flutter instability occurs causing the plate to oscillate with
coupled pitching and heaving vibrations. These flutter vibrations drive
the tip of the beam, straining the piezoelectric layers and generating an
electric current which can then be rectified and stored.
A system of coupled equations describing the structural, aerodynamic,
and electromechanical aspects of the system are derived and
presented. The model uses unsteady, nonlinear aerodynamics
modeling to predict the aerodynamic forces and moments acting on
the structure and to account for the effects of vortex shedding and
dynamic stall. These nonlinear effects are included to predict the
limit cycle behavior of the system over the range of wind speeds the
device will experience in operation on the helicopter rotor application.
40
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Conf. 7643: Active and Passive Smart Structures and Integrated
Systems IV
and thermal energy within a soft ferromagnetic working body. While in
operation, the working body of this device is thermally cycled about
its Curie point, such that its magnetic susceptibility is also cycled at
the same frequency. The resulting phenomenon is a periodic magnetic
force of attraction between the working body and a permanent
magnet. The developed model quantifies the efficiency of thermalto-magnetic energy conversion in this device. This model is based
on previous theories of efficiency for thermomagnetic generators;
however, modifications to these theories were made in order to match
the expected physical states of this cycle. An upper-bound relative
efficiency is calculated by assuming a perfect single-domain structure,
whose spontaneous magnetization is described by Brillouin’s function.
This idealized system assumes gadolinium as the working body, and
operates at room temperature between a ΔT of 5 K. A basic schematic
of a regenerative cascade cycle design is provided to show that a
much larger ΔT can be achieved.
7643-47, Session 5
Vibro-impacting power harvester
S. D. Moss, I. G. Powlesland, S. C. Galea, Defence Science
and Technology Organisation (Australia); G. P. Carman, Univ. of
California, Los Angeles (United States)
The certification of retro-fitted structural health monitoring (SHM)
systems for use on aircraft raises a number of challenges. One critical
issue is determining the optimal means of supplying power to the
systems, given that access to existing aircraft power-system is unlikely
to be permitted. Other conventional options such as primary and
secondary cells can be difficult to certify and would need periodic
replacement or re-charging, which in an aircraft context would pose
a serious maintenance issue. Previously, the DSTO has shown that a
structural-strain based energy harvesting approach can be used to
power a device for SHM of aircraft structure [1]. Acceleration based
power harvesting from airframes is more demanding (than a strain
based approach) since the vibration spectrum of an aircraft structure
varies dynamically with flight conditions, and hence a frequency agile
or (relatively) broadband device is required to maximize the energy
harvested. This paper will discuss the modelling and experimental
validation of a novel power harvesting technique that utilizes the
vibro-impact mechanism to harvest milli-Watts of power from RMS 400
milli-g mechanical vibrations of frequency 29-39 Hz, using a 49 gram
flying mass.
7643-50, Session 6
Feasibility of a multidimensional wave
energy harvester
S. Behrens, A. Fowler, Commonwealth Scientific and Industrial
Research Organisation (Australia)
A typical limitation of current wave energy harvesters is that they often
harvest energy in only one degree of freedom, e.g. from the heaving
motion of the waves. Hence, wave motions in additional degrees of
freedom such as swaying, pitching and rolling are unutilised. This
problem may be addressed by developing a multi-dimensional wave
energy harvester which is able to capture the unutilised wave energy
using six degrees of freedom.
[1] S. C. Galea, S. van der Velden, S. Moss, I. Powlesland, “On the way
to autonomy: the wireless-interrogated and self-powered ‘smart patch’
system,” Encyclopaedia of Structural Health Monitoring, 1st Ed., Vol. 3,
Chpt. 76, pp.1329-1350, John Wiley & Sons, ISBN 978-0-470-05822-0,
2009
[TRACK 1: Energy Harvesting and Scavenging]
The multidimensional wave energy harvester design consists of a
watertight frame, with a proof mass suspended within the centre of the
frame via elastic supports. The motion of the mass is used to generate
electrical power through a number of transducers, which are placed
in parallel with each element of the suspension system. By placing
a load impedance across the terminals of each transducer, electrical
power can be extracted from the device. Thus, wave motions along any
translational or rotational axis will result in the generation of electrical
power through the inertia of the mass and the transducer elements.
7643-48, Session 6
Design of energy harvesting systems for
harnessing vibrational motion from land and
air vehicles
A. M. Wickenheiser, E. Garcia, Cornell Univ. (United States)
A Simulink/SimMechanics model of the multidimensional wave
energy harvester has been developed. A preliminary simulation of the
performance of the harvester using recorded wave data has resulted
in an average power output of 127mW, confirming the initial feasibility
of the design and encouraging further investigation into the concept;
further wave data including both translational and rotational wave
motions will be captured in order to guide the further development
of the design. The paper will report on the performance of a physical
version of the final design, and hence evaluate the feasibility of the
multidimensional wave energy harvester.
In much of the vibration-based energy harvesting literature, devices
are modeled, designed, and tested for dissipating energy across a
resistive load at a single base excitation frequency. This paper presents
several practical scenarios germane to tracking, sensing, and wireless
communication on land and air vehicles. Measured vibrational data
from these platforms are used to provide a time-varying, broadband
input to the energy harvesting system and are recreated in a laboratory
setting for experimental design verification. Several circuit topologies
are compared, including a simple resistive load (to provide a baseline),
a passive rectifier circuit, and active, switching methods. Under
various size and mass constraints, the optimal design is presented
for each of the aforementioned circuit topologies, and an estimation
of the maximum average power harvested under ideal conditions is
given. Subsequently, the inefficiencies due to mechanical damping,
circuit quality factor, rectifier losses, and active component power
consumption are discussed. Finally, power management issues are
considered in the design of a circuit for intermittent power expenditure
in the presence of low levels of available energy.
TRACK 1: Energy Harvesting and Scavenging.
7643-51, Session 6
Thermoelectric energy harvesting as a
wireless sensor node power source
C. G. Knight, Commonwealth Scientific and Industrial Research
Organisation (Australia); J. P. Davidson, James Cook Univ.
(Australia)
7643-49, Session 6
S. M. Sandoval, C. Hsu, G. P. Carman, Univ. of California, Los
Angeles (United States)
Size and power requirements of wireless computing and mobile
devices are decreasing and this has allowed data collection across
a range of spatial and temporal ranges. These devices have power
requirements that often necessitate batteries as a power source. As
the power requirements decrease, alternative energy sources become
available.
A model of efficiency for a unique thermal energy harvesting device
is developed, which predicts an upper-bound relative efficiency of
30%. This unique device is based on the coupling between magnetic
Thermal energy requires a higher temperature source and a lower
temperature sink. Energy is extracted as heat flows from the hot side to
the cold side. The magnitude of the difference between the source and
An efficiency analysis of a novel thermal
energy harvesting device
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Conf. 7643: Active and Passive Smart Structures and Integrated
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sink determines both the efficiency and rate at which the energy can be
extracted.
7643-53, Session 6
A device has been designed and tested to exploit the temperature
difference between a sun warmed plate and a heat sink immersed in
water. The concept uses a solid-state thermoelectric device to extract
electrical power from the heat flow. Theoretical estimations of power
available from measured temperature differences are compared with
the results of the designed device. Experiments were completed at a
variety of winter time, environmentally available temperature differences
with power outputs of 50mW achieved with rudimentary devices.
The air to water temperature gradients were typically below 10K.
Results indicate that maximum power output approached 2.5% of the
predicted Carnot limit.
Study of underwater performance of solar
cells with change in depth and salinity
K. Joshi, S. Priya, Virginia Polytechnic Institute and State Univ.
(United States)
There’s lot of interest in scientific community in harvesting Ocean
energy. Especially for use of underwater surveillance vehicles to serve
their energy needs without depending on battery or external sources.
Solar cells can be used as the source of power on board for these
vehicles. Since these vehicles are working under ocean waters and
may need to dive at various depths need was identified to evaluate
performance of solar cells at various depth and various salinity levels
observed in the ocean. This work presents results of experimental
investigation of the performance of solar-cell as the parameters depth
from surface and salinity level varies.
The results show that such a system could power a wireless node
continuously in areas where a source of thermal energy is available.
We are currently in the process of powering a CSIRO Fleck wireless
node to transmit temperature and battery voltage at regular intervals
throughout the day.
7643-52, Session 6
7643-102, Poster Session
Theoretical analysis of acceleration
measurements in a model of an operating
wind turbine
Implement trigger for a NI data acquisition
card PCI 5105 in the measurement studio
development environment for a high speed
demodulator based on fiber Fabry-Pérot
tunable filter (FFP-TF)
J. White, Purdue Univ. (United States)
Wind loading from turbulence and gusts can cause damage in
horizontal axis wind turbines. These unsteady loads and the resulting
damage initiation and propagation are difficult to predict. Unsteady
loads enter at the rotor and are transmitted to the drivetrain. The
current generation of wind turbine has drivetrain-mounted vibration
and bearing temperature sensors, a nacelle-mounted inertial
measurement unit, and a nacelle-mounted anemometer and wind
vane. Some advanced wind turbines are also equipped with strain
measurements at the root of the rotor. This paper analyzes additional
measurements in a rotor blade to investigate the complexity of these
unsteady loads. By identifying the spatial distribution, amplitude, and
frequency bandwidth of these loads, design improvements could be
facilitated to reduce uncertainties in reliability predictions. In addition,
dynamic load estimates could be used in the future to control highbandwdith aerodynamic actuators distributed along the rotor blade
to reduce the saturation of slower pitch actuators currently used for
wind turbine blades. Local acceleration measurements are made
along a rotor blade to infer operational rotor states including deflection
and dynamic modal contributions. Previous work has demonstrated
that acceleration measurements can be experimentally acquired on
an operating wind turbine. Simulations on simplified rotor blades
have also been used to demonstrate that mean blade loading can
be estimated based on deflection estimates. To successfully apply
accelerometers in wind turbine applications for load identification, the
spectral and spatial characteristics of each excitation source must
be understood so that the total acceleration measurement can be
decomposed into contributions from each source. To demonstrate
the decomposition of acceleration measurements in conjunction with
load estimation methods, a flexible body model has been created with
MSC.ADAMS©. The benefit of using a simulation model as opposed
to a physical experiment to examine the merits of acceleration-based
load identification methods is that models of the structural dynamics
and aerodynamics enable one to compare estimates of the deflection
and loading with actual values. Realistic wind conditions are applied
to the rotor blade with virtual accelerometers installed along the rotor
blade. The accuracy of the acceleration decomposition methods will be
compared to the actual modeled sources of acceleration for verification
of the data analysis algorithms. Furthermore, the deflection and load
estimates will also be compared with the true loads. Verification
of acceleration decomposition and loading estimation is critical in
developing confidence and insight before analyzing turbine operational
data.
42
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H. Zhang, Stevens Institute of Technology (United States); S.
Yang, Yantai Univ. (China); L. Fan, P. Wang, Stevens Institute of
Technology (United States); X. Zhao, Z. Wang, Yantai Univ. (China);
H. Cui, Stevens Institute of Technology (United States)
A NI (National Instruments) high-density data acquisition card PCI
5105 is installed in a high speed demodulator based on Fiber FabryPérot Tunable Filter (FFP-TF) for Weigh-In-Motion (WIM) system. The
instability of spectra of fiber Bragg grating (FBG) sensors caused
by intrinsic drifts of FFP-TF needs a suitable trigger time obtained
by a trial-and-error method. However, the driver of PCI 5105 in
Measurement Studio development environment does not provide
analog trigger type but only digital trigger type. In latter mode, only two
choices, rising or falling edge trigger, can be chosen and the trigger
time is not flexible any more. Moreover, the high level of original trigger
signal chosen from tuning voltage of FFP-TF is dramatically larger
than the maximum input overload voltage of PCI 5105 card. To resolve
this incompatibility, a scheme of low-cost, easy-to-install differential
electrical converter to change analog trigger signal into digital trigger
signal is presented. The obtained results of frequency response about
this converter clearly demonstrate that this method is effective when
the frequency of trigger signal is less than 3,000 Hz. This converter can
satisfy current requirement of this kind of demodulation, since mostly
actual working scanning frequency of FFP-TF is less than 1,000 Hz.
This method may be recommended to resolve similar problems for
other NI customers who have developed their data acquisition system
based on Measurement Studio.
7643-103, Poster Session
Shake table tests of semi-active fuzzy
control for seismic response reduction with
piezoelectric friction damper
D. Zhao, Yanshan Univ. (China) and Dalian Univ. of Technology
(China); H. Li, Dalian Univ. of Technology (China)
The seismic reduction of the semi-active fuzzy control system including
a new type of piezoelectric friction damper and fuzzy controller is
investigated on the MTS shake table using a two-storey steel structure
under various earthquake records. The hysteresis performance
of the damper under linear increased voltage is tested on MTS in
advance. The force generation of the actuator in the damper under
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type observer is used to estimate those not measurable states from the
displacements in only one shaft point and, therefore, making possible
the synthesis of an optimal LQR control based on the estimated
state feedback. The control forces obtained from LQR control are
introduced to mathematical model of actuators and taking into account
their dynamics, we get the voltages input necessary to provide the
unbalance compensation forces. The proposed control scheme
is proved by numerical results and then, validated experimentally
on a test rig which was designed and constructed. Numerical and
experimental results show significant reductions in the unbalance
response of the overall system.
different preload is also tested before the implementation of the shake
table test. The relationship between force generation and voltage is
nearly linear. The preload force acted on the damper is determined
by nonlinear time-history analysis under normal earthquakes. The
semi-active fuzzy control algorithm is used to adjust the voltage of the
piezoelectric actuator according to the structure response. This method
has benefit to produce required voltage to be input to the damper so
that the desired force can be produced and thus decrease the structure
responses. The implementation of the control algorithm is used in
dSPACE by SIMULINK. The seismic reduction of the control algorithm
is investigated under several earthquakes. Experimental results indicate
that the proposed semi-active fuzzy control system consisting of a
T-S fuzzy controller and piezoelectric friction damper can be efficient
in reducing the inter-storey drifts and acceleration under earthquake
excitations.
7643-108, Poster Session
Ultrasonic piezoelectric cleaning of acoustic
vector sensing elements
7643-104, Poster Session
S. Cravens, R. M. Barrett, The Univ. of Kansas (United States)
Multimodal vibration control of a plant using
synchronized switch damping based on
negative capacitance
The Microflown is an acoustic vector sensor that utilizes two small
diameter filaments to determine particle velocity incited by a sound
source. This technology is presently employed in several applications
including acoustic holography and determination of “noisy”
components in automobiles and machinery. These applications are
found in clean environments where there is little risk of environmental
fouling of the sensor. However, there are a wide variety of applications
for this device that require the ability to clean debris from the
Microflown filaments. This debris consists of environmental agents
including but not limited to dust, pollen and water. This is problematic
because the Microflown operates on similar principles to hot wire
anemometry which means a small particle which covers even a small
portion of one of the filaments renders the sensor essentially useless.
H. Ji, J. Qiu, Nanjing Univ. of Aeronautics and Astronautics, Nanjing
(China)
In this article, a new semi-active SSD (Synchronized Switch Damping)
approach based on negative capacitor is proposed and applied to
the multimodal vibration control of a beam. A negative capacitance
is designed to substitute the inductor in the classical switched
shunt circuit of SSD control. Due to special properties of negative
capacitance, switched discharging of the piezoelectric element
can induce voltage inversion on it. The switched voltage on the
piezoelectric element under steady state depends on the ratio of the
capacitance of the piezoelectric and the negative capacitance. The
switch control strategy based on negative captitance is the same
with the classical SSD method based on inductor. In single mode
vibration control using SSD approach, optimal control performance is
obtained when the voltage on the piezoelectric actuator is switched
at each extremum of displacement. Experimental results showed that
better control performance can be achieved if switching actions are
skipped at some of the extrema in multi-mode control. Hence the
switch control strategy is the most important issue in the application
of SSD approaches in multi-mode vibration control. In this study, the
fundamental theory of optimal switch control in SSD approaches for
multi-mode vibration control is investigated. The new SSD method
based on a negative capacitance has been applied to the multimodal
vibration control of a plant and its control results were compared with
those of previously developed SSD techniques using inductance. Very
good control performance was achieved using the new switched shunt
circuit.
This paper presents an investigation into the effects of environmental
debris on the sensitivity of a hot wire anemometer. A method of
cleaning the unwanted particles from the sensor using piezoelectric
actuators, excited at ultrasonic frequencies is also presented. To
simulate a Microflown sensor, a boron fiber has been dusted and
then shaken using a piezoelectric actuator. The dust particles were
successfully removed from the fiber at a frequency of approximately 20
kHz.
7643-109, Poster Session
Feasibility study on self-powered active
vibration control using a piezoelectric
actuator
K. Nakano, M. Ohori, A. Tagaya, The Univ. of Tokyo (Japan)
A self-powered active vibration control is a system that produces a
control force using energy generated from vibration and carries out
the control without power sources. In previous study, the self-powered
active vibration control was achieved using an electromagnetic
actuator and its suppression performance and power balance between
the consumed and the generated energy were examined.
7643-105, Poster Session
Active unbalance control in an asymmetrical
rotor system using a suspension with linear
actuators
However, in the field of smart structures, a piezoelectric transducer is
a major actuator. Since it is light and responses quickly, it is suitable
for an actuator of a distributed control system. As many actuators are
utilized in this system, many power sources, sensors and wires are
needed, which makes the hardware very complex.
M. Arias-Montiel, G. Silva-Navarro, Ctr. de Investigación y de
Estudios Avanzados (Mexico)
This work deals with the problem of the active unbalance control in
an asymmetrical rotor-bearing system with two disks supported by
an active suspension based on two lateral linear actuators. For the
analysis and control synthesis a mathematical model is developed
using Finite Element Methods (FEM). A linear quadratic regulator
(LQR) is applied in order to minimize the displacements of the two
disks by means of the application of an active bearing with control
forces provided by an arrangement of two linear actuators. The control
scheme is designed to attenuate the overall system response in the
natural frequencies (resonances), taking into account the unbalance
response associated to both disks and shaft and, hence, controlling the
system performance during the first modes. To do this, a Luenberger
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Then the author proposes to realize the self-powered active vibration
control using a piezoelectric actuator. It is quite different from an
electromagnetic actuator, since it produces force from electric charge,
while mechanical deflection induces voltage. An equation to estimate
the power generated by the piezoelectric transducer is derived and the
feasibility is examined through a power balance analysis. The results of
the numerical simulations and experiments show the proposed system
can achieve active vibration control under the condition where the
generated energy exceeds the consumed energy.
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Conf. 7643: Active and Passive Smart Structures and Integrated
Systems IV
Multifunctionality of smart structures combining conventional
structures with active materials has been demonstrated on laboratory
scale worldwide. Until now, large scale production of such systems
are limited by the deficit of applicable series technologies and the
considerable expenditure to mount a lot of damageable components.
7643-110, Poster Session
Piezoelectric energy harvester operating in
flowing water
E. Bischur, S. Pobering, M. Menacher, N. Schwesinger, Technische
Univ. München (Germany)
It was an objective of the present project to develop a technology for
the manufacture of active compound structures that combines the
assembly of semi finished products and compound manufacturing in
one single step. Semi-finished products may be piezoelectric actuators
or sensors, clamping elements, joints, mechanical and electrical
connections and electronic circuits, for examples.
The first piezoelectric energy harvesting device is presented which
converts energy out of laminar flowing water without any rotating parts
and hereby scalable to micrometer dimension.
The harvester converts the energy out of the bending of a piezoelectric
bimorph cantilever. The body disturbs the laminar flow and the
consequences are vortexes behind it in flow direction. This effect
caused by the bluff body is called “von Kármán’s vortex street”. Thus
with the cantilever fixed behind the bluff body the vortexes cause
alternating pressure differences above and beneath the cantilever and
as a result the cantilever starts to bend up and down. The bimorph now
oscillates in a media depending resonance frequency.
A possible approach for a batch production of such active structural
components is to use injection molding. This was demonstrated using
the example of a compound actuator with integrated stress-strain
transformation. Such devices can be used in mechatronic machine
components. The compound actuator, according to our design,
comprises two stack actuators, mechanical and electrical connections
and prestressing elements within one injection molded matrix.
Design sketch, simulation, actuator design and fabrication technology
are described in this paper. The approach can be used in all technical
fields where active structural components are applicable.
A macroscopic model of this harvester was build consisting of nine
piezoelectric bimorph modules in a dimension of L x W x T = 20mm x
12mm x 0.35mm with two active piezoelectric layers each.
The results of this project are based on the cooperation of several
institutes of the Fraunhofer-Gesellschaft in Germany.
Earlier measurements of the bimorphs in the wind channel proved the
working principle. The open-circuit voltage generated by the cantilever
was investigated at flow velocities between 4.5m/s and 45m/s. The
produced voltage shows strong coupling with the velocity and also the
position of the cantilever relating to the others affects it.
7643-112, Poster Session
Characterization of multifunctional
piezoelectric fibers as structural capacitors
for energy storage
First measurements in the water channel at velocities between 0.2
m/s and 0.9 m/s showed a similar behavior as in air. Due to the much
higher density of water the reachable velocity is quite lower than in air.
However, with the energy density in water is quite higher than in air the
power generation is much better also at lower velocities.
J. W. Shaffer, Y. Lin, H. A. Sodano, Arizona State Univ. (United
States)
The voltage generated of one cantilever rises almost exponentially with
velocity. For the comparison of the values gained in water and air they
are converted to the same velocity. Assuming an exponential increase
the generated effective voltage in water at 2.0m/s is approximately
300mV which is compared to the value in air (10mV) about 30 times
higher.
Multifunctional composites are structural materials that can carry
external loads as well as provide an additional performance related
functionality. This additional functionality could include vibration
control, sensing and actuation, and energy generation and storage.
Interest in these composites is derived from the increase in safety
and performance, with minimal gain in complexity, they can provide
to a system. For instance, in unmanned air vehicles (UAVs), soldier
systems, and space structures where weight and energy consumption
often dominate the structural design, multifunctional materials can
improve system efficiency by incorporating energy harvesting or
storage components with the structural elements. The concept of
utilizing the structure as a source of energy has been investigated by
several researchers. Neudecker et al. (2003) developed a fiber based
Li-ion battery for integration into composites. Electrostatic capacitors
have also been studied; however they primarily utilize the addition of a
dielectric powder to the matrix which results in very low performance.
Lin and Sodano (2009) performed one study that achieved equal
energy density to commercial ceramic capacitors by coating a SiC fiber
with a BaTiO3 layer. The core fiber provided strength and flexibility,
but its conductivity also allowed it to act as an electrode. While this
design proved effective for energy storage, the fiber diameter (140 m)
is generally too large to be effectively incorporated into a carbon fiber
reinforced composite. To address this issue a novel thin film deposition
technique will be developed to coat carbon fibers with lead zirconate
titanate (PZT). Cathodic electrolytic deposition will be used which
allows the individual carbon fibers to be coated while in the tow. The
deposition process will be characterized, and methodologies to obtain
crack-free coatings will be explored. Carbon fibers have been widely
used as composite reinforcements due to their exceptional mechanical
properties, and PZT has been extensively studied because of its very
high electromechanical coupling and dielectric coefficients. Therefore,
the resulting multifunctional fiber could have excellent mechanical,
piezoelectric, and dielectric properties. This multifunctional fiber can
convert mechanical energy to electrical energy, which in turn can
be stored for use by other electrical devices. This paper will discuss
the characterization of the energy storage capabilities of the PZT
multifunctional fiber by comparing experimental results to theoretical
expressions derived from Gauss’s Law for cylindrical capacitors.
Energy densities of different PZT coating thickness samples are
An effect that was considered in flowing water is the selfsynchronization of the modules arranged horizontally in a row.
To make the power usable generated by the oscillating bimorph a lowpower circuitry was build up. The circuitry consists of a center-tapped
rectifier with capacitors for energy storage and a low-power logic part
consisting of an analog switch, transistors and resistors. The circuitry is
controlled by itself by designing the electronic devices matching to the
proper value. The system gives energy to the load if the voltage applied
to the capacitors reaches a predefined value. The release of the energy
happens stochastically because the analog switch is only controlled by
the applied voltage level.
If a time-controlled activation of the load is needed the circuitry can be
extended with a monostable flip-flop which controls the analog switch.
The system was characterized and optimized in the wind channel
at a velocity of 8.0m/s. The model was able to supply the load with
approximately 2mW in an average time interval of 760ms.
The introduced system offers new possibilities for converting energy
of flowing water using microstructured devices in conjunction with a
relatively easy circuitry.
TRACK 1: Energy Harvesting and Scavenging
7643-111, Poster Session
Manufacture of active piezoelectric
components using plastic injection molding
H. Roscher, Fraunhofer-Institut für Werkzeugmaschinen und
Umformtechnik (Germany); T. Moritz, L. Seffner, FraunhoferInstitut für Keramische Technologien und Systeme (Germany); C.
Anselment, D. Just, Fraunhofer-Institut für Chemische Technologie
(Germany)
44
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characterized by testing their capacitance and breakdown voltage. The
coating thickness that provides the maximal energy storage capacity
will be determined by comparing the energy densities and the results
will show that the energy density of this novel multifunctional fiber is
significantly higher than previously developed structural capacitors.
(SMA) to drive a flight control system. The paper begins discussing
the development of SMA as well as well as aircraft applications. The
paper continues with the physical properties of SMA and how to take
advantage of these properties with an electric current. The paper then
describes the development of the actuator as an antagonistic system
utilizing a Wheatstone bridge with variable resistors to develop a
closed loop feedback system. The paper proceeds to describe how
a demodulator circuit from JR NES 911 subscale servoactuator was
implemented so that the SMA actuator could interpret signals from a
radio-control transmitter-receiver; as well as, diodes to control which
SMA wire would be actuated depending on the signal voltage. The
diodes were replaced with transistors as the power requirements of
the SMA were increased and required a secondary power source for
an airworthy actuator. The paper follows the prototype design with
details of the test aircraft and operational procedures. During tests the
actuator proved capable of 20 degrees of deflection in either direction
as well as 7.5 oz*in of torque. The actuator was placed in a modified
radio controlled sailplane of 78.5 inch span and was used to control
the rudder. The aircraft was flown through maneuvers to demonstrate
the actuator had sufficient rudder control in flight. The paper concludes
stating the success of the actuator and for the first time, precise servo
actuation using SMA was achieved and demonstrated.
TRACK 1: Energy Harvesting and Scavenging
7643-113, Poster Session
Damping capacity in shape memory alloy
honeycomb structures
M. Boucher, C. W. Smith, The Univ. of Exeter (United Kingdom); F.
L. Scarpa, Univ. of Bristol (United Kingdom); W. Miller, The Univ.
of Exeter (United Kingdom); M. N. Hassan, Univ. Putra Malaysia
(Malaysia)
SMA honeycombs have been recently developed by several Authors [1,
2] as innovative cellular structures with self-healing capability following
mechanical indentation, unusual deformation (negative Poisson’s
ratio [3]), and possible enhanced damping capacity due to the natural
vibration dissipation characteristics of SMAs under pseudoelastic and
superelastic regime. In this work we describe the nonlinear damping
effects of novel shape memory alloy honeycomb assemblies subjected
to combined mechanical sinusoidal and thermal loading. The SMA
honeycomb structures made with Ni48Ti46Cu6 are designed with
single and two-phase polymeric components (epoxy), to enhance
the damping characteristics of the base SMA for higher-frequency
vibration. The unit cells are represented by FE models using pseudoelastic and superelastic material laws, and used to extract parametric
design surfaces of the stiffness and hysteresis versus the geometric
parameters of the honeycomb topology (Figure 1). Assemblies of
composite SMA unit cells are manufactured using ribbons curved in
a OX-shape mould, some of which are connected by an interlayer
of epoxy, and tested under uniaxial dynamic mechanical loading.
General good agreement has been recorded between the experimental
results and the numerical simulations related to the single phase SMA
honeycomb (Figure 2), with the two-phase cellular structures showing a
definite trend in terms of enhanced damping capacity.
7643-117, Poster Session
A comparative experimental study
on structural and interface damping
approaches for vibration suppression
purposes
Y. Liu, ETH Zürich (Switzerland)
Dynamic loadings in automotive structures may lead to reduction
of driving comfort and even to failure of the components. Damping
treatments are applied in order to attenuate the vibrations and improve
the long term fatigue behaviour of the structures. This experimental
study is targeting applications in floor panels that are mounted to the
load-carrying primary structure of the vehicle. The Objective is to reach
outstanding damping performance considering the stringent weight
and cost requirement in the automotive industry. An experimental
setup has been developed and validated for the determination of the
damping properties of structural specimens also considering interface
damping effects.
7643-114, Poster Session
Small-scale modular wind turbine
This contribution is structured in three main parts: test rig design,
experimental results and discussion. Reliable and easy-to-use devices
for the characterization of the damping properties of specimens
between 200X40 mm2 and 400X400 mm2 are not available “on the
shelf”. In this context, we present a flexible experimental set-up which
has been realized to (1) support the development of novel damping
solutions for multi-functional composite structures, (2) characterize
the loss-factor of the different damping concepts, including boundary
effects, and (3) validate in-house developed simulation tools. A variety
of novel passive and active damping treatments have been investigated
including viscoelastic, coulomb, magnetorheological (MR), particle,
magnetic and eddy current damping. The particle, interface as well as
active damping systems show promising performance in comparison to
the classical viscoelastic treatments.
C. Vernier, S. Bressers, Virginia Polytechnic Institute and State
Univ. (United States)
This paper reports the fabrication and characterization of a horizontalaxis, small-scale modular windmill that is capable of charging small
electronic devices such as cell phone and powering a remote sensor
network. The design criteria for the windmill included (i) portability,
which implies that windmill was modular in architecture allowing on-site
assembly in few minutes, (ii) packaging, which implies that windmill
can be carried in a bottle of volume 2.49 liters and bottle itself became
the base stand, and (iii) low start-up wind speed. The turbine was
designed to operate in the wind speed range of 5 to 12 mph. It was
found that windmill can start at low wind speeds of 5.5 mph, and once
started it was able to maintain sustainable rotation at 4.5 mph. Results
are reported on selection of motor, blade design, turbine structure,
and implementation of modularity. Performance characterization was
conducted using a home-built low-speed wind tunnel. It was found that
the fabricated windmill can generate 157 mW power at nominal wind
speed of 8mph and 500mW power at peak wind speeds of 11 mph.
7643-118, Poster Session
Suspension system with magnetorheological damper and energy regeneration
Z. Wang, Z. Chen, Hunan Univ. (China)
7643-116, Poster Session
Semi-active control systems are becoming more and popular
because they offer both the reliability of passive systems and the
versatility of active control without large power demands. In particular,
magnetorheological (MR) dampers have received great attention
from the community. However, the systems based on MR damper
still require external power supply. Harvesting energy from structural
vibration is quite a new and challenging research field. One potential
Development and flight test of a shape
memory alloy flight control system
M. T. Brennison, R. M. Barrett, The Univ. of Kansas (United States)
This paper chronicles an investigation of using shape memory alloys
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Conf. 7643: Active and Passive Smart Structures and Integrated
Systems IV
Finally, calculated and verified methods about the axial force of the
column with and without MR dampers were presented in the paper.
Simulated example gave an explanation on the influence of column on
the MR damper structure.
application of energy harvesting is to provide power for a control
system. Therefore, a new suspension system with MR damper and
energy regeneration is presented. The system includes four key parts:
a rack and pinion gearing, a permanent magnet direct-current (DC)
generator, a current-adjusted MR damper, and a control circuit. The
system can work in two different modes that are passive or semiactive according to the complexity of the control circuit. In the semiactive mode, the sky-hook control method is adopted. The system
is embedded with a quarter-car model to control the vibration of
suspension system. Random and bump excitations are considered to
test the suspension system and investigate its performance. Simulation
results have showed the feasibility and effectiveness of proposed new
vehicle suspension system in this paper.
7643-121, Poster Session
A novel above-knee prosthetic knee based
on magnetorheological effect: design and
testing
D. Wang, L. Xu, Chongqing Univ. (China)
In this paper, the principle and structure of an integrated aboveknee prosthetic mechanism based on four-bar linkage and
magnetorheological (MR) effect are proposed and realized to imitate the
instant center of rotation of knee joint accurately and the controllable
bending moment. In the developed integrated above-knee prosthetic
knee, the four-bar linkage is designed according to human body
kinematics and dynamics, and the up and below links of the four-bar
linkage are connected with the piston rod and cylinder of the MR fluid
damper, respectively. The control for the MR fluid is realized with the
fluid gaps in the piston of the MR fluid damper, which will simplify the
structure of the cylinder and will be beneficial to the material selection
of the cylinder. According to the proposed principle and realized
structure, a polycentric above-knee prosthetic knee mechanism based
on MR effect is designed and fabricated. The characteristics of the
developed above-knee prosthetic knee mechanism based on the MR
effect, including the controllable damping ratio and motion accuracy,
are tested. The research results indicate that the developed integrated
above-knee prosthetic knee mechanism possesses the following
advantages: (1) the structural integration is skillfully achieved, through
which the structure can be simplified and the installation space and
weight can be saved, (2) the instant center of rotation of normal human
being can be imitated accurately, and (3) the bending moment of the
developed integrated above-knee prosthetic knee mechanism can be
continuously changed with a short response time and large controllable
damping ratio.
7643-119, Poster Session
Harvesting energy using a piezo-composite
generating element (PCGE)
C. M. T. Tien, N. Goo, Konkuk Univ. (Korea, Republic of)
Energy can be reclaimed and stored for later use to recharge a
battery or power a device through a process called energy harvesting.
Piezoelectric is being widely investigated for use in harvesting energy
from motion such as body movement and machine vibration. This
paper presents a simple analytical model to describe output voltage
effectiveness of a Piezo-Composite Generating Element (PCGE)
from vibration and its experimental verification. PCGE is composed
of layers of carbon/epoxy, PZT ceramic and glass/epoxy. During the
manufacturing process, the stacked layers were cured at an elevated
temperature of 177 Celsius Degrees in an autoclave, which made the
PCGE pre-stressed due to a mismatch in the coefficients of thermal
expansion between the constituent layers. The effect of the prestressed on the performance of output voltage therefore was studied.
For the experiments, three kinds of lay-up configurations of PCGE
were utilized to verify the model and to approve its ability to convert
oscillatory mechanical energy into electrical energy. The predicted
performances are much in agreement with experimental ones.
(SSN03/Track 4: Magneto Rheological Systems)
7643-120, Poster Session
7643-122, Poster Session
The disadvantage effect of
magnetorheological damper on the hosting
structures
Performance optimization of an integrated
relative displacement self-sensing
magnetorheological damper
X. Li, Sr., Shandong Jianzhu Univ. (China); H. Li, Dalian Univ. of
Technology (China)
D. Wang, X. Bai, Chongqing Univ. (China)
Magnetorheological (MR) damper is a kind of semi-active control
device that uses MR fluid to provide controllable damper by adjusting
its parameters according to the instantaneous response of the
hosting structures, which is quite promising for civil engineering
applications. The aseismic reinforcement of the structures is a widely
used engineering technology. In the paper, the method of reinforcing
aseismic structures by MR damper is presented.
In order to let magnetorheological (MR) dampers move into the
industrial marketplace, Wang and Wang (Smart Materials & Structures
2009 18 095025) proposed and explored an integrated relative
displacement sensor (IRDS) technology to make MR dampers selfsensing based on electromagnetic induction and the principle of an
integrated relative displacement self-sensing MR Damper (IRDSMRD)
based on the IRDS technology. Although the function of the relative
displacement sensing property can be integrated into MR dampers and
the designed IRDSMRD possesses the large controllable damping ratio
and the good relative displacement sensing performance utilizing the
IRDS technology, in order to integrate the IRDS into the MR damper,
the damping performance of the IRDSMRD will definitely influence
its sensing performance and vice versa. In order to maximize the
performance of the IRDSMRD, including decreasing the nonlinearity
of the IRDS, the damping performance and sensing performance of
the IRDSMRD should be compromised carefully, which needs to be
realized by performance optimization. In this paper, the optimization
method to optimize the performance of the IRDSMRD, including the
performance of the damping force and the performance of the IRDS
of the IRDSMRD, is proposed and realized based on the finite element
analyzing results and experimental results of the IRDSMRD. In order to
realize the performance optimization of the IRDSMRD, the performance
index is determined by the weighted function of the reciprocal value of
Firstly, the experiment system of a three-floor reinforced concrete
frame-shear wall eccentric structure has been built based on Matlab/
Simulink software environment and hardware/software resources of
dSPACE.
And then a shaking table test for the hosting structure with and without
MR dampers is implemented subjected to three different ground
motions using rapid control prototyping (RCP) technology. Due to
FBG’s superior ability of explosion proof, immunity to electromagnetic
interference and high accuracy, especially fitting for measurement
applications in harsh environment, the FBG strain sensors were
used in this experiment for forces measurement of the columns. The
experimental results show that the coupled translation and torsion
responses are significantly mitigated by MR dampers. Unfortunately,
the experimental results also show that the increase on axial force of
the column was discovered due to MR dampers fitted in the hosting
structure.
46
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Conf. 7643: Active and Passive Smart Structures and Integrated
Systems IV
the damping force and the nonlinearity of the IRDS. The constrained
optimization problem is solved to minimize the performance index. The
optimized results are validated by finite element analyzing results and
experimental results, which indicate that the sensing performance and
damping performance of the IRDSMRD can be compromised through
the optimization method. (SSN03/Track 8: Modeling, Simulation,
Optimization, Signal Processing, Control, and Design of Integrated
Systems)
[3] Seelecke, S. and Muller I., “Shape memory alloy actuators in
smart structures: Modeling and simulation,” ASME Journal of Applied
Mechanics, 23-46 (2004).
7643-127, Poster Session
Radar tower frequency control and
earthquake response analysis
7643-123, Poster Session
Z. Wu, Zhengzhou Univ. (China); Y. Li, North China Univ. of Water
Conservancy and Electric Power (China); F. Wang, D. Wang,
Zhengzhou Univ. (China)
BATMAV: a 2-DOF bio-inspired flapping
flight platform
In order to control floods, droughts and other natural disasters, the
Chinese government decided to introduce the U.S. Doppler weather
radar. For the sake of avoiding the impact of surrounding buildings
on the radar, Radar Tower is usually higher, generally up to 100
meters. As the radar performance reasons, the required fundamental
frequency of Radar Tower should not be less than 1Hz. For such a
tall building, how to control the frequency of Radar Tower is an issue
worth studying. Through a lot of calculation and analysis, research
paper reached a number of increase natural vibration frequencies of
laws: 1) Lowering center of gravity of the structure Lowering center of
gravity can significantly improve the structural natural frequency. The
two structures have the similar shapes, the lower center of gravity, the
greater the frequency. 2) Setting leaning bracing Setting the leaning
bracing is a very effective measure to improve the overall stiffness of
the structure. Leaning bracing pivot height, leaning bracing and the
ground level into a different angle, the influence on the overall stiffness
of the structure is not the same. Pivot height is higher, making a greater
contribution on the overall stiffness of the structure. When the angle
between the leaning bracing and the Radar Tower increases, the
structural stability enhances; bracing enlarging length, bar increasing
flexibility and improving the frequency Radar Tower is little effect.
G. Bunget, P. Cook, S. S. Seelecke, North Carolina State Univ.
(United States)
The overall objective of the BATMAV project is the development of
a biologically-inspired Micro-Aerial Vehicle for flapping flight. While
flapping flight in MAV has been previously studied, this paper presents
a platform that features bat-inspired wings able to actively fold their
elbow joints and passively their wrist joints. The wings are assembled
through superelastic SMA joints and are actuated by SMA ‘muscle’
wires that mimic the pectoral and biceps of the natural bat flier. These
‘muscle-wires’ exhibit actuation frequencies of 10Hz corresponding
to the range of bat flapping frequencies. Aerodynamic parameters like
flapping frequency, lift and thrust are studied and compared with a
kinematic model and with the aerodynamics of the natural flier.
7643-124, Poster Session
FE analysis of SMA-based dual-joint flexible
nozzle used in smart inhaler system
3) Reducing the mass concentration of the upper part of structure
N. Lewis, S. S. Seelecke, North Carolina State Univ. (United States)
Structure of the upper part, especially at the top of the mass of the
structure, produces the natural frequencies of a greater impact. For
the high-rise structure, reducing the mass at the top of the structure
can be significantly improved natural frequency. 4) Increasing crosssection moment of inertia For the frame structure, increasing the beam
and column cross-section size of the structure proceed to magnify the
natural frequency. 5)Enlarging the thickness or number of shear walls
For the frame - shear wall structure or wall structure, by increasing the
number and thickness of shear walls is to improve the structure of the
self-vibration frequency.
Recently, a novel patent-pending Smart Inhaler system has been
developed at NC State University [1]. The Smart Inhaler design
concept has the potential to improve pulmonary ailment treatment
by targeting the delivery of inhaled aerosol medication to specific
locations within the human lung [2]. This targeted delivery will reduce
the amount of healthy lung tissue exposed to potentially harmful
medications and enable new oral uptake methods for, e.g., lung cancer
treatment. However, controlled delivery can only be accomplished if the
medication is injected into an inhaled stream of properly conditioned
laminar flow from a precise location. In particular, the medication
must be injected into the inhaled flow using a small nozzle that can
be positioned without disturbing the flow. This paper presents a finite
element analysis (FEA) for a dual-joint flexible nozzle used in the Smart
Inhaler design. The nozzle uses shape memory alloy (SMA) wires for
their unique dual sensing and actuating capabilities. The FEA program
ABAQUS was chosen to model the Smart Inhaler system because of
its effectiveness in modeling materials with non-linear behavior and
its widespread commercial availability. The SMA wires were modeled
using a mesoscopic free energy model for SMA behavior [3] and
implemented in ABAQUS together with the Smart Inhaler nozzle. For
each wire actuation, the required voltage, corresponding heat input,
and the resulting forces on each SMA wire were determined together
with the electric resistance change, and the position of the nozzle tip
was mapped. The results from the simulation were validated against
measurements taken with the Smart Inhaler prototype using a video
camera system and the LabVIEW Machine Vision software by National
Instruments. Using SMA actuator wire models in ABAQUS will help
optimize the Smart Inhaler design and assist in the development of
other SMA wire-actuated projects in the future.
In the above structural frequencies adjustment method, increasing
leaning bracing, and reducing the top mass of the structure are the
most obvious effects of all. At the same time, paper also discusses on
the Radar Tower of seismic response. Analyses of the methodology
used for earthquake are response spectrum method, time history
analysis method and random vibration analysis. Three methods of
calculation results show that: Radar Tower performance is to meet
China’s seismic code to regulate internal force and displacement.
7643-54, Session 7a
Performance analysis of discrete wholespacecraft vibration isolation platforms for
flexible spacecrafts
B. Fang, Y. Zhang, Y. Li, Harbin Institute of Technology (China)
Abstract: The vibration environment of spacecrafts during launching
is worse than that during its orbital movement. The whole-spacecraft
vibration isolation technology can improve the dynamic environment
of the spacecrafts. The whole-spacecraft vibration isolator is installed
between the spacecraft and the rocket, with its stiffness and damping
being the key components to achieve the vibration isolation. A number
of researchers have investigated the whole-spacecraft vibration
isolation based on rigid spacecrafts, but few have discussed flexible
spacecrafts. In this paper, a disc-type discrete whole-spacecraft
[1] Pausley, M. and Seelecke, S., “Multifunctional SMA-based Smart
Inhaler System for Improved Aerosol Drug Delivery -Design And
Fabrication,” Proceedings of SPIE, the International Society for Optical
Engineering, 10-13 March, 2008, San Diego, California, USA.
[2] Kleinstreuer, C. and Zhang, Z., “Targeted drug aerosol deposition
analysis for a four-generation lung airway model with hemispherical
tumors,” ASME Journal of Biomechanical Engineering, 197-206 (2003).
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47
Conf. 7643: Active and Passive Smart Structures and Integrated
Systems IV
vibration isolation platform with a new type of damping is adopted
to study the vibration isolation performance of flexible spacecrafts.
The isolator series with the cone shell adapter series. The damper
of the platform consists of two rib plate and one viscoelastic layer,
with the up-shear plate connected with the up-board of the isolator,
the low-shear plate directly connected with the rocket. The dampers
can offer maximal shearing forces. When the flexible spacecraft have
longitudinal and lateral vibration, the viscoelastic dampers can offer
vertical and horizontal shear damping forces. The dynamical equations
of the whole-spacecraft vibration isolation system are established, and
the transmissibility from bottom of the isolator to some key points on
the flexible spacecraft is computed. The isolation performance of the
vibration isolation coupling system for flexible spacecrafts is analyzed.
Then, the isolation performance of the vibration isolation platform is
investigated by vibration table experiment with sine sweep signals. The
testing data for the flexible spacecrafts show that , in the frequency
range from 10Hz to 150Hz, the vibration transmissibility at the first
lateral natural frequency be decreased by 15%, and that by 40% at the
second lateral natural frequency. The vibration transmissibility at the
first longitudinal natural frequency be decreased by 10%, and that by
50% at the second longitudinal natural frequency. The analysis results
and the testing data show that the discrete whole-spacecraft vibration
isolation platforms have good isolation performance in wide frequency
range to lateral and longitudinal vibration, and the vibration isolation
platforms can be applied to flexible spacecrafts.
7643-56, Session 7a
Active sensor/actuator assemblies
for vibration damping, compensation,
measurement, and testing
V. M. Ryaboy, P. S. Kasturi, Newport Corp. (United States)
The vibration control module known as IQ damper® was introduced
as part of active vibration damping system for optical tables and
other precision vibration isolated platforms. Detailed description of
the actively damped optical table (SmartTable®) was presented at the
SPIE Smart Structures and Materials Symposium in 2005. The system
damps natural vibrations of isolated platforms, and monitors the
residual vibration in real time through analog and digital interfaces.
The paper describes steps to expand the application of these units
to other tasks, namely, (1) dynamic testing of structures and (2)
compensation of forced vibration in local areas. The sensor-actuator
assemblies, including signal conditioning circuits, form compact
dynamically symmetric modules with mechanical interfaces to an
optical table.
In application to dynamic testing, the actuator is excited to generate
the white noise, and the sensor signal is processed to calculate the
dynamic compliance. The SmartTable controller is programmed to
perform basic functions of a signal analyzer. The test data show
that the vibration control modules can be used to measure dynamic
compliance characteristics of optical tables with precision comparable
to that of dedicated vibration measurement systems.
7643-55, Session 7a
Integration of adaptive components by
incremental forming processes
Vibration damping of most significant structural modes had been
implemented using feedback controls of a small number of properly
placed active dampers. However, this would not affect forced tonal
vibration. The forced vibration may be caused, for example, by tonal
disturbance at 60 Hz, 120 Hz, etc., from rotating electrical equipment
nearby. In some practical situations, such tonal vibrations may be
very visible or even dominating the vibration spectrum on the table
surface. Current state of the art does not offer a practically feasible
way to suppress all vibration, forced and normal, over the total table
surface. However, by placing vibration control modules around a local
area of the table supporting a vibration sensitive device, it is possible
to abate forced tonal vibration in this area. MIMO and SISO algorithms
of feedback control for vibration compensation will be discussed along
with experiments demonstrating stable concerted work of several
vibration control modules.
M. Türk, P. Groche, Technische Univ. Darmstadt (Germany)
The Institute for Production Engineering and Forming Machines at the
TU Darmstadt researches the reduction of uncertainty of bar structures
by integrating adaptive components into the bars. As sensors, these
components allow a monitoring of appearing loads, as actuators they
allow an active influencing on appearing disturbances. Compared
with conventional integration methods, which are usually differential
methods like bolting or bonding, incremental forming processes appear
particularly attractive for this task of integration. They feature the
advantage that the forming of the parts as well as the integration of the
active components can be realized in one process. On the other hand
the forming and the local stresses are influenceable in wide ranges
by the path of the tools. A large challenge with this kind of integration
represents the sensitivity of the adaptronic components.
7643-57, Session 7a
For a first estimation of the arising loads on the components which
should be integrated, finite elements simulations of the integration
process are accomplished. For this, a 3D-Modell of a spinning process
is provided with the software Abaqus.
Performance evaluation of energy recycling
semi-active vibration suppression method
with multiple piezoelectric transducers
In this process, a ring is formed into the blank sheet by two steps. With
this model an optimization of the tool path takes place regarding a
minimization of the load of the component which should be integrated.
At the same time it must be ensured that a safe load transmission
between the ring and the blank sheet is ensured.
S. Shimose, K. Minesugi, J. Onoda, Japan Aerospace Exploration
Agency (Japan)
Study of the Energy Recycling Semi-active Vibration Suppression
using piezoelectric transducers have performed by the author’s group.
In the proposal method, piezoelectric transducers are connected
to the inductive switched shunt circuit, and it makes better use of
counter electromotive force to suppress the vibration. We developed
1] a control method of selected modes in multiple modes, 2] a control
method of self-sensing using a piezoelectric transducer also as a
sensor and 3] an analog switching circuit of full self powered system.
And we verified these methods by many experiments. Moreover we
had applied this method to Actual Satellite Structural Model.
By following experimental tests, first parts with integrated passive
rings could be produced. Despite the integration of the rings and the
resultant cranks and undercuts it becomes a permanent compound.
An important aspect for resuming investigations is the experimental
detection of the load, which affects the rings during the process. A
direct interaction between the ring and the movement of the tool would
be built by mounting a sensor system directly on the ring. By the exact
determination of the forces on the ring during the forming process
and the simultaneous, appropriate regulation of the infeed of the tool
it would be possible to keep the load of the compound part within
defined limits.
The results of experiments using this method showed that its
performance was strongly dependent on how piezoelectric transducers
were connected each other in series or in parallel. It is because the
connection affects a frequency and total resistance of the shunt circuit.
Another process to produce compound structures represents the
rotary swaging. For this a design is generated, at which a ring-shaped
component is integrated into a hollow bar. The joining procedure takes
place via an infeed swaging process, whereby an axially form closure is
produced. For the investigation of the arising loads during the process
a finite element model is provided, too.
48
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We will report an evaluation of performance dependent on the
connection of multiple piezoelectric transducers in this method.
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Conf. 7643: Active and Passive Smart Structures and Integrated
Systems IV
Various actuation strategies for morphing tensegrity structures are
explored. Two exciting solutions to the development of these active
structures are “clustered” and “strut routed” actuation. Clustered
actuation exploits the existence of cable elements in a tensegrity
structure by allowing cables to be run over frictionless pulleys
or through frictionless loops at the nodes. Strut routed actuation
utilizes an active cable that is routed around the bar elements before
connecting two nodes. Mechanics analysis to describe the actuation
response will be presented. It has been shown that stable pre-stress
states can be found under certain clustering patterns. This paper
also presents the loading response of clustered and strut routed
actuating tensegrity structures. An important aspect of this work is the
development of robust manufacturing strategies for active tensegrity
structures. Important considerations such as size scale, material
selection, three dimensional limitations, and overall complexity must
be considered when designing a structure that is to be constructed.
Multiple connectivity schemes and actuation techniques are presented.
Planar tensegrity beams have been fabricated that utilize both
actuating strategies. Tests on these beams have been carried out to
compare the loaded response with the analytical predictions.
7643-58, Session 7a
Design of optimized piezoelectric HDDsliders
P. H. Nakasone, Escola Politécnica da Univ. de São Paulo (Brazil);
J. Yoo, Yonsei Univ. (Korea, Republic of); E. C. N. Silva, Escola
Politécnica da Univ. de São Paulo (Brazil)
As storage data density in hard-disk drives (HDDs) increases for
constant or miniaturizing sizes, precision positioning of HDD heads
becomes a more relevant issue to ensure enormous amounts of data
to be properly written and read. Since the traditional single-stage
voice coil motor (VCM) cannot satisfy the positioning requirement of
high-density tracks per inch (TPI) HDDs, dual-stage servo systems
have been proposed to overcome this matter, by using VCMs to
coarsely move the HDD head while piezoelectric actuators provides
fine and fast positioning. Thus, the aim of this work is to apply topology
optimization method (TOM) to design novel piezoelectric HDD heads,
by finding optimal placement of base-plate and piezoelectric material
to high precision positioning HDD heads. Topology optimization
method is a structural optimization technique that combines the finite
element method (FEM) with optimization algorithms. The laminated
finite element employs the MITC (mixed interpolation of tensorial
components) formulation to provide accurate and reliable results.
The topology optimization uses a rational approximation of material
properties to vary the material properties between ‘void’ and ‘filled’
portions. The design problem consists in generating optimal structures
that provide maximal displacements, appropriate structural stiffness
and resonance phenomena avoidance. The requirements are achieved
by applying formulations to maximize displacements, minimize
structural compliance and maximize resonance frequencies. This paper
presents the implementation of the algorithms and show results to
confirm the feasibility of this approach.
7643-115, Session 7a
Review of smart material technologies for
active parachute applications
E. A. Favini, C. Niezrecki, J. Chen, D. Willis, E. Niemi, Univ. of
Massachusetts Lowell (United States)
Parachutes are widely used for airdrop/aerial delivery of personnel
and cargo. The performance (drag, lift, stability, etc.,) of a parachute
is a function of the physical properties of the canopy fabric (such as
porosity) and geometry of the canopy (such as air-vent openings).
These variables typically remain constant during descent and therefore
the parachute retains constant drag and lift. The ability to change these
variables and the parachute drag and lift characteristics during flight
in a controlled manner will greatly widen the performance envelope
of a parachute and the maneuverability and versatility of the airdrop
mission. In particular, it would be advantageous to design a parachute
that descends swiftly but reduces its rate of descent as it approaches
landing. By accomplishing this, the total time for an airdrop would
be reduced, which would elevate the safety of personal and valuable
cargo drop operations.
7643-59, Session 7a
Simultaneous thrust vector control and
vibration isolation of satellites using
steerable smart platforms
M. N. Ghasemi-Nejhad, K. Ma, Univ. of Hawai’i (United States)
This paper provides a literature review of existing smart material
technologies in an effort to improve the performance characteristics
and enhance the safety of existing parachutes and parafoils. By
harnessing the actuation abilities of smart materials, a change in the
porosity or the shape of the canopy at critical locations may enable
controllable and reversible changes to the parachute lift, drag, descent
rate, and glide ratio. The materials considered for the smart material
based parachutes include: shape-memory polymers, electro-active
polymers, shape-memory alloys, piezoelectric based actuators/fibers,
fiber optic sensors, and pneumatic based actuators.
This paper presents an innovative concept, control strategies and
experimental verification of simultaneous thrust vector control
and vibration isolation of satellites. First, the innovative concept is
introduced by employing a smart platform as an active structural
interface between the main thruster of a satellite and the satellite
structure. Second, the inverse kinematics and singularity analysis of the
smart platform are performed. Third, and control, thrust vector control
model of satellites with smart platforms is deduced. Fourth, a multiple
loop control strategy is proposed. It includes three cascaded feedback
loops for nonlinear compensation of actuators, smart platform control
and trust vector control, respectively, and a combined feedbackfeedforward control scheme for vibration isolation. Finally, experiments
are carried out and experimental results are illustrated and discussed.
The cascaded multiple feedback loops compensate the hysteresis (for
piezoelectric stacks inside the three linear actuators that individually
have simultaneous precision positioning and vibration suppression),
dead-zone, back-lash, and friction nonlinearities very well, and provide
precision and quick smart platform control and satisfactory thrust
vector control capability. The vibration controller isolates 97% of the
vibration energy due to the thruster firing. The experimental results
demonstrate that the simultaneous thrust vector control and vibration
suppression is achieved with satisfactory performance.
Within this work, a state-of-the-art summary of the performance
metrics of each smart material technology (wrt. displacement,
force, response time, actuation mechanism, reliability, commercial
availability, controllability) and how these materials could potentially
be utilized in a new parachute design is presented. Each technology
is rated for implementation feasibility based on the practical design
requirements for parachute systems. The design criteria include smart
materials that can produce large strains with high actuation forces.
The materials must have low weight, high mechanical flexibility, and
high reliability to maintain or improve the operating characteristics
of modern parachutes. The response time of the required materials
must also be sufficiently short depending on the application (e.g for
low-altitude drops). The actuation performance of the smart materials
must be controlled. If the actuation performance is not reversible,
the parachute must be disposable with minimal costs for materials
and manufacturing. The control mechanisms considered for the
smart materials include: the application of an electric field, voltage,
light, localized temperature change, pneumatic inflation, physical
deformation, global temperature change, chemical or pH change, and
the application of a magnetic field.
7643-60, Session 7a
Design and manufacturing strategies for
active tensegrity structures
N. Houle, K. W. Moored III, T. Kemp, H. Bart-Smith, Univ. of Virginia
(United States)
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Conf. 7643: Active and Passive Smart Structures and Integrated
Systems IV
is mimicked. The actuation angle of robotic fish was both estimated
by analysis and measured by experiment to verify the design. The tail
beat angle and the speed of robotic fish in water are also measured at
various input power to test performance of the fish robot.
7643-61, Session 7b
Bio-inspired thorax design for wing flapper
of micro-air-vehicle
W. X. Teo, G. Lau, Nanyang Technological Univ. (Singapore); H. K.
H. Li, DSO National Labs. (Singapore)
7643-64, Session 7b
Development of a propulsion system for
a biomimetic swimmer and the effect of
complex filament on its performance
Wing-flapping insects are impressive and effective natural flyers. Flight
thorax is the oscillating mechanism that flaps the wings. The thorax
stores elastic energy and enables efficient flight. This inspires us a
bio-mimetic design of wing flapping mechanism for micro air vehicles
(MAV). In this paper, we propose a thorax design using compliant
flexures and a vibration motor. The thorax structure is excited into
resonant vibrations using a vibration motor without gears. This design
concept eliminates frictional loss from using gears and revolute joints.
Hence, it can potentially reduce the frictional loss of energy, which is an
issue for a typical actuator system using a motor and gears.
A. Tran-Le, N. Ha, N. Goo, Konkuk Univ. (Korea, Republic of)
In this paper, a biomimetic propulsion concept inspired by the motility
mechanisms of bacteria such as E. Coli was studied basically. E.
Coli and other bacteria use rotating one or several helical filaments
to swim. The performance of the rotating filament mechanism was
estimated by modeling a dynamics of helical wave propulsion. The
dynamic model was considered that a rigid helical filament in fluid of
viscosity , rotated at one end at frequency with the other free. We
applied the Resistance Force Theory (RFT) on this model to calculate
the thrust force and required torque rotating the helical filament. The
Buckingham PI theorem (non-dimensional analysis) was also used to
optimize the design. The non-dimensional analysis results shown that
both the thrust force and required torque were functions of geometry
only. An optimum design is one yields the maximum thrust force and
minimum required torque to rotate the filament. An increase in the
amplitude of the helical filament will increase both thrust force and
required torque. As for the diameter of the helix, the curve of thrust
force looks like parabolic shape and yields the highest thrust force
at a value of it. An increase in the wave length of the helix, both the
thrust force and required torque dramatically and converge to a certain
value. Beside we considered the effect of “complex” filament imitated
from Rhizobium Meliloti bacteria on the thrust force. The procedure for
making complex filament and plain filament were presented in detail. To
validate the theoretical results for helical wave propulsion and compare
the complex and plain filament together, an experiment setup was
carried out to measure the thrust force produced by single filament in
silicone oil. The experimental results were shown to be agreement with
the theoretical values predicted by the RFT model and the maximum
thrust force of complex filament was achieved at pitch angle s =
450. In addition, we found that the thrust force generated by complex
filament had a value about 10 higher than that of plain filament with the
same equivalent diameter, de. Moreover, a novel velocity measurement
setup was designed to measure the velocity of the robot in more
accurate fashion.
Two designs of the frames are presented, fabricated and compared.
The designs are fabricated using carbon-fiber-reinforced epoxy
bonded to a substract of polyimide films. The un-reinforced regions
form the flexural joints. A vibration motor with a rotating unbalance
mass is adopted to excite the thorax structure. Wing flapping motion
is achieved through the lever design mechanism of the thorax and
amplifies the vibrating motion into angular displacement of the wing.
The prototype of less than 5 grams and thoracic frame diameter of 27
mm was demonstrated to achieve a resonant wingbeat frequency of 20
Hz with wing stroke amplitude of 30 degrees. Its performance is shown
to be comparable to those of large insects.
7643-63, Session 7b
Design and demonstration of a fish robot
actuated by a SMA-driven actuation system
C. H. Le, H. C. Park, Konkuk Univ. (Korea, Republic of)
Electric motor has been widely used as an actuator in robotic
world. However, heavy, large size, noisy, and complicated are some
disadvantages of this type of actuator. Recently, artificial muscles have
been developed to overcome these problems. As an application of
artificial muscles, fish robots have been developed by implementing
artificial muscles in their actuation systems. Most recently reported fish
robots are driven by shape memory alloy (SMA), ionic polymer metal
composite (IPMC), and piezoelectric ceramic (PZT).
This work presents a fish robot actuated by 0.1mm diameter SMA
wires. It is aiming to reduce the power consumption as well as
the response time. The fish robot has two main parts: the bending
actuation system and artificial tail fin. The bending actuation system
converts a linear displacement of SMA to bending angle of fish body.
The fish robot body is constructed by several bending actuators in
order to amplify the bending angle of fish robot. In each segment
bending actuator, SMA wires are attached side by side of an elastic
beam. The bending motion of the actuator was created due to the
contraction and the relaxation of the SMA wires. The elastic energy
stored in the elastic beam during heating phase of SMA wire is released
in cooling phase, so that the actuator can quickly recover to the initial
position. For the artificial tail fin, the SMA wires are embedded to an
elastic substrate layer and located between the substrate layer and the
skin layer. SMA wires are connected to the substrate layer at several
contact points. The skin layers are adhered to the elastic substrate, so
that the SMA wires, substrate layer, and skin can bend together during
operation. The elastic property of the substrate plays an important role
in this application because it provides elastic force which can make the
SMA wires to recover faster right after the electric power is switched
off.
7643-107, Session 7b
Biomimetic wing design for the development
of pigeon-inspired flapping-wing MAV
N. Mahardika, H. C. Park, Konkuk Univ. (Korea, Republic of)
Pigeon is one of those nature flyers that have very complex wing
motion. Their wing motion consists of flapping, lead-lagging, feathering
and wing feathers separation. They can also actively flex down
their outer wing during upstroke.Many researchers have studied the
kinematics of pigeon wing include this feature, but the aerodynamic
benefits of that complex motion still not fully investigated. This
becomes a challenge for researchers to investigate the effect and
benefits of that motion. Many researchers have implemented some
structural connections on the wing spar that act as a spring for
outer wing flexion, but their flapping mechanism mostly produces
only flapping motion without lead-lag motion. We believe that the
lead-lag motion also needs to be included in investigating the effect
of outer wing flexion. For the investigation of this feature, we have
made a flapping mechanism based on slider crank configuration that
can create lead-lag motion to mimic the pigeon’s tip path. We have
designed and fabricated a 50cm span biomimetic wing based on a
pigeon wing, the main spar of the wing is modified by installing the
spring between inner and outer wing. Finally, the kinematics test is
The SMA wires are heated by using DC power supply. In order to
provide a precise control, we experimentally and numerically studied
the relationships between strain of the SMA and heating temperature,
the bending angle of actuator and input power, and heating current and
speed response.
To achieve a large thrust force, body and/or caudal fin (BCF) movement
50
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conducted to measure the wing amplitude and twisting angles. Highspeed camera images of the wing motion are used to evaluate and
improve the wing performance. The force measurement by using load
cell is conducted to measure the thrust and lift. Based on the analysis
of high-speed camera images and force measurement, we can analyze
the parameters that affecting the performance of the wing. This study
hopefully can contribute to the area of flapping-wing MAV wing design,
particularly on the effect of outer wing flexion combined with lead-lag
motion.
7643-67, Session 8a
Broadband pulsed flow using piezoelectric
microjets
J. M. Hogue, J. Solomon, F. Alvi, J. Clark, W. S. Oates, Florida
State Univ. (United States)
The ability to actively control high speed flows is an area of research
that has stemmed from the advances in robust actuators and their
integration into aircraft structures including impinging jets, cavities,
and jet inlets. These actuators are under development to understand
fundamental flow characteristics of a pulsed flow microjet for active
flow control. Recent research has shown substantial reductions
in flow separation and jet noise using steady mass flow microjets.
Reductions in mass flux without performance losses are desired by
actively pulsing the microjet. Two piezoelectric actuators have been
designed and tested to investigate this concept for broadband flow
control. A piezohydraulic actuator was the initial test platform for active
flow control. The actuator includes a piezoelectric stack actuator
and hydraulic circuit to achieve sufficient displacement amplification
to throttle a 400 micron diameter microjet. This system is shown to
provide broadband pulsed flow actuation up to 800 Hz. Key parameters
contributing to dynamic actuation are shown to include hydraulic
fluid behavior, biased microjet air pressure, and voltage inputs to the
stack actuator. An actively deforming converging-diverging nozzle was
also designed using a compact piezoelectric stack actuator coupled
to a micronozzle. The nozzle was designed to achieve an average
Mach number of 1.5 and 20%-30% change in Mach number during
piezoelectric actuation. The design of the actuator will be given as well
as preliminary flow and characterization data. A set of key parameters
have been identified and used to guide the design of the actuator.
Supersonic flow was achieved as illustrated using micro-schlieren
techniques to quantify the flow field during steady and pulsed flow.
The new actuator is expected to provide a route towards compact
broadband pulsed microjet actuation for a broad class of aerospace
flow control surfaces.
7643-65, Session 8a
Multiscale analysis of the effect of nanotube
functionalization on damping characteristics
of polymeric composites
A. Liu, K. W. Wang, Univ. of Michigan (United States); C. E. Bakis,
The Pennsylvania State Univ. (United States)
Chemically functionalized carbon nanotubes have been used as
polymer-composite reinforcement in a number of researches [Geng
et al, 2002; Zhu et al, 2004; Liu et al, 2004, Gojny et al, 2003, 2005].
Most of the studies are focused on its elastic properties. Very little
has investigated the effect of nanotube functionalization on damping
properties of polymeric composites, especially with theoretical analysis.
From previous study [Zhou et al., 2004; Liu et al, 2006], the interfacial
shear strength between the nanotube and the polymer as well as
that between nanotubes in a rope play a very important role in
damping characteristics. In this presented paper, the influence of CNT
functionalization on interfacial shear strength and hence on damping
characteristics of CNT-based composites is investigated with a
multiscale model.
The sequential multiscale approach consists of two parts. First of all,
the interfacial shear strength between the functionalized nanotube and
the polymer is calculated by simulating a CNT pull-out test using the
molecular dynamics method. The shear strength values obtained from
atomic simulation are then applied to a micromechanical damping
model of a representative unit cell of a CNT/polymer composite.
TRACK 7: Aircraft, MAV/UAV and Morphing systems
With this multiscale model, polyethylene composites with functionalized
SWNTs are investigated. The effect of nanotube functionalization on
interfacial shear strength is explored by pulling out the SWNT from
crystalline polyethylene matrix which is connected to the SWNT with
different number of functional groups. With the shear strength values
obtained from molecular dynamics simulation, the effective loss factors
of the composites are presented. The analysis results indicate that
the nanotube functionalization increases the interfacial shear strength.
However, the increased shear strength can either enhance or reduce
the effective loss factor of composite, depending on the combined
effect of interfacial shear strength and operational stress range.
7643-68, Session 8a
Distributed intelligence using gallium nitride
based active devices
P. Ramesh, G. N. Washington, S. Rajan, The Ohio State Univ.
(United States)
This research seeks to develop a novel branch of materials systems
called Distributed Intelligent Materials Systems (DIMS) which
incorporate actuation, sensing, and electronics as inherent parts
of the material structure and have the potential to have intelligence
built-in. As a candidate device we highlight a microcantilever optical
switch with Gallium nitride (GaN) as host for a DIMS device. GaN is
a wide-bandgap compound semiconductor that has several material
characteristics, which enable it to outperform other semiconductor
materials for electronic applications. In addition, it displays exceptional
chemical inertness, has a relatively high piezoelectric coefficient, good
mechanical strength and toughness and is transparent to wavelengths
in the visible spectrum.
7643-66, Session 8a
Microfibrous metallic cloth for damping in
printed circuit boards
G. T. Flowers, Auburn Univ. (United States)
As a result of the relatively low intrinsic damping in printed circuit
boards, vibration and shock loading may excite vibration modes
that lead to vibration-induced damage of the PCB and attached
components. An investigation of techniques to enhance the damping
in printed circuit boards is conducted. Experimental evaluation of the
effects of several damping treatments was performed. Of particular
interest were the effects of potting materials and microfibrous metallic
cloth sandwich configurations. The results from different configurations
for each type of treatment are compared and the results discussed.
An overall summary of the results is presented and conclusions/
observations are discussed.
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In this research we develop and fabricate a GaN-based,
piezoelectrically actuated, microcantilever optical switch/waveguide.
While the GaN-material offers the benefits mentioned above, the
piezoelectric actuation and the cantilever design provide benefits of
lighter weight, compactness, speed of actuation, reduced structural
complexity enabling easier fabrication and low wear and tear due
to minimal moving parts. The proposed design has a conventional
unimorph configuration with GaN actuated in d31 mode. In this
configuration, a flat metal electrode and a 2-D electron gas (2DEG)
layer are used to apply an electric field in the top layer thereby causing
it to extend along the cantilever axis. The passive resistance of the
lower layer to this extension causes the cantilever to bend. The
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Conf. 7643: Active and Passive Smart Structures and Integrated
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deflection of the unimorph cantilever tip, which is a key variable of
interest, depends the cantilever length, applied field, ratio of active/
passive layer thicknesses, overall cantilever thickness and the ratio of
elastic moduli of active/passive layers.
7643-71, Session 8b
Autonomic structural materials with
controlled toughening
The unimorph is fabricated as a micro-cantilever by using a GaN on a
GaN substrate, with conducting metal and 2DEG electrodes. First, the
GaN is deposited using molecular beam epitaxy. The cantilever is then
etched using a combination of inductively coupled plasma etching,
electron-beam evaporation and liftoff, and a photoelectrochemical
(PEC) etch. The microcantilever is subjected to static and dynamic
testing to quantify device performance.
M. E. Garcia, H. A. Sodano, Arizona State Univ. (United States)
The field of Structural Health Monitoring (SHM) has grown significantly
over the past few years due to the safety and performance enhancing
benefits as well as the potential life saving capabilities offered by the
technology. Current advances in SHM systems have lead to a variety
of techniques capable of identifying damage; however, few strategies
exist for using this information to quickly react to environmental or
material conditions needed to repair or protect the system. Rather,
current systems simply relay this information to a central processor
or human operator, who then decides on a course of action, such
as altering the mission or scheduling a repair operation. Biological
systems exhibit many advanced sensory and healing traits that can
be applied to the design of material systems. For instance, bones
are the major structural component in vertebrates; however, unlike
modern structural materials, bones have many properties that make
it effective for arresting the development and propagation of cracks
and subsequent healing of the damaged region. The foremost goal
for the development of future adaptive structures is to provide the
material itself with the ability to mimic biological systems, such as
bones, and autonomously adapt to impede the progression of damage
and subsequently heal the damaged structure. One of the challenging
issues in the design of autonomous materials is that the materials
respond actively in delivering the stimulus to the damage site without
complex locating algorithms. In order to overcome this complication,
an autonomous material system is devised that uses Shape Memory
Polymers (SMPs) with an embedded fiber optic network. Using SMPs,
a novel system is developed that employs an optical fiber network as
both a damage detection sensor and a network to deliver stimulus to
the damage site, initiating adaptation and healing. In the presence of
damage, the fiber optic fractures allowing a high power laser diode
to deposit a controlled level of thermal energy at the damage site,
locally reducing the modulus and blunting the crack tip. The shape
memory polymer not only provides a sharp glass transition, but also
allows for the application of an induced global pre-strain, which under
thermal loads induces the shape memory effect to close the crack. It
will be shown that the material can be significantly toughened and that
control algorithms combined with the shape memory properties can
further increase the toughening effect. The entire system will be able
to effectively sense damage and self toughen similarly as bone does
autonomously.
7643-69, Session 8a
Nano-silicon based photonic crystal stamps
with electron beam lithography (EBL)
technology
R. Jannesary, Johannes Kepler Univ. Linz (Austria)
we report on using e-beam lithographically technology for enabling the
mass replication of custom-designed and prepared Nano-structures via
establishing nanoimprint processes for pattern transfer into UV curable
pre-polymes. By EBL, the new nano-fabrication technology based on
the concept of disposal master technology (DMT) is suitable for mass
volume manufacturing of large area arrays of sub-wavelength photonic
elements.
We will present some kinds of PhC and waveguides for fabrication of
nanoimprint Electron beam lithography stamps in Si. (a) a photonic
crystal of Si-rods in air optimized in that with electron beam lithography
(EBL) pattern create on resist and after lift-off, there is a mask of Cr
on Si, then the pattern transfer into Si was performed using reacting
ion etching with an etch gas. We use the positive resist PMMA for
EBL exposure. Resist thickness, exposure dose, development time
and parameter for etching have been optimized in this method was
fabricated (b) in the second method lift-off was not performed and
metal mask was used as master.
7643-70, Session 8b
Variable stiffness fluidic actuator based on
F2MC and piezoelectric-hydraulic pump
G. Kim, S. Li, K. Wang, Univ. of Michigan (United States)
7643-72, Session 8b
Recently, new biological-inspired fluidic flexible matrix composite
(F2MC) has been developed for autonomous structural tailoring and
high-mechanical-advantage linear/torsion actuator. Although the
actuation function and the variable stiffness function of fluidic FMC
(F2MC) have been successfully demonstrated, their full potentials are
not yet manifested due to the limitations of the currently employed
conventional pressure sources and simple on/off valve control action.
In order to use F2MC as an actuator, the stand-alone pressure
actuation (control) system has to be essentially incorporated. However,
current hydraulic/pneumatic actuation systems are bulky and relatively
heavy, reducing the promising potential of F2MC actuator (i.e., high
power density).
Non-invasive measurement techniques for
measuring bilayers and protein activity in
droplet-interface-bilayers
M. A. Creasy, D. J. Leo, Virginia Polytechnic Institute and State
Univ. (United States)
Cell membranes are made of phospholipids, proteins, and
carbohydrates. The phospholipids are the passive structure of the
membrane that acts as a barrier between the inner and outer portions
of the cell. The proteins are the active structure of the membrane
that allows signaling, energy conversion, and open channels. The
carbohydrates are usually attached to either the phospholipids or
proteins and assists in the aforementioned activity. A Droplet-InterfaceBilayer (DIB) is an artificial means of making a cell membrane using
natural or artificial membrane components. Water droplets in oil are
used as an interface for the membrane components to self assemble
into an organized structure that mimics a cell membrane. Electrical
measurements are used to test the bilayer properties by applying an
artificial potential across the membrane and measuring the resulting
current. This research shows that the electrical properties of the bilayer
can be measured non-invasively (without an electrode placed in the
water droplet). The electrodes can touch the exterior of the droplets,
where a monolayer is formed, and either attach to the monolayer or
To address the aforementioned issue, we synthesize a new multifunctional fluidic actuator that can provide both high efficient actuation
and actively tunable stiffness. This structure design incorporates two
innovative ideas: a flexible matrix composite (F2MC) and a compact
piezoelectric-hydraulic pump (PHP). By integrating a transverse
honeycomb F2MC tube structure with the PHP, one can create a
monolithic compliant bending actuator. In addition, one can achieve
both the desired shape (position) and variable stiffness through the
PHP.
52
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form a bilayer at the droplet electrode interface. The actual connection
is dependent on electrode preparation and both scenarios will add
a resistor and capacitor (RC) circuit to the electrical measurement of
the system. A model of the RC circuit is incorporated into the system
model and properties of the DIB are extracted from the system model
that is matched to the measured data.
7643-74, Session 8b
Comparison of the throughput of techniques
for prototyping protein-bound suspended
bilayer lipid membranes
V. B. Sundaresan, Virginia Commonwealth Univ. (United States)
7643-73, Session 8b
Suspended lipid bilayer membranes (BLM) offer an ideal environment
for characterizing membrane-bound proteins used in biosensors,
energy harvesting devices and drug screening platforms. The
plethora of techniques used for forming suspended BLM relies on
manual processes to trigger self-assembly and protein reconstitution.
The most popular techniques such as painting, tip-dip method,
Langmuir-Schaeffer technique, microfluidic platforms, droplet
interface techniques and agar-supported membrane self-assembly
while being successfully used to demonstrate protein reconstitution
have not been compared against each other for their throughput of
membrane formation. The substrate material, protein reconstituted
into the membrane and the orientation of the membrane limits the
applicability of each technique. A one-on-one comparison of the
membranes formed by different techniques is missing and hence this
article attempts to address the void by comparing the throughput
of membrane formation, long-term stability of the membrane and
applicability of different techniques for different protein-based devices.
An automated fabrication setup for each technique (painting, falling
droplet, microfluidic platform and tip-dip method) is developed so that
the membranes formed from a large sample (>50) is compared with
each other. The reconstitution of a suitable protein such as alamethicin,
gramicidin and GPCR cell lines will be tested for protein activity to
estimate the efficiency of reconstitution. The results will be significant
to compare and contrast the membrane self-assembly processes and
protein reconstitution by different techniques and to extend each of
these techniques to form a block co-polymerized BLM for proteinbased devices.
Constructing precise bio-inspired material
systems in flexible substrates using the
regulated attachment method
S. A. Sarles, D. J. Leo, Virginia Polytechnic Institute and State Univ.
(United States)
The principles of molecular self-assembly permit the construction of
synthetic biomolecular material systems that mimic the architecture
and active functionality of their natural analogues. One such material
system is the lipid bilayer, a two-molecule thick fluid membrane
composed of phospholipid molecules that mimics the plasma
membrane of plant and animal cells. Researchers have formed lipid
bilayers using a number of techniques since the early 1960’s and their
findings provided valuable information about the structural properties
of cell membranes and the functions of transmembrane molecules,
such as proteins. However, the fragility of these molecular assemblies
has prevented their use beyond controlled studies in a laboratory
environment. The droplet interface bilayer (DIB) that emerged in
recent years provided an alternative approach for bilayer formation,
in which a lipid bilayer is formed at the interface of lipid-encased
water droplets submersed in oil, and showcased the utility of active
biomolecular systems. The primary advantage of this technique is
the ability to construct precise biomolecular material systems, where
the arrangement and composition of the droplets determines the
collective properties of the network. Early demonstrations include a
light-activated current source using bacteriorhodopsin proteins and
a full-wave bridge rectifier with genetically-modified alpha-hemolysin
channels.
7643-75, Session 9a
Post-buckled precompressed (PBP) solid
state adaptive rotor
However, the advantages of DIB networks are offset by several
challenges in creating large arrays, including: dispensing and
manipulating large numbers of small droplets (<100μm diameter),
altering the compositions of molecules in specific parts of the network,
controlling the sizes of the interfaces, and designing the system for
portability. Recently, we developed a new method for bilayer formation,
called the regulated attachment method (RAM), in which durable lipid
bilayers are formed in a flexible substrate. This technique employs
control of a deformable substrate through an applied mechanical
force to regulate the attachment of adjacent lipid-encased aqueous
volumes submersed in oil. RAM further departs from the DIB in that
the size of a lipid bilayer is controlled by varying the dimensions of an
aperture in the flexible substrate that separates neighboring aqueous
volumes. In this manner, the regulated attachment method provides
key advantages over droplet interface bilayers for constructing durable
and useful biomolecular networks. First, the size of the bilayer can be
prescribed and, unlike DIBs, bilayer size is independent of the size or
shape of either aqueous volume. Second, RAM affords precise control
over the composition of the network, even allowing the introduction of
species into specific lipid bilayers after network formation. Third, the
regulated attachment method enables direct integration into portable
microfluidic lab-on-chip type devices for creating precise biomolecular
networks that feature durable lipid bilayers assembled on the micro- or
sub-micron scale.
R. M. Barrett, R. Barnhart, L. Kerth, The Univ. of Kansas (United
States)
The paper begins with a brief historical review of solid state adaptive
rotor systems which stretch back to patents first filed in 1989. An
historical summary takes the reader through early linear/conventional
rotor systems of the 1990’s and the lull in progress experienced in the
late 1990’s prior to the discovery of nonlinear/postbuckled actuation
methods. This paper covers modeling techniques and design principles
for Post-Buckled Precompressed (PBP) Solid State Adaptive Rotors
using piezoelectric torque-plate actuators mounted at the rotor hub.
The nonlinear solid state arrangement allows for full control of blade
pitch deflections through +26/-7 deg, flapping through +18/-5 deg.
and even lead-lag articulation of +/-5 deg. In addition to allowing
conventional blade motions and control with a solid state mechanism,
pitch-flap equivalent δ3 coupling is achieved by using inherent
properties of the actuation system. Analytical modeling begins with
fundamental Classical Laminate Plate Theory expressions. These
are expanded to include plate imperfection models to account for
Post-Buckled Precompression. A 20cm x 5cm PZT-5H piezoelectric
torque-plate actuator was built into the root of a helicopter rotor blade
assembly. The 120cm diameter rotor assembly was whirl-stand tested
through 700 RPM showing excellent correlation between theory and
experiment. High speed tests were conducted at rates of up to 5/rev.,
again, showing excellent correlation between theory and experiment.
The paper concludes with a feasibility assessment, showing the PBP
rotor possesses three times more control authority than the next
closest adaptive control technique for collective, cyclic and high speed,
high authority individual blade control.
Our work from here is focused on developing more-complex flexible
substrates that employ the regulated attachment method to create
self-contained biomolecular networks featuring tailored lipid bilayer
interfaces. Specifically, we plan to investigate alternative methods such
as embedded magnets for opening and closing apertures and develop
novel applications for these networks, including color-change materials
and low-power energy-harvesting networks.
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Energy and variational methods are used to derive the governing
equations and the resulted governing equations are solved using the
Rayleigh-Ritz method in conjunction with the Lagrange multipliers
method. Furthermore, the mathematical model of the shim stack is
implemented in a mono-tube hydraulic damper model and the effects
of various shim stack configurations are studied.
7643-76, Session 9a
Robustness of orthogonal eigenstructure
control to actuators failure
M. Rastgaar Aagaah, Massachusetts Institute of Technology
(United States); M. Ahmadian, Virginia Polytechnic Institute and
State Univ. (United States)
7643-78, Session 9a
Orthogonal eigenstructure control has been recently developed by
the authors for vibration control in structures. This control method
is applicable to the multi-input multi-output linear systems. In this
paper, the robustness of the method to the failure of the actuators is
investigated. It is shown when an actuator fails, the control gain matrix
still is able to control the systems, since the closed-loop eigenvectors
are within the achievable eigenvectors set. A system of lumped
masses has been used to elaborate the method; then, the problem
of failed actuators in the vibration control of a plate is investigated.
Finite element method is used for modeling the plate to simulate the
dynamical behavior of the system. Five cases are considered and the
suppression of the vibration in a plate with three working actuators
is compared to the suppressed vibration of the plates with one failed
actuator. Also, the behaviors of the system with failed actuators are
compared to the systems that are designed to operate with exactly
lesser control actuators. It is shown that the number of moved closedloop eigenvalue pairs is equal to the number of working actuators. The
closed-loop poles in all the systems are moved to the vicinity of one
specific area, which results in a robust control.
Free space optical coupling of embedded
reflection-based fiber Bragg grating sensors
through panel surfaces
L. Qiu, M. E. Teitelbaum, K. W. Goossen, D. Heider, Univ. of
Delaware (United States); D. J. O’Brien, E. D. Wetzel, Army
Research Lab. (United States)
In recent decades, optical fiber has proven useful for many sensor
applications. Specifically, fiber Bragg grating (FBG) sensors have
shown great utility for integrity management and environmental sensing
of composite structures. One major drawback of FBG sensors however,
is that they suffer from cumbersome and fragile techniques for bringing
the sensing light into and out of the structure since the optical fiber
must be routed through the surface of the composite (i.e. pigtailing). In
this paper, a novel method of free space passive coupling of light has
been investigated. The use of 45-degree-angled mirrors integrated into
fibers was used as an input and output coupling technique. With the
difficulty of directly integrating the mirrors onto the tiny single mode
fibers, a novel method of coupling to the sensor via splicing and fusing
a multimode fiber to the single mode FBG was explored. Using this
method, we have previously demonstrated free space optical coupling
to transmission-based FBG sensors embedded inside a composite
panel. In this paper, we are able to couple the reflected light of the
embedded FBG sensors through the panel surfaces with the 45degree-angled mirrors. Therefore, we conclude that this novel space
coupling method can be used to effectively couple the transmitted and
reflected light for embedded FBG sensors.
7643-77, Session 9a
Shim stack deflection analysis in hydraulic
dampers using energy methods
A. Farjoud, M. Ahmadian, Virginia Polytechnic Institute and State
Univ. (United States)
This paper presents a detailed analysis of the deflection of the shim
stacks used in hydraulic dampers. In hydraulic dampers, a stack of
circular disks (shims) is mounted on each side of the main piston to
create a pressure drop as the hydraulic oil is passed through the piston
from one side to the other. A stiff shim stack creates a high pressure
drop across the piston, resulting in high damping. A softer shim stack
creates less pressure drop and smaller damping. In practice, shims
can be added or removed from the shim stack assembly to tune the
damper and generate the desired damping force characteristics as
a function of velocity. Tuning a damper requires taking the damper
apart, making the changes to the shim stack assembly, and putting the
damper back together. This takes a considerable amount of time and
effort. Therefore, mathematical modeling of the shim stack assembly
becomes a crucial part of the analysis of hydraulic dampers.
7643-79, Session 9a
Vibration based analysis of an increasing
delamination in a carbon/epoxy composite
structure
M. Mehdizadeh, S. J. John, RMIT Univ. (Australia)
This paper reports on the assessment of variable damage
configurations in a carbon/epoxy composite material using its vibration
response. This paper highlights the application of vibration based
testing on Carbon/Epoxy composite beams for damage detection.
Such composites are commonly used in the aerospace and marine
industry. The study comprises of testing carbon/epoxy composite
beams with various embedded delaminations with a mechanical
actuator and a Scanning Laser Vibrometer (SLV) as a sensor for
recording the frequency response and the subsequent analyses
of the acquired dynamic response based on Displacement and
Curvature Mode Shapes. This paper also reports on an innovative
way of extending an existing delamination by a fatigue crack-growth
technique. Pre- and Post-crack growth curvature-mode shape analyses
were undertaken, reported and compared. . The ASTM E399-90
standard is used for the experiment and a careful fatigue crack growth
routine was designed and implemented to advance the delamination in
a controlled manner.
The goal of the study presented here is to provide a model of the shim
stack assembly in order to accurately predict the level of damping
for different configurations of the shim stack. The shims that are
stacked on each other will deflect under the pressure created by
the hydraulic oil, and at the same time slide against each other. This
important characteristic of the shim stack needs to be accounted for
in the mathematical model and makes the analysis complicated. For
the sake of simplicity, in past studies the shim stack is approximated
by the deflection of a single disk and formulas for a single disk are
used. This, however, introduces a significant amount of error in the
damper hydraulic model. In this paper, the deflection of shim stacks
is analyzed and compared with the single disk approximation. It is
found that this approximation fails to agree with the more accurate
model of representing the shims individually. Therefore, a more detailed
and accurate model is necessary for better simulating the damping
characteristics of hydraulic dampers as a function of relative velocity
across the damper.
Composite materials are supplanting conventional metals in aerospace,
civil and marine industries. Composite materials have excellent
mechanical properties such as good strength-to-weight ratios, however
they are prone to sub-surface flaws such as delaminations, which are
difficult to detect. Thus, it is important that the initial defect be detected
before it initiates into a serious flaw. There are a number of local- and
global-damage detection methods for the detection and localisation
of the damage in a composite material.The research study conducted
This study provides the results of an analytical study that considers
different cases. First, the shear deformations are neglected. Then
the shear deformations are included in the model and the results are
compared with the simple case. It is found that the shear deformations
are not negligible and should be included in the mathematical model.
54
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cascade, because the flexible robot presented in this work can be
described as a cascade interconection of two dynamical systems being
the set of rigid modes the first system and the set of flexible modes the
second system. The second one is the energy-based control method
called strain feedback. Stability analyses are provided for both control
methods. Finally, the overall system performance is illustrated by some
experimental results obtained with both control methods.
here primarily deals with the structural health monitoring of composite
materials by analyzing vibration signatures acquired from a laser
vibrometer. The primary aim of the project is to develop a vibration
based structural health monitoring (SHM) method for detecting flaws
such as delamination within the composite beams. Secondly, the
project emphasizes on the method’s ability to recognize the location
and severity of the damage within the structure. The system proposed
relies on the examination of the displacement mode shapes acquired
from the composite beams using the laser vibrometer and later
processing them to curvature mode shapes for damage identification
and characterization. Other identification techniques such as a C-scan
has been applied to validate the location and size of the defects with
the structures tested.
7643-81, Session 9b
Configuration of a shear web based
actuation system
In addition to this, this paper also introduces a method to
experimentally compute the critical stress intensity factor, KIC based on
ASTM E399-90 for the composite beam. Based on this, a technique for
extending the defect has been proposed and validated using concepts
of fatigue and fracture mechanics. The experimental procedure to
extend the defect using fatigue was validated using the SLV system.
Displacement and Curvature mode shapes were acquired and analyzed
post-fatigue crack extension.
F. J. Natterer, Deutsches Zentrum für Luft- und Raumfahrt e.V.
(Germany)
Shape adaptive systems and structural configurations are necessary
to fulfil the demands of a future unmanned aerial vehicle structure.
Predominantly the present approaches are based on a passive
load-bearing structure having smart actuation systems deforming
the passive structural configuration elastically in the wanted shape.
Therefore the actuation system can be based on discrete actuators,
like electrically driven motors using gearing systems to transform the
displacement into the structure or on smart material configurations
places on the load bearing passive structure, deforming the structure
within the elastic region into the wanted shape.
Upon analyzing and comparing the displacement and curvature mode
shapes before and after crack extension, the original and extended
delamination were identified satisfactorily.The output from these plots
enabled the successful identification of both the location and extent of
damage within the structure with an accuracy of 96.5%.
This paper demonstrates the feasibility of examining features of
curvature mode shape analyses when comparing its effect on different
damage configurations. In the discussions above, it is clear that
damage parameters such defect size can be delineated using the
curvature mode shape analyses. The fatigue crack growth technique
employed in this paper enabled an escalation in the damage size
without necessarily introducing additional damage features such
as impact and local indentations around the original damage
configuration. This technique thus, enables an added dimension of
study of damage analyses, which has proved perhaps too cumbersome
and complex in the past. The experimental program here comprises
of testing Carbon/epoxy composite laminated plates with embedded
delaminations both before and after crack propagation using the SLV
actuator-sensor measurement system. This was corroborated using
Finite Element Analyses (FEA) models.
Using smart materials within load-bearing structures, elastic and
static strength properties vary between passive and active structures.
Matching these properties is a great challenge for future structural
configurations. This is a successful approach for certain applications,
e.g. smart rotor blade.
The availability of two-dimensional smart actuator configurations with
distinct actuation orientation allows the definition of a distinct load
bearing active structure. Therefore the so called “web” of a sparequivalent configuration was substituted by such a smart material
actuator also known as macro fibre composite (MFC). Activating the
web of the active cantilevered spar-configuration is resulting in a
free end displacement. The main advantage lies in the fact that this
approach will allow larger active displacements in comparison to a
passive structural configuration with applied smart material actuators.
7643-80, Session 9a
Within the paper the process of developing the shear web based
actuation system with configuration details will be illustrated and future
steps will be proposed.
Modeling and control for a planar robot with
one rigid link and one flexible link
7643-82, Session 9b
J. F. Peza-Solis, G. Silva-Navarro, R. Castro-Linares, Ctr. de
Investigación y de Estudios Avanzados (Mexico)
Piezoelectrically actuated insect scale
flapping wing
This work describes the modeling and control of
S. Mukherjee, R. Ganguli, Indian Institute of Science (India)
an experimental platform associated to a two joint robot with one rigid
link attached to a main frame which is fixed to the base of the robot
and one flexible link attached to the end of first rigid link to form a
robotic arm, whose motion is restricted to an horizontal plane, so that
the gravity effects are neglected. The modeling problem is addressed
using the Euler-Lagrange formalism and the so-called Euler-Bernoulli
beam equation is used to describe the dynamical behavior for the
flexible link. Since the flexible link is attached to a moving frame
associated to the rigid link motion, the clamped-free modal shapes
cannot longer be assumed in the modeling of the flexible link. Thus,
the modal shapes are derived by using inertial boundary conditions at
both extremes of the flexible link and its first three modal shapes are
included in the model in order to achieve good accuracy. The design,
construction and integration of an experimental set-up developed for
this work is also presented. The vibration amplitude of each modal
shape considered in the flexible link is estimated via a set of three
strain gages fixed at specific locations along the flexible link. These
strain gages are employed as deflection sensors for the flexible link.
Two main control schemes are then devised for controlling the end
tip position of the flexible robot. The first one is the so-called passive
velocity feedback based on the backstepping technique used for
passivity-based control designs of nonlinear systems performing a
Research interest on micro air vehicles (MAVs) has been growing
because they have a large number of potential military and commercial
applications. The potential applications of current fixed wing MAVs
are limited due to maneuver constraints, incapability to hover and
stall at low speeds. Rotary wing MAVs can hover but they suffer
from low figure of merit, high power consumption and significant
noise signatures. Nature provides flapping flyers such as birds and
insects which represent a very successful design for intelligent MAVs
with much better performance than conventional wings and rotors
in terms of hovering capability, maneuverability, acoustic signature,
specific power requirement etc. Lightweight, flexible and adaptive/
morphing wing structures make an important contribution to the
overall performance of a flapping wing MAV. Thus, MAV flapping wing
design represents one of the major challenges to efficient flight in the
low Reynolds-number regime. Currently, flapping wing mechanisms
rely on pneumatic and motor-driven flapping actuators which lead to
high weight and system-complexity. Moreover, natural flapping flyers
generate lift and thrust using complex wingbeat kinematics which can
not be easily mimicked with these conventional actuators. Piezoelectric
fan (piezofan) which couples a piezoelectric unimorph to an attached
flexible wing is competent to produce large deflection especially
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Conf. 7643: Active and Passive Smart Structures and Integrated
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proximity aerodynamic and dynamics test will be performed.
at resonance. In this paper, we analyze and design an insect-scale
piezoelectrically actuated flapping wing. Numerical simulations are
used to achieve several aspects of insect wingbeat kinematics by the
flapping wing. Finally, aerodynamic performances are evaluated using
a design oriented model for the unsteady aerodynamics of a flapping
wing.(TRACK 2: Biological-inspired Systems and Bio-MEMS)
I want to submit this paper to the following track:
TRACK 7: Aircraft, MAV/UAV and Morphing systems
7643-86, Session 9b
Ornithopter transition trajectories
7643-84, Session 9b
J. M. Dietl, E. Garcia, Cornell Univ. (United States)
Modeling and experimental validation of a
bistable mechanism for chord extension
morphing rotors
Current ornithopter research concerns ornithopter construction, power
sources, wing design, maximizing thrust, energy efficiency, steady flight
trajectories, and flight stability. Another goal is to control unsteady
maneuvers: the transition from hovering flight to forward flight, turns,
and vertical takeoff and landing.
T. E. Johnson, M. I. Frecker, F. Gandhi, The Pennsylvania State
Univ. (United States)
The design of stable trim conditions for forward flight and for hover
has been achieved. In forward flight, an ornithopter is configured like a
conventional airplane or large bird. Its fuselage is essentially horizontal
and the wings heave in a vertical plane. In hover, however, the body
pitches vertically so that the wing stroke in the horizontal plane. Thrust
directed downward, the vehicle remains aloft while the downdraft
envelops the tail to provide enough flow for vehicle control and
stabilization. To connect these trajectories dynamically is the goal.
A concept for SETE plate extension that was recently proposed is the
use of a bistable arch for chord extension. In the previous work, the
bistable concept is applied to a helicopter rotor blade. In this work,
the developed concept for SETE plate extension is modeled and
experimentally validated. There are four foci of this paper: (1) Stress
Analysis of the Arch, (2) Model Validation via Experiment, (3) Force
Study using Nonlinear Finite Element Analysis, and (4) Actuation using
SMA Wires. A stress analysis is conducted on the arch because the
living hinges possess high levels of Von Mises stress which could lead
to yielding and facture. Following the stress analysis, the arch with
living hinges is fabricated using Delrin and tested using a 10kN Instron
machine. An experiment is conducted using the Instron machine
where force versus displacement data is measured for the arch and
compared to the Non-Linear FEA model. Following validation of the
numerical model, additional force studies are conducted using the
Non-Linear FEA model to determine arch robustness while subjected to
aerodynamic load. Lastly, SMA wires are added to the arch to actuate
the arch between its stable states. The modeling and experimental
validation of the arch-plate system are expected to show that the
bistable arch and plate system is an effective solution to aircraft chord
extension.
The naïve approach-to choose two stable trajectories and switch
between them-has been accomplished. A new approach is to establish
an open-loop trajectory through a trajectory optimization algorithmoptimized for shortest altitude drop, shortest stopping distance, or
lowest energy consumption. This path itself could be stabilized.
This serves to establish the feasibility of new maneuvers in mechanical
flapping flight. It also will make it easier to perform the maneuvers by
computer assisted control or by providing an example for a pilot to use.
7643-87, Session 10a
Adaptive control of base-isolated buildings
using piezoelectric friction dampers against
near-field earthquake
7643-85, Session 9b
O. E. Ozbulut, M. Bitaraf, S. Hurlebaus, Texas A&M Univ. (United
States)
Aircraft dynamics and wind tunnel testing of
two linked UAV systems
This paper investigates the effectiveness of two adaptive control
strategies for modulating control force of piezoelectric friction dampers
(PFD) that are employed as semi-active devices in combination with
laminated rubber bearings for seismic protection of buildings. The
first controller developed in this study is a direct adaptive fuzzy logic
controller. It consists of a higher-level supervisory fuzzy controller and
a sub-level direct fuzzy controller. In the hierarchical control scheme,
high-level controller modifies universe of discourse of both premise and
consequent variables of the sub-level controller using scaling factors
in order to determine command voltage of the damper according
to current level of ground motion. The sub-level fuzzy controller
employs isolation displacement and velocity as its premise variables
and command voltage as its consequent variable. In order to specify
appropriate scaling factors for variables of the sub-level controller, the
high-level controller uses ground velocity as its input variable to acquire
information on the characteristics of seismic excitation.
E. A. Cuji, E. Garcia, Cornell Univ. (United States)
This paper presents an analysis of close proximity aerodynamics and
aircraft dynamics of two conjoined UAVs. Conjoined UAV concept
allows for rapidly deployable ISR platform using individual UAVs with
wingspans small enough to be deployed from any general aviation
airfields. Then individual UAVs will link at high altitude to create an
aerodynamically efficient aircraft which has long endurance capabilities
and can be able to cruise for extended periods at very low power. As
the UAV approach each other for wingtip docking there will be strong
aerodynamic coupling between the UAV wings tips. Determining
the aerodynamic coupling effects on all the forces and moments
is essential to determine a trajectory and controls for each UAV to
perform the docking maneuver. Simulation and wind tunnel testing of
close proximity effects on lift, drag, roll pitch and yaw moments for
two UAV wings will be performed. The proximity aerodynamics effects
between the UAVs wings will be analyzed as a function of its relative
position in all three directions: chord-wise (x - direction), span-wise (y direction), and vertical direction (z - direction).
The second controller is based on the simple adaptive control (SAC)
method, which is a type of direct adaptive control approach. The
objective of the SAC method is to make the plant, the controlled
system, track the behavior of the model or the structure with the
optimum performance. By using SAC strategy, any change in the
characteristics of the structure or uncertainties in the modeling of the
structure and in the external excitation would be considered because
it continuously monitors its own performance to modify its parameters.
Here, SAC methodology is employed to obtain the required force
which results in the optimum performance of the structure. Then, the
command voltage of the PFD is determined to generate the desired
force.
A look-up library of aerodynamic forces and moments for all relative
positions and angles of attack between the two UAVs will be
developed. In this study we will examine how the close proximity
aerodynamics affects the dynamics and stability of the UAVs. The
aircraft dynamics analysis will be done in Simulink, which will include
the close proximity aerodynamic look-up library. An aerodynamic
disturbance intensity field will be performed, utilizing both simulation
and wind tunnel data, to determine a trajectory for the two UAVs to
approach each other for docking. A wind tunnel verification of the close
56
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and considered in the simulations together with maximum passive
operation of the friction damper. Time-history analyses of a baseisolated five-story building are performed to evaluate the performance
of the controllers. Fault-normal and fault-parallel components of eight
historical earthquakes are used as external excitation. A total of nine
performance indices are defined and computed for each controller to
assess the simulation results. Results reveal that developed adaptive
controlllers can succesfully improves sesimic response of the baseisolated buildings against various types of earthquakes.
F. Bachmann, P. Ermanni, ETH Zürich (Switzerland)
This work has been inspired by scientific and technological challenges
investigated in the frame of the European research project DREAM.
This strongly interdisciplinary project aims at the development of
novel approaches for structural vibration damping with piezoelectric
actuators and autonomous shunt circuits.
During the last decades, vibration damping using piezoelectric
actuators has been intensively investigated. Fundamental research
in the area of actuators ultimately led to the realization and
commercialization of ready to use actuators with well defined interfaces
for electrical contacting. However, actuators available on the market
are well-suited for superficial applications. Thus structural integration
of piezoelectric actuators into composite structures still remains an
actual field of research. Open issues concern the development of viable
solutions for the integration of piezoelectric actuators and shunt circuits
into an electrically conducting environment such as a CFRP laminate.
TRACK 3
7643-88, Session 10a
Vibration absorption in a building like
structure by means of piezoelectric patches
and positive acceleration feedback
Besides, wiring and connection to the shunt circuit, mechanical
integrity of the host structure, strength and damage tolerance of the
smart damping system are of paramount importance. These challenges
become even more evident, when dealing with high loading conditions,
exceeding the allowable strain of commercially available actuators. In
this context our contribution is presenting a novel integration method
based on a mechanical pre-stressing of the monolithic piezoelectric
actuator. Numerical and experimental investigations conducted in our
lab show that this solution clearly has a beneficial impact on the failure
onset of the piezo-ceramic element.
M. A. Rios, G. Silva-Navarro, Ctr. de Investigación y de Estudios
Avanzados (Mexico)
This paper is about vibration absorption in a building like structure,
by means of piezoelectric patches. The experimental plant consists
in a bolted aluminum structure. It is approximately 3 ft high and has
three levels. Piezoelectric patches are used to actuate the structure.
A piezoelectric accelerometer is used to sense the vibration in the
structure. The whole structure system is on a frictionless slider. An
electrodynamical shaker is used to perturbate the structure at several
harmonic conditions. Modeling of the structure is made by finite
elements. To proper identify structural parameters in the experimental
plant, modal analysis techniques are used. The experimental plant
is instrumented and connected to a personal computer via a data
acquisition (DAQ) system. The DAQ software is a National Instruments
CompactDAQ system. Reading the sensors and closed loop control
are implemented using LabVIEW software. The control scheme is a
Positive Acceleration Feedback. It gave god performance in a wide
range of frequencies. Numerical and experimental results are shown.
7643-91, Session 10a
An active non-contact radial and axial
bearing system actuated by high power
piezoelectric transducers
S. Zhao, J. Wallaschek, Leibniz Univ. Hannover (Germany)
A novel active squeeze film journal bearing actuated by high power
piezoelectric transducers is developed aiming for noncontact axial
and radial suspension of a rotating. The bearing system includes a
journal bearing and a thrust bearing, both based on squeeze film
ultrasonic levitation. The journal bearing consists of three piezoelectric
transducers mounted on housing. Each transducer has a concave
radiation surface which covers 100 degrees of a cylindrical surface. The
thrust bearing consists of a circular plate driven in its flexural vibration
mode by a piezoelectric transducer. An electromagnet motor is built
into the spindle to rotate the spindle at high speed.
7643-89, Session 10a
Using coupled piezoelectric circuits to
enhance damage detection of periodic
structures
J. Zhao, J. Tang, Univ. of Connecticut (United States)
Mathematical models based on Reynolds equation are developed
to predict the levitation force of the proposed bearing system. Both
analytical and numerical solutions are carried out. The analytical results
give good insight to the characteristics of the system with acceptable
accuracy. The numerical results agree well quantitatively with the
experimental results. The analytical model is integrated into the model
of the electro-mechanical system to describe the total dynamics of the
bearing system. Experimental results are carried out using a prototype
system. The spindle is suspended in both axial and radial directions
without mechanical contact. The run-out errors at various rotational
speeds are measured. The maximum radial and thrust load-carrying
forces are measured as 53 and 120 N. The axial and radial position
of the spindle is measured by the integrated eddy current sensors.
Positioning of the spindle is realized by actively adjusting the vibration
amplitudes of the transducers.
Spatially periodic structures such as turbine bladed-disk are widely
used in engineering systems. The timely detection of damage/
fault in these structures has obvious significance. Modern sensing
technologies, such as the blade-tip-timing technology, allow the
measurement of vibratory response of rotating bladed-disks, which
yields the possibility of on-line health monitoring. Generally, the
damage-induced frequency change is small. Moreover, the natural
frequencies for such structures generally are clustered, which makes
it difficult to use the frequency-shift information to analyze damage
occurrence. In this research, we propose to integrate identical
and coupled piezoelectric circuitries to all substructures, aiming at
amplifying the vibration pattern difference induced by the damage
occurrence. Specifically, circuitry elements leading to negative
resistance will be incorporated. It will be shown that properly designed
negative resistance elements and coupling capacitances can greatly
amplify the damage-induced response difference, thereby highlighting
the damage occurrence in the inspection stage. We carry out
systematic analysis to demonstrate that such amplification effect is
robust with respect to the inherent mistuning of the healthy structure.
(Track 5)
7643-92, Session 10a
7643-90, Session 10a
Semi-solid state adaptive impedance
composites for HIRF protection
Integration of encapsulated piezoelectric
actuators in highly loaded CFRP structures
R. B. Bramlette, M. T. Brennison, R. M. Barrett, The Univ. of Kansas
(United States)
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This paper investigates the feasibility of piezoelectric-based adaptiveimpedance composites (AIC) as a method of protecting aircraft
equipment from lightning strike events and the resultant high-intensity
radiated fields (HIRF). The paper begins with a summary of a typical
aircraft lightning strike event and the requirements necessary to
shield hardware from the effects. The paper then describes the
development of the AIC, and the mechanics involved in the impedancebased switching effect. To further explain and analytically derive the
performance of the AIC, classical laminated plate theory (CLPT) and
plate vibration theory were applied.
presence of nonlinearities. To the best of the authors’ knowledge, this
is the first time that the effects of nonlinear constitutive equations of
piezoelectric materials on helicopter vibration reduction are inspected.
In order to introduce the piezoelectric nonlinearity into the formulation,
an extended expression of the strain energy per unit length is
considered as a starting point. Strain and electrical field components
have been derived and substituted into the strain energy per unit
length. After this step, the variational-asymptotic method is to be
applied to obtain an asymptotically exact strain energy formulation
for the electro-mechanical composite beam model. Two-dimensional
cross sectional analyses is to be carried out to obtain the cross
sectional stiffness constants. The geometrically exact beam theory,
which takes into account all possible deformations of the beam and
which has the small strain assumption as the only restriction, is going
to be used to derive the one-dimensional exact beam equations. The
cross sectional constants, which will have been derived as a result
of the cross sectional analyses, are going to be used in these onedimensional exact beam equations. The composite blade model, the
actively controlled trailing edge flaps and the actuators are going to be
modeled in the multibody dynamics code DYMORE, which uses the
geometrically exact beam theory.
The paper then describes the manufacture and high voltage testing
of several AIC prototypes built to a weight of 15 g (0.53 oz.) and a
material cost under $20. Testing revealed that the AIC architecture
provided closed- to open-circuit switching as fast as 77 μs. The voltage
necessary to alter the AIC’s impedance was observed between 20 and
60 V DC. Slightly altering the dimensions of the AIC appeared to control
this ‘activation voltage.’
The paper closes with an evaluation of the AIC architecture comparing
the test data and the analytical predictions with the lightning strike data
gathered by ONERA which indicated the AIC speed was over 30 times
faster than the necessary minimum to shield equipment from HIRF. This
final evaluation also includes a comparison of the AIC’s performance
and architecture to conventional MOSFET-based switching in similar
high voltage applications.
7643-95, Session 10a
7643-93, Session 10a
Fabrication of a piezofiber/aluminum
composite and its characterization
Multi-cell active acoustic metamaterial with
programmable bulk’s modulus
H. Asanuma, T. Chiba, J. Kunikata, Chiba Univ. (Japan); H. Sato,
National Institute of Advanced Industrial Science and Technology
(Japan); M. N. Ghasemi Nejhad, Univ. of Hawai’i (United States)
A. M. Baz, Univ. of Maryland, College Park (United States); W. N.
Akl, Nile Univ. (Egypt)
This paper presents fabrication and characterization of a metal-core
lead zirconate titanate (PZT) fiber/aluminum composite. In order to
embed the fragile fiber in the matrix, the interphase forming/bonding
(IF/B) method invented by Asanuma, which has already enabled
embedding fragile optical fiber with a FBG sensor in an aluminum
matrix, was applied. The effects of fabrication conditions, that is,
hot-pressing condition such as temperature, pressure and time,
and the size of the U-groove to align and protect the fiber, on the
microstructure of the composite were investigated. The optimum
conditions obtained to embed it without fracture and chemical reaction
were the temperature of 873 K, the pressure of 2.2 MPa and the period
of 2.4 ks in a vacuum of 100 Pa at the U-groove diameter and depth
of approximately 0.3 mm. By measuring the output voltage generated
from the composite in the sizes of 20 mm x 20 mm x 0.55 mm having
a piece of the fiber of 20 mm long and 0.2 mm in diameter with a
platinum core of 0.05mm in diameter in the center of the matrix, which
was poled at 300 V for 1.8 ks after the hot-pressing and attached on a
plate and vibrated, it was clarified that it generates notably high voltage
such as 86.6.7 mV at a very small strain of 0.00142 % at the oscillation
frequency of 19.7 Hz and its waveform corresponds well with that of
the strain measured with a strain gauge attached on it.
Considerable interest has been devoted to the development of various
classes of acoustic metamaterials that can control the propagation
of acoustical wave energy through these materials. However, all the
currently exerted efforts are focused on studying passive metamaterials
with fixed material properties. In this paper, the emphasis is placed
on the development of a new class of composite one-dimensional
acoustic metamaterials with effective Bulk’s modulii that are
programmed to vary according to any prescribed pattern along the
volume of the metamaterial. Actively controlled Helmholtz resonators
coupled with the main acoustic cavities are introduced to provide the
capability for programmable effective Bulk’s modulus. The theoretical
analysis of this class of multi-layered composite active acoustic
metamaterials (CAAMM) is presented and the theoretical predictions
are determined for an array of fluid cavities coupled with an array
of controllable Helmholtz resonators with piezoelectric boundaries.
These smart boundaries are used control the overall Bulk’s modulus
of the individual cavity through direct acoustic pressure feedback.
The interaction between the neighboring cells of the composite
metamaterial is modeled using a lumped-parameter approach.
Numerical examples are presented to demonstrate the performance
characteristics of the proposed CAAMM and its potential for generating
prescribed spatial and spectral patterns of Bulk’s modulus variation.
{Work funded by ONR]
7643-145, Session 10a
Design, fabrication, and experimental results
of a peristaltic micropump using LIPCAs
with flexibly supported diaphragms
7643-94, Session 10a
Effects of piezoelectric nonlinearity on
helicopter vibration reduction
A. Tran-Le, N. Goo, Konkuk Univ. (Korea, Republic of)
The micropump is one of the important components in micro-fluidic
systems such as micrototal analysis systems, lab-on-a-chips, and
micro-dosage systems. Many kinds of actuators are used to make
the diaphragm of micropump: piezoelectric, thermopneumatic,
electrostatic and electromagnetic actuators are widely studied. Among
these kinds of actuators, the piezoelectric actuator was the first to
be used in micropump. This paper presents the design, fabrication
and experimental results of a peristaltic micropump using lightweight
piezo-composites curved actuators (LIPCAs) as its diaphragms with
flexible supporters. The most important parts of the micropump, the
diaphragms, are made of LIPCAs due to their advantages of short
O. Ozdemir Ozgumus, Istanbul Teknik Üniv. (Turkey); D. H. Hodges,
Georgia Institute of Technology (United States)
The purpose of this paper is to present the development of an
asymptotically correct electro-mechanical composite beam model
that accounts for the nonlinear behavior of piezoelectric materials and
to evaluate the effects of this nonlinear formulation on the vibration
reduction problem of composite helicopter blades that have actively
controlled plain trailing edge flaps. Most studies related to active
control of helicopter vibration using smart materials neglect the
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the series TMD, using three different methods: fixed-point method,
H∞ control and H2 control methods. The analytical expressions
of the optimum are obtained with some approximations. Finally,
the optimization results using different optimization methods are
compared, together with the ones using numerical method previously
done by the author.
response time, high output force and high displacement at high
operational frequency. The high vertical deflection of circular LIPCAs
enhances the flow-rate of the micropump and reduces the death
volume of pumping chamber to make the micropump self-priming. In
addition, thin PDMS layers playing the role of active valves are located
on the top of diaphragms in the inlet and outlet pumping chambers to
prevent the reserved flow and maintain high back-pressure. Moreover,
a flexible supporting method is introduced to improve the performance
of the actuators. The flexible supporters for the diaphragms are
made of PDMS material for its low level of stiffness and good sealing
property. Experiments are conducted to investigate the performance
of the micropump and also check the leakage of active valves during
closing condition. With LIPCAs and a flexible supporting method, the
performance of the micropump is improved. This peristaltic micropump
is found to be a promising candidate for bio-medical application due to
its bio- compatibility, portability, bi-directionality, and simple effective
design.
7643-98, Session 10b
Innovative hybrid mass damper system
for structural vibration control with energy
harvesting capabilities
C. Zhang, Harbin Institute of Technology (China)
Based on the driving principles of linear motors used in magnetic
suspended vehicles and the energy preserving techniques of fly-wheel
batteries, as well as the AMD(Active Mass Damper/Driver) and passive
TMD(Tuned Mass Damper) control techniques which have been widely
studied and used in the field of vibration control for Civil Engineering
structures, this paper proposes an innovative EHMD(Electro Hybrid
Mass Damper) control system which has the multiple functions,
such as electromagnetic driving, energy transforming and preserving
capabilities etc. To be specific, during the small amplitude vibration of a
tall building, the tuned EHMD control system can absorb and transform
the vibration energy of the main structure into electrical energy and
preserve it into system batteries. When the structure undergoes
earthquake attacks or strong wind excitations, the stored energy can
be released to drive the actuators to exert active control force onto the
main structure to suppress its vibration. In this paper, one set of bench
scale EHMD control system will be developed, and the parameter
optimization and compatibility problems will be studied. Second, the
mathematical models of “electro-mechanical-energy” relations for
the system will be established. Then, thorough performance tests will
be carried out to validate these theoretical models. Furthermore, the
control algorithms considering control-structure-interaction effect will
be proposed and experimentally verified through shaking table tests.
At last, the stability of the EHMD system will be investigated. Upon
properly design, the EHMD system can transform the unpleasant
vibrations of the main structure into electrical energy and store them
into the electro-chemical batteries which can be restored and reutilized.
Recycling the waste energy into useful energy, the promising EHMD
control system can also overcome some key problems of traditional
active control systems, such as energy-dependent and time-delay etc.
7643-96, Session 10b
The innovative direct driving volume control
based AMD system for structural vibration
control
C. Zhang, Harbin Institute of Technology (China)
The research and application of vibration control techniques for civil
engineering structures have made a significant progress during the last
several decades. Some new devices have been successfully applied in
many practical projects. However, owing to the limitations of traditional
AMD (Active Mass Damper/Driver) control systems, the innovation
of various actuators aimed at different application problems are still
the hot topics for researchers. The defects of traditional hydraulic
cylinder actuated AMD system include constitutional complexity, large
volume, low energy efficiency and high cost etc. To overcome these
problems, Direct Driving Volume Control (DDVC) system, also called
as non-Valve hydraulic servo actuator, based on the hydraulic volume
control principles is introduced into the AMD control system. The
innovative DDVC based AMD system, abbreviated as DAMD, is the
integration of three main parts: servo rotary motor, fixed volume pump,
and hydraulic cylinder with double-end pistons. This paper discusses
the mathematical models of controlling motor, energy transformation
loops and hydraulic relations of cylinders with pumps, which forms up
the whole electro-mechanical models of the DAMD control system.
Through numerical simulations, the key influential factors on system
dynamics are analyzed and optimized for scaled model experimental
systems. At last, the dynamical characteristics of each component of
the whole DAMD system as well as the improving strategy is studied
and proposed. Based on the previous modeling and analysis, the
equations of state for structure - DAMD system is developed, and
numerical simulations for structure subjected to earthquake excitations
with DAMD control system are studied. The results show that DAMD
control system is feasible to replace traditional AMD control system to
realize equivalent effective active control forces for structural vibrations.
7643-99, Session 10b
Parameter optimization and experimental
verifications of displacement feedback
based time delay compensation
C. Zhang, Harbin Institute of Technology (China)
Time delay is a more common effect in the vibration active control of
structures, which not only degrades the performance of the control
system but also introduce instability to the whole system. In this paper,
the first part presents the stability analysis of a SDOF system with time
delay feedback control loops. The purpose is to find the analytical
solution of the maximum allowable delay constant, which can be
used as a criterion for deciding whether or not to consider time delay
compensation. Then, an innovative time delay compensation method,
by actively increasing time delay constant when actual time delay is
larger than the maximum allowable values, is proposed and numerically
studied. The parametrical impact analysis and weight coefficient
optimization proves that the system is conditional stable under Partial
Displacement Feedback based active increasing time delay control
strategy. At last, the experimental study is conducted on a single
floor shear type frame structure model, where various excitations are
input into the structure-delayed controller system. Both the numerical
and experimental results demonstrate that the proposed time delay
compensation control algorithm is effective in reducing the dynamic
response of the structure and the system stability can be guaranteed.
7643-97, Session 10b
Analytical solutions for the optimal series
tuned mass dampers
L. Zuo, Stony Brook Univ. (United States)
Recently the authors proposed a novel configuration of tuned mass
damper (TMD), in which multiple auxiliary absorbers are connected
to the primary system in series. This so called series TMD has been
proved to be more effective and robust than all other types of TMDs
with the same mass ratio, such as the classic TMD, parallel multiple
TMDs, multi-degree-of-freedom (DOF) and three-element TMD.
The parameters of the spring stiffness, damping coefficient and
mass distribution ratio among the auxiliary masses were optimized
numerically using decentralized H2 and H∞ control methods. This
paper studies analytical solution of the parameters optimization of
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Conf. 7643: Active and Passive Smart Structures and Integrated
Systems IV
7643-101, Session 10b
Modeling and simulation of an amplified
structural damping system in a seismicallyexcited truss tower
K. Walsh, Ohio Univ. (United States); K. Cronin, Florida State Univ.
(United States); M. Rambo-Roddenberry, Florida A&M Univ. (United
States)
Truss towers are a critical component in the communication
infrastructure that serves as a lifeline to modern society. However, their
flexibility combined with low inherent damping make them vulnerable
to dynamic loads. Protecting tower structures can be achieved through
the use of passive, active, or semi-active control devices. The purpose
of the present work is to investigate a passive amplified structural
damping system, specifically the scissor-jack damper, for controlling
vibrations in seismically excited truss towers. In order to carry out the
present investigation, models of both the truss tower and scissorjack damper system are developed. For the truss tower, a 3D finite
element model is first created in Matlab. To reduce computational
effort during dynamic analysis, a bi-model method is employed to
represent the 3D truss tower as a dynamically equivalent 2D model.
The resulting dynamically equivalent 2D model is then represented by
the lumped-mass model for the subsequent dynamic analysis in the
Matlab environment. For the scissor-jack damper, a new formulation
for the amplification factor equation of the device is presented. The
new formulation accounts for the large deformations experienced by
the device as a result of the large displacements present in the flexible
tower during seismic loading. Accounting for these large changes in
the device geometry is important as they have a significant effect on
the amplification factor and the resulting damper forces applied to
the tower. The 2D tower model and scissor-jack damper model are
integrated in the Matlab environment to conduct numerical analysis.
In order to capture the interaction between the structure and control
device, it is necessary to solve for the value of the amplification
factor and corresponding amplified damper forces at every time step.
At each time step in the analysis, the displacements and velocities
corresponding to levels at which concentrated masses are located
are determined. These displacements and velocities are then used
to calculate the displacements and velocities at remaining levels of
the tower by applying pre-determined transformation matrices. Once
the displacements and velocities at all levels of the tower have been
determined, the displacement-dependent amplification factors of the
scissor-jack devices, and velocity-dependent forces of the dampers,
can be calculated. The resulting amplified force is then applied back
to the structure to determine its response at the next time step. By
repeating the process throughout the simulation, it is possible to
capture the interaction of the device and structure, and evaluate the
effectiveness of the scissor-jack damper for controlling vibrations
in seismically-excited truss towers. The response of the tower with
scissor-jack damper systems is simulated for four major earthquakes.
The effectiveness of the scissor-jack damper is demonstrated
through time-histories of the tower’s second level displacement and
acceleration responses. These results indicate that the system is
effective in reducing both the displacement and absolute acceleration
of the tower without exceeding practical limits on the damper’s stroke
capacity
60
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Conf. 7644: Behavior and Mechanics of Multifunctional Materials and
Composites IV
Monday-Thursday 8-11 March 2010
Part of Proceedings of SPIE Vol. 7644 Behavior and Mechanics of Multifunctional Materials and Composites 2010
7644-01, Session 1
7644-04, Session 1
Phasefield modeling of switching of
polarization vortex in ferroelectric
nanotubes
Phase-field model with phase
transformations of rhombohedral 95/5 PZT
W. Dong, C. Valadez, C. S. Lynch, Univ. of California, Los Angeles
(United States)
J. Wang, M. Kamlah, Forschungszentrum Karlsruhe GmbH
(Germany)
Lead zirconate titanate (PZT) is a ceramic perovskite material that
possesses piezoelectric, pyroelectric and ferroelectric properties. It
is widely used in devices such as transducers, sensors, actuators,
and capacitors. This paper will take a more in-depth look at the
piezoelectric and ferroelectric properties of the 95/5 PZT. Experimental
data is used to construct a phase-field model that shows a polar
rhombohedral PZT being poled in the presence of an electric field and
then depoled under hydrostatic compressive stress. The experimental
data is used to provide the coefficients of the constitutive equations as
well as for comparison with the model to determine its accuracy. The
polarization is calculated using a phase-field model that looks at the
lowest energy surface of a set of energy functions from different phases
that are super-positioned.
By means of the phasefield method, we investigate the response of
polarization vortices in ferroelectric nanotubes to a curled electric field.
First, we describe the theory applied and it’s numerical implementation
with special attention to a non-curlfree contribution to the electric
field. Next, it will be shown that there is a critical curled electric field
magnitude, at which the switching of the polarization vortex takes
place. As a result, a hysteresis type dependence of the toroidal
moment of polarization on the vorticity of the electric field occurs. The
details of this switching process are demonstrated and discussed.
7644-02, Session 1
The structure of the paraelectric:
ferroelectric phase boundary interface
7644-05, Session 2
New unifying concepts for modeling smart
materials
C. M. Landis, A. Kontsos, The Univ. of Texas at Austin (United
States)
W. S. Oates, Florida State Univ. (United States)
A continuum thermodynamics framework is used to model the
structure of the paraelectric-ferroelectric interface in barium titanate.
A phase-field modeling approach is applied and the model equations
are solved by the finite element method. The crystallographic theory
of martensite is used to compute the orientation of the austenitemartensite interface, i.e. the paraelectric-ferroelectric interface,
along with the appropriate lamination scheme in the ferroelectric
phase to enforce overall mechanical and electrical compatibility
with the paraelectric phase. The crystallographic theory provides
initial conditions for the finite element scheme, which is then used to
relax the structure of the phase boundary and domain walls near the
interface. Details of the energy and entropy changes across the phase
boundary are presented
Field-coupled mechanics theories encompass a broad spectrum of
material models aimed at predicting constitutive behavior of materials
that deform in the presence of electric or magnetic fields, temperature
changes, light or chemical exposure. Many of these materials can also
act as sensors or novel adaptive structures that change their elastic,
damping, or photonic properties. The majority of these models are
focused on a specific type of field-coupled response or a particular
composition. Limited work has been conducted on developing a
unified theory that can predict the constitutive behavior of a broad
class of smart materials. Such theories are useful for quantifying
underlying field-coupled mechanics concepts to facilitate future
materials development and design of adaptive structures. A new
unified smart material modeling approach is presented and compared
to compositions in the literature including ferroelectric materials,
magnetostrictive compounds, and liquid crystal elastomers. The
theoretical approach employs nonlinear continuum mechanics coupled
to a set of order parameters that govern electro-magnetic behavior and
liquid crystal phase evolution within an elastomer. Unifying concepts
are obtained by determining a set of coupling parameters using finite
deformation without introducing explicit phenomenological constants
such as piezoelectric or magnetostrictive constants or liquid crystal
phase transformations that are coupled to elastomer strain. Extensions
of the model to more complex materials including multiferroics and
photomechanical liquid crystal elastomers will also be discussed.
7644-03, Session 1
A finite deformation phase-field theory for
ferroelectrics
W. Li, C. M. Landis, The Univ. of Texas at Austin (United States)
A phase field theory for ferroelectric incorporating finite deformation
kinematics is presented. The general theory is presented first and terms
commonly identified as Maxwell stresses are derived and discussed.
The theory is Lagrangian as the governing equations are solved in
the reference configuration. To investigate the consequences of the
theory the standard free energy used in many phase field models for
ferroelectric is adapted to the finite deformation framework simply by
replacing the infinitesimal strain, the material polarization with their
finite deformation counterparts. The finite element method is then
implemented to numerically solve the governing equations and a model
problem is investigated to compare the finite deformation theory with
its linear kinematics counterpart.
7644-06, Session 2
Reduced-order model development for highorder smart systems
S. F. May, R. C. Smith, North Carolina State Univ. (United States)
The use of finite element or finite difference techniques to discretize
nonlinear smart material system models can yield full-order numerical
models that accurately characterize the system dynamics but do so
at significant computational cost. This can preclude the use of these
full-order models for uncertainty analysis, sensitivity analysis, system
design, or real-time control implementation. In this paper, we discuss
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Conf. 7644: Behavior and Mechanics of Multifunctional Materials and
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the construction of reduced-order system models using proper
orthogonal decompositions (POD) with updates. Through the use of
snapshots constructed from the full-order models, fundamental physics
is retained while significantly improving efficiency for high-speed
implementation. Using updates allows more flexibility when trying to
balance the accuracy and the speed of the simulation. By updating the
POD basis at specific times throughout the interval, we can increase
the accuracy of the model by using a greater amount of the information
given by the snapshots, while we can increase the speed of the
simulation during times when using less information will still result in
sufficient accuracy.
Korsunsky, Univ. of Oxford (United Kingdom)
Imaging of domains is a key step in understanding the microstructure
and hence the properties of ferroelectric single crystals. This
understanding is essential for exploiting engineered domain
configurations to achieve enhanced performance. In this paper, single
crystals of Barium Titanate are observed by reflection topography
using unfocussed monochromatic synchrotron X-ray light. A 10x10mm
polished surface of an unpoled crystal was mapped to form a
composite image, indicating a fine structure of a- and c- domains.
By making use of the angular separation of the diffracted reflections
and specimen rocking, the relative tilts between adjacent domains
about two orthogonal axes were found. Angular resolution better than
0.1mrad in tilt measurements allowed the local elastic curvature of
lattice planes to be observed. The resulting composite images show
well defined boundaries between regions of distinct microstructure,
and give an indication of the proportion of the domain types present.
Over large regions of the crystal the domain structure was finer than
the X-ray camera resolution of 6.5μm; AFM imaging of domains was
then used to confirm the typical domain spacing. The results are
interpreted in the context of models of compatible microstructure in
tetragonal crystals using optical microscopy of etched crystals and
AFM imaging to assist the interpretation. The technique shows promise
for mapping fine microstructure in single crystals, through the use of
high resolution X-ray cameras and is successful in revealing lattice
orientation information that is not normally available in optical or AFM
measurements.
7644-07, Session 2
Adaptive nonlinear control design for
hysteretic smart systems
X. Fan, R. C. Smith, North Carolina State Univ. (United States)
Ferroelectric and ferromagnetic actuators are being considered for a
range of industrial, aerospace, aeronautic and biomedical applications
due to their unique transduction capabilities. However, they also exhibit
nonlinearities and hysteresis that must be accommodated in models
and control designs to meet stringent performance criteria.
We investigate the problem of hysteresis control through the approach
of adaptive nonlinear control designs which determine control signals
that directly incorporate actuator nonlinearities.
In this paper, an adaptive nonlinear control architecture is developed
for a class of smart hysteretic systems that models hysteresis using the
homogenized energy model. The proposed control structure ensures
the global stability of the entire system and achieves the stable tracking
performance within a reasonable precision under certain conditions.
Simulation results illustrate and validate the effectiveness of the
proposed nonlinear control approach.
7644-10, Session 3
A variational model of ferroelectric rank-2
laminate domain structures
N. Tsou, J. E. Huber, Univ. of Oxford (United Kingdom)
The equilibrium domain arrangements of ferroelectric single crystals
are significantly affected by the applied loads and boundary conditions.
Domain structures evolve towards a minimum energy (equilibrium)
state. In this paper, a variational method, which minimizes a functional
based on free energy and dissipation, is developed to model the
evolution of several typical rank-2 laminate domain patterns in the
tetragonal crystal system. Periodic laminates which satisfy domain
compatibility across every junction where domains meet (not only
compatible on average across their higher domain interfaces) are
studied. These domain patterns include the well-known herringbone
configuration and also a pattern consisting of an array of polarization
vortex structures. The unit cells for both types of domain pattern
dictate a set of domain walls whose positions may vary while
maintaining the same topology. The positions of domain walls are
treated as thermodynamic variables in the formulation, and the total
dissipation rate is then a function of the velocities of the domain walls.
By using this model, many features normally observed in ferroelectric
single crystals can be reproduced, such as the dielectric hysteresis
loop and butterfly loop. The characteristics of the hysteresis loop
for different topologies, as well as under different applied loads and
boundary conditions are discussed. The model is readily extended to
apply to higher rank laminate structures and other crystal systems.
7644-08, Session 2
Finite element analysis of ferroelastic/
ferroelectric strain incompatibility in radially
poled thick walled ferroelectric cylinders
S. Liu, C. S. Lynch, Univ. of California, Los Angeles (United States)
A linear analysis predicts that extraordinarily high electric fields are
required to radially pole thick walled ferroelectric cylinders. In practice,
the required poling fields are significantly lower than predicted by the
linear analysis, but the process can result in cracking that originates
at the outer surface electrode and propagates to the inner surface
electrode, dielectric breakdown, and specimen destruction.. This
occurs predominantly when the electric field is radially inward (positive
electrode on the outside and ground on the inside). A finite element
analysis using a multiaxial micromechanics based constitutive law is
performed. Results indicate that polarization reorientation initiating at
the inner surface and propagating outward significantly reduces the
required poling field predicted using a linear analysis, and that the
incompatibility of the poling strain with the displacement field of an
expanding cylinder leads to a large compressive stress at the inner
surface and a large tensile stress at the outer surface. It is postulated
that microcracking at the outer surface coupled with a high potential
at the outer surface associated with an inward pointing electric field
attracts charge carriers through the fluid to the cracks and drives
these charge carriers into the cracks, causing them to propagate as
conducting cracks with resulting dielectric breakdown.
7644-11, Session 3
Fabrication and characterization lead
zirconate titanate (PZT) single crystal film by
PZT cubes alignment
Y. Lin, H. A. Sodano, Arizona State Univ. (United States)
7644-09, Session 3
Piezoceramic materials have attracted intense attention for sensing,
actuation, structural health monitoring and energy harvesting
applications in the past two decades due to their excellent capability
in coupling the energy between mechanical and electrical domains.
Among all the piezoceramic materials, lead ziconate titanate (PZT)
has been extensive studied and used in academic and industry areas
attributed to its high piezoelectric coupling coefficient. Single crystal
Mapping of domain structure in barium
titanate single crystals by synchrotron X-ray
topography
P. Potnis, J. E. Huber, J. P. Sutter, F. Hofmann, B. Abbey, A. M.
62
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Conf. 7644: Behavior and Mechanics of Multifunctional Materials and
Composites IV
PZT materials have higher piezoelectric coupling coefficients than
poly crystalline ones attributed to the perfectly aligned dipoles in
crystals. This paper will introduce a novel fabrication technique for a
PZT single crystal like film by tape casting aligned PZT single crystal
cubes fabricated by alternating electric field. A mixture of PZT cubes
and additives composed of dispersants, binders and plasticizers will
be cast in a Teflon mold and a high frequency alternating voltage will
be applied through the thickness of the film. After the alignment, a
sintering process will be carried out to remove all the additives and
form a dense single crystal like PZT film. XRD and SEM analysis of the
cross section of the final film with and without the alignment process
will be performed and compared to show the success of the alignment.
Finally, atomic force microscopy (AFM) will be used to directly measure
the piezoelectric strain coupling coefficient of the aligned PZT cubes
film and the results will show that the coupling coefficient is close to
that of the single crystal PZT.
depoling of Pb(ZrxTi1-x)O3 (PZT) ceramics across morphotropic phase
boundary (MPB). The drastically different switching characteristics of
PZT ceramics across MPB has been captured, and good agreement
with experiments has been observed. The effects of the transformation
strains and spontaneous polarizations are highlighted, confirming
the proposition of Li et al. [2005. Domain switching in polycrystalline
ferroelectric ceramics. Nature Materials 4, 776-781] that the strain
compatibility plays a dominant role in domain switching in ferroelectric
ceramics.
7644-12, Session 3
J. Fulcher, Y. C. Lu, Univ. of Kentucky (United States); G. P. Tandon,
D. C. Foster, Air Force Research Lab. (United States)
7644-15, Session 4
Thermomechanical characterization of
environmentally conditioned shape memory
polymer using nanoindentation
Triple-scale analysis and fabrication of new
biocompatible MgSiO3 piezoelectric thin
films
Shape memory polymers (SMPs) are an emerging class of active
polymers that have dual-shape capability, and are therefore candidate
materials for multifunctional reconfigurable structures (i.e., morphing
structures). However, the ability to reconfigure is currently limited by
the material systems that can provide both rapid reconfiguration and
long-term durability. To date, the SMPs have not been fully tested to
work in relevant environments (variable activation temperature, fuel
and water swell, UV radiation, etc.) required for Air Force missions.
In this study, epoxy-based SMPs were conditioned separately in
simulated service environments designed to be reflective of anticipated
performance requirements, namely, (1) exposure to UV radiation for 125
cycles, (2) immersion in jet-oil at ambient temperature, (3) immersion
in jet-oil at 49oC, and (4) immersion in water at 49oC. Subsequently,
the novel high-temperature indentation method was used for in situ
measurements of shape recovery ability and temperature-, time- and
rate-dependent mechanical properties of conditioned SMPs.
H. Hwang, Doshisha Univ. (Japan); Y. Uetsuji, Osaka Institute of
Technology (Japan); T. Katayama, E. Nakamachi, Doshisha Univ.
(Japan)
The biocompatible piezoelectric materials, which can be applied to
medical devices such as health monitoring system and drug delivery
system, are strongly required. In this study, a new biocompatible
MgSiO3 piezoelectric thin film is designed using a triple-scale analysis
based on the first-principles calculation and fabricated using the
sputtering method.
At first, a crystal structure and piezoelectric constants of biocompatible
material, MgSiO3, were analyzed by the first-principles calculation.
Next, a best substrate for MgSiO3 thin film was searched using
the triple-scale analysis. Finally, piezoelectric properties of MgSiO3
thin film were calculated by finite element analysis based on the
homogenization theory. As a result, lattice parameters of MgSiO3
crystal, a=b=0.3449nm and c=0.3538nm, and aspect ratio c/a=1.026
were obtained. And piezoelectric stress constants, e33=4.57C/m2 and
e31=-2.20C/m2, were calculated. Additionally, it was indicated that
[111] orientation of MgSiO3 on Au(111) substrate had a high possibility
of epitaxial growth among other substrate candidates, and it had a high
value of piezoelectric constants.
The shape recovery tests were conducted based on both lowtemperature (<Tg, where Tg is the glass transition temperature) and
high-temperature (>Tg) indentations. Both sharp tip and a blunt tip
were used for the indentation to generate low and high level stresses,
respectively. Elastic and viscoelastic properties of the environmentally
conditioned SMPs were measured. Results show that environmental
conditions have affected both the shape recovery ability and
mechanical properties of the SMPs. Conditioned SMPs generally
exhibit higher moduli and creep exponents in comparison with an
unconditioned one. During free recovery, the indentation impressions
of all SMPs disappeared as temperature reached above Tg. However,
the surfaces of some conditioned SMPs were unable to fully recover to
their original profiles for a given time.
Next, MgSiO3 thin film was fabricated on Au(111) substrate using
the sputtering method. Crystal structures were measured using
the x-ray diffraction, and piezoelectric constants were obtained by
the ferroelectric testing system. Diffraction angles of MgSiO3 were
calculated by employing the numerically analyzed lattice parameters.
Consequently, x-ray diffraction patterns of MgSiO3 showed a strong
concentration at [111] orientation. This result coincides with numerical
result. Furthermore, piezoelectric strain constant of MgSiO3 thin film,
d33=145.93pm/V, was observed.
7644-17, Session 4
Development of a McKibben artificial
muscle using a shape-memory polymer
K. Takashima, RIKEN (Japan); J. M. Rossiter, Univ. of Bristol
(United Kingdom); T. Mukai, RIKEN (Japan)
7644-13, Session 3
McKibben artificial muscle actuators have many attractive features
such as small, lightweight, simple, soft and flexible. When these
actuators are applied to robotic joints, the joints are driven by pairs
of the actuators located antagonistically for the increase of the joint
stiffness. However, the force is not so large and these actuators have
non-linear characteristics and hysteresis. Therefore, the objective of
this study is to develop a McKibben artificial muscle using a shapememory polymer (SMP). SMPs can be deformed above their glass
transition temperature (Tg) by applying a small load. They maintain their
shape after they have been cooled to below Tg. They then return to the
predefined shape when heated above the glass transition temperature.
Exploiting these characteristics, we coated the braided mesh shell of
a commercial McKibben artificial muscle and made a prototype of the
McKibben artificial muscle using the SMP. When this new actuator
is warmed above Tg, the SMP can deform. Then, when the internal
Domain switching in ferroelectric ceramics
across morphotropic phase boundary
W. Tang, D. Fang, Tsinghua Univ. (China); J. Li, Univ. of Washington
(United States)
A two-scale micromechanics model is developed in this paper to
analyze domain switching in ferroelectric ceramics, using a probabilistic
domain switching criterion based on energetic analysis. The
microstructure of ferroelectric ceramics at two distinct length scales,
domains and grains, has been carefully analyzed. The interaction at
domain level is accounted for by energy minimization theory, while
the fluctuation at grain level is analyzed using ellipsoidal two-point
correlation function. The model has been implemented by Monte Carlo
method, and applied to simulate the electric poling and mechanical
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Conf. 7644: Behavior and Mechanics of Multifunctional Materials and
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behavior of nanowires are shown for the nanowire length range of 30200 nm and for different diameter-length ratios.
bladder is pressurized, the actuator shortens and/or produces a load
if it is coupled to a mechanical load. After the actuator becomes the
desirable length, the actuator is cooled to below Tg and the SMP can
be fixed in a rigid state even if without a air supply. Consequently, this
actuator can maintain its length more rigidly and accurately. In this
study, we tested the fundamental performance of this prototype. The
experimental results of a preliminary proof-of-concept investigation
conducted on this prototype confirm the feasibility of this new actuator.
7644-19, Session 5
Mechanical characterization of Ni-Ti-Hf high
temperature shape memory alloys
G. Ded, H. E. Karaca, Univ. of Kentucky (United States); R. D.
Noebe, NASA Glenn Research Ctr. (United States); B. Basaran,
Univ. of Kentucky (United States)
7644-96, Session 4
Jetsum: SMA actuator based undersea
unmanned vehicle inspired by jellyfish biomechanics
Shape Memory Alloys (SMAs) have the ability to produce very high
actuation strain, stress and work output as a result of reversible
martensitic phase transformations; however, their high temperature
commercial applications have been limited due to their low
transformation temperatures (below 100°C) or unsatisfactory shape
memory properties. In order to overcome these handicaps, NiTi is
alloyed further with ternary elements such as Pd, Pt, Au, Hf and Zr
to make it display remarkable SM properties at higher temperatures.
Among those, Ni-Ti-Hf is the most promising alloy family due to its
low production cost. On the other hand, Ni-Ti-Hf suffers from unstable
shape memory behavior and lack of superelasticity due to its low
strength and high transformation hysteresis.
S. Bressers, Virginia Polytechnic Institute and State Univ. (United
States)
Previously, we have reported an undersea unmanned vehicle (UUV)
inspired by the locomotion of medusa jellyfish, termed JetSum [Proc.
SPIE 7287, 72871G (2009)]. The design of JetSum utilized shape
memory alloy (SMA) actuators in wire form to replicate the two-phase
contraction-relaxation cycle of natural jellyfish locomotion. In this
paper, we report on design modifications that address problems
related to performance of locomotion and power consumption. The
changes include implementation of a full continuous bell, bolstering
critical sealing junctions, and optimization of input signal. A LabVIEW
controller program was developed to automate and optimize the
driving of JetSum enabling optimization of performance. In particular,
the response of the SMA actuators, and consequently performance
of the vehicle, was investigated by varying the magnitude, frequency,
and duration of the input signals. JetSum locomotion in underwater
conditions was recorded by using a high-speed camera and analyzed
with image processing techniques developed in Matlab. The results
show that JetSum was able to achieve instantaneous velocities up to 7
cm/s and instantaneous accelerations up to 19 cm/s2.
In this study, thermo-mechanical treatments have been utilized to tailor
the microstructural, mechanical and shape memory properties of the
Ni-Ti-Hf high temperature shape memory alloys. Extensive mechanical
characterization studies have been conducted to determine the shape
memory behavior of thermomechanically treated NiTiHf alloys. It
has been revealed that transformation temperatures and mechanical
response can successfully be adjusted by precipitation formation.
Precipitates can alter both the composition and the strength of the
matrix where stable superelastic and shape memory behaviors with
low transformation hysteresis at temperatures above 100 C can be
observed in NiTiHf alloys.
7644-20, Session 5
7644-18, Session 5
Passive damping of composites with
embedded shape memory alloy wires
Phase transformations and shape memory
effects in finite length nanostructures
R. de Oliveira, A. Sigg, V. J. Michaud, J. E. Månson, Ecole
Polytechnique Fédérale de Lausanne (Switzerland)
R. V. N. Melnik, Wilfrid Laurier Univ. (Canada); L. Wang, Hangzhou
Dianzi Univ. (China); O. Tsviliuk, JSC Rodovid Bank (Ukraine)
Shape memory alloy (SMA) integration as thin wires into host
composite materials is reaching potential applications as actuators and
damping devices in a variety of industries. In this study, NiTi wires were
embedded during the infusion processing of woven CFRP composite
plates with the purpose to passively increase their damping.
In a number of nanostructures, the energy as a function of lattice
spacing exhibits two distinct minima that correspond to fcc and bct
phases. Such nanostructures may also exhibit shape memory effects
which has been confirmed by both experimental and computational
methodologies.
Two types of NiTi wires, having the same diameter of 0.2 mm, were
considered, one superelastic at room temperature, the other one
martensitic. For the first one, a martensitic transformation was induced
by applying a pre-strain of 2.5% before embedding the wires. The
coexistence of austenite and martensite provides damping through the
mobility of boundaries between the two phases. For the second type
of wires, the enhancement of damping was based on the presence of
martensite.
While many theoretical results up to date have been obtained
for infinitely long nanowires, including those obtained with ab
initio calculations, the question has remained on whether phase
transformations is a generic effect for the same material-type
nanowires of finite length. Although there has been mounting evidence
towards a positive answer to this question, comprehensive studies
of nanowires of finite length are limited due to the fact that the
methodologies applied for their studies are computationally expensive.
In addition, there are a number of questions that remain open at a large
extent, including questions related to temperature-dependent phase
stability.
The passive damping effect produced by the SMA wires was evaluated
from free vibration tests on composite beams, neat or with increasing
amounts of SMA wires. Resonance frequency and damping ratio were
measured as a function of temperature. Improvement in damping was
verified, at room temperature, for both types of SMA wires and was
observed to be dependent on vibration amplitude. For small-amplitude
free vibrations, martensitic wires present more interest as they provide
an increase in damping of around 50 % for a volume fraction of wires
of 5%. The effect changes for temperatures close to the transformation
temperature of the wires. Practical guidelines will thus be given as a
function of the actuation temperature, allowed density increase and
manufacturing practice.
In this contribution, we develop a relatively simple and computationally
inexpensive model to study phase transformations in finite
nanostructures with our major focus given here to nanowires of finite
length. We show that in the latter case, the models describing shape
memory effects at the mesoscopic level can be reduced to a 2D
case (and in the case of nanowires of infinite length, to the 1D case).
We study the cubic-to-tetragonal transformations in which case the
2D analogue of the model describes the square-to-rectangle phase
transformations. Several representative examples of mechanical
64
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the material response is defined by an SMA transformation-plastic
yield constitutive model implemented in a user material subroutine. It
is shown that the irrecoverable plastic zone formed during indentation
can help drive the subsequent shape memory effect in the material.
The analysis process mimics the three experimental steps; for the
first, the indention of the material is simulated using axisymmetric or
plane-strain assumptions for the simulation of spherical or cylindrical
indenters, respectively. The second step simulates the planarization of
the material surface to be flush with the maximum indentation depth.
This is accomplished by removing the elements above this depth from
the analysis. The third step models the transformation of the SMA and
the protrusion and subsequent retraction of the indent during heating
and cooling, respectively. The results of this analysis are compared to
experimental data; it is observed that the phenomena of protrusion and
retraction in planarized indentations can be effectively modeled using
these advanced analysis tools.
7644-21, Session 5
Characterization of indentation response
and shape memory surface morphology
of Ni-Ti-Hf-Cu and Ni-Ti-Hf-Pd high
temperature shape memory alloys
A. Hatemi, G. Ded, H. E. Karaca, B. Basaran, Univ. of Kentucky
(United States)
Instrumented indentation technique is one of the most commonly
used testing methods to characterize the mechanical properties of
a wide range of materials at small scales. In this study, a systematic
investigation is conducted on the indentation by Vickers and spherical
indenters and two-way shape memory surfaces in subsequent thermal
cycling of thermally treated NiTiHfCu and NiTiHfPd high temperature
shape memory alloys (HTSMAs). Indentation depth and work recovery
ratios as functions of indentation geometry, load, rate and depth,
and thermal treatment are determined to reveal the shape memory
and superelastic behavior of these alloys. Moreover, by employing
optical profilometry method, the change in indent geometries during
temperature cycling is revealed. It has been shown that thermally
reversible surface protrusions, based on the two-way shape
memory effect, can be induced and their shape can be controlled
at temperatures higher than 100 C. This may lead to many potential
applications where controllable surface roughness at high temperatures
is desired, such as MEMS, surface morphing and tribological systems.
It has been shown that indentation and optical profilometry techniques
provides very useful information on the mechanical behavior of
HTSMAs at micro scale for high temperature applications where
NiTiHfCu and NiTiHfPd alloys could be considered as excellent
candidates in variety of high temperature applications.
7644-23, Session 5
Processing and characterization of
composite shape memory alloy (SMA) thin
film structures for microactuators
S. Mandepudi, Kennametal Inc. (United States); H. D. Ackler,
Skyline Solar, Inc. (United States)
The high work to volume ratio and the stress recovery of Shape
Memory Alloy (SMA) thin films with temperature makes them an
ideal choice for microactuators. However, these materials have not
gained widespread acceptance due to issues associated with phase
transformation. Primary concerns are rapid change in stress at the
transformation temperature giving the actuator a step function like
response and a significant shift in transformation temperatures due
to a wide hysteresis. In the present research, TiNiCu (53.59at%Ti,
39.05at%Ni), TiNi (50.32at%Ti) and TiNiHf (39.56at%Ti, 48.63at%Ni)
composite SMA thin films that display close to linear stress
temperature behavior (slope: 2-7 MPa/C) with high stress recovery
(300-550MPa), wide transformation range (60-130C) and low hysteresis
(10-30C) were fabricated. Properties were achieved through the
deposition of SMA thin films with varying composition in a layered
(composite) format on Si wafers. The TiNi+TiNiCu composite exhibited
a two-step transformation (slopes of 2.5 and 3.9 MPa/C) without a
significant impact on stress recovery. Displaying identical recovery
stresses, the TiNiHf film possessed a 65C transformation range and
the TiNiHf+TiNi composite exhibited a wider range of 120C. In addition,
the hysteresis dropped by 30C for the composite compared to a single
layer TiNiHf film. For the annealing conditions identified, a three-layer
composite structure exhibited the best characteristics (transformation
range of 130C and a recovery of 550 MPa) with a significant drop in
hysteresis values compared to single and two layer films. A strong
correlation between deposition conditions, annealing parameters and
transformation characteristics was observed for all the SMA films.
7644-22, Session 5
3-D finite element analysis of indentation
recovery due to the shape memory effect
J. Nolan, D. J. Hartl, D. C. Lagoudas, Texas A&M Univ. (United
States); D. S. Grummon, Michigan State Univ. (United States)
The rapid growth of micro-scale devices in current technology markets
creates a drive to explore the potential of existing technologies to
enhance the effectiveness and capability of these devices. Shape
Memory Alloys (SMAs), long used as actuators in a variety of
applications, exhibit behavior that demonstrates great promise for
micro-actuation use. Thus, incorporating the unique properties of
these materials into new actuation applications is a focus that merits
extensive research. One outgrowth of this is the study of indentation
recovery due to the shape memory effect. Recent observations
of indentation recovery in SMAs indicate that these repeatable
deformations suggest a strong potential for micro-actuation use. Prior
and current experiments have examined indentation recovery and
tested its actuation ability, motivating further study using analytical
methods. This work discusses the 3-D Finite Element Analysis (FEA)
of the shape memory effect in an SMA material subject to indentation
using a new SMA transformation-plastic yield constitutive model.
7644-24, Session 5
Low-hysteresis in Ti50Ni50-xPdx alloys
V. K. Srivastava, X. Chen, R. D. James, Univ. of Minnesota (United
States); R. Delville, D. Schryvers, Univ. Antwerpen (Belgium)
Experimental observation of the shape memory recovery associated
with indentations in SMAs is accomplished with a three-step
procedure. First, an SMA specimen is indented with a spherical or
cylindrical micro-indenter. The surface layer of the material is then
removed to make the new surface layer flush with the maximum depth
the indenter achieved in the material. The final step involves the heating
of the indented SMA material to generate a surface protrusion due to
the austenitic phase transformation; subsequent cooling causes the
protrusion to retract and the surface to return to its pre-heating state
via the martensitic phase transformation.
In previous work [1,2,3] a relationship between the hysteresis and the
middle eigenvalue λ2 of the distortion matrix was found, with the size
of the hysteresis dropping sharply near λ2 = 1. The condition λ2 = 1 is
a necessary and sufficient condition for a perfect, untwinned interface
between austenite and martensite. Recent work also links the size of
hysteresis to fatigue resistance of NiTi alloys.
In earlier work [3] λ2=1 was achieved for the systems TiNiPd, TiNiPt
and TiNiAu and this coincided with the minimal hysteresis in all three
cases. Furthermore, untwinned, atomically sharp interfaces between
the austenite and martensite in Ti50Ni40Pd10 were observed by high
resolution electron microscopy [4] and fully transformed martensitic
alloy Ti50Ni39Pd11 showed unusual large twinless plates [5]. When
Numerical analysis of this experimental procedure is used to examine
the mechanisms underlying the shape memory effect that contribute
to the indent recovery. In particular, the deformation of the SMA
material necessitates the study of the influence of plasticity on the
indent recovery. The Abaqus FEA Suite is used for this analysis, and
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Conf. 7644: Behavior and Mechanics of Multifunctional Materials and
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interaction between transformation and creep occurring simultaneously
has been recently studied in compression [10] and a thermodynamic
model was developed to capture this interaction. However the
experimental and modeling effort were limited to one actuation cycle.
the size of the hysteresis was plotted vs. λ2, there was a sharp drop
in all three cases. The minimal hysteresis of those studies occurred
for Ti50Ni39Pd11 and was ~12 degree Celsius. Since the drop is so
sharp, it is possible that this is not actually the minimum hysteresis.
The present study was designed to define the minimum. In this paper,
we report carefully measured lattice parameters and transformation
temperatures of Ti50Ni50-xPdx, 8.5≤x≤11, using increments Δx =
0.25, and new high resolution images of these alloys. The minimum
hysteresis measured by DSC (differential scanning calorimetry) among
these alloys is found to be ~6 degree Celsius for Ti50Ni40.5Pd9.5.
Hysteresis vs. λ2 appears smooth, rather than cusp-like, at this
tolerance level.
7644-27, Session 6
A 3D model for the dynamical sensing
response of Galfenol with applications to
energy harvesting
1. R. D. James and Z. Zhang, A way to search for multiferroic materials
with ‘unlikely’ combinations of physical properties, in Magnetism and
Structure in Functional Materials (ed., Lluis Manosa, Antoni Planes,
Avadh Saxena), Springer Series in Materials Science, vol. 79, SpringerVerlag (2005).
P. C. Weetman, G. Akhras, Royal Military College of Canada
(Canada)
A 3D model for the dynamical sensing response of magnetostrictive
Galfenol is developed. The model calculates the fraction of magnetic
moments oriented along each of the energetically preferred directions
of the crystal as a function of time, which is used to determine the total
magnetization versus time. The model is appropriate for axial and shear
stresses and magnetic field biases applied at various orientations.
2. J. Cui, Y. S. Chu, O. Famodu, Y. Furuya, J. Hattrick-Simpers, R. D.
James, A. Ludwig, S. Thienhaus, M. Wuttig, Z. Zhang and I. Takeuchi,
Combinatorial search of thermoelastic shape memory alloys with
extremely small hysteresis width. Nature Materials 5 (2006), pp. 286290
In a previous work (P. Weetman and G. Akhras, Appl. Phys. Lett.
95, 072504 (2009)), a 1D dynamic sensing model was developed
using a self-consistent rate equation technique. This model was only
appropriate for cases where a single stress and a magnetic field bias
are both applied along an axis about which rotational symmetry can be
approximated. In order to simulate the dynamic sensing response for
arbitrary geometries and loading conditions, the model is expanded to
3D.
3. Z. Zhang, R. D. James and S. Müller, Energy barriers and hysteresis
in martensitic phase transformations, Acta Materialia 57 (2009), pp.
4332-4352.
4. R. Delville, S. Kasinathan, Z. Zhang, J. Van Humbeeck, R.D. James
and D. Schryvers, Phil. Mag., accepted (2009)
5. Rémi Delville, D. Schryvers, Z. Zhang and R. D. James, Scripta
Materialia, 6 (2009), pp. 293-296.
Results are presented for the sensing response for two systems: a
Galfenol crystal with 19% at. wt. Ga oriented along the axis, and
a Galfenol crystal with 18% at. wt. Ga oriented along the axis. The
second system cannot be modeled in 1D, calculations have to be
performed using the 3D model only. Finally, as an example application,
the sensing system is incorporated into a simple AC energy harvesting
system. Extra non-linear effects due to a magnetic field induced by
the pick-up coil must be incorporated into the self-consistent model.
Output voltage versus applied stress is calculated for the first sensing
system.
7644-25, Session 5
Simulation of austenite-martensite interface
in microstructures and hysteresis
C. Lei, L. Li, J. Li, Univ. of Washington (United States)
We utilize the nonconventional multivariant model to simulate the
Austenite-Martensite interface in microstructure. Separation of
length scales between the Austensite-Martensites and the twinnedMartensites are critical here. An innovative two-scale algorithm
has been introduced to deal with the problem. Microstructures of
common crystal systems are simulated using this approach, and
good agreement with experimental observations is obtained. We then
attempt to verify the thermal hypothesis in microstructure raised by
R.D. James on whether the middle eigenvalue being zero is a critical
criterion for thermal hysteresis in the linearized theory.
7644-28, Session 6
Modeling the magneto-elastic interactions
of magneto-sensitive composites
Z. A. Aga, L. E. Faidley, Iowa State Univ. (United States)
Our previous experimental studies of Magnetorehological Elastomers
(MREs), composite materials made up of ferromagnetic particles
suspended in polymer matrix, showed that they are capable of
changing their mechanical properties in response to an external applied
magnetic field. These field induced change in properties are attributed
to the magnetic interaction between the ferromagnetic particles as
well as the accompanying elastomeric response of the polymer matrix,
which results in magneto-elastic effects. One of the magneto-elastic
effects is the change in dimension or shape of the material due to
applied magnetic field i.e., magnetostriction. Experimental evidence
shows that the magnetostriction of MREs is comparable to (or in some
cases higher than) other common giant magnetostrictive alloys such as
Terfenol. In addition, the magnetostriction of MREs displays hysteresis,
an effect that results from some form of dissipation of energy during the
magneto-elastic interaction. MREs can also change their stiffness when
exposed to magnetic field as a result of the same magneto- elastic
effect. Applications utilizing the magnetostrictive property of MRE are
few; however, it is believed that they can be used for actuators and
sensors. In order to expand the possible application of these materials,
their experimental and theoretical understanding is of paramount
importance. For that purpose, the main focus of this study is to model
magnetostriction of MREs using thermodynamics and micromechanics
theories. An effort will be made to incorporate the hysteresis effect
into the model unlike the preexisting mathematical models of these
materials by making use of thermodynamic internal variables that take
7644-26, Session 5
Modeling and experimental study of
simultaneous creep, plasticity and
transformation of high temperature shape
memory alloys during cyclic actuation
U. Desai, J. Monroe, P. K. Kumar, G. Chatzigeorgiou, I. Karaman, D.
C. Lagoudas, Texas A&M Univ. (United States); R. D. Noebe, G. S.
Bigelow, NASA Glenn Research Ctr. (United States)
High Temperature Shape Memory Alloys (HTSMAs) represent a class
of Shape Memory Alloys (SMAs) with transformation temperatures
greater than 100ºC [1, 2]. These alloys are formed by alloying binary
NiTi with a third alloying element such as Platinum, Palladium, Gold,
Hafnium or Zirconium [3, 4]. Thermally induced transformation behavior
of these alloys under load has been widely studied to understand their
actuation performance [5-8]. More recent efforts have focused on
improving the formability of these alloys [9]. As a consequence of their
high transformation temperatures, the HTSMAs can be exposed to a
temperature regime where creep behavior can occur simultaneously
during the transformation. The creep behavior of ternary NiTiPd and the
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into account the dissipation mechanism for the hysteresis effect. The
results from the developed model will be compared to our experimental
results.
7644-31, Session 6
Finite element modeling of magnetostrictive
thin film actuator considering the nonlinear
magnetic field for MEMS
7644-29, Session 6
H. Lee, C. Cho, Inha Univ. (Korea, Republic of)
Power generating by high pulse mechanical
stimulation of magnetic coupled NdFeB and
Terfenol-D
For the design and optimization of the magnetostrictive actuators,
numerous theoretical and numerical models have been proposed.
Although articles on modeling of magnetostriction by using generic
algorithm, artificial neural networks or Preisach hysteresis model
have reported by several authors, most of the previous studies are
devoted to the numerical model, especially finite element model.
On account of extensive researches in this area, various electrical
and mechanical devices can be analyzed using the finite element
technique. Also, some of them have been successfully commercialized.
But the direct application of these finite element models to the
magnetostrictive MEMS devices poses some serious problems.
Firstly most finite element models are concerned with the longitudinal
motions of Terfenol-D rods. Thus they cannot be effectively used for
the magnetostrictive thin films which have the shape of membrane, or
plate. Secondly, although there is an exception, they also assume linear
properties. Since it is usual to apply high external magnetic field to
magnetostrictive MEMS devices to obtain high strain outputs, nonlinear
magnetic properties with magnetic field should be considered.
Therefore, specific finite element tools are needed to design MEMS
devices utilizing magnetostriction as a deriving principle, and analyze
their performance.
D. Lewandowski, J. Kaleta, P. Wiewiórski, R. Mech, Wroclaw Univ.
of Technology (Poland)
Rising requirements for a new constructions, devices and machines
force engineers to monitoring them all day long. An atractive solution
seems to be applications of wireless sensors. However, there is a
barrier limiting their apply which is the need to supply them with
an electrical power over extended period of time without using
addtional wiring or batteries. The potentail solution which can provide
this problem seems to be an energy harvesting. Most methods of
obtaining the energy from the external sources e.g. vibrations, is to use
piezoelectric materials. However, the amount of energy generated by
piezoelectric materials is smaller than most electronic devices need.
Therefore, new method to generating a pulse of energy and conditionig
for other loads devices must be developed. This paper proposes a
new energy harvesting device based on magnetostrictive material. In
course of experiments with using Terfenol-D rods as actuators and
sensors it has been observed interesting phenomenon. Mechanical
stroke (e.g.energy beetwen 10J and 100J in infinite time) to magnetic
core based on Terfenol-D rod (diameter 8mm, length 50 mm), NdFeB
permanent magnets and coil allowed get electric power signal enough
to supply device of 100 Ohm load on their active state (tipical low
power controller). In comparison to the same magnetic circuit build with
other typical ferromagnetic materials e.g. Armco iron, showed effect 10
times lower or none. Tests and experiment showed important role of
coupling Terfenol-D and NdFeB permanent magnets, their configuration
and variable coil parameters determined this effect. Regard to the
results authors proposed construction of new impulse harvesting
method based on Terfenol-D material for low impedance load.
In this work, two-dimensional and three-dimensional finite element
model considering nonlinear magnetic properties are presented.
Examples are solved to verify the validity of the developed program. To
validate this model experimentally, a flexible magnetostrictive actuator
is fabricated by depositing a thin film of NiFe on a flexible polyimide
substrate. The magneto-mechanical characteristics of the actuator
are measured, and the results of magnetostriction using suggested
numerical FE model are compared with the experimental results.
Finally, the results are discussed.
7644-33, Session 6
7644-30, Session 6
Magnetostrictive properties of
Tb0.24Dy0.76Fe2-xNix thin films for wireless
micro actuators and application to array
type micro transporter
Image analysis of the microstructure of
pseudo-1-3 magnetostrictive composites
X. Dong, Dalian Univ. of Technology (China); X. Guan, Harbin
Institute of Technology (China); J. Ou, M. Qi, Dalian Univ. of
Technology (China)
H. Lee, B. Kim, C. Cho, Inha Univ. (Korea, Republic of)
In this paper, the effect of Ni on the magnetic, magnetomechanical
properties of the Tb0.24Dy0.76Fe2 system for wireless micro
actuator with the effect of deposited film thickness of TbDyFeNi
on silicon substrate were investigated. To examine the properties,
Tb0.24Dy0.76Fe2-xNix, (x=0, 0.5, 1.2, 2.0) films were sputter-deposited
on the silicon substrate with the condition as: Ar gas pressure of below
1.2E-9 torr, DC input power of 200W and heating temperature of up to
300°C. After the sputter process, magnetization and magnetostriction
of each sample were measured. X-ray diffraction studies also carried
out to certificate the film structure and thickness of the sputtered film.
From the investigation, unique property was used to build a novel
wirelessly controlled array type micro transporter. The micro actuators
with film thicknesses of 0.1, 0.5, 1, 2 μm were fabricated by silicon
micromachining with selective DC magnetron sputtering techniques.
For the operation, the array type micro transporters have comb shape
with each branch size of 150 μm × 800 μm × 50 μm and TbDyFeNi
was sputtered on the back side of the each branch for the actuation.
Each branch was attracted by externally applied magnetic fields up to
5kOe and motion of the branches made transportation movement. As
an application result, transported distances of the actuators to external
magnetic fields were observed.
Due to the shape anisotropy of the particles, applying a magnetic field
during the manufacture process of polymer-bonded Terfenol-D could
orient the major axis of the particles along the field direction and form
a pseudo-1-3 type composite. Compared to 0-3 composites prepared
without magnetic field, 1-3 type shows much larger magnetostrictive
performance, which has been proved by several experimental studies.
In this paper, the microstructure of the magnetostrictive composites
prepared under different magnetic field was observed and analyzed.
Magnetostrictive composites were fabricated using Tb0.3Dy0.7Fe2
powder and a three-part unsaturated polyester resin with a low
viscosity of 0.2 (25oC) and a high elastic modulus of 3Gpa. The shape
of the particles is irregular, and the distribution of the particle size is in
the range of 30μm to 500μm. Comparison of Gaussian fitting curves
of the angles between the major axis of particles and the arrangement
field direction among all the three composites shows the tendency
of the angles converge at 0o increasingly significant with increasing
arrangement field. It indicates the microstructure along the field
direction approximates 1-3 architecture with increasing arrangement
field, which is responsible for the changing magnetostrictive
properties with the magnetic field applied during the manufacture of
magnetostrictive composites.
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Conf. 7644: Behavior and Mechanics of Multifunctional Materials and
Composites IV
7644-16, Poster Session
7644-73, Poster Session
A preliminary study on effect of gamma
radiation on shape memory polymer
composite filled with carbon nanotube
Nonlinear bending response of
Terfenol-D/PZT laminated devices under
electromagnetic fields
X. Wu, Y. Liu, J. Leng, Harbin Institute of Technology (China)
K. Mori, F. Narita, Y. Shindo, Tohoku Univ. (Japan)
Abstract: As a new type of smart material, shape memory polymer
(SMP) receives increasing attention in recent years. SMP has found
various applications including heat-shrink connector, biomedical
devices and deployment structure, etc. However, SMP materials
have not fully exerted their technological potential applications
especially in spatial structure, largely due to the limited anti-irradiation
performance for polymer materials. Hence, some gamma radiation
shielding additives are added into shape memory polymer to prepared
SMP composite to increase its anti-irradiation property. In this paper,
in addition to the fabrication of SMP composite filled with carbon
nanotube, the effect of gamma radiation on thermo-mechanical
properties of the composite were investigated. Results show that glass
transition temperature (Tg) determined by DSC decreased by 5°C after
the irradiation. According to DMA test, the gamma radiation has a slight
influence on storage modulus, loss modulus and tan delta, respectively.
No considerable change was found both in tensile strength and
elongation at break after the gamma radiation due to the tensile test.
Finally, the shape recovery ratio is near 100% for the composite both
with and without the gamma irradiation. Based on the above results,
it can be demonstrated that the composite prepared in the study
possesses not only good thermo-mechanical properties but unique anti
gamma radiation performance, which shows potential application of
aerospace fields.
Magnetostrictive alloys and piezoelectric ceramics play a significant
role as active electronic components in many areas of science and
technology, such as smart structures and devices. Tb0.3Dy0.7Fe2
(Terfenol-D) is a highly magnetostrictive alloy of iron and rare-earth
metals, and has a unique advantage over the other smart structures
and devices. In recent years, it has been found that the laminated
composites of Terfenol-D and Pb(Zr, Ti)O3 (PZT) ceramics possess
superior magnetoelectric (ME) effect. One of the limitations for
practical use of the composites of Terfenol-D alloys and PZT ceramics
is nonlinear behavior. In order to optimize the performance of the
Terfenol-D/PZT laminated devices, it is important to understand the
nonlinear behavior of the devices under electromagnetic fields.
In this work, we present the nonlinear bending response of Terfenol-D/
PZT laminated devices under electromagnetic fields in a combined
numerical and experimental investigation. The fabricated devices
consist of thin Terfenol-D and soft PZT layers. The magnetostriction
of the Terfenol-D layer bonded to the surface of the PZT layer
was measured as a function of applied magnetic field. A nonlinear
finite element analysis is also carried out, and the second-order
magnetoelastic constant in Terfenol-D layer bonded to the PZT layer
was evaluated. The nonlinear deflection and internal stresses for the
Terfenol-D/PZT laminated devices under applied electromagnetic fields
are then discussed. In addition, the induced voltage due to applied
magnetic field and induced magnetic field due to applied electric field
for the devices are examined.
7644-52, Poster Session
EMI shielding performance study of tri-layer
nano stealth composites
7644-75, Poster Session
Modeling and simulation of corrosion
mechanism for glass fiber reinforced plastic
in sea water
D. Song, Harbin Institute of Technology (China)
Due to the great progress of stealth technology in recent years, the
stealth materials preparation has become an active research field.
Nano stealth composites are specially promising in stealth materials.
Among of these nano composites, CNTs and ferromagnetic nano
powder cause more concerns because of their excellent EMI shielding
characteristics. In this paper, a method for preparing tri-layer nano
stealth composite film is proposed. Using H2SO4, HNO3 mixture for
MWCNTs carboxylation, dispersant CTAB is added into surface-treated
CNTs, nano Fe and nano Fe3O4 respectively. These three mixtures
are dispersed by ultrasonic vibration so that they form homogeneous
films in EPOXY matrix. Vector network analyzer is utilized for EMI
SE measurements. According to experiment data, EMI shielding
performance curves are generated when CNTs vary from 4%-10%wt,
nano Fe 10%-15%wt, nano Fe3O4 15%-30%wt respectively in the
frequency bands of 3.22-26.5GHz. Simultaneously, variation trends
of these curves are analyzed. A new type of multi-layer nano stealth
composite film is fabricated by superposing the three films prepared
above, with nano Fe layer as matching layer, CNT layer as absorbing
layer, and nano Fe3O4 layer as the reflecting layer. Adjusting the
thickness and the content components to change the parameters
such dielectric constants, optimal configurations are obtained with
consideration of peak value, the EMI SE frequency bandwidth and
the electrical conductivity respectively. These experiments improve
the adaptability of the film in various working conditions. Experiment
curve fits to computing curve referencing multilayer material theory of
transmission lines. It demonstrates the effectiveness of the preparation
method of tri-layer nano stealth composite film.
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J. Yin, Harbin Institute of Technology (China)
Through summarizing and analyzing the physical corrosion theories of
polymer, a theoretical model is constructed to depict the relationship
between relaxation time with temperature, stress and humidity. The
correlation between physical corrosion behavior and external factors is
predicted from semi-experimental profile. In sequence, the morphology
of polymer and fiber was investigated by the scanning electron
microscopy (SEM) in comparison with that of non-immersed samples.
The dynamic mechanical thermal analysis (DMTA) methods were
used to study the evolution of thermomechanical properties against
immersed time. It is found that the glass transition temperature (Tg)
and storage modulus were significantly reduced with immersion time
increase. Then the hardness, tensile strength and bending strength of
GFRP were tested by their corresponding mechanical measurements.
7644-76, Poster Session
A phenomenological rate-related model for
the super-elastic shape memory alloy
B. Zhou, Harbin Engineering Univ. (China)
There is increasing interest in using superelastic shape memory alloys
(SMAs) in civil, mechanical and aerospace engineering, attributed to
their large recoverable strain, high damping capacity, and excellent
fatigue property. Experimental phenomena show the mechanical
behaviors of SMA is related to loading rate. In this study a new raterelated constitutive model of SMA is developed based on Zhou’s
constitutive model which ignores the dependence of mechanical
behaviors of super-elastic SMA on the loading rate. Numerical
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Conf. 7644: Behavior and Mechanics of Multifunctional Materials and
Composites IV
10 MHz), but a sharp drop off for frequencies greater than 10 MHz.
Electrical response to vibrational inputs has also been investigated
using a Macro Fiber Composite (MFC) to provide the input vibrations.
The MFC was fixed to a solid surface and the composite fixed to the
MFC’s other surface, to maximize transmission of vibrations to the
composite. Operating the MFC with various wave functions 200-800
Vpp, 1-5Hz, the composite demonstrated a response in the mV range.
Response was notably higher, reaching 200 mVpp for square and
ramp input waveforms. On the other hand, sine wave inputs resulted
in much lower voltage responses from the composite (approximately 1
mVpp). In addition, displacement curves with applied voltage are also
measured.
simulations and comparison with the previous experimental results
show that the new constitutive model well predicts the mechanical
behaviors of SMA and reflects the influence of loading rate.
7644-77, Poster Session
Simulation models for design and
production of active structural parts with
deformed piezoceramic-metal-compounds
W. Drossel, S. Hensel, B. Kranz, Fraunhofer-Institut für
Werkzeugmaschinen und Umformtechnik (Germany)
7644-79, Poster Session
This paper deals with simulative investigations of piezo-metalcompounds which are developed within the Transregional Collaborative
Research Centre “Production technologies for light metal and fiber
reinforced composite based components with integrated piezoceramic
sensors and actuators” with the promotion of the German Research
Foundation.
Bio-inspired unmanned undersea vehicle
C. F. Smith, A. Villanueva, S. Priya, Virginia Polytechnic Institute
and State Univ. (United States)
Inspired by the sub-umbrella structural and actuation features of
jellyfish, artificial bell designs were created mimicking the mesoscale details and analogous propulsion mechanism. Artificial jellyfish
unmanned undersea vehicle (UUV) was fabricated consisting of
silicone as the matrix material and shape memory alloy (SMA) as the
actuation material. UUV was characterized for its performance and
tailored to achieve vertical motion. SMAs were selected for actuation
because they are simple current-driven device providing large strain
and blocking force. However, electrical power requirements were
found to be quite high in the underwater conditions. It was identified
that by including “joints” in the structural material forming the bell the
overall power requirement can be reduced as it lowers the resistance
to compression. An analytical model was developed that correlates the
deformation achieved with the morphology of the joints. Experiments
were conducted to characterize the effect of both joint shapes and
structural materials on the motion. Results are compared with that
of natural medusa gastrodermal lamella and analyzed using the
theoretical model. By including the features inherently present in natural
jellyfish, the propulsion efficiency was found to be increased.
One concept is the integration of laminar piezo-modules in structural
parts during the forming process. The compound of sheet metal layers
and piezo-module is formed by deep drawing, stretch forming and
3-point bending.
To locate the limits of formability of the piezo-modules information
about strains and stresses are necessary. On the other hand detailed
finite-element-models with a discretization in the dimension of the
piezo material are not suitable for forming simulation concerning the
size of the simulation model.
Due to the periodic structure of the piezo-modules the simulation
method of representative volume elements can be used to homogenize
the material parameters. The estimated homogenous material
parameters show a good conformance with measurements published
by the manufacturer of the piezo-modules. With the homogenized
material parameter, the piezo-module can be integrated in the forming
simulation as simplified model.
In order to achieve the real strains and stresses of the piezo material
the strains/stresses obtained with the homogenous material have to be
superimposed with the phase concentrations from the unit load cases.
Special consideration has to be given to the bending load due to the
forming of the sheet metal.
7644-83, Poster Session
Verification of the simulative determined loading of the piezo-modules
is done by comparison with damage images achieved by computer
tomography.
Characterization of tensile mechanical
response of epoxy resins
M. Yekani Fard, Y. Liu, A. Chattopadhyay, Arizona State Univ.
(United States)
7644-78, Poster Session
For any mechanical simulation of composite material, properties
of fiber and matrix must be known. When conducting mechanical
simulation of polymer matrix composites using micro-mechanics
approach, experimental tensile stress strain diagrams are needed for
constitutive modeling of the resin matrix material. The mechanical
response of a two phased Epon 863 (recently known as FS-A23) and
hardener EPI-CURE 3290 (recently known as FS-B412) is investigated
in tensile loading. The resin is tested at low strain rate of about 100
str/sec in room temperature. The tensile properties will be measured
using actuator data, extensometers, and optical measurement
techniques. Two kinds of dog-bone geometry with uniform and
reduced thickness are used. Load deflection records measured
through the loading mechanism of the testing machine are adjusted by
subtracting extraneous deformations associated with the compliance
of the machine. Yield tensile stress, maximum tensile strength, tensile
strength at failure, modulus of elasticity, strain hardening ratio, yield
tensile strain, strain at the maximum strength, strain at the failure, and
toughness of the material up to specified extensions will be calculated
and reported. The tensile stress strain response of the polymer will be
simplified using the characteristic points.
Characterization of a Pt-core PZT fiber/Al
matrix composite
M. Richeson, K. M. Mossi, Virginia Commonwealth Univ. (United
States); J. Kunikata, H. Asanuma, Chiba Univ. (Japan)
The objective of this study is to characterize a piezoelectric composite
sensor/actuator fiber. The composite is manufactured of a platinumcore lead zirconate titanate (PZT) fiber (diameter: 0.22 mm) inserted
into an aluminum matrix, which serves the purpose of being the ground
terminal. Fabrication of the composite is accomplished in three steps.
First, a stainless steel wire (diameter: 0.35 mm) is used to press an
indentation into an aluminum plate (thickness: 0.4 mm), into which the
PZT fiber is inserted. A sheet of copper foil (thickness: 0.01 mm) is
used as an insert material to prevent destruction of the PZT fiber during
hot pressing. Next, a second aluminum plate (thickness: 0.2 mm) is
placed on top of the first and the two are hot pressed together at 873
K, 2.2 MPa for 40 minutes. The composite is then cut to the dimensions
30 mm x 1.8 mm x 0.55 mm and poled at 300 V for 30 minutes. The
finished sample is soldered to a connector for ease of testing. This
study characterizes the described compoiste by testing its impedance,
capacitance, voltage sensitivity response to vibrational inputs, and
deformation due to electrical input. Results show a capacitance in
the 500-700 pF range throughout the frequency spectrum (100 Hz to
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69
Conf. 7644: Behavior and Mechanics of Multifunctional Materials and
Composites IV
the higher variation as compared to the single phase piezoelectric or
magnetostricitve materials.
7644-84, Poster Session
Design of RF MEMS switches without pull-in
instability
7644-89, Poster Session
R. C. Smith, North Carolina State Univ. (United States); T.
Skorczewski, Univ. of California, Davis (United States); G. Richards,
Kent State Univ. (United States); C. Proctor, North Carolina State
Univ. (United States); C. Shen, The Univ. of Iowa (United States);
M. Wang, Northern Illinois Univ. (United States); J. Zhang, The
Pennsylvania State Univ. (United States); P. Zhong, The Univ. of
Tennessee (United States); J. E. Massad, Sandia National Labs.
(United States)
Effect of surface modified Fe3O4
nanoparticles on rheology of bidisperse
magnetorheological fluids
H. Cheng, C. Zhou, Q. Zhang, Wuhan Univ. of Technology (China);
N. M. Wereley, Univ. of Maryland, College Park (United States)
We study the effects of Fe3O4 nanoparticles on bidisperse MR fluids,
and determine an optimum percentage of nanoparticles to increase
stability and yield stress. Fe3O4 nanoparticles were prepared via
chemical co-precipitation and surface modified with a silane coupling
agent. Nanoparticles were characterized via FTIR, XRD, SEM, and
VSM. These results show that the nanoparticles (about 20nm diameter)
were paramagnetic, with typical Fe3O4 crystal structure. These surface
modified Fe3O4 nanoparticles were used as an additive to prepare
a novel MR fluid in combination with carbonyl iron microparticles
suspended in silicone oil. MR fluid stability and rheological properties
were experimentally investigated. The results show that adding a small
percentage of the surface modified Fe3O4 nanoparticles into the MR
fluid results in a significant change in the sedimentation stability, offstate viscosity and yield stress of the MR fluid. A critical concentration,
that is 1.5 wt%, was determined. Below this critical concentration, the
sedimentation ratio decreases, and the yield stress increases as Fe3O4
nanoparticle concentration incerases. Furthermore, at this 1.5wt%
nanoparticle concentration, the sedimentation ratio reaches a minimim
15% value, and yield stress increases by 26% at 0.6T, compared with
the MR fluid without Fe3O4 nanoparticles. Beyond this critical value,
the sedimentation ratio and the off-state viscosity increase, and the
yield stress decreases. Thus, a key conclusions is that adding an
appropriate concentration of surface modified Fe3O4 nanoparticles into
MR fluids can improve the stability and yield stress of MR fluids.
Micro-electro-mechanical systems (MEMS) switches for radiofrequency (RF) signals have certain advantages over solid-state
switches, such as lower insertion loss, higher isolation, and lower static
power dissipation. Mechanical dynamics can be a determining factor
for the reliability of RF MEMS. The RF MEMS ohmic switch discussed
in this paper consists of a plate, suspended over an actuation pad
by four double-cantilever springs. Closing the switch with a simple
step actuation voltage typically causes the plate to rebound from its
electrical contacts. The rebound interrupts the signal continuity and
degrades the performance, reliability and durability of the switch. The
switching dynamics are complicated by a nonlinear, electrostatic pull-in
instability that causes high accelerations. Slow actuation and tailored
voltage control signals can mitigate switch bouncing and effects of
the pull-in instability; however, slow switching speed and overlycomplex input signals can significantly penalize overall system-level
performance. A step toward one solution is to consider a pull-in-free
switch design. One goal is to determine how simple RC-circuit drive
signals and particular structural properties influence the mechanical
dynamics of an RF MEMS switch designed without a pull-in instability.
In this investigation, we develop a validated modeling capability and
subsequently study switch behavior for variable drive signals and
switch design parameters.
7644-87, Poster Session
7644-90, Poster Session
Plane stress analysis of a clamped-clamped
beam with piezoelectric/piezomagnetic
sensors under uniform temperature
Dynamic analysis of slider crank mechanism
and two-link manipulator using constraint
technique
K. Arumugam, K.S. Rangasamy College of Technology (India) and
Indian Institute of Technology Madras (India); N. Natesan, S. Raju,
Indian Institute of Technology Madras (India)
M. M. Hegaze, A. M. El-Nady, E. Morgan, Military Technical College
(Egypt)
A finite element model involving the mechanical, electrical and
magnetic fields have been used to analyze the behaviour of electric
and magnetic potential of mild steel clamped - clamped beam
embedded with multiphase magnetoelectroelastic or piezoelectric
or magnetostrictive patches in the thermal environment. The current
formulation demonstrates to predict the thermal deformation and
sensor behaviour of the piezoelectric/piezomagnetic, piezoelectric
and magnetostrictive patches under uniform temperature load. The
uniform temperature rise 50°C is considered for the present study.
A sensor patch is embedded to the base structure (mild steel) on its
top surface is considered. The sensor patch is made of piezoelectric
material PZT-4, magneotstrictive material Terfenol-D epoxy and
multiphase magnetoelectroelastic material (BaTiO3-CoFe2O4) with
different volume fraction. The behaviour of the sensor is performed
for patch located at fixed end and middle of the beam due to uniform
temperature rise and symmetry boundary condition about the middle of
the beam. The transverse displacement, electric and magnetic potential
are plotted along the length on the top surface of the sensor layer.
The numerical study compares the behavior of sensor on electric and
magnetic potential of the piezoelectric, magnetostric and multiphase
magnetoelectroelastic sensor material. The numerical simulation shows
that the electric and magnetic potential depends on the location of
the sensor patch. The advantageous to place the sensor patch at the
middle of the beam for clamped-clamped beam in a uniform thermal
environment. The multiphase magnetoelectroelastic sensor shows
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The important of the slider crank mechanism and two-link mechanism
is that they are the key-player in many mechanical and structural
systems. A family of joints in form of library to carry out kinematical and
dynamical analyses of mechanical systems was introduced in earlier
work by authors. Joint programming package was designed employing
the proposed joint library. In this paper, parametric investigations
have been carried out on two different types of mechanisms, closed
loop mechanism (slider-crank mechanism) and open loop mechanism
(two-link manipulator) to illustrate their effects on the response of the
systems. The proposed applications have been described based on the
type of joints and the number of degrees of freedom of the mechanism.
Based on Lagrange multipliers theorem, the dynamic and inverse
dynamic analyses have been carried out to calculate the reaction
forces.
7644-91, Poster Session
Finite element analysis of fatigue damage
of composite laminated structures under
stochastic loading
M. M. Hegaze, M. M. Abo El Dahab, Military Technical College
(Egypt)
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Conf. 7644: Behavior and Mechanics of Multifunctional Materials and
Composites IV
Composite materials are increasingly believed to be the materials of
the future with potential for application in high performance structures.
One of the reasons for that is the indication that composite materials
have a rather good rating with regard to life time in fatigue. The
present paper comprises theoretical and experimental research into
the implementation of composite materials in structure applications.
A finite element derivation was carried out based on Mindline theory.
Experimental measurements were carried out with two different types
of composite materials, carbon/epoxy and glass/epoxy in order to
obtain fatigue life diagrams (S/N diagrams) to be used for the fatigue
damage assessment. Fatigue damage assessments were developed
to predict the fatigue behavior of laminated structures based on
damage by initiation under random load. A computer program was built
based on the proposed finite element theory to carry out the previous
analyses. The validation of the developed program for some analyses
such as stress analysis, natural frequency analysis and fatigue analysis
was successfully achieved using a number of composite case studies.
A parametric study was also carried out to illustrate the potential of the
program to be used as a good optimization tool.
that can be efficiently matched to the DEAP load/deformation behavior.
7644-92, Poster Session
E. Starke, U. Marschner, G. Pfeifer, W. Fischer, Technische Univ.
Dresden (Germany); A. B. Flatau, Univ. of Maryland, College Park
(United States)
This paper presents a mechanical model and experimental
investigation of a commercially available DEAP coupled with such
a negative-rate bias spring (NBS). A simple model is introduced to
explain the non-linear snap-through behavior of the bi-stable NBS, and
subsequently the coupled behavior of a parallel NBS/DEAP system is
studied. The paper also presents experimental results obtained with
a number of different NBS prototypes, which are used to validate the
model predictions. Finally, comparisons are made with conventional
spring systems to illustrate the potential for stroke increase.
7644-97, Poster Session
Influence of a non-uniform stress on the
electromechanical
transduction coefficient of a
magnetostrictive unimorph
Attenuation behavior of multimode optical
fibers bended several times and comparison
with current models
When a magnetostrictive layer is attached to a support beam, the
magnetic properties of the magnetostrictive layer are sensitive
to bending of this unimorph structure. The changes of the
magnetic properties can be sensed by a planar coil on top of the
magnetostrictive layer or a solenoid around the unimorph structure.
As a utilization of this a magnetostrictive bending sensor can be build
up which, besides the sensor application, is also potentially suited
for energy harvesting. This paper deals with the development of an
electromechanical network model for the magnetostrictive unimorph
structure. Only small variations of the mechanical, magnetic and
electrical quantities around an operating point can be assumed. This
allows the development of an efficient linear network model of the
structure. For typical applications a non-uniform stress distribution
in the magnetostrictive layer results. Thus the electromechanical
transduction coefficient varies over the magnetostrictive layer area.
To account for the spatial varying properties, the unimorph and the
coil are discretized into finite electromechanical network elements. A
good approximation of the mode shape for dynamic applications up to
the first bending mode can be achieved by employing about 10 finite
network elements. By simplifying the finite network model an easy to
use network model is obtained which enables the fast calculation of
the sensor properties. The network modeling of the bending sensor
by non-uniform stress is supported by FE-models. Based on the new
network model magnetostrictive systems can be analyzed as well as
new designs optimized efficiently.
K. Rodriguez Carmona, A. M. Lucero, Ctr. de Investigación en
Materiales Avanzados, S.C. (Mexico)
The applications of optical fiber today are multiple
(Telecommunications, Medical, military industry, aerospace, civil
engineering). Due to their high functionality and versatility is of vital
importance to study deeply the behavior of the optical signal when the
fiber is subjected to bending under various curvatures. Such studies
are the basis for the construction of analytical models that can predict
the behavior of the attenuation of a multimode fiber when it is flexed.
This paper presents an overview of recent analytical models that have
been developed for the study and simulation of light attenuation inside
optical fibers. Specifically in this work those models were evaluated
and compared with experimental data. This data were obtained from
a complete characterization of the optical signal traveling through the
optic fiber under one geometric configuration circular.
To perform this characterization was designed a closed circuit in
which one end of the fiber was connected to the OTDR equipment
and the other end connected to an oscilloscope. With this design we
observed the behavior of transmitted light when the fiber is bent. The
characterization results allow to assess the models established by
various authors, evaluating the experimental data was observed that
the models proposed to date not entirely correct, because they do
not consider some factors that are crucial for optimal prediction of
the behavior of light transmitted from an optical fiber when it is flexed.
These factors will then be presented and discussed.
7644-98, Poster Session
Field induced variation of Austenite and
Martensite phase coexistence region in
Ni55Fe20Al25 shape memory alloy
7644-95, Poster Session
Mechanical behavior of coupled DEAP
actuator and negative-rate bias spring
system
A. Lakhani, P. Kushwaha, R. Rawat, P. Chaddah, Univ. Grants
Commission (India)
In this paper, we report the effect of temperature and magnetic field on
the resistivity and magnetoresistance in the annealed polycrystalline
ferromagnetic shape memory alloy Ni55Fe20Al25. The resistivity and
magnetoresistance measurement were carried out using home made
resistivity setup with Oxford superconducting magnet system. Results
of these measurements are presented down to 5K and up to 8 Tesla
magnetic fields in various different cycles of zero field cooled and
field cooled states. These results provide the evidence of martensite
transformation and phase coexistence (austenite and martensite) by
first order phase transition at different fields. Ni-Fe-Al ternary alloys are
relatively new Ferromagnetic shape memory alloys and are promising
materials as smart materials.
M. Hodgins, A. York, S. S. Seelecke, North Carolina State Univ.
(United States)
When a high electric field is applied across a dielectric electro-active
polymer, the stiffness in the in-plane direction decreases. This change
in stiffness can be used to generate linear actuation in the out-ofplane direction if the DEAP is subject to a suitable bias force. This bias
force is commonly provided by a linear spring, but a recent patent
application by Artificial Muscle, Inc. [1] suggests the use of so-called
negative-rate bias springs to increase the achievable stroke. These
springs are geometrically non-linear systems with bi-stable mechanical
characteristics featuring a negative stiffness between equilibrium points
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Conf. 7644: Behavior and Mechanics of Multifunctional Materials and
Composites IV
7644-34, Session 7
7644-36, Session 7
Stability of the magnetomechanical problem
in magnetic shape memory alloys
Constitutive model prediction of magnetomechanical coupling response of magnetic
field-induced phase transformations in
NiMnCoIn magnetic shape memory alloys
G. Chatzigeorgiou, K. Haldar, D. C. Lagoudas, Texas A&M Univ.
(United States)
Considerable research effort has focused the recent years in magnetic
shape memory alloys (MSMAs), due to their ability to generate large
recoverable magnetic field induced strains. The coupling of the
mechanical problem, with the generation of large strains, and the
magnetic problem in MSMAs leads to a strong nonlinear behavior with
very interesting characteristics.
D. C. Lagoudas, K. Haldar, B. Basaran, I. Karaman, Texas A&M
Univ. (United States)
The unique characteristic of magnetic field induced phase
transformation of NiMnCoIn magnetic shape memory alloys (MSMAs)
lies in the generation of large transformation strains accompanied by
high actuation frequency and high actuation stress. The macroscopic
functionality of MSMAs originates from the coupled evolution of highly
heterogeneous magnetic and elastic domain microstructures under
external magnetic, mechanical, and thermal conditions. Experiments
are performed on single crystal alloys. It is observed that applied stress
in combination with the applied magnetic field facilitates the release
of magnetic energy of the material. This combined effect produces
considerable amount of inelastic strain.
In this work we use an existing thermodynamically based model for
MSMAs and we study numerically a special case, in which a MSMA
specimen under constant compressive stress is subjected to a
magnetic field in a perpendicular direction of the applied stress. Solving
the coupled magnetomechanical boundary value problem we observe
that, during the reorientation process, the material presents strong nonuniformity in the distribution of the magnetic, the stress and the strain
field. Localized zones of stress, strain and magnetic field concentration
are observed inside the specimen. This non-uniformity affects the
reorientation process, since there are areas inside the specimen with
large differences in the martensitic variant volume fraction.
Motivated by experiments, a constitutive model is proposed to
take account of magnetic field induced phase transformation from
martensitic to austenitic phase. The stress favored martensitic phase
is paramagnetic, while the magnetic field favored austenitic phase is
ferromagnetic. The austenitic phase is triggered off when high magnetic
field is applied to the initially compressed martensitic phase.
The explanation for this peculiar phenomenon is the loss of ellipticity
of the coupled magnetomechanical problem during the martensitic
reorientation. Instability analysis is performed for the coupled
magnetomechanical problem, where magnetic body forces and
magnetic body couples are taken into account. The analysis reveals
that there are areas in the material, where the system of partial
differential equations transform from elliptic to hyperbolic. We also
study parametrically the non-dimensional problem and we identify the
conditions under which the magnetomechanical problem presents loss
of ellipticity.
In the present work, microstructure dependence of martensitic phase
transformation is taken into account by introducing internal variables
into the model. Internal variables are needed to account for strong
effects of domain microstructure processes on MSMA properties, for
example nonlinearity, irreversibility and varying elastic and magnetic
coupling. Without explicitly considering domain configuration
and evolution, the microstructure dependence is approximated
phenomenologically by certain evolution laws of the selected internal
variables, such as the volume fraction of the martensitic phase and the
rotation of the magnetization vector in the ferromagnetic austenite.
7644-35, Session 7
The constitutive response is derived in a consistent thermodynamic
way. The relation between the strain and the magnetic constitutive
response is calibrated from the experimental data. The constitutive
responses of magnetization versus magnetic field and strain versus
magnetic field is then predicted and compared with the experimental
results. The proposed model has the ability to predict the nonlinear,
hysteretic magnetic field induced strain and magnetization response.
Magneto-mechanical behavior of magnetic
shape memory alloys under simultaneously
variable magnetic and mechanical loading
C. Ciocanel, H. P. Feigenbaum, Northern Arizona Univ. (United
States)
The macroscopic behavior of the MSMA has been investigated
through experiments performed on prismatic specimens loaded
with either constant transversely applied magnetic field and variable
uniaxial mechanical stress or variable magnetic field and constant
uniaxial mechanical stress. The former loading condition resembles
the operation of the MSMA as a sensor, while the latter mimics the
operation of a MSMA actuator.
7644-37, Session 7
Mechanisms of domain switching in
ferromagnetic shape memory alloys
V. M. Stoilov, O. Rashwan, Univ. of Windsor (Canada)
Phenomenological models have been developed to capture the
macroscopic behavior under these loading conditions.
A continuum thermodynamics formulation for micromagnetics coupled
with mechanics is devised to model the evolution of magnetic domain
and martensite twin structures in ferromagnetic shape memory
alloys. The theory falls into the class of “sharp-phase-front” modeling
approaches. In addition to the standard mechanical and magnetic
balance laws, a continuity of the chemical potential is postulated.
Nucleation of variants and propagation of twin boundaries were
investigated under combined magneto-mechanical loading and
compared to recent experiments. The analysis demonstrated that
phase boundary motion results in significant deformation and allowed
estimation of the overall deformation in a ferromagnetic shape
memory material. It has been shown that the overall deformation in
ferromagnetic shape memory alloys is accompanied by evolution
of particular domain patterns. The choice of such configurations
is dictated by the requirement that domains remain compatible
during evolution, giving rise to a low-energy path for the overall
switching. The construction of this pattern is achieved using multirank
laminates. Finally, numerical solutions are presented to investigate the
fundamental interactions between the magnetic domain wall and the
martensite twin boundary in ferromagnetic shape memory alloys.
No experimental or theoretical work has been done to investigate
the material response under simultaneously varied magnetic and
mechanical loading. For such a loading condition one would need
to know when reorientation from variant 1 to variant 2 occurs and
when reorientation from variant 2 to variant 1 occurs. In practice, this
condition mimics a MSMA that is used as an actuator to preserve the
position of a load whose intensity varies in time, or an MSMA that is
used as both an actuator and a sensor, the former requires changing
the magnetic field and the latter requires changing stress. From a
theoretical perspective, these conditions are an important step towards
a 3D model, where it will need to be determined if reorientation from
variants 1 to 2, 1 to 3, 2 to 1, 2 to 3, 3 to 1, and/or 3 to 2 is occurring.
This work presents experimental and simulated results for MSMA
elements loaded with simultaneously varied magnetic and mechanical
loading and discusses some of the challenges associated with the true
3D modeling of the magneto-mechanical response of these materials.
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Conf. 7644: Behavior and Mechanics of Multifunctional Materials and
Composites IV
7644-38, Session 8
7644-40, Session 8
Multiferroic nanofibers by electrospinning
Thickness ratio effects on quasistatic
actuation and sensing behavior of laminate
magnetoelectric cantilevers
S. Xie, Xiantan Univ. (China) and Univ. of Washington (United
States); J. Li, Univ. of Washington (United States)
Multiferroic materials possess two or more types of orders
simultaneously that couple the electric and magnetic fields, and
composite multiferroics have been widely explored for their excellent
magnetoelectric coupling. In this letter, we report a strategy to hybrid
multiferroicity at nanoscale.Multiferroic CoFe2O4-Pb(Zr0.52Ti0.48)
O3(CFO-PZT), NiFe2O4-Pb(Zr0.52Ti0.48)O3(NFO-PZT) and
nanocrystalline BiFeO3(BFO) nanofibers are synthesized by sol-gel
process and electrospinning. After being calcined, the diameters of
multiferroic fibers are in the range from 100 to 300 nm. CFO-PZT
and NFO-PZT composite nanofibers are obtained by calcined in air.
However, pure perovskite BiFeO3 nanofibers are obtained by using
Ar as protective atmosphere. The spinel structure of CFO, NFO and
perovskite structure of PZT, BFO are verified by x-ray diffraction(XRD)
and high resolution transmission electron microscopy(HRTEM). Energy
dispersive spectroscopy(EDS) and TEM indicate that ferroelectric
phase and ferromagnetic phase grains are randomly distribute in
the multiferroic composite nanofibers, and with grain size around
30 nm.The multiferroicity of the composite nanofibers are confirmed
by piezoresponse force microscopy(PFM) and magnetic hysteresis.
The structures and properties of the composite nanofibers are also
compared with single-phase PZT, CFO, and NFO nanofibers. Excellent
ferroelectric and ferromagnetic properties have been observed,
which could enable multiferroic devices at nanoscale. For single
phase multiferroic BFO fibers, excellent piezoelectricity and clear
ferroelectric domain structure of the ultrafine fibers are characterized
by high voltage piezoresponse force microscopy. Enhanced weak
ferromagnetism arising from the nanocrystalline structure of ultrafine
fibers is also observed.
Y. Wang, J. Atulasimha, Virginia Commonwealth Univ. (United
States)
Magnetoelectric materials have been a subject of increasing research
interest due to their technological applications in magnetic field
sensing devices, coil-less transformers, tunable microwave and read/
write devices. In all these studies, the extension configuration has
been extensively studied. However, the behavior of magnetoelectric
composites in cantilever mode has rarely been studied. Compare to the
extension configuration, cantilever configurations offer advantages as
a co-located actuators and sensors for use in micro-surgical ablation
tools and cutting tools for machining. However, an important design
parameter for such applications is the ratio of the magnetostrictive to
piezoelectric layer.
Among the various combinations of magnetostrictive and piezoelectric
materials, the Terfenol-D/PZT composites have been widely studied
because of the large magnetoelectric (ME) voltage coefficient,
which ranges from 1.3V/cm Oe to 4.8V/cm Oe. But, Terfenol-D/PZT
composites are not suitable for the cantilever structure since Terfenol-D
is brittle and has low tensile strength. Hence, iron-gallium (Galfenol)
alloys with very high tensile strength of the order of 500 MPa are used
instead of Terfenol-D in this research. Most prior work on modeling
laminate magnetoelectric behavior focuses on linear regimes. While a
non-linear magneto mechanical plate model has been developed for a
laminated structure with galfenol and aluminum layer, it does not have
the ability to model variation in stress at different cross-sections along
the thickness and cannot be applied to magnetoelectric materials.
Hence, in this work,we need to develop a modeling tool for analyzing
the effect of thickness ratio in magnetoelectric cantilevers.
7644-39, Session 8
7644-41, Session 8
Static and dynamic characterization of a
magnetoelectric cantilever cutting tool
Integration of magnetoelectric laminate
composites and prestress consideration
V. B. Sundaresan, J. Clarke, Virginia Commonwealth Univ. (United
States)
T. Wu, Univ. of California, Los Angeles (United States)
A magnetoelectric self-sensing cantilever actuator is under
development for use as a surgical tool in minimally invasive surgery.
The cantilever is fabricated from Galfenol and Lead Zirconia Titanate
and the electrical output from piezoelectric component is used as
the self-sensing signal. The self-sensing signal, the tip displacement
and the force generated by the cantilever depend on the thickness
ratio of the magnetostrictive and piezoelectric layers. The work
presented in this paper analyzes the static and dynamic response of
the magnetoelectric strip for different thickness ratios by developing
a mathematical model for the system using variational principle. The
static and dynamic characterization of the magnetoelectric cantilever in
bending is derived from constitutive equations for the magnetoelectric
material. The equivalent stiffness and mass of the magnetoelectric
cantilever is derived using variational principles for calculating the tip
displacement in the cantilever. The mechanical and electrical response
predicted by this model is validated with experimental data for use in
a feedback loop. In addition, the electrical boundary condition of the
piezoelectric layer is varied to influence the actuation properties of
the cantilever tool for controlled actuation. The model developed for a
single cantilever is extended to a two-segment cantilever arrangement
in which one of the segments behaves like a floating base permitting
easy positioning of the actuator at any location for actuation. The
benefits of such an arrangement and real-time control of the actuation
properties of this tool is significant in minimally invasive surgery where
remote actuation with a fixed support is desired.
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Magnetoelectric (ME) laminate composites have attracted substantial
attention due to their strong coupling produced by the product property
relation between the piezoelectric and piezomagnetic phases[1, 2].
These materials have also been prposed for a variety of sensors based
measurements such as high sensitive magnetometers. [3, 4] However,
studies of the integration of these ME composites into structural
systems has not yet been evaluated. For example, ME laminates
could be used in graphite epoxy composites much the same fashion
that piezoelectrics, fiber optic sensors, or magnetostrictive sensors
have been proposed [5-7]. Futhermore, the influence of mecanical
loads on the ME laminate composite reponse has not been evaluated.
Therefore, substantial work remains in the area of evaluate ME
laminate composites into a wide range of structres including aerospace
composites.
Experimental results shows the electric-field-induced magnetization
as a function of DC magnetic field bias Hbias and different mechanical
loads. The induced magnetization is normalized to the maximum
value at 0 kN load bias. In general, each curve follows the trend that
an optimum DC magnetic field bias Hbias exists to maximize the
CME response. However, the CME response is also dependent upon
the applied mechanical load bias and the mechanical bias shifts
the optimal response. For example at 0 kN, i.e. absence of load,
the maximum CME response occurs at the Hbias of 4.5 Oe. As the
compressive load increases, the optimum Hbias increases and the
curves shifts to higher magnetic bias fields. On the other hand, for
tensile loads, the optimum Hbias shifts to lower magnetic fields as
compared to higher magnetic fields for compressive loading. The
maximum CME response drops dramatically under tensile loads. At
6 kN mechanical load condition, the induced magnetization is almost
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Conf. 7644: Behavior and Mechanics of Multifunctional Materials and
Composites IV
characteristics of hydrogels. Though few models were developed for
simulation of hydrogel characteristics, these are based on programs
implemented in individual laboratories, which are difficult to access.
Hence, our model is implemented using more generic finite element
software COMSOL and in this process, we developed a methodology
that can be used with any software having similar capabilities.
zero and begins to vanish. In general, these results indicate that the
mechanical load bias has a significant influence on the magnetoelectric
effect.
7644-42, Session 8
The effect of buffer solution concentration, fixed charge density,
solution pH (2-12), and electric potential (0 to 2V) on the swelling or
deflection characteristics are studied in separate simulations. The
results are compared with other published experimental investigations
and they are in agreement.
Monte Carlo simulation of multiferroic
BiFeO3
Y. Yang, L. Li, J. Li, Univ. of Washington (United States)
Magnetoelectric multiferroics such as BiFeO3 (BFO), which
simultaneously possess magnetic and ferroelectric orders, are of
great interest to both fundamental studies and practical applications
because of the promising coupling between magnetic and electric
order parameters. In this work, a lattice model of multiferroic BFO is
developed. We consider a two-dimensional square lattice of threedimensional dipoles and magnetic spins, with dipoles ferroelectrically
coupled and spins antiferromagnetically coupled. Furthermore, the
spins are indirectly coupled with dipoles through the ferroelastic
interactions. The electric, magnetic, and elastic energies of the lattice
are evaluated, and the equilibrium distribution of dipoles and spins are
realized through the Monte Carlo simulation. The coupled ferroelectric
and antiferromagnetic domains are observed, and the electric switching
of magnetic spins are investigated.
7644-45, Session 9
Fabrication and characterization of ionic
polymer gel actuators
C. Jo, H. E. Naguib, Univ. of Toronto (Canada)
Poly-AMPS (PAMPS) gel is fabricated and its electroactive behavior
is studied. A weakly cross-linked anionic PAMPS gel is produced by
radical polymerization using 2-acrylamido-2-methylpropane sulfonic
acid (AMPS) monomers, where N,N’-methlenebisacrylamide (MBAA)
and -ketoglutaric acid are used as a crosslinking agent and radical
initiator, respectively. The polymerization is carried out at 323 °K for
at least 24 hours. Poisson’s ratio, Young’s modulus and the degree
of swelling of gel samples are measured as physical properties. Also,
swelling and deswelling experiments are conducted in a surfactant
solution using n-dodecyl pyridinium chloride (C1nPyC1). The chemomechanical properties of PAMPS gel are studied in a cationic dilute
solution of surfactant under the electric fields. First, the effect of design
parameters on the bending deformation and dynamic responses is
investigated. As design parameters, sample thickness, current density,
ion concentration in the surfactant solution, and cross-linking degree of
gel are selected in this study. And then, the correlation effect between
the parameters is investigated and the optimum condition of design
parameters on the actuation is analyzed based on this data. Also, for
the consideration of the effect of crosslinking type on the speed of
swelling deformation, copolymerization experiments are conducted
at low temperature and compared with the results using radical
polymerization.
7644-43, Session 9
Large deformation and electrochemistry of
polyelectrolyte gels
W. Hong, Iowa State Univ. (United States); X. Zhao, Z. Suo, Harvard
Univ. (United States)
Immersed in an ionic solution, a network of polyelectrolyte polymers
imbibes the solution and swells, resulting in a polyelectrolyte gel.
The swelling is reversible, and is regulated by ionic concentrations,
mechanical forces, and electric potentials. This paper develops a field
theory to couple large deformation and electrochemistry. A specific
material model is described, including the effects of stretching the
network, mixing the polymers with the solvent and ions, and polarizing
the gel. We show that the notion of osmotic pressure in a gel has
no experimental significance in general, but acquires a physical
interpretation within the specific material model. The theory is used
to analyze several phenomena: a gel swells freely in an ionic solution,
a gel swells under a constraint, electric double layer at the interface
between the gel and the external solution, and swelling of a gel of a
small size.
7644-46, Session 9
Piezoelectric polymer foams: preparation
and charging conditions as well as touchsensor and ultrasonic transducer properties
M. Wegener, Fraunhofer-Institut für Angewandte Polymerforschung
(Germany)
7644-44, Session 9
Cellular space-charge electrets, so-called ferroelectrets, represent a
new class of piezoelectric transducer materials. Their piezoelectric
activity arises from (i) optimised structural and elastic properties of the
foamed polymer film and from (ii) trapping of charges with different
polarity at opposite void surfaces within the foam forming electrical
dipoles. A mechanical stress applied across the film thickness leads
to a large film-thickness change, if the polymer film is prepared with
an elastically optimised cellular structure. Thus, the size of electrical
dipoles is varied, which leads to an electrical signal across the sample
thickness. Such an electrostatic or condenser principle is used in
different transducer devises. However, here this transducer principle is
incorporated into the material itself.
Stimuli responsive hydrogel simulation
K. J. Suthar, Western Michigan Univ. (United States) and Argonne
National Lab. (United States); M. K. Ghantasala, Western Michigan
Univ. (United States); D. C. Mancini, Agonne National Lab. (United
States)
This paper presents the results of simulation of the swelling of
hydrogels in steady state conditions with emphasis on its response
to the environmental stimuli; such as solvent pH, and external
electrical potential. Our numerical model employed and our simulation
methodology is described in detail. Recent technological development
in the area of biomedical field requires new kind of material, which
are capable of sensing chemical change in surrounding. This type
of sensing is an important aspect of a material. Recent rise of new
nanotechnology promises many such application Hydrogels were found
to be ideal for this purpose and hence, there is growing interest in using
them for this application. This necessitates a thorough understanding
of its pH characteristics in general.
Very high piezoelectric activities with piezoelectric d33 coefficients up
to several hundred pC/N were found on ferroelectrets. The underlying
polarization effects as well as the dependence on the elastic properties
and the foam structure itself is currently a broad research field. A
detailed picture of the structural, electrical, and electromechanical
features of ferroelectrets was first developed on cellular polypropylene
films and recently proofed by the development of cyclo-olefine,
polyethylene terephthalate and polyethylene naphthalate ferroelectrets.
We have demonstrated a methodology for simulating pH sensitive
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Conf. 7644: Behavior and Mechanics of Multifunctional Materials and
Composites IV
electromechanical coupling. This high electromechanical coupling and
flexibility offered by the novel active composites will provide material
systems with ultimate sensing, actuation, structural health monitoring
and energy harvesting and storage functionalities.
Here, the ferroelectret concept is discussed briefly. In detail, the
dependence of piezoelectric properties on cellular morphology and
thus on elastic properties, on performed charging and on usage
conditions is presented for different ferroelectrets. Furthermore,
possibilities to integrate ferroelectrets in touch sensors as well as in
audible and ultrasonic transducers are demonstrated and the final
transducer properties are discussed.
7644-49, Session 10
Nonlinear actuation response in
polyvinylidene fluoride (PVDF)-based
nanocomposites
7644-47, Session 9
Characterization of healable polymers
S. J. Deshmukh, Z. Ounaies, Texas A&M Univ. (United States)
C. Nielsen, O. Weizman, S. Nemat-Nasser, Univ. of California, San
Diego (United States)
Poly(vinylidene fluoride) (PVDF) is the only commercially-available
piezoelectric polymer. Research on enhancing its electromechanical
properties by optimizing parameters such as mechanical stretching
and poling conditions is abundantly available. However, to date, this
approach has led to modest improvement in performance. An alternate
approach is to enhance the electromechanical properties of PVDF
by adding nanoinclusions. In this study we demonstrate the creation
of a non-linear electromechanical response in non-piezoelectric
(unstretched and unpoled) poly(vinylidene fluoride) (PVDF). The
PVDF-SWNT nanocomposites are prepared by solution casting.
Following drying, curing and electrode deposition, the experimental
characterization takes place by focusing on three aspects:
Materials with an internal mechanism for damage repair would
be valuable in isolated environments where access is difficult or
impossible. To this end, a fibrous composite structure is envisioned
with a healable polymer matrix. Current work is focused on
characterizing neat polymers with reformable cross-linking bonds.
These bonds are thermally reversible, the result of a Diels-Alder
cycloaddition between furan and maleimide monomers. Candidate
polymers are examined using modulated differential scanning
calorimetry (MDSC) to confirm the presence of reversible bonding.
One polymer, 2MEP3FT, was expected to have these bonds, but none
were observed. A second polymer, 2MEP4FS, with a modified furan
monomer does exhibit reversible bonding. Further MDSC testing
and dynamic mechanical thermal analyses (DMTA) are conducted to
determine material properties such as glass transition temperature,
Young’s modulus and quality of the polymerization. Healing efficiency
is established using the double cleavage drilled compression (DCDC)
fracture test. A column of material with a central hole is subjected
to axial compression, which drives cracks up and down the sample.
Removing the load allows the crack faces to come together, a
necessary condition for the reestablishment of broken bonds. This
healing process is accelerated with a heat treatment. By retesting the
sample, a healing efficiency of the polymer is determined. The effect of
multiple fracture/healing cycles on the healing efficiency of the polymer
is considered.
a) Actuation response
b) Dielectric characterization
c) Morphology characterization
The actuation response of PVDF nanocomposites to applied electric
field is tested using cantilever bending and thickness actuation
configurations. The resulting strains are found to have a quadratic
dependence on applied electric fields, indicative of an electrostrictive
response.
The dielectric and electrical characterization is carried out using a
Novocontrol broadband dielectric spectrometer. The dielectric constant
shows an increase from 11 for pure PVDF to 233 for PVDF-0.4%SWNT
nanocomposite (measured at 1 Hz ). This high dielectric constant value
at low frequency indicates an enhancement in interfacial and induced
polarization in PVDF due to addition of SWNTs.
7644-48, Session 10
The effect of SWNTs on the polar crystalline morphology of PVDF
is also studied using Fourier transform infrared spectroscopy (FTIR).
Finally, we also investigate the effect stretching has on the actuation
response through an increase in the polar phase and a decrease in
Joule heating.
Giant piezoelectric effect in nanocomposites
with aligned PZT nanowires
C. C. Andrews, Y. Lin, H. A. Sodano, Arizona State Univ. (United
States)
7644-50, Session 10
The use of piezoelectric materials have become quite common in a
wide range of applications, including structural health monitoring,
power harvesting, and actuation. However, piezoelectric materials are
often prone to breakage and are difficult to apply to curved surfaces
when in the monolithic form. Many solutions produced involve 0-3
active composites which alleviate the issue with brittleness which
allow the composites for application on curved surfaces but in turn
significantly reduce the composites electromechanical coupling. The
research presented in this paper will create a nanowire alignment
technique to fabricate 0-3 active nanocomposites with aligned
piezoelectric nanowires. PZT (Lead Zirconate Titanate) nanowires are
used in the creation of the nanocomposites and can be synthesized
with a hydrothermal method for which the time of the run and
the mineralizer concentration can control the morphology of the
nanowire shape. Once the nanowires are mixed with a polymer an
AC electric field is used to align the nanowires in the direction of the
voltage. With direct measurement of the effective electromechanical
coupling through inverse piezoelectric effect using an Atomic Force
Microscope (AFM), our results will experimentally demonstrate the
role of nanowire alignment on achieving high electromechanical
coupling in 0-3 nanocomposites. Electromechanical coupling of the
active composites with less than 50% volume fraction aligned PZT
inclusion could achieve as high as that of bulk piezoelectric materials.
The nanocomposites developed in this paper pave the way for new
and innovative applications previously unobtainable due to limited
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Microwave absorbing properties of
nanocomposites with surface treated ferrite
nanoparticles as filler
A. Jänis, Swedish Defence Research Agency (Sweden); R. T.
Olsson, Royal Institute of Technology (Sweden)
Analysis of microwave absorbing properties of different polymer
(epoxy) based nanocomposites are presented. The ferrite nanoparticles
employed as filler materials were produced by a co-precipitation
method, which was adapted for production of large amount at low
cost. The nanoparticles of interest for this study were cobalt ferrite
nanoparticles. For better dispersion of nanoparticles in matrix the
surface treatment of nanoparticles with silane compounds was
performed. The influence of the treatment on mechanical and
microwave absorbing properties of nanocomposites was investigated.
Magnetic core-shell cobalt ferrite-silsesquioxane-epoxy
nanocomposites have been prepared with uniform nanoparticle
distribution. The nanoparticles were surface-treated with methyl(MTMS), aminopropyl- (APTMS), glycidoxypropyl- (GPTMS) trimethoxysilane. The optimum coating process was performed in a water/
methanol solution on the particles directly after their synthesis
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Conf. 7644: Behavior and Mechanics of Multifunctional Materials and
Composites IV
indentation experiments. Results reveal that the surface treated carbon
nanotubes and short carbon fiber distribute homogeneously and form
three-dimensional conductive networks within the epoxy matrix. In this
way, the resistance of composite materials greatly reduced significantly.
The capacity of transmiting electric current is increased, and the
Damage resulting from the strikes reduce. The characterization of
mechanical properties also indicates that the incorporation of nanoconductive fillers also enhanced the material elastic modulus and
hardness significantly.
without prior drying. The GPTMS-coatings were 30 nm thick and the
nanoparticles dispersed well in epoxy without sedimentation (Figure
1). The MTMS-coated nanoparticles (3 nm coating) formed weak
agglomerates in epoxy but showed no sedimentation (Figure 1). The
APTMS-coated particles formed stronger agglomerates, which led
to sedimentation of the particles during molding. The GPTMS-based
composites showed higher fracture toughness than the MTMS-based
composites. This was attributed to the presence of larger agglomerates
in the latter systems and to the stronger interface between coating
and epoxy in the former systems. The material properties, permittivity
and permeability, of GPTMS-based composites were measured in the
frequency range between 3.95 MHz and 18 GHz. The nanocomposites
showed no influence of surface coating on measured permeability.
The conclusion can be done that surface treatment in form of
GPTMS-coating does not disturb magnetic properties but improve the
mechanical properties of the nanocomposites.
7644-54, Session 10
Electrothermal actuation of highperformance polyimide nanocomposites
A. T. Sellinger, D. H. Wang, L. S. Tan, R. A. Vaia, Air Force Research
Lab. (United States)
7644-51, Session 10
The novel property combinations offered by polymer nanocomposites
(PNC) afford unique opportunities for sensor and actuator-based
devices. Carbon nanotube (CNT) additives, both below and above
percolation, have been shown to reduce the electric-fields required
to induce actuation by up to two-orders of magnitude in various
electrostrictive and piezoelectric polymers. This behavior is commonly
attributed to local electric field modification and charge accumulation
within the PNC. Alternatively, low percolation threshold and tunable
conductivity can also promote actuation via resistive (Joule) heating
at relatively low applied fields. Infrared imaging of polyimide (CP2)
nanocomposites containing single wall nanotubes (SWNTs) and carbon
nanofibers (CNFs) reveals temperature increases in excess of 225 oC
at fields no greater than 0.01 MV/m applied in-plane. Thus, depending
on the mechanical boundary conditions employed, thermal expansion
driven buckling or mechanical softening of the polymer at Tg (209 oC)
can result in macroscopic strains of up to 5%. Upon removal of the
field, convective cooling is estimated to occur at rates in excess of 104
oC/s, suggesting reversible strain cycling may operate at frequencies
above 0.5 kHz. Consequently, under the application of an AC voltage,
both the temperature and shape of the PNC oscillate in accordance
with the applied frequency, with maximum strains exceeding those
previously reported by over two-orders of magnitude for a given
applied field.
Nano-clay/poly(vinylidene fluoride)
composite films as sensor and actuator
element
G. Murasawa, D. Wakabayashi, E. Yamada, A. Nishioka, K. Miyata,
T. Koda, Yamagata Univ. (Japan)
Poly(vinylidene fluoride) (PVDF) is a piezoelectric polymer material. In
general, it is necessary to give large extension to PVDF film when PVDF
film is used as sensor or actuator element. However, we recently found
that PVDF shows piezoelectricity without large extension when Nanoclays are uniformly dispersed into it.
The aim of present study is to investigate the possibilities of Nanoclay/PVDF composite films as sensor and actuator element. Firstly,
Nano-clay/PVDF composite films are fabricated by solvent casting.
Also, PVDF films given large extension are prepared as comparative
material. Next, the electric displacement versus electric field hysteresis
loop is measured for Nano-clay/PVDF composite films and PVDF films
given large extension. Then, we investigate the oscillation generated
from element by electric spike wave. In this time, the dispersive waves
propagating in solid with broad frequency are also detected by present
prepared films. Finally, we discuss the possibilities of Nano-clay/PVDF
composite films as sensor and actuator element.
7644-56, Session 10
7644-53, Session 10
Investigations of the key mechanism of
carbon-nanotube actuators and their
dependencies
Carbon nanotubes/ short carbon fiber
nanocomposites for lightning strike
protection
S. M. Geier, Deutsches Zentrum für Luft- und Raumfahrt e.V.
(Germany)
C. Wu, Y. Liu, J. Leng, Harbin Institute of Technology (China)
Carbon Nanotubes show in the presence of an electrical field and ions
interesting deflection effects. Therefore CNT material has the potential
for building up flexible and adaptable structures. The deflection-needed
ions are provided by electrolytes, which can be liquid electrolytes.
With the development of modern aviation industry and materials
science, the structural components of aircraft platforms are being
transitioned from metals to polymeric matrix composites. However,
the composite material belongs to electrically insulating materials.
If struck by lightning it would be damaged more easily than other
structures. The matrix resin may be degraded and vaporize, and the
reinforcement fibers may break. Catastrophic structural damage may
occur. Current aircraft structural composites are commonly protected
using approaches such as lying of metallic meshes and foils. However,
these are not ideal solutions because they increase significant weight
and may be difficult to repair.
Within this presentation we focus on the mechanical and actuator
properties of different CNT based structures. On one hand the so
called bucky-papers (BP) are investigated regarding the dependency
of actuator performance on the alignment of the tubes (random or
aligned CNT) and the materials purity. On the other hand the usage of
CNT-arrays is investigated. The actuator properties are measured by an
in-plain experimental set-up using liquid electrolytes. Further on solid
electrolytes which are better useable for structural applications are
investigated.
In this paper, we use multi-walled carbon nanotubes(MWNTs) and short
carbon fiber(SCF) as reinforcement, and epoxy resin as matrix. We
prepare conductive nanocomposites for lightning protection of aircraft.
MWNTs and SCF are treated via acidification and surface modification,
mechanical milling, ultrasonic dispersion method. The CNTs/SCF
Epoxy (EP) conductive nanocomposites are prepared by casting
method. The characterizations of materials microstructure, electrical
and mechanical properties are investigated by scanning electron
microscope (SEM), resistance instrument, tensile test machine and
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7644-55, Session 11
Development and control design for macro
fiber composite actuators
M. Stuebner, R. C. Smith, North Carolina State Univ. (United States)
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Conf. 7644: Behavior and Mechanics of Multifunctional Materials and
Composites IV
monolithic Terfenol-D alloy. The magnetostrictive response has been
studied as a function of the Terfenol-D particle size distribution, and
the content of magnetostrictive particles in the composite. The highest
response was obtained for a composite having 70% volume fraction
of particles. Investigated composite are promising magnetostrictive
material enable to create a new type of actuators and magnetic field
sensor.
Macro Fiber Composites (MFC) show significant durability and flexibility
in addition to being lightweight and providing broadband inputs.
However, they also exhibit hysteresis and constitutive nonlinearities
that must be incorporated in models and control designs to achieve
the full potential of the devices. They are presently being considered for
a range of applications including positioning and control of membrane
mirrors and configurable aerospace structures. These applications
require high precision control. In this talk, we discuss a model that
quantifies the hysteresis and constitutive nonlinearities and develop
a nonlinear control design for the displacement. The constitutive
model is constructed using the homogenized energy framework for
ferroelectric hysteresis and used to develop resulting system models.
The performance of the models is validated with experimental data
and numerical simulations are used to illustrate abilities of the control
architecture.
7644-88, Session 11
Non-linearity in piezo-fiber reinforced
composites: an asymptotic approach
S. S. Padhee, D. Harursampath, Indian Institute of Science (India)
Development of Piezoelectric Fiber Reinforced Composites (PFRC)
has enabled new applications towards electro-thermo-mechanical
sensing, actuation and power harvesting. The conformability of PFRC
enables them to be conveniently incorporated on or into many reallife structures whose surfaces, in general, are curved. They have a
strong, voltage dependent actuation authority and can interact with
dynamic systems at frequencies from about 1Hz to 1MHz. Because
these piezoelectric fiber diameters are much smaller than the typical
wavelengths of interest, homogenization techniques become both
necessary and useful to describe the behavior.
7644-57, Session 11
Micromechanical analysis of viscoelastic
damping performance of active piezocarbon fiber polymer composites
Q. Dai, K. Ng, Michigan Technological Univ. (United States)
Recent studies showed the active piezo-carbon fiber polymer
composites may achieve significant and simultaneous improvements in
sensing/actuating, stiffness, fracture toughness and vibration damping,
and these characteristics can be of particular importance in various
civil, mechanical and aerospace structures. This study conducts the
micromechanical analysis and finite element simulation to examine
the damping characteristics of active piezo-carbon fiber polymer
composites under the dynamic cyclic loadings. The viscoelastic
properties of polymer matrix are considered with time-dependent
relaxation modulus. The active piezo-carbon fibers used in this study
are adopted from a recent study (Lin and Sadano, 2008). The damping
performance is compared with the active piezo-carbon fiber and
regular carbon fiber polymer composites with the same fiber volume
fractures. It is found that the electric-mechanical coupling behavior
can absorb dynamic energy and delay structure responses with higher
viscoelastic damping. The effects of aspect ratios of piezo-carbon
fibers on viscoelastic damping performance are also investigated. This
study showed the promise in using this type of polymer composites to
improve structure dynamic stability.
Through this work, an asymptotically correct model will be presented
for the micro-electro-mechanical analysis of PFRC, using Variational
Asymptotic Method (VAM). VAM is a mathematical tool developed by
Berdichevskii [1979]. This method enables solutions in closed form
even to some complex problems with inherent small parameters. VAM
has been employed in the current work as a tool to split the original 3D
electro-mechanical problem of a representative volume element into a
1D problem tangential to the length of the piezo-fiber and a 2D crosssectional problem. Apart from splitting the problem for dimensional
reduction and computational efficiency, VAM also directly provides
accurate solutions to the 2D cross-sectional problem, incorporating the
influence of both the primary material constituents in an asymptotically
correct fashion. Thus VAM enables one to analyze the original problem
in a mathematically rigorous and yet computationally tractable manner.
The unit cell of the PFRC considered here, consists of a single
piezo-fiber of circular cross-section surrounded by a piezoelectrically
inactive polymer matrix. The size of the matrix sleeve is based on the
volume fraction. The circular cross-section is significant because of
the commercially available version of the PFRC, namely the Macro
Fiber Composites (MFC) originally developed by NASA. This unit cell is
treated as a slender beam. To simplify the analysis and provide certain
insights, mechanical and electric effects were studied independently
first, then they were rigorously coupled. Hence, this work consists
of three broad sections. First section deals with the mechanical
analysis of PFRC. The structure is homogenized and effective material
constants are obtained. Second section deals with the electric effect
of PFRC and effective dielectric coefficients are obtained. Third
section deals with the fully coupled analysis of the PFRC and effective
piezoelectric coefficients are obtained as a function of the piezoelectric
coefficients of the constituent fiber. The analytical results obtained are
then used to explore possible implications for design and analysis as
well as numerical studies.
7644-58, Session 11
Magnetomechanical properties of
magnetostrictive composites with high
volume fraction Terfenol-D powder
D. Lewandowski, J. Kaleta, R. Mech, Wroclaw Univ. of Technology
(Poland)
The role of Smart Magnetic Materials (SMM) is still increasing. One
type of SMM are Giant Magnetostrictive Materials (GMM) which can be
represented by i.e. Terfenol-D. The biggest difficulty with mechanical
application of GMM is its brittleness. On the other hand, increase of
frequency generate meaningfully eddy currents. These disadvantages
tend to search new solutions in a form of composite materials with
giant magnetostriction (GMMC). The matrix for GMMC most often is an
epoxy resin with magnetostrictive material inside (in a form of powder,
flakes or tiny rods made of i.e. Terfenol-D). Several composites, with
outstanding magnetostrictive properties, have been synthesized
combining an epoxy resin with polycrystalline powders of Terfenol-D.
Composites consisting particles with a different size distribution.
Application of appropriate way of compression allowed to achieve
composites consisting near 70% volume fraction of Terfenol-D powder
in comparison with about 48% volume fraction of reinforcement in
traditional production way. Composites had random and preferential
orientation which was obtained by curing the material respectively
with or without a magnetic field. The quasistatic magnetomechanical
properties of the composites were investigated and compared with
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7644-59, Session 12
Mechanically-tunable composite filter at low
frequencies
S. Wheeland, A. V. Amirkhizi, S. Nemat-Nasser, Univ. of California,
San Diego (United States)
Previous studies into the possibility of a plasmonic medium of a
coiled conductor array in air have shown promise. This work serves to
evaluate the possibility of creating a mechanically-tunable composite
filter at low frequencies. Copper springs of various gauges were
created with varying starting pitches using a coil winder. These springs
were then embedded into a flexible host polymer. The mechanical
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Conf. 7644: Behavior and Mechanics of Multifunctional Materials and
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remnant strain, and stress distribution, including their component in
both Cartesian and polar coordinates, have been studied in order to
determine what material/geometry variables need to be addressed to
optimize MFCs as strain sensors.
and electromagnetic properties of each spring design were predicted
and tested. Two horn antennas were used to characterize the overall
electromagnetic (EM) properties of the composite. The pitch of each
spring was increased mechanically through application of force to
the entire polymer-metal composite at equal intervals, with an EM
test completed at each step. Using an Agilent 8510C Vector Network
Analyzer (VNA), the frequency spectrum within the microwave range
was scanned. Relative amplitude and phase measurements were
taken at equal frequency and pitch steps. With no polymer surrounding
the springs, plasmon turn-on frequencies were observed to span the
microwave bands as the pitch of the springs were increased. Similar
results are expected with the springs embedded in a polymeric matrix.
These results suggest a method of creating a mechanically-tunable
composite filter for use at low frequencies.
7644-62, Session 12
Influence of content level and particle size
of nickel powders on piezoresistivity of
smart cement-based composites
B. Han, J. Ou, Harbin Institute of Technology (China)
The piezoresistivity of cement-based composites has attracted a lot
research attention due to its potential application in structural health
monitoring. In order to explore the influence of content level and
particle size of nickel powders on the piezoresistivity of cement-based
composites, the electrical resistivity of cement-based composites
containing nickel powders with particle sizes in the range of 3-7μm,
2.6-3.3μm and 2.2-2.8μm was measured and its variation under
uniaxial compression was studied. The differences in electrical
conductivity and piezoresistivity of these composites were investigated
by examining the morphology of composites using scanning electron
microscope. The experimental results show that content level and
particle size of nickel powders are two key factors that influence the
piezoresistivity of cement-based composites, which are due to the
different conductive characteristics in composites. It is also found that
the cement-based composite containing 24 vol.% of nickel powder
with particle size in the range of 3-7μm possesses moderate electrical
conductivity and the best piezoresistivity among cement-based
composites with different content levels and particle sizes of nickel
powders.
7644-60, Session 12
Mechanically tunable plasmon frequency
using a spring array
C. J. Schuil, A. V. Amirkhizi, S. Nemat-Nasser, Univ. of California,
San Diego (United States)
Composites with plasma frequencies in microwave range can be used
as electromagnetic filters. The permittivity of a material transitions
from negative to positive at the plasma frequency. Below the plasma
frequency, the material is highly reflective. Above the plasma frequency,
it is transparent. There are a couple of established ways to make
composites with plasma frequencies in the microwave range. One
method is to embed wire coils in a material. Wire coils have four
parameters that affect the plasma frequency: pitch, wire thickness,
coil inner diameter, and coil spacing. Springs are a form of wire
coils with a mechanically adjustable pitch. For this project, an array
of non-magnetic springs was placed in a test frame. The springs
alternated between left and right-handed in order to reduce system
chirality. Two horn antennas, one on each side of the test frame, were
used to send and receive microwave signals. The horn antennas
were connected to a vector network analyzer (VNA). The VNA returns
scattering parameters that were used to calculate the permittivity
and permeability of the system. Between each set of measurements,
the springs were uniformly extended. This increases the pitch of the
springs while leaving the other spring parameters constant. For each
spring extension, the permittivity adheres to the Drude-Lorentz model
and is zero at the plasma frequency. Furthermore, increasing the
pitch of the springs increases the plasma frequency of the material.
Therefore it was experimentally determined that the material has a
mechanically tunable plasma frequency.
7644-63, Session 13
Rapid nanoimprinting and piezoresponse
force microscopy of ferroelectric
poly(vinylidene fluoride-trifluoroethylene)
copolymer films
Y. Liu, J. Li, Univ. of Washington (United States)
Patterned poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)]
ferroelectric films with feature size down to nanometer scales have their
scientific and technological significances. In this talk, we demonstrate
an enhanced rapid nanoimprinting process on P(VDF-TrFE) copolymer
films with feature size down to 100nm in just 3 minutes. The structure
and crystallinity of the thin film were measured by scanning electron
microscope, atomic force microscope and X-ray diffraction. The
ferroelectricity of the imprinted films was investigated by surface
potential measurement and piezoresponse force microscopy. Electrical
properties of P(VDF-TrFE) films were also studied utilizing switching
spectroscopy PFM (SSPFM) mode, which allowed real-space mapping
of switching behavior and electromechanical activity. The SSPFM
measurements were carried out at different temperatures. The obtained
piezoresponse phase hysteresis loop and amplitude butterfly loop
results showed that the coercive field of the film is reduced with
the increase of temperature and finally lost when the temperature
approached the Curie temperature. Also, the effects of imprinting
conditions have been investigated, and the optimal imprinting
parameters for excellent pattern transfer have been identified.
The application of the imprinted polymeric pattern as a four-state
ferroelectric memory has also been demonstrated and discussed.
7644-61, Session 12
Strain sensing applicability of macro fiber
composites
D. M. Pisani, C. S. Lynch, S. Liu, Univ. of California, Los Angeles
(United States)
Piezoelectric macro fiber composites (MFCs) have been widely
used as planar-actuator devices due in part to their robust flexibility,
directional actuation, and utilization of the d33 piezoelectric mode.
By investigating the converse piezoelectric effect, MFCs can be used
as a dual strain sensor-actuator. The current manufactured MFC
yields severe hysteresis in even moderate uniform strain fields of 200
microstrains. These non-linearities prove challenging in developing
a high precision strain sensor. In order to fully develop a sensor/
actuator, an optimized MFC must be designed. To understand the
non-linear behavior of current MFCs, a 2-d finite element code has
been developed to run piezoelectric material simulations on the MFC
geometry. This code contains a fully multiaxial micromechanics model
based on a constitutive law and domain switching criterion. It solves
the linear piezoelectric problem with incremental electric potential
loading and subsequently unloading, resulting in a strain and electric
field calculation of each element. From the finite element model,
polarization, polarization reorientation (remnant polarization), strain,
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7644-64, Session 13
Voltage creep effect on actuation behavior
of cellulose electro-active paper (EAPap)
G. Yun, J. Kim, J. Kim, Inha Univ. (Korea, Republic of); C. Yang,
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Conf. 7644: Behavior and Mechanics of Multifunctional Materials and
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is strained the charge concentration is decreased. A comparison
demonstrating the importance of adding the mechano-chemical
coupling effect on the electromechanical model is presented. Finally a
comparison between the numerical model and experimental data of the
mechanical displacement response due to an applied electric potential
is established.
Andong National Univ. (Korea, Republic of)
The voltage creep behavior on actuation performance of cellulose
based electro-active paper (EAPap) has been studied. Because the
actuation of EAPap is originated from both the inner ionic movement in
cellulose and its piezoelectric behavior, the actuation can be affected
by the external field. When the external field applied, cyclic hysteresis
of P-E loop is observed. In order to investigate the detail of actuation
behavior of EAPap actuator, the detail actuation response - called
voltage creep- is required. The voltage creep which can reduce the
response and the actuating accuracy of actuator is one important issue
in order to control the micro/nano scaled positioning of smart material
devices. In this paper, we present the voltage creep phenomena of
EAPap, which will give more detail information to understand EAPap as
well as other polymer based smart materials.
7644-67, Session 13
Actuation and sensing of a dielectric EAP
actuator
A. York, M. Hodgins, S. S. Seelecke, North Carolina State Univ.
(United States)
Dielectric Electro-Active Polymers (DEAP’s) have become attractive
material for various actuation and sensing applications such as
light weight and energy efficient valve and pumping systems. This
paper provides a systematic experimental investigation of the quasistatic and dynamic electro-mechanical properties of a commercially
available DEAP actuator. Experiments are conducted to observe the
actuators performance under various spring biased and mass loaded
conditions. The force and stroke capabilities are investigated while
the actuator is electrically loaded with cyclic voltages from the low to
high frequency regime. The sensing capabilities of the actuator are
tested using a method similar to that used by Jung et al. 2008 which
uses the DEAP actuator as a variable capacitor in a high pass filter
circuit [1]. This sensing circuit produces a direct voltage output when
the actuator is displaced. This response is studied under a variety of
excitation schemes and displacement rates. The resulting behavior of
the actuator is then correlated to the viscoelastic and electro-static
properties observed during previously conducted electro-mechanical
characterization tests. All experiments are conducted with a particular
focus on the hysteretic and rate-dependent material behavior.
7644-65, Session 13
Modeling the transduction of IPMC in 3D
configurations
D. Pugal, K. J. Kim, Univ. of Nevada, Reno (United States); A.
Aabloo, Univ. of Tartu (Estonia)
The Finite Element Analyze (FEA) methods have proven to be
applicable for modeling the basic transduction sheets(cantilevers) of
ionic polymer-metal composite (IPMC). Simple physical models can
simulate ion transport and corresponding strain. More complicated
models also add the effect of the electrode, both surface and
electrochemical ones.. In this work we propose a FEA model for IPMC
materials of different shapes. The new model is fully three dimensional.
When dealing with 3D transduction, the electrode surface geometrical
properties of IPMC becomes more important as well. For instance,
there are several ways how to attach the electrodes to a cylindrical
IPMC to get various deformation modes. The proposed model
considers the electrode placement and provides sufficiently accurate
transduction estimate for more complicated IPMC structures.
7644-68, Session 14
7644-66, Session 13
The effect of scaling on performance of
elastomer composite actuators
Finite element modeling of the
electromechanical coupling in ionic polymer
transducers
L. D. Peel, Texas A&M Univ.-Kingsville (United States); J. W. Baur,
D. C. Foster, D. Phillips, A. McClung, Air Force Research Lab.
(United States)
B. J. Akle, W. Habchi, Lebanese American Univ. (Lebanon); T.
Wallmersperger, Univ. Stuttgart (Germany); D. J. Leo, Virginia
Polytechnic Institute and State Univ. (United States)
Reconfigurable composite and hybrid systems have the potential
to enable adaptive structures and vehicles that are optimized for
a given performance need. Compact actuation that is seamlessly
integrated into the materials system has the potential to provide rapid
reconfiguration with a fine level of displacement control without the
significant weight and volume of traditional mechanized devices. This
study investigates the effects of scale (diameter and length) on the
performance of McKibben-like Rubber Muscle Actuators (RMA). When
pressurized, the diameter of cylindrical RMAs increases and length
decreases to produce axial forces over 30X greater than produced
by equivalent pneumatic cylinders. A series of RMAs with nominal
braid diameters of 0.05 to 0.50 inches were fabricated, with two
lengths for each diameter. Actuation force results match well with
predictions. Individual test results vary due to variation in activation
pressures, as expected, but also vary with lengths greater than critical
lengths, which was not expected. Although actuation force per unit
diameter decreases as diameter decreases, actuator force per unit
cross-sectional area does not vary with diameter. If one assumes
that the actuators are loaded in parallel, and that each actuator has a
minimum critical length, then the force per unit volume should increase
as diameter decreases which would enable ready integration into an
adaptive composite system. However, the increase in force per unit
volume may be inversely effected by activation pressure and actuator
length. More investigation into the effects of activation pressure and
actuator length on actuator force per unit volume is needed.
Several researchers are actively studying Ionomeric polymer
transducers (IPT) as a large strain low voltage Electro-Active Polymer
(EAP) actuator. EAPs are devices that do not contain any moving parts
leading to a potential large life time. Furthermore, they are light weight
and flexible. An IPT is made of an ion saturated polymer usually Nafion,
sandwiched between two electrodes made of a mixture of Nafion and
electrically conductive particles usually RuO2 or platinum. Nafion is
an acid membrane in which the cations are mobile while the anions
are covalently fixed to the polymer structure. Upon the application of
an electric potential on the order of 2V at the electrodes the mobile
positive ions migrate towards the cathode leading to bending strains
in the order of 5%. Our earlier studies demonstrate that the cations
develop thin boundary layers around the electrode. Later developments
in this finite element model captured the importance of adding particles
in the electrode. This study presents the electromechanical coupling in
ionic polymer transducers. Since all our earlier models were restricted
to the electro-chemical part, here we will introduce the chemomechanical coupling. This coupling is performed based on previous
studies (Akle and Leo 2006) in which the authors experimentally
showed that the mechanical strain in IPTs is proportional to a linear
term and a quadratic term of the charge accumulated at the electrode.
The values of the linear and quadratic terms are extracted from
experimental data. Furthermore this finite element model captures the
mechano-chemical coupling through the fact that once the material
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Conf. 7644: Behavior and Mechanics of Multifunctional Materials and
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Textile composites are being widely used in the fields of astronautics,
space, marine, automotive and off-shore due to the special properties
compared with traditional laminate composites, combing high
stiffness and strength at low density, high tolerance, high-specific
energy absorption behavior and excellent in plane shear behaviour.
3D four-step braided composites, one kind of textile composites, are
manufactured by braided preforms impregnating and solidifying with
resin material. The mechanical behavior of the braided composites
under tensile loading is studied by experiment and computational
micromechanics. The interfacial debonding between yarn and
matrix which is one of main damage modes is found in experiment.
Interfacial damage is considered by cohesive zone model in FEA of a
representative volume cell (RVC) of the braided composites. Interfacial
damage evolution law adopts energy type damage evolution in which
the fracture energy is defined by the function of the mode mix using
the Benzeggagh-Kenane (BK) fracture criterion. A parametrical study
is evaluated the effect of interfacial properties on the stress-strain
curve and corresponding failure modes. The damage development
of the braided composites with interfacial damage is discussed. It is
found that the interfacial damage which is one of factors to cause the
nonlinear stress-strain relation can decrease the tangential modulus but
not control the ultimate strength. The interfacial strength is one of main
parameters to influence the interfacial damage.
7644-69, Session 14
Effect of particle size and volume fraction
on tensile properties of fly ash/polyurea
composites
J. Qiao, Harbin Institute of Technology (China) and Univ. of
California, San Diego (United States); A. V. Amirkhizi, S. NematNasser, Univ. of California, San Diego (United States)
Polyurea is the generic term for the block copolymer formed from the
reaction of diisocyanates with polyamines. It has several interesting
and superior mechanical properties, e.g. some polyureas are able
to reach tensile strengths of 6000psi and stretch up to over 500%
strain. Fly ash which is a by-product of coal burning or heavy fuel oil
combustion consists of hollow particles with porous shell. Accordingly,
it has been introduced into various polymers and metals to reduce
cost and achieve low density or other special properties. This work
develops a composite which is made of fly ash and polyurea. A onestep method was chosen to make pure polyurea and polyurea matrix
for the composites based on Isonate® 2143L (diisocyanate) and
Versalink® P-1000 (diamine). Various composite samples were made
by changing the size of fly ash particles and volume fraction of fly ash.
The tensile properties of the pure polyurea and fly ash/polyurea (FA/
PU) composites were analyzed using an Instron load frame with a 1
kN Interface model 1500ASK-200 load cell. We present the results of
a collection of experiments for which the volume fraction and average
size of the fly ash particles were varied and the tensile stress-strain
curves, tensile strength, specific tensile strength and strain at break
were determined.
7644-72, Session 14
Bending mechanical properties of metal
honeycomb sandwich structure with
interface connection defects
X. Kong, X. He, L. Shi, Harbin Institute of Technology (China)
7644-70, Session 14
Thermal protection system is one of the key technologies of reusable
launch vehicle (RLV). The ARMOR TPS is one of important candidate
structure of RLV. ARMOR TPS has many advantages, for example:
fixing easily, longer life, good properties, short time of maintenance
and service. In comparison with traditional TPS, the ARMOR TPS
will be the best selection for all kinds of RLV. So the ARMOR thermal
protection system will be used in aviation and spaceflight field more
and more widely because of its much better performance. ARMOR
TPS panel is above the whole ARMOR TPS, and the metal honeycomb
sandwich structure is the surface of the ARMOR TPS panel. So the
metal honeycomb sandwich structure plays an important role in the
ARMOR TPS, while it bears the flight dynamic pressure and stands
against the flight dynamic calefaction. Because the active environment
of metal honeycomb sandwich structure is very formidable, it can
produce interface connection defects which can exist in the process
of manufacture as well. Bending mechanical properties of the metallic
honeycomb sandwich structure with defects are analyzed to obtain
damage tolerance of the structure. The effect of shape, dimension and
location of defects on the bending mechanical properties is conducted
by experimental study. Then finite element analysis is performed to
validate the experimental results. Haynes214 which is a kind of super
alloy materials with high performances is chosen as both face sheet
and core in this paper.
Ballistic performance of polyurea-coated
armor grade ceramic tiles
A. Samiee, Univ. of California, San Diego (United States)
The use of ceramics as energy absorbents has been studied by many
researchers and some improvements in the ballistic performance of
ceramic tiles have been made by coating them with different classes
of materials (e.g. E-glass/epoxy, carbon-fiber/epoxy, etc.). Using
ceramics for energy absorbing applications leads to a significant weight
reduction of the system. Therefore, any modification to the ceramic
configuration in the system which leads to more energy absorption
with the same or less areal density is significant. On the other hand,
polyurea has been proved to be an excellent energy dissipating agent
in many applications. Inspired by this, we are studying the effect of
coating ceramics with polyurea and other materials, on the energy
absorption and ballistic performance of the resulting ceramic-based
composites.
In this study, we investigate the effect of a layer of polyurea on its
ballistic efficiency. To this end, we have performed a set of penetration
tests on polyurea-ceramic composites. In our experiments, a high
velocity projectile is propelled to impact and perforate the ceramicpolyurea composite. The velocity and mass of the projectile are
measured before and after it has pierced the sample. The change
in the kinetic energy of the projectile is evaluated and compared for
different polyurea-ceramic configurations (e.g., polyurea on front face,
polyurea on back face, polyurea between two ceramic tiles, etc.). The
experimental results suggest that polyurea is not as effective as other
restraining materials such as E-glass/epoxy and carbon-fiber/epoxy.
7644-99, Session 14
Three-dimensional piezoelasticity solution
for piezolaminated
angle-ply cylindrical shells featuring
imperfect interfacial
7644-71, Session 14
Interface damage analysis of braided
composites subjected to axial tensile
loading
bonding
J. Liang, G. Fang, Q. Lu, Y. Wang, Harbin Institute of Technology
(China)
Predicting the effect of imperfect interfacial bonding in composite
laminates on their response is extremely important for reliable
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S. Kapuria, Indian Institute of Technology Delhi (India); A. Kumar,
Indian Institute of Technology, Delhi (India)
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Conf. 7644: Behavior and Mechanics of Multifunctional Materials and
Composites IV
design of structures made of such laminates, as used in aircrafts,
spacecrafts, submarines etc. The problem becomes more pertinent
in smart laminated structures integrated with piezoelectric sensors
and actuators, due to presence of high transverse stresses under
actuated condition. The work presents an analytical three-dimensional
solution for simply supported angle-ply piezoelectric (hybrid) laminated
cylindrical shells in cylindrical bending with interlaminar bonding
imperfections, in an electro-thermo-mechanical loading environment.
The bonding imperfection is modeled by considering the jump in the
displacements, electric potential and temperature across the nonrigid interface proportional, respectively, to the associated tractions,
transverse electric displacement and heat flux. The solution includes
the case when electric potentials are prescribed at the interfaces for
effective actuation. A mixed formulation of governing equations is
developed in terms of eight primary variables. The variables for each
layer are expanded in Fourier series in circumferential coordinate to
satisfy the boundary conditions at the simply supported ends. The
governing equations get reduced to ordinary differential equations in
thickness coordinate with variable coefficients and these are solved
by the modified Frobenius method. Numerical results are presented
for hybrid composite and sandwich plates with varying imperfection
compli- ance. The effects of panel thickness and location of imperfect
interface on the response is studied for cross-ply panels while the
effect of ply-angle on the sensitivity towards imperfection is studied for
angle-ply panels. The effect of weak bonding at elastic-piezoelectric
interface on the actuation authority of the piezoelectric layer is also
investigated. The presented results would also help assessing 2D shell
theories that incorporate interlaminar bonding imperfections.
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81
Conf. 7645: Industrial and Commercial Applications of Smart
Structures Technologies IV
Monday-Tuesday 8-9 March 2010
Part of Proceedings of SPIE Vol. 7645 Industrial and Commercial Applications of Smart Structures Technologies 2010
7645-01, Session 1
7645-03, Session 1
Development and commercialization
strategy for piezoelectric energy-harvesting
power sources for gun-fired munitions
A mechanical battery for powering wireless
sensor nodes in harsh environments energy
harvesting session
J. S. Rastegar, R. T. Murray, Omnitek Partners, LLC (United
States); C. M. Pereira, H. Nguyen, U.S. Army Armament Research,
Development and Engineering Ctr. (United States)
P. Constantinou, C. Aird, P. H. Mellor, D. Smith, J. D. Booker, P.
Flewitt, C. E. Truman, Univ. of Bristol (United Kingdom)
In the future nuclear waste may be stored in sealed underground
repositories. The ability to provide a means of monitoring the
environment of the sealed repository after a period of several decades
would be beneficial. An array of Wireless Sensor Nodes (WSNs) is
proposed for this purpose. To power these devices an alternative
energy source, other than chemical batteries, is required. Batteries are
unsuitable as their capacities will deteriorate over long periods, due to
self-discharge, and may be prone to the harsh nuclear environment.
A novel class of piezoelectric-based energy-harvesting power sources
has been developed for gun-fired munitions and similar high-G
applications. The power sources are designed to harvest energy
primarily from the firing acceleration, but from in-flight vibratory
motions as well. During the firing, a spring-mass element reacts to the
axial acceleration, deforming and storing mechanical potential energy.
After the projectile has exited the muzzle, the spring-mass element
is free to vibrate, and the energy of the vibration is harvested using
piezoelectric materials.
This paper explores the potential of using a ‘mechanical battery’, as
an alternative source of energy, because these will not degrade over
time. The ‘mechanical battery’ comprises a compressed magnetic
spring and associated conversion electronics. The system consists
of three annular magnets, longitudinally arranged along a shaft, with
opposing magnetisation directions. This topology is proposed due to a
low number of parts and can provide sufficient energy to the WSN. The
central magnet is allowed to move between the two outer magnets,
which are fixed to a frame. In a ‘charged’ state the central magnet is
held against one of the outer magnets, storing energy as work has
been done against the resultant force to hold the magnet in place. On
release the central magnet moves through a coil, co-axially placed with
the magnets, with a decaying oscillatory motion. As a result, the stored
energy is partially dissipated into electrical energy if a load is attached.
These piezoelectric-based devices have been shown to produce
enough electrical energy for many applications such as fuzing, and are
able to eliminate the need for chemical batteries in many applications.
When employed in fuzing applications, the developed power sources
have the added advantage of providing augmented safety, since the
fuzing electronics are powered only after the projectile has exited the
muzzle and traveled a safe distance from the weapon platform.
An overview of the development of these novel power sources
is provided, especially designing and packaging for the high-G
environment. Extensive laboratory and field testing has been performed
on various prototypes; the methods and results of these experiments
are presented. In addition to presenting the development and
validation of this technology, methods for integrating the generators
into different classes of projectiles are discussed along with strategies
for manufacturing and a side-by-side comparison with competing
technologies. This technology is currently at DoD Technology
Readiness Level 7, and strategies for elevating through the final two
levels and transitioning to commercialization are discussed.
In order to supply energy to a WSN the induced voltage needs to be
rectified and stored intermediately in a capacitor, and then supplied to
the WSN via conditioning electronics. It will be shown in the final paper
that there is an optimal capacitance for which maximum energy is
stored for a demonstrated configuration. The stored energy is sufficient
to supply a WSN, including overcoming initial start up costs and
conversion losses, for approximately seventy ‘acquire and transmit’
cycles. This is possible as the energy cost of an ‘acquire and transmit’
cycle is of the order of 0.5mJ and the stored electrical energy is
approximately 200mJ, extracted from a stored energy of 2J.
7645-02, Session 1
Multi-source energy harvester to power
sensing hardware on rotating structures
The final paper will detail the development of a design tool for such
systems. The tool comprises theoretical models of parameters such
as the mechanically stored energy, the electromagnetic coupling
coefficient and rules for the optimal initial conditions for maximum
energy transfer from the mechanical to electrical domain. These are
verified using measurements from the prototype.
A. D. Schlichting, S. A. Ouellette, C. Carlson, K. M. Farinholt, G.
Park, C. R. Farrar, Los Alamos National Lab. (United States)
The U.S. Department of Energy (DOE) proposes to meet 20% of
the nation’s energy needs through wind power by the year 2030.
To accomplish this goal, the industry will need to produce larger
(>100m diameter) turbines to increase efficiency and maximize energy
production. It will be imperative to instrument the large composite
structures with onboard sensing to provide structural and structural
health monitoring capabilities to understand the global response and
integrity of these systems as they age. A critical component in the
deployment of such a system will be a robust power source that can
operate for the lifespan of the wind turbine. In this paper we consider
the use of discrete, localized power sources that derive energy from
the ambient (solar, thermal) or operational (kinetic) environment. This
approach will rely on a multi-source configuration that scavenges
energy from three different energy harvesting technologies:
photovoltaic, thermoelectric, and piezoelectric. Each harvester is first
characterized individually in the laboratory, then they are combined
through a multi-source power conditioner that combines the output
of each harvester in series to power a small wireless sensor node that
has active-sensing capabilities. The advantages/disadvantages of each
approach are discussed, along with the proposed design for a field
ready energy harvester that will be deployed on a small-scale 19.8m
diameter wind turbine.
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7645-04, Session 1
Wireless energy transmission to supplement
energy harvesters in sensor network
applications
K. M. Farinholt, G. Park, C. R. Farrar, Los Alamos National Lab.
(United States)
In this paper we present a method for coupling wireless energy
transmission with traditional energy harvesting techniques to power
structural health monitoring based sensor nodes. The goal of this
study is to develop a system that can be permanently embedded
within civil structures without the need for on-board power sources.
Wireless energy transmission is included to supplement energy
harvesting techniques that rely on ambient, or environmental, energy
sources. This approach combines several transducer types that harvest
ambient energy with wireless transmission sources, providing a robust
solution that does not rely on a single energy source. Experimental
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Structures Technologies IV
results from laboratory and field experiments are presented to address
duty cycle limitations of conventional energy harvesting techniques,
and the advantages gained by incorporating a wireless energy
transmission subsystem. Methods of increasing the efficiency, energy
storage medium, target applications and the integrated use of energy
harvesting sources with wireless energy transmission will be discussed.
shape memory alloy, which allows large deformations but ensures that
the nominal shape is recovered upon return deformation. The link has
been used as a locking/unlocking element in a larger morphing aircraft
structure. The paper will present the details of the link itself and its
functional requirements, and then will present a finite element analysis
of the link, comparing the numerical load and deformation results to
the experimental behavior. Features of the modeling process that will
facilitate future designs will be highlighted.
7645-05, Session 2
7645-07, Session 2
Next generation control system for reflexive
aerostructures (SMP session)
Fabrication and testing of a shape memory
polymer active rigidity ‘smart joint’ for wing
morphing on a bat-inspired MAV
M. Maddux, Cornerstone Research Group, Inc. (United States)
Cornerstone Research Group Inc. (CRG) has developed a composite
structural solution called reflexive composites for aerospace
applications featuring CRG’s healable shape memory polymer (SMP)
matrix. An integrated structural health monitoring (SHM) system
autonomously monitors structural health of composite aerospace
structures, while integrated intelligent controls monitor data from the
SHM system to characterize damage and initiate prioritized healing
through discrete heat application. Healing occurs through the reptation
process and the damaged region returns to near net original shape
through shape memory effect.
F. Geeng, J. E. Manzo, E. Garcia, Cornell Univ. (United States)
While many SMA wire actuators exist for spacecraft and robotics
applications, few currently exist for micro-aerial vehicles (MAV). Cornell
University’s LIMS Laboratory seeks to integrate its active rigidity SMA
‘smart joint’ in a biologically inspired bat wing MAV to explore flight
characteristics of different morphed wing camber configurations.
The smart joint is composed of a matrix of shape memory polymer with
embedded shape memory alloy for strain actuation. Through selective
ohmic heating via pulse-width modulated (PWM) signal, the required
temperature profile is achieved to simultaneously allow polymer
compliance and SMA actuation, thereby inducing joint bending.
Feedback using strain gauges and thermocouples allows the joint to
achieve a range of actuation to allow for multiple wing configurations.
Compression After Impact (CAI) testing was conducted on composite
reinforced shape memory polymer samples to investigate the
effectiveness of healing mechanisms on mechanical performance and
the ability of SHM system to characterize damage were examined.
Impacted samples were compression tested before and after healing
cycles to assess compressive strength of healable composite samples.
SHM scans throughout test cycles were used to characterize material
damage. Restoration of mechanical performance was demonstrated
through healing, while SHM data showed location and extent of
damage and mitigation of damage post-healing.
Design and fabrication details for the joint and control system is shown.
Finite element and experimental test results are compared to those
from an analytical model, which is also used to predict and optimize
joint behavior. Computational fluid dynamics analysis and wind tunnel
test results for different morphed camber configurations are presented,
showing delayed stall and increased lift. A concept membranous bat
wing vehicle is presented, with test flight data as available.
Intelligent controls software was refined to assess damage intensity
through analysis of SHM and test data, facilitating the prognostic
health monitoring capabilities of the reflexive system. Data output from
the intelligent controls will serve as input to Integrated Vehicle Health
Management (IVHM) systems, with potential application to Integrated
Resilient Aircraft Controls (IRAC).
7645-08, Session 2
Reflexive composite technology has the ability to reduce maintenance
required on composite structures through healing, offering potential
to significantly extend service life of aerospace vehicles and reduce
operating and lifecycle costs.
Shape memory polymer (SMP) venting
mechanism for munitions
M. J. Fisher, Cornerstone Research Group, Inc. (United States)
Cornerstone Research Group (CRG) is developing temperatureactivated pressure venting mechanisms using shape memory polymer
(SMP) to meet insensitive munitions (IM) requirements for solid rocket
motors and other munitions. SMPs are polymers whose qualities
have been altered to give them dynamic shape “memory” properties.
Under thermal stimuli, SMP can exhibit a radical change from a rigid
thermoset to a highly flexible, elastic material. SMP-based pressure
venting mechanisms, coupled with conventional impact-resistant
containers or composite cases, will offer low-cost, failsafe mitigation of
violent responses to thermal stimuli, as part of a systems approach to
meeting IM requirements.
7645-06, Session 2
Analysis of a large-deformation shape
memory polymer locking link
W. W. Clark, J. C. Brigham, C. Mo, Univ. of Pittsburgh (United
States); S. Joshi, NextGen Aeronautics, Inc. (United States)
In recent years, there has been a great deal of interest in “morphing”
structures, that can exhibit drastic changes in their shapes and then
hold those shapes to perform specific functions. The design of these
structures is complicated by the fact that during a typical morphing
maneuver, the deformations and stresses can become much larger
than a typical structure would experience during a deformation in its
elastic range. In addition, the advent of new materials, such as shape
memory polymers (SMP) enable a structural element to effectively
exhibit two different elastic moduli, a stiff modulus that enables the
structure to retain its shape before and after a morph, and a soft
modulus that enables the morph to occur. Finally, the stimulus that
enables the modulus change can also affect the structural element,
its surrounding materials, and the time required to undergo a morph.
For example, conventional SMP is heat-activated, so the application
of high heat can complicate the stress field and even damage the
material. This paper illustrates some of the design challenges of a
morphing structure by presenting a finite strain, large deformation
computational analysis of a composite SMP link. The link is made up
of shape memory polymer (the softening material) and a backbone of
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CRG demonstrated the feasibility of an SMP-actuated venting system
designed to relieve confinement in a solid rocket motor subjected to a
slow cookoff environment. In CRG’s venting design, an SMP composite
provides the triggering mechanism for releasing confinement at
a specified temperature. CRG constructed a prototype venting
mechanism based on an internal retaining ring design and successfully
tested it in a lab-scale thermal environment, and in full-scale slow
cookoff testing in an analog solid rocket motor.
7645-09, Session 2
Reflexive marine systems for autonomous
structural repair
M. Maddux, Cornerstone Research Group, Inc. (United States)
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Cornerstone Research Group Inc. (CRG) has developed a composite
structural solution for application in marine environments featuring
CRG’s healable shape memory polymer (SMP) matrix. Healable
matrix restores mechanical performance in the composite postfailure. Reflexive composite features the integration of three emerging
technologies: marine compatible healable polymer composites,
structural health monitoring (SHM), and intelligent controls.
thermal or moisture stimuli, the SMP exhibits a radical change from
a rigid thermoset to a highly flexible, elastomeric state. The dynamic
response of the SMP can be tailored to match the degradation
profile of the perishable item. SMP-based EET sensors require no
digital memory or internal power supply and provide the capability of
inexpensive, long-term lifecycle monitoring of thermal and moisture
exposure over time.
An integrated SHM system autonomously monitors structural health of
the marine vehicle. Integrated intelligent controls monitor data output
from the SHM system to determine if detected anomaly is damage and
initiates a targeted healing cycle through discrete heat application to
the damaged area. The healing process returns the damaged region to
near net original shape by shape memory effect and matrix healing.
This technology was developed through Phase I and Phase
II SBIR efforts with the Navy. Here, CRG presents progress in
commercialization efforts to scale-up production. Fabrication scaleup, process refinements, and quality control efforts will be discussed
with an emphasis on transitioning SMP materials from lab-scale
development to a production environment.
Adapting reflexive composite solution to marine environments involved
development of a marine-compatible resin and optimization of signal
parameters for SHM functionality underwater. CRG’s healable resin
was tested and evaluated for fresh and salt water resistance. Its
healing capabilities were studied after exposure. Parallel testing was
conducted using two industry standard marine compatible resins.
CRG’s healable SMP was able to regain between 50-100% of its K1C
fracture toughness post failure after healing of completely failed water
soaked neat samples.
7645-14, Session 3
The characterization of a deployable
sandwich beam with shape memory polymer
foam core
Z. Xu, Nanjing Univ. of Science & Technology (China)
By healing damage and micro-cracks, this technology significantly
reduces maintenance required on composite structures, offering the
potential to significantly extend the service life of marine vehicles and
reduce operating and lifecycle costs.
The characterization of a self deployable sandwich beam with a new
kind of shape memory polymer composite foam core (SMCF) was
studied. In SMCF the shape memory epoxy was used as the matrix,
the hollow microsphere and the chopped carbon fiber were used as the
filler and strengthen material. During the material fabricate procedure,
a small amount of aluminum powder and NaOH solution were added to
the mixture as the foaming agent. A set of tensile tests, compress tests
,impact tests and thermal-mechanic tests were preformed on SMCF
to determine the strength, failure strain, glass transition temperature,
shape fixity and shape recovery properties at different temperature.
The obtained shape memory foam owned the fiber reinforced cellular
microstructure, with ultra-light mass, higher bulk strength and ductility
and more than 500% compression/deployment ratio while keeping
the basic shape memory behavior. The recovery strain was almost
100% at the 500% compression ratio after several cycles of training
and the strength degration was negligible after multiple compressiondeployment cycles. Long carbon fiber reniforced composite sheets
were glued to the upper and lower surface of SMCF core completely
as the skin of the sandwich structure. Packing/deploying test, three
point bending test at packed and deployed state were performed on
sandwich beams to verify the feasibility, reliability of the deployment,
the stiffness and the strength of the beam. From the researching results
it can be indicated that the deployable beam described in this paper
has a significant potential in space applications.
7645-10, Session 3
Shape memory polymer activated by
microwave
Y. Zhang, F. Zhang, Z. Xu, Nanjing Univ. of Science & Technology
(China)
Shape memory polymers (SMPs) with the characteristics such as
large recoverability, easy shaping procedure, low density and cost,
easy control of recovery temperature and so on which have motivated
a flurry of interest to exploit their applications . In these SMP based
devices or structure, such as medical devices and deployable
structures. One of the key challenges is how to activate them reliably.
In this paper a novel SMP composite material mixed with Tetra-needle
zinc oxide whisker (T-ZnOw) particles were invented and this SMP/TZnOw composite materials owned the ability to absorb microwave
and to transfer the microwave energy to heat efficiently while keeping
the basic characters of SMP material. Tensile tests and cyclic thermomechanical experiments were performed on the SMP/T-ZnOw with
different particles weight fraction to assess the impact of the T-ZnOw
particles on the mechanical and memory properties of the samples.
The heating efficient of the composite by low power microwave was
tested with the different T-ZnOw particles ratio and it was found that
the temperature in the samples increased rapidly with the T-ZnOw ratio
for a fixed exposure time. Finally a prototype of a SMP device was
deployed under the microwave exposure to demonstrate the feasibility
of SMP actuation by microwave.
7645-15, Session 3
Characteristics of shape memory polymer
foams filled with hollow microsphere
F. Zhang, Y. Zhang, Z. Xu, Nanjing Univ. of Science & Technology
(China)
(SMP SESSION)
7645-13, Session 3
M. D. Rauscher, E. Havens, T. E. Havens, Cornerstone Research
Group, Inc. (United States); J. McFerran, Naval Surface Warfare
Ctr. Dahlgren Div. (United States)
Shape memory polymers (SMPs) are fairly recently developed
functional polymers that find applications in many aspects, such as
medical treatment, mechanism, aerospace and so on, due to the
advantage of high shape recovery, good machining function and low
cost etc. As a new class of shape memory polymers, shape memory
polymer foams (SMPFs) have great potentials in some special areas
because of the smaller density, high compress/deployment ratio as well
as the shape memory properties.
Cornerstone Research Group Inc. (CRG) has developed environmental
exposure tracking (EET) sensors using shape memory polymers (SMPs)
to monitor the degradation of perishable items, such as munitions,
medicines, or foods, by measuring the cumulative exposure to
temperature and moisture. SMPs are polymers whose qualities have
been altered to give them dynamic shape “memory” properties. Under
In this paper, a new kind of epoxy based SMP foam composite
(ESMPF) was developed. The hollow microsphere was applied
as the filler and strength composite material in SMPF and a small
amount of aluminum powder and NaOH solution were added to the
epoxy/microsphere mixture as the foam starting agency during the
manufacture process. The tensile test, compress test and thermalmechanic cyclic test were performed to determine the strength,
Shape memory polymer environmental
exposure sensors
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shape memory properties, ultra-compress ratio and deploy ability of
the SMPF. Comparing with the pure epoxy based SMP, the density
of SMPF composite was decreased and the strength and ductility
increased greatly. The ultra-compress ratio could be 400% at the
temperature above Tg and the shape recovery ratio was almost 100%.
The experiment results indicated that the obtained ESMPF have
significant potential applications in self-deployable structures.
7645-20, Session 4
Active material based active sealing
technology, part 1: active seal requirements
vs. active material actuator properties
A. L. Browne, General Motors Corp. (United States); C. P. Henry,
W. B. Carter, G. Herrera, G. P. McKnight, HRL Labs., LLC (United
States); N. L. Johnson, I. Bazzi, General Motors Corp. (United
States)
7645-16, Session 3
Deployment dynamics of fiber-reinforced
shape-memory polymer structure
Current seals used for vehicle closures/swing panels are essentially
flexible, frequently hollow structures whose designs are constrained
by numerous requirements, many of them competing, including door
closing effort (both air bind and seal compression), sound isolation,
prevention of water leaks, and accommodation of variations in vehicle
build. This paper documents a collaborative research study/exploration
of the feasibility of and approaches for using active materials with
shape and stiffness changing attributes to produce active seals, those
whose geometry and stiffness could be changed on demand, i.e.
seals with improved performance. Included as a major focus was the
assessment of polymeric active materials because of their potential
ease of integration into the current seal manufacturing process.
Potential materials were evaluated in terms of their cost, activation
mechanisms, and mechanical and actuation properties. Based on
these properties, simple designs were proposed and utilized to help
determine which materials are best suited for active seals. In terms of
study findings, the only concepts that were judged feasible (though not
yet practical) with current technology were those utilizing respectively
SMA’s (shape memory alloys) and EAP’s, (electroactive polymers).
However, even with these, considerable engineering development
was felt to be required to fabricate, produce, and manufacture these
concepts in a robust manner and to be able to provide the tunable
range of responses desired in cost and performance competitive
designs.
X. Lan, Y. Liu, J. Leng, Harbin Institute of Technology (China)
A fiber reinforced thermosetting styrene-based shape-memory
polymer composite (SMPC) is developed, and then a deployable
hinge is designed and fabricated using the SMPC. The main objective
is to systematically analysis the deployment dynamics of SMPC
hinge. Firstly, the theory of deployment dynamics of SMPC shell is
presented. Then, the shape recovery performance is investigated by
finite element analysis (FEA), such as deployment moment vs. angle,
stress distributions, etc. The deployment process of curved SMPC
shell is simulated by the geometrically nonlinear analysis. During the
analytical research, the relationship of deployment moment and angle
is derived by using dynamic theory. In addition, during the macroscopic
shape recovery process, the shape recovery performance of SMPC
is decided not only by the shape memory effect of SMP but also
by the microstructural deformation mechanism of fiber and SMP.
Hence, the microstructural deformation mechanisms of SMPC is
investigated by using SEM. Results show that the fiber microbuckling
is needed to achieve high package strain and avoid fiber failure. With
the microbuckling, SMPC materials are suitable for use in deployable
space structure components because of their high strain-to-failure
capability.
Paper submitted for consideration for the Smart Materials and Devices
for Vehicle Applications Workshop
7645-17, Session 4
Magnetostrictive actuator with hydraulic
stroke amplification for active powertrain
mounts
7645-21, Session 5
S. Chakrabarti, M. J. Dapino, The Ohio State Univ. (United States)
J. Park, G. N. Washington, The Ohio State Univ. (United States)
A hydraulically amplified Terfenol-D actuator is developed to be used
as an actuator in active engine mounts. A measure of the actuator’s
performance is obtained through electromechanical tests in the
mechanically-blocked and mechanically-free conditions. In order to
better understand how the actuator compares with current technology,
benchmark tests are performed on a commercial electrodynamic
actuator presently being used in active mounts. The magnetostrictive
actuator gives a higher frequency bandwidth of operation with lower
electrical power consumption. A dynamic model is developed for
the actuator. Eddy current losses are modeled as a one-dimensional
magnetic diffusion problem in cylindrical coordinates. The JilesAtherton model is used to describe the magnetization state of the
material as a function of applied magnetic fields. Magnetostriction,
which is modeled as a single-valued function of magnetization,
provides an input to the mechanical model describing the system
vibrations. Friction at the elastomeric seals is modeled using the
LuGre friction model for lubricated contacts. The model results provide
accurate frequency and time domain fits to the experimental data. A
major drawback of the driver material (Terfenol-D) is that it is brittle and
would need to be packaged extremely carefully to ensure it remains
intact inside the vehicle. An alternative solution to that could be to
replace Terfenol-D with Galfenol (an alloy of Iron and Gallium) which is
machinable and much more robust. A similar actuator would be built
based on Galfenol and the performance of the two devices will be
compared.
(SMART VEHICLES WORKSHOP)
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Smart material database compilation and
material selection tool development
In this paper, information on the various aspects of smart materials
is compiled in an easy-to-consult format by conducting extensive
survey of published articles and including the properties of the
materials. Although many different types of smart materials are being
widely used in various engineering applications, it is hard to find
good documentation on the various aspects of smart materials. The
compilation of a comprehensive database on smart materials enables
to expedite a material selection process in the design of smart material
devices or systems. Using this, industrial application designs with the
materials can be improved in a time-efficient and cost-effective way.
We show the compiled database in a legible format such as GUI based
computer software that determines and simulates what material to use
based on properties and performance. The types of smart materials
include piezoelectric (polymer/ceramic) materials, dielectric elastomer,
shape memory alloys, electro-rheological and magneto-rheological
fluids, and thermoelectric materials. According to their functionalities,
they are categorized into four groups: actuator, sensor, energy
generator, and passive structural materials. The various properties
of the materials in each group are characterized and compiled in a
database. Currently available mathematical models and potential
applications are identified to select the best model for a given purpose.
In addition, we have developed a simple but effective model in case
of no suitable model is determined. Finally, the current and potential
applications of the materials are addressed and the associated
system-level models for selected materials are developed to show the
performance of the overall system.
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Conf. 7645: Industrial and Commercial Applications of Smart
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Resistively heated SMA actuators have been demonstrated for
applications that require very fast actuation. However, SMA actuators
have hitherto been at a disadvantage in applications that require rapid
reset in addition to rapid actuation. This is because the reset time for
an SMA actuator, which is determined by the time required to cool the
actuator below its Mf temperature, tends to be high when the heat
loss rate from the SMA elements is low. We present a compact quick
release mechanism that provides a rapid reset capability to the system
by effectively decoupling the SMA actuator from the rest of the system
during the actuator cool down period using an auxiliary SMA actuator.
After the decoupling, the SMA actuator cools down at a rate dictated
by the local heat transfer conditions while the remainder of the system
(esp. the output load) resets at a rate dictated by its own dynamics.
Subject to proper sizing of the two actuators, the output load can
experience a reset time that is comparable to its actuation time. The
system as a whole resets when both SMA actuators have cooled to a
temperature below Mf. While this system can be adapted for different
kinds of output loads (e.g. constant, linear spring, etc), it is especially
useful for constant output loads, as in this case the auxiliary SMA
actuator needs to supply only a fraction of the work output of the main
SMA actuator. This leads to a compact and low cost system.
7645-22, Session 5
Numerical simulation of the activation
behavior of thermal shape memory alloys
R. Neugebauer, A. Bucht, K. Pagel, J. Jung, Fraunhofer-Institut für
Werkzeugmaschinen und Umformtechnik (Germany)
Problems in using SMA in industrial applications are often caused
by the simply fragmentary knowledge about the complex activation
behavior. To solve this problem, Fraunhofer IWU developed a Matlabbased simulation tool to emulate the properties of an SMA wire. The
tool is based on the energy balance. The contained terms result of the
characteristic material behavior combined with the thermal, electrical
and mechanical conditions. The model validation is realized by a
labarotary experiment where the SMA-actuator elevates a constant
mass. It is shown that there is almost no difference between the
measured and the simulated movement of the actuator. Due to the
good compliance of model and reality, it is possible to use it in a control
loop. Therefore the model is implemented in a microcontroller-based
rapid-prototyping-system. With the knowledge of the actual current
and the measured voltage the electrical resistance of the SMA-actuator
can be computed. Thereby the correlation between the resistance and
the displacement of the wire is used. The transfer of the results into an
industrial application is exemplified by the integration of an actuator in
a throttle flap used in air condition systems of cars. The SMA-based
drive will be compared to an electric drive regarding performance,
control quality, weight and dimensions.
7645-25, Session 6
Ultrasonic-assisted microforming using
Terfenol-D
A. T. Witthauer, L. E. Faidley, G. Kim, Iowa State Univ. (United
States)
7645-23, Session 5
Ultrasonic vibration has long been used in forming processes to
reduce the force required for forming, due to a measured “ultrasonic
softening,” where all ultrasonic energy is concentrated along
dislocations, causing further dislocations and an overall reduction in
yield stress. There are also measured reductions in friction, which result
in improved surface finish and tolerance. These benefits are especially
useful in microforming processes, where material size effects begin to
dominate. When the cross-section of the work piece becomes only a
few grains thick or less, there are marked increases in both yield stress
and friction, as well as reduced repeatability as grains are no longer
allowed to deform in their preferential directions.
Modeling and validation of shape memory
alloy actuated toothed linear ratchet drive
(TOTLRAD) architecture
B. M. Barnes, D. E. Brei, J. E. Luntz, Univ. of Michigan (United
States)
There are many linear actuator applications that require significant
expandability relative to an initial compact package size while
maintaining a zero power hold. These range from extreme load
applications in the kilonewton range for automotive applications
(e.g. hood lifting devices) to gram loading in medical applications
(e.g. implantable actuators). These applications tend to impose other
limiting constraints (environmental, biocompatibility, robustness, etc)
and severe packaging restrictions making conventional actuation
technologies like pneumatics, hydraulics, and electromechanical
drives non-viable. While smart material actuators theoretically have
the required energy density, current direct actuation architectures do
not provide the performance and packaging form factor to meet the
constraints. This paper presents a generic Toothed Linear Ratcheting
Drive (TOTLRAD) architecture utilizing shape memory alloys that
provides zero power hold and large displacements by accumulating
repeated actuations of shape memory alloy wires. Ratcheting leverages
compact packaging with high expandability while maintaining the
high energy density, and high force capacity of the material at various
size scales. The basic performance models are derived using a state
machine kinematic model of the ratchet architecture combined with
a Simulink implementation of a thermodynamic shape memory alloy
material model which is validated using a planar experimental setup.
The modeling foundation presented here enables optimum design of
linear ratcheting actuator systems for high stroke, compact actuators
ranging in force requirements across fields as diverse as medical and
automotive.
Most ultrasonic-assisted forming processes use piezoelectric
transducers, whereas this study will explore the possible advantages
of using Terfenol-D to provide both ultrasonic vibration and bulk
forming motion. The goal is to develop a solid-state forming device,
which should eliminate backlash from the system, potentially further
improving geometric tolerancing. The device will include an ultrasonic
stage, which consists of a simple Terfenol-D rod and coil, as well as a
bulk motion stage, which will involve some sort of mechanical strain
amplifier; possibly a lever type system. Terfenol-D should also provide
an advantage over piezoelectric transducers in that it is strong enough
to handle the force required for forming directly, simplifying system
design. Furthermore, its frequency response band is much wider than
that of a piezoelectric transducer, allowing less stringent frequency
response requirements for the die, which could allow simpler and
cheaper die design.
7645-26, Session 6
Active metal matrix composites with
embedded smart materials by ultrasonic
additive manufacturing
R. M. Hahnlen, M. J. Dapino, The Ohio State Univ. (United States);
M. Short, K. Graff, Edison Welding Institute (United States)
7645-24, Session 5
(Smart Vehicle Workshop) This paper deals with the development of
active metal-matrix composites manufactured by Ultrasonic Additive
Manufacturing (UAM), an emerging manufacturing process that
allows the embedding of materials into metals through ultrasonic
consolidation. In the UAM process, successive layers of metal tapes
are ultrasonically bonded together to form a metal matrix composite.
A compact quick-release mechanism for
rapid reset of SMA actuated systems
N. D. Mankame, R. J. Skurkis, General Motors Corp. (United
States)
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Conf. 7645: Industrial and Commercial Applications of Smart
Structures Technologies IV
Current methods of creating these composites involve sintering
and forging which generally require temperatures up to 565°C. In
comparison, composites created through UAM typically experience
a maximum process temperature of 150°C while some have been
constructed at temperatures as low as 65°C. Being a low-temperature
process, UAM offers unprecedented opportunities to create parts both
with embedded materials (e.g., metals, fiber optics, printed circuits,
polymers, smart materials, etc.) and arbitrarily shaped internal features
(e.g., internal cooling channels, designed anisotropies, etc.).
possible to have both detection and suppression of vibration and noise
accomplished with a single multifunctional composite.
7645-27, Session 6
Friction control in automotive seat belt
systems by piezoelectrically generated
ultrasonic vibrations
UAM operates on the principle of Ultrasonic Metal Welding (UMW).
In UMW, ultrasonic vibrations created by a piezoelectric transducer
are transferred to clamped work pieces by a transversely vibrating
sonotrode. The vibrating sonotrode imparts a static pressure and
transverse ultrasonic motion to the top piece that creates a relative,
friction-like action at the interface of the two work pieces. The relative
interface motion causes shear deformations of contacting surface
asperities, dispersing interface oxides and bringing clean metal-tometal contact and metallic bonding between the surfaces.
S. Bharadwaj, B. R. Burton, M. J. Dapino, The Ohio State Univ.
(United States)
Active control of friction between sliding surfaces is a problem of
significant interest in automotive applications. It has been shown
that the friction force between sliding surfaces can be reduced by
superimposing ultrasonic vibrations on the sliding velocity. The
application of ultrasonics to actively modulate friction coefficients
can be utilized in various vehicle systems (e.g., gear trains, sliding
door/window mechanisms, seat belt systems, engine cylinders,
brake systems, etc.) which often present contradicting requirements.
Seat belts, in particular, are not adaptive and must be designed as
compromise for various occupants and loading conditions. Mechanical
pretensioners and load limiters partially address the trade-offs but at
the expense of added mass and weight. This research investigates
ultrasonic lubrication as a principle for enabling adaptive seat belts with
controllable force at the interface between the D-ring and webbing. By
precisely controlling the seat belt force during a crash event, superior
restraint will be achieved.
In this research, UAM is used to construct an apparently solid
metal block with embedded smart materials. The embedded smart
materials will allow for the composite to have sensing and actuation
properties. This research focuses on the creation of active metal matrix
composites by embedding NiTi and Galfenol into aluminum matrices.
Our work shows UAM’s ability to embed relatively large diameter
shape memory NiTi wires within an Al 3003-H18 matrix. These samples
were constructed by placing NiTi wires at the interface of two Al
3003-H18 tapes and then ultrasonically welding the tapes together.
When embedding NiTi wires with diameters ranging from 0.001” to
0.015” the energy from the ultrasonic vibrations causes plastic flow
of the aluminum tapes around the wires completely enveloping them
in the matrix. Galfenol embedding trials have attempted to make
magnetostrictive UAM composites by placing a 0.015” thick strip of
Galfenol between two Al 3003-H18 tapes.
This work shows that out-of-plane ultrasonic vibrations are effective
in reducing friction in the case of seat belts. These vibrations are
generated using an ultrasonic transducer under harmonic excitation
and transmitted to the interface by a half-wavelength horn. The
harmonic modulation in the normal force about a mean value results in
a reduction in the average friction force at the interface.
The Al-NiTi composites have the ability to change stiffness and are
expected to exhibit sensing abilities and geometric stability over
extended temperatures ranges in contrast to passive structures
made from aluminum. The large difference in elastic modulus, over
100%, between the low temperature martensite phase and the high
temperature austenite phase provides a mechanism for actively
changing the stiffness of the composite through thermal activation. The
large stiffness change can be applied in tunable vibration absorbers
or for actively changing the path mobility in structure-borne noise with
the goal of minimizing noise propagation. The sensing capabilities of
NiTi have also been demonstrated by observing a change in electrical
resistivity as the material is subjected to strain. By utilizing property
changes as a result of thermal excitation in NiTi we expect to see
an increase in stiffness related to the amount of NiTi embedded in
the composite. The same material can be used to sense applied
stress and strain as the stress induced phase transformation and
elastic deformation changes the resistivity of the embedded NiTi
alloy. Geometric stability of Al-NiTi composites is due to the shape
memory effect of the embedded NiTi alloy. As temperature increases,
the expansion of the aluminum matrix is opposed by the contraction
of the NiTi wires. The counteracting strain of the matrix and NiTi
reinforcement results in a partial transformation of the NiTi and a
negative net strain of the composite. These behaviors are the subject of
composite modeling efforts.
Under normal loads up to 670 N at a speed of 0.025 m/s, 58% friction
reduction is obtained. The trends show a decrease in the effect with
increasing sliding velocity and increasing normal load.
n summary, this research investigates the potential of ultrasonic
vibrations in controlling friction in an automotive seat belt system.
By applying out-of-plane vibrations, frictional force at the interface
between the D-ring and webbing is reduced. Small changes in friction
force have a large effect on the chest force. Active control of friction
would help improve the performance, efficiency, and lifetime of such
sliding mechanisms.
7645-28, Session 6
Deformation modelling: embedding of
communication device in SMC using
numerical and FE models
E. Sulic, B. Pell, S. J. John, RMIT Univ. (Australia)
Use of SMC in manufacturing of vehicle body components for both
structural and non-structural applications has been increasing over last
20 years, driven by OEM’s and their need for lighter more fuel efficient
vehicles. In parallel the number of entertainment and communication
systems in the vehicles has also been expanding. Current services
such as GPS, digital radio, and cellular phone, and future services such
as vehicle-to-vehicle and vehicle-to-roadside communications require
use of antennas to send/receive signals that are necessary for these
services to function.
The low-temperature UAM process allows, for the first time, the
creation of smart material based metal matrix composite structures
with truly embedded multifunctionality. We have made Al-NiTi
composites with shape memory NiTi wires and have conducted
preliminary work in embedded Galfenol. Samples currently in
development focus on creating additional Al-Galfenol composites.
We will investigate the properties of these active composites as
variable stiffness, sensing, and, with Al-NiTi composites, thermally
invariant structures. Challenges will include the characterization
of the interface between the aluminum and the embedded smart
material for active build tests as well as increasing the proportion of
embedded smart materials for increased functionality. Future work
will extend the variable stiffness properties of the active composites
to vibration damping. By increasing composite stiffness, natural
frequency of a given system will also increase in a controlled manner.
The sensing properties of the active composite will make it possible
to measure internal stresses. By utilizing both properties, it may be
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Development of one single wideband antenna that is capable of
receiving all of the services listed above would represent significant
advantage for any OEM. Taking this approach one step further and
embedding such an antenna in a composite vehicle body panel ‘smart
composite component’ would combine benefits of lower vehicle
weight, lower assembly complexity and shorter assembly time. During
initial embedding trials of such an antenna into SMC, a noticeable
antenna deformation was observed, requiring the development of a
numerical model capable of predicting this deformation.
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Conf. 7645: Industrial and Commercial Applications of Smart
Structures Technologies IV
harnesses as the structural mass of those structures tends to become
smaller and the quantity of attached cables continues to increase,
largely due to the ever-increasing complexity of such structures.
Contributions of cables to structural dynamic responses were observed
but never studied, except for a low scale research effort conducted
at the Air Force Research Laboratory, Space Vehicles Directorate.
Presently cables are included in numerical models as nonstructural
mass at best. These models are able to capture the system dynamics
at low frequencies but do a poor job in mid to high frequency range.
A more complex, yet practical approach to modeling cables was
attempted in this effort. Studied cables adhere to space industry
practices identified through an extensive industry survey. Experimental
procedures and computational techniques for extracting structural
properties of the cables were developed, and an extensive database
containing cable properties was created. A simple beam was used
as a two-dimensional test article to validate experimentally-derived
cable properties and to refine the assumptions regarding boundary
conditions. Finally, a bus-like panel with cables attached was designed,
and finite element models were developed. The results of finite element
models were then compared with the real structure that was tested in
the laboratory. The comparison indicated that linear models can be
used to predict the structural response of cabled structures.
Since the material under consideration is viscoelastic, a numerical
model has been developed. The results obtained using this model are
than compared to the experimental results, showing some correlation.
Development of ANSYS FE model for the antenna embedding scenario
is also used to validate numerical model and intended as an additional
tool that can be used in further work on similar thermoset polymers.
Results of all three (numerical, experimental and FE) methods are
presented and discussed in this paper.
7645-29, Session 6
Design and analysis of supporting structure
with smart struts for active vibration
isolation
B. Kim, G. N. Washington, R. Singh, The Ohio State Univ. (United
States)
(SMART VEHICLES WORKSHOP) This paper addresses the modeling
and analysis of a supporting structure with smart struts in harsh
vibratory environment. Especially, for most helicopters, gearbox
vibrations have higher frequencies and multi-spectral contents causing
serious structure-borne noise transmission. In order to deal with this
problem, the dynamic responses of both passive supporting and active
smart struts and their interactions are investigated.
7645-32, Session 7
High and low temperature cyanate ester
shape memory polymers for space
applications
Current active control methods are limited mostly to sinusoidal control
and not appropriate to deal with modulated, multi-spectral vibration
and noise signals. Thus, improved multi-spectral control algorithms
are needed in order to attenuate amplitudes at higher gear mesh
frequencies and sidebands simultaneously, along with new smart strut
designs. Three novel model-based and nonlinear control algorithms
are proposed and their performances are validated and compared with
conventional techniques.
R. D. Hreha, B. Collins, Cornerstone Research Group, Inc. (United
States)
Cornerstone Research Group, Inc. (CRG) is designing and developing
a family of space-qualifiable, cyanate ester shape memory polymers
(SMP) for application in self-deployable space structures, space seals,
aeroshells, and future aircraft systems. Having already demonstrated
the feasibility of the current cyanate ester shape memory polymer
(SMP) as a space-qualifiable material, CRG is refining its existing
cyanate ester SMP to provide a material with a high level of utility
across a range of aerospace applications. During a NASA Phase I
SBIR, CRG was able to show that elastomeric cyanate ester materials
having a very broad range of thermal and mechanical properties could
be formulated using a relatively small amount of CRG’s synthesized
monomers and other low-cost, commercially available components.
The cyanate ester elastomer materials exhibited excellent thermal
stability, maintaining their properties to temperatures below -100C and
as high as 300C. CRG’s work with DoD and commercial aerospace
customers has also helped to identify the proposed material as a
durable, lightweight alternative to current state-of-the-art materials for
space and aircraft systems.
An experimental setup of a supporting structure is constructed with
smart struts while incorporating appropriate boundary conditions.
Conventional and novel control algorithms are being applied to
demonstrate the feasibility from narrow and broadband control
perspective with a single smart strut. Next, effects on changing the
location of the smart inserts are investigated. Passive struts, active
struts, and combinations of passive and active struts are analyzed and
tested in order to determine the best combination for effective vibration
attenuation. Additionally, geometric and kinematic effects due to
asymmetric strut installations are observed regarding their location and
orientation angles.
Techniques proposed in this research are expected to be implemented
for various applications of active vibration and noise control including
engineering structures and vehicles.
7645-30, Session 7
7645-33, Session 7
On the effects of electrical cables on
structural dynamics of cabled structures:
overview and results summary
A novel voice coil actuator for fast steering
mirror system
E. V. Ardelean, Schafer Corp. (United States); L. M. Robertson III,
S. A. Lane, Air Force Research Lab. (United States); V. Babu?ka,
Sandia National Labs. (United States); J. C. Goodding, D. M.
Coombs, CSA Engineering, Inc. (United States)
B. Shi, S. Chen, X. Ding, Huazhong Univ. of Science and
Technology (China)
Voice coil actuator (VCA) has been widely used in many scanning
and driving systems such as fast steering mirror (FSM) system ,
precision positioning platform, etc. The performance and parameters
of VCA is the critical factor to the capability of the whole system.
However, it still remains a crucial problem that the magnetic leakage
has greatly depressed the performance of VCA. Recently, a novel
VCA with concentration flux-line structure is presented .It can greatly
reduce the magnet leakage so as to enhance the performance of VCA
by a great deal. Another advantage of this VCA is it has much less
electromagnetic interference on other electronic devices. In this paper
briefly presents the theory model, finite element analysis (FEA) process,
fabrication details and experiment results of the novel voice coil
actuator which will be used in a fast steering mirror system. According
An overview of the study of the effects that electrical power and signal
cables introduce on the dynamic response of cabled structures is
presented, along with a summary of the most significant results. This
was a three-year effort conducted at the Air Force Research Laboratory
in the attempt to discover a set of practical approaches for updating
well-defined dynamical models of cable-free structures, where
knowledge of the cable type, position and tie-down method is known.
While cables can be found on many different types of structures, the
focus of this effort was on precision, low-damping, and low-firstmodal-frequency structures. Dynamics of large precision structures can
be significantly influenced by subsystems such as electrical cables and
88
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Conf. 7645: Industrial and Commercial Applications of Smart
Structures Technologies IV
to the experiment results the output force of the VCA is 3.4N/A with
a coil of 240 turns and the stroke is ±2.5mm. Driven by this VCA the
scanning angle of the FSM can achieve ±4.6°in a close-loop system
when the scanning frequency is 100Hz.
Ailerons and flaps of most modern aircrafts are through mechanical
hinges to control surface deflection in order to change the camber of
the wing. The hinge devices are heavy, complex, and inefficient. To
overcome these shortcomings, a flexible variable camber wing (FVCW)
concept is presented, which is using the flexible wing skin technology,
and cancels the traditional mechanical hinge.
7645-34, Session 7
As a novel bionic actuator, pneumatic artificial muscle has high
power to weight ratio. In this paper, a variable trailing-edge camber
wing drived by pneumatic artificial muscles (PAMs) is developed. It
comprises a flexible skin, a sheet, and a honeycomb structure. The
sheet is used to replace the traditional hinges to keep surface smooth
during the camber changing. The role of flexible skin is to maintain the
upper and lower surfaces smooth during the wing morphing. PAM can
only be used to contract by a single way, unable to provide thrust and
the flexure hinge is designed to obtain thrust. The variable camber wing
model is manufactured to validate the morphing concept.
Characterization of varied geometry shape
memory alloy beams
L. M. Gravatt, J. H. Mabe, F. T. Calkins, The Boeing Co. (United
States)
Shape Memory Alloys (SMA) have proven to be a lightweight, low
cost alternative to conventional actuators for a number of commercial
applications. Future applications will require complex shape change
and a detailed understanding of the performance of more complex
SMA actuators is required. The purpose of this study is to validate
engineering models and design practices of various SMA beams for
future applications. Until now, SMA actuators have been fabricated
into relatively simple beam shapes. Boeing is now fabricating beams
in more complicated geometries in order to determine their strength
and shape memory characteristics. These more complicated shapes
will allow for lighter SMA actuators as well as provide more complex
shape control. Some of the geometries evaluated include vertical and
horizontal I-beams, sine wave and triangular wave beams, a truss, and
a beam with perforated circular holes along the length.
Wind tunnel test results show that the wing camber increases with
increasing air pressure. When PAMs are filled with the pressurized air,
the trailing-edge will be deformed downwards and the lift of aerofoil will
be increased.
7645-37, Poster Session
Nanojoining and fabrication of
nanojunctions using nano-particles
M. Yavuz, W. Wu, H. Alarifi, A. Hu, N. Y. Zhou, Univ. of Waterloo
(Canada)
A total of 11 beams were tested. These include simple rectangular
beams made out of Aluminum, 55% NiTinol (NiTi), 57% NiTi, and 60%
NiTi (% Nickel by wt.) as well as the more complex shapes made from
57% NiTi, Each sample was put through a number of characterization
tests. These include a 3 point bend tests to determine stress/strain
properties, low load thermal cycling to determine transformation
temperatures, thermal cycling under an range of isobaric loads to
determine actuator properties, and blocked force tests with varying
preloads. Experimental results were then compared to modeled results.
Electrically conductive connections between nano building blocks
are not straightforward. Instead of desired ohmic contacts, tunnel
junctions or weak links of a high contact resistance typically at 200 kΩ
for contact regimes on the order of 1 nm2, are often generated. So, the
gap-sensitive contact resistance makes it difficult to join nano-buildingblocks with repeatable performance in nano-devices. In this research
double wall carbon nano tubes (DWCNT) were successfully joined to
metallic electrodes to make a prototype of a low resistant, mechanically
durable (higher fracture points) energy saving carbon nano tube
filament light bulb. It was also shown that nano-size particles used
in brazing of nano/micro-wires caused in reduction of brazing point
around 100degC and increase the fracture point of the joint interface.
7645-35, Session 7
Optimal control of piezoelectric elements for
active vibrations suppression of blades
F. Botta, Univ. degli Studi di Roma Tre (Italy)
7645-38, Poster Session
It is well known that the blade vibrations, in gas turbines, can involve
failures and a reduction of the blade’s life because of fatigue related
phenomena. The adoption of the piezoelectric elements, during the
last years, has received considerable attention by many researcher
for its great potential in mechanical, aerospace, aeronautical and civil
engineering. Recently also the studies of blades with a piezoelectric
coat are beginning to appear. These could be very interesting with
reference to the problems mentioned above, indeed this type of
materials are very efficient for active control of vibrations.
Study on the novel Li polymer battery using
polyindole electrode
Z. Cai, Tianjin Polytechnic Univ. (China)
This study is intended to develop a polyindole-based Li polymer
secondary battery system, which has a high electromotive force
together with excellent cycle property and is capable of fast charging
and discharging. The batteries include polyindole as the cathode and
Li as the anode. LiBF4 was used as the electrolytic solution with about
3.0V electromotive force. The battery achieves about 80~70mAh/g at
discharge current densities of 10~103 A/m2. As the theoretical capacity
of polyindole is 84 mAh/g, its capacity occurrence rate is 95% at the
discharge current density of 10 A/m2 with a very high reaction rate. In
addition, a discharge capacity at discharge current density of 103 A/m2
maintains 87% of capacity relative to that at 10 A/m2. This indicates
that this battery is excellent in fast charge and discharge properties.
The cyclic life of the battery, which is measured at the current density
of 10 A/m2 with the discharge depth 60% at 25 , is about 30000 times.
This shows the battery system has very excellent cycle property.
The aim of this work is to propose an analytical method to drive
piezoelectric elements for active vibrations control and, consequently,
increasing fatigue life of blades. A quadratic objective function has
been defined and a closed loop feedback control has been used. The
modal shapes of the blade have been obtained by Galerkin method.
The results are compared, and validated, with those obtained by a finite
elements code.
7645-36, Session 7
Pneumatic artificial muscle and its
application on driving variable trailing-edge
camber wing
W. Yin, L. Liu, Y. Chen, Y. Liu, J. Leng, Harbin Institute of
Technology (China)
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Conf. 7645: Industrial and Commercial Applications of Smart
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7645-39, Poster Session
Research on thermo-mechanical properties
of styrene-based shape memory polymer
composite
B. Zhou, Harbin Engineering Univ. (China); Y. Liu, X. Lan, J. Leng,
Harbin Institute of Technology (China)
SMART VEHICLES WORKSHOP
Shape memory polymer (SMP) is a promising smart material which is
under intensive investigation at present. Its advantages are the high
strain recovery, low density, low cost and so on. However the low
strength, low stiffness and low recovery stress are its disadvantages.
So the styrene-based fiber reinforced shape memory polymer
composite (SMPC) is fabricated and its mechanical behaviors are
experimentally and theoretically studied in this paper. The glass
transition behaviors of SMPC and SMP are investigated through
tests of Dynamic Mechanical Analyzer (DMA). Three glass transition
critical temperatures are defined and a method to determine their
values based on DMA test is given out. A glass transition model is
developed to predict the glass transition behaviors of SMPC and
SMP. The material properties of strength and stiffness of SMPC and
SMP are investigated through one-cycle three-point bending tests.
Both bending strength and stiffness are calculated based on results of
test. Experimental results show both strength and stiffness of SMPC
are much higher than those of SMP. The material training behaviors
of SMPC and SMP are investigated through multi-cycle three-point
bending tests. A material training model is supposed to describe the
material training behaviors of SMPC and SMP.
90
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Conf. 7646: Nano-, Bio-, Info-Tech Sensors and Systems
Monday-Thursday 8-11 March 2010
Part of Proceedings of SPIE Vol. 7646 Nanosensors, Biosensors, and Info-Tech Sensors and Systems 2010
is thermodynamically more stable than anatase phase, the anatase
phase of TiO2 nanostructures can be transformed to rutile phase by
thermal process. In this investigation, anatase pahse of TiO2 nanorods
were synthesized with low temperature process. Diameter and length
of the nanorods were 3~4 nm and 35 nm, respectively. The nanorods
were annealed at 750 and 850 C to transform anatase phase to rutile
phase. The transformation rate was extremely slow compared with
other nanoparticle and thin films case. The cause of the slow phase
transformation was analyzed in this article.
7646-02, Session 2
Iron oxide nanotubes: syntheses,
characterizations, and magnetic behaviors
J. Xie, L. Chen, V. K. Varadan, Univ. of Arkansas (United States)
Nanotechnology involves controlled syntheses of nanomaterials,
characterizations of their unique properties, and assemblies of
functional nano-enabled devices. Magnetic nanotubes exhibit unique
structural and magnetic properties and can have wide ranging
applications because of their manipulation by external fields, substance
encapsulation, and multifunctionalization. Here we report our efforts
to synthesize and characterize the magnetic iron oxide nanotubes.
Hematite ( -Fe2O3) nanotubes, maghemite ( -Fe2O3) nanotubes and
magnetite (Fe3O4) nanotubes were obtained by different chemical
techniques such as template synthesis and hydrothermal method.
Scanning and transmission electron microscopy were performed to
investigate their morphologies and structures. Their crystallinities
were confirmed by using X-ray diffraction. To manipulate magnetic
nanotubes, experiments were conducted to study their response when
magnetic fields were applied. These magnetic nanotubes are expected
to find versatile applications such as drug delivery, neuroscience,
hypothermia treatments, etc.
7646-06, Session 4
Nanotechnology for condition-based
maintenance
J. Riddick, Army Research Lab. (United States); S. H. Choi, NASA
Langley Research Ctr. (United States)
Condition-based maintenance (CBM) has emerged as an effective
strategy for reducing the life cycle costs of existing and future Army
vehicle systems. The advent of nanotechnology presents the opportunity
to integrate prognostic and diagnostic capabilities necessary for CBM
into vehicle systems without dramatic weight penalty. The present
study details two separate nanotechnology-based systems to be used
in CBM for Army vehicles. The first is a microspectrometer that uses
nanotechnology to diagnose the state of vehicle engine components
and on-board systems. Because of its small size, the microspectrometer
can be placed in and around vehicle critical components in order to
monitor the state of operation. The microspectrometer depends on
RF and wireless power transmission to transmit measured data to be
incorporated into CBM scheme. The second nanotechnology concept
presented is thermo-electric (TE) materials that convert heat energy to
electricity. The TE materials take advantage of an engineered lattice
construction to generate electricity at a greater efficiency level than
existing photovoltaic cells. The TE materials can be used to supplement
the power demands of CBM systems in a variety of vehicles, from
combustion engine vehicles to rotorcraft, and also any vehicle that
operates in extreme temperatures or desert conditions.
7646-03, Session 2
Photoreduction of Au(III) to form
Au(0) nanoparticles using ferritin as a
photocatalyst
R. K. Watt, R. J. Hilton, J. Keyes, Brigham Young Univ. (United
States)
Gold metal nanoparticles, have applications in bio sensing, technology,
nano-tube formation, and cancer therapy, but are difficult to form
reproducibly in well-defined size distributions. We report a method to
synthesize gold nanoparticles within the ferritin cavity (8 nm) or using
ferritin as a scaffold for coating gold on the outside surface (12 nm).
The intrinsic iron oxide core of ferritin is a semi-conductor and light can
excite electrons to an excitation band producing a powerful reductant
when a sacrificial electron donor fills the hole. The target metal ions
bind to ferritin and accept the excited electron. The reduction of the
first ion creates a nucleation site making the reduction of other ions
more favorable. Since light is a reactant, we can control the particle
formation by the time of light exposure or by varying the wavelength of
light. We can also vary the concentration of the photocatalyst, which
also acts as a nucleation site for photo reduction of the metal ions. We
have designed a modified spectrophotometer to monitor the rate of the
reaction and have taken samples at various time points to characterize
by electron microscopy (EM). This report will discuss the EM
characterization of these samples as well as the kinetic characterization
of the formation of the nanoparticles. Interestingly buffers and salt
drastically alter the rate, extent and final product formed in these
reactions.
7646-07, Session 4
A systems engineering approach to
designing, modeling, and networking
wireless nano sensors and systems
S. X. Mohan, Univ. of Arkansas at Little Rock (United States)
The wireless nano sensors networks and their real-world applications,
such as structural health monitoring, implantable medical devices,
intelligent highway systems, and others, combine sensing, networking,
wireless communication, computation, and user interfaces in large
complex systems. The design and implementation of such complex
systems need to take into consideration their intended functionality,
operational requirements, and expected lifetime. Systems engineering
provides the design and implementation framework to successfully
bring large complex systems into operation by integrating all
engineering disciplines into a structured development process, starting
with identification of the need, and defining the initial concept, to
formulating the requirements to detailed design, development and
then, implementation. Systems engineering facilitates the integration
of multiple engineering disciplines and the communication process
between them into a common framework
7646-04, Session 2
Slow phase transformation of TiO2 nanorods
Y. Chen, K. S. Kang, K. H. Yoo, J. Nayak, J. Kim, Inha Univ. (Korea,
Republic of)
The design of nanosensor networks and systems encompass multiple
areas of research, which include the following:
Nanocrystalline TiO2 has chemical physical stability, high refractive
index (2.5~2.7), and high photocatalytic ability and has been widely
employed in photocatalytic, photoelectrochemical, and photovoltaic
applications. Controlling the crystal phase is important for specific
applications due to the phase dependence of photocatalytic, optical,
and electronic properties. Wet chemical synthesis of TiO2 nanoparticles
or nanorods has anatase phase. However, since the rutile phase
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1. Design of nanosensors and modeling
2. Design of wireless interfaces
3. Design of reliable sensor networks that sense and collect data reliably
4. Design of backbone networks capable of reliably transporting
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Conf. 7646: Nano-, Bio-, Info-Tech Sensors and Systems
sensing capability from measuring the surface resistivity taking into
account the absorption of sensing species. Our results show new
possibilities for the low-cost high performance environmental sensors
for numerous potential applications. The details of the results will be
presented.
collected data to remote servers
5. Design of secure servers for data transfer
This paper provides a systems engineering models and analysis
methodologies that are applied to the performance modeling
of sensors and that can be adapted to large complex systems
encompassing the above design steps. The paper models dynamic
behaviors of nanowires, insights into the design of nanostructured
wireless interfaces to provide wireless capability to nanosensors,
and networking techniques that allows for failure recovery, data
security, and QoS. Performmance results are provided based on either
theoretical calculations or simulations.
7646-10, Session 5
Formation of bismuth telluride with
metallic nanoparticles for thermoelectric
applications
7646-08, Session 5
S. Iwanaga, The George Washington Univ. (United States); G. C.
King, Y. Park, NASA Langley Research Ctr. (United States); K. Lee,
Federal Highway Administration (United States); S. H. Choi, NASA
Langley Research Ctr. (United States)
Vibration control of beam using piezoelectric
electro-active paper sensor
Bulk samples of Bismuth Telluride (Bi2Te3) nanoparticles clad in
silver were made to observe the effect of cladding on thermoelectric
properties of bulk samples. Silver nanoparticles suspended in aqueous
solution were created, and pellets of Bi2Te3 were fabricated with these
nanoparticles. Measurements of thermoelectric properties including
Seebeck coefficient, electrical conductivity, and thermal conductivity,
and materials characterization techniques including X-ray Diffraction
and Scanning Electron Microscopy indicated enhancements in
thermoelectric properties, attributed to the metallic nanoparticles
located between Bi2Te3 grains.
J. Kim, H. C. Lee, H. S. Kim, Catholic Univ. of Daegu (Korea,
Republic of)
Cellulose-based Electro-Active Paper (EAPap) has been discovered
as a smart material that can be used as a sensor and actuator.
Its advantages include low voltage operation, light weight, low
power consumption, biodegradability and low cost. EAPap is made
of cellulose paper coated with thin electrodes. EAPap shows a
reversible and reproducible bending movement as well as longitudinal
displacement under electric field. The out-of-plane bending
deformation is useful for achieving flapping wings, micro-insect robots,
and smart wall papers. On the other hand, in-plane strains, such as
extension and contraction of EAPap materials are also promising for
artificial muscle applications.
7646-11, Session 5
Deposition of thin sodium-potassium
niobate (NKN) films on piezoelectric
cellulose EAPap
Piezoelectricity is one of major driving mechanism of a cellulose-based
EAPap. Although the potential of EAPap as a piezoelectric sensor is
promising, the application of EAPap as a piezoelectric sensor has not
been clearly studied yet. In order to use EAPap as a useful sensor, it
is important to demonstrate EAPap as an actual piezoelectric sensor.
Therefore, beam vibration control using EAPap sensor is investigated
in the present paper. The EAPap sensor and piezoceramic patch will be
attached on top and bottom surfaces of an aluminum cantilever beam.
The beam vibration data will be obtained from EAPap sensor and the
piezoceramic patch will suppress the beam vibrations as an actuator.
Simple velocity feedback control algorithm will be used to control beam
vibration. The final paper will present effective vibration suppression
of the cantilever beam with EAPap sensor and propose EAPap as a
promising piezoelectric sensor.
S. Jang, J. Kim, J. Kim, Inha Univ. (Korea, Republic of); J. Koh,
Kwangwoon Univ. (Korea, Republic of)
Cellulose based EAPap is a natural piezoelectric polymer. However,
compared to piezoelectric based ceramic materials e.g. PZT, it is
necessary to enhance its piezoelectric property for device applications.
Thin (Na,K)NbO3 (NKN) film NKN is a lead-free piezoelectric material
which possesses a similar piezoelectricity and curie temperature
compared with PZT. To enhance the piezoelectricity of EAPap film, thin
NKN layer was deposited on cellulose paper by RF magnetron sputter.
In this paper, we report the optimized deposition condition of NKN layer
growth on EAPap without damages. The structural analysis and the
optical properties of NKN deposited cellulose films were investigated
by XRD, AFM, FTIR, UV visible measurements. Also, the electrical
properties and its piezoelectricity of the composite cellulose film were
characterized. The enhanced properties of composite cellulose material
can be used for acoustic based sensors, flexible electronics and
piezoelectric actuator.
7646-09, Session 5
Environmental sensing in composite oxide
semiconductor films
A. K. Pradhan, Norfolk State Univ. (United States)
Environmental Sensing in Composite Oxide Semiconductor Films
7646-12, Session 5
A.K. Pradhan, R. Mundle, G. Kogo, R. B. Konda, O. Bamiduro, O.
Yasar, M. Bahoura, F. Williams and K. Song
Growth and properties of PZT -based
perovskite multilayers for sensor
applications
Center for Materials Research & Department of Engineering, Norfolk
State University, 700 Park Ave., Norfolk, VA 23504.
>>>
Multicomponent semiconductor oxides mainly composed of elements
like indium, zinc, tin or gallium are very promising new class of
materials for application in transparent electronics, multifunctional
sensors and other electronic applications. The major characteristic
of these materials is high mobility, and the electrical behavior is a
consequence of a conduction band primarily derived from spherically
symmetric heavy-metal cation ns orbital with (n-1)d10 ns0 (n 4)
electronic configuration. The carrier transport becomes insensitive
to the degree of disorder of the film, and makes this class of quasipolycrystalline and amorphous semiconductors attractive for numerous
applications. We report here on the environmental sensing, such as
ultra-violet-radiation and various gases of pulsed-laser deposited
composite semiconductor films. These films demonstrate outstanding
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R. B. Konda, Norfolk State Univ. (United States)
Polarization properties, which depend on different voltages and
different temperatures, crystal structures, and surface morphology have
been demonstrated for PZT/Pt/Si, STO/PZT/STO/PZT/Pt/Si, and BTO/
STO/BTO/STO/Pt/Si multilayer perovskite samples. The effects of the
thickness of the PZT film layer also investigated for PZT/Pt/Si multilayer
sample. The multilayer perovskite samples were fabricated with using
magnetron sputtering and pulsed laser deposition (PLD) techniques.
PZT/Pt/Si samples were fabricated with different PZT film thickness.
Surface morphology was investigated by atomic force microscopy
(AFM). The hysteresis loops of PZT/Pt/Si multilayer samples were
obtained by Probe Station which was connected to ferroelectric
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Conf. 7646: Nano-, Bio-, Info-Tech Sensors and Systems
In this paper, we design an ultrasensitive nanocalorimeter array for
accurate and rapid evaluation of biohazard materials at the early stage
of biological attacks or environment threaten. Here we propose an
isothermal titration nanocalorimeter arrays with significantly reduced
sample volume 1-2uL, high temperature sensitivity 10 uK, and high
throughput. The nanocalorimeter array contains SU-8 microcantilevers
and free standing thin polymer diaphragms, which integrate integrated
thermistors of low thermal noise and resistive microheaters for power
compensation. The proposed label- and immobilized free technology
will enable direct and high-throughput evaluation of the Gibbs free
energy, enthalpy, entropy, and specific heat of the interaction of
biohazard samples and biological recognition molecules.
analyzer.The other multilayer samples were compared for their surface
morphology. Characterization of crystal structures and polarization of
varying thickness samples are under progress
7646-13, Session 5
Carbon nanocomposite-based contact
mode interdigitated center of pressure
sensor
T. Xu, C. Park, N. Guerreiro, J. H. Kang, J. S. Harrison, J. Hubbard,
Jr., National Institute of Aerospace (United States)
7646-18, Session 7
A carbon nanocomposite-based contact mode interdigitated center
of pressure sensor (CMIPS) has been developed. The experimental
study demonstrated that the CMIPS has a capability to measure the
overall pressure as well as the center of pressure in one dimension,
simultaneously. A theoretical model for the CMIPS is established
here based on the equivalent circuit of the CMIPS configuration as
well as the material properties of the sensor. The experimental results
match well with the theoretical modeling predictions. This theoretical
model will provide guidelines for future advanced sensor development
based on the CMIPS. A system mapped with two or more pieces
of the CMIPS can be used to obtain information from the pressure
distribution in multi-dimensions. As an intelligent system component,
the inexpensive CMIPS can be used broadly for improving sensing
and control capabilities of aircraft and measurement capabilities of
biomedical research as well as chemical industries. The details about
experimental and theoretical investigations for the CMIPS will be
presented in this paper.
Homeland security monitoring sensors and
early warning relay and diagnostic system
V. K. Varadan, Univ. of Arkansas (United States)
No abstract available
7646-19, Session 7
PEDOT:PSS coated SWNT based gas sensor
S. Badhulika, Univ. of California, Riverside (United States)
PEDOT :PSS coated singlewalled carbon nanotube gas sensors
Sushmee Badhulika ,Ashok Mulchandani
Department of Electrical Engineering ,Department of Chemical and
Environmental Engineering
7646-16, Session 7
Bourns College of Engineering ,University of California,Riverside 92521
Nanowire gas sensors and wireless sensing
network for electronic-nose development
Single walled carbon nanotubes (SWNTs) have been put into use for
sensing gases and vapor phase analytes because of their unique
properties like small size,low power consumption, stability and high
specific area. The sensing behavior is mainly due to
H. Yoon, P. T. Hankins, S. Oh, Univ. of Arkansas (United States); C.
L. Brantley, U.S. Army Research, Development and Engineering
Command (United States); E. Edwards, P. B. Ruffin, U.S. Army
Aviation and Missile Research, Development and Engineering Ctr.
(United States); Y. M. Kim, V. K. Varadan, Univ. of Arkansas (United
States)
the fact that the SWNT consists solely of surface such that every
single carbon atom is in direct contact with the environment and hence
changes in their local environment has a direct impact
on the electronic properties of the SWNTs that can be easily identified.
However, certain limitations like inability to identify gases with low
adsorption energies and low concentrations led to the development of
hydrid sensors that combine the merits of a conducting polymer like
solution processibility and flexibility with those of SWNTs that act as a
conduit for charge transfer.
In this research, we developed nanowire gas sensors and wireless
sensing system with Zigbee and Wi-Fi protocols. Nanowire gas sensors
have been developed with large surface area of tin oxide on vertically
aligned nanowires and part per billion level of solvent vapor sensitivity
has been obtained. With the wireless sensing system, resistive
electrical signals from the sensors were input to a Zigbee wireless
module and the sensing signals were transmitted to Wi-Fi for recording
signals outside. This wireless gas sensing system has been tested
various condition including the environment with isopropyl alcohol
vapors for the early detection of explosion and hydrogen sulfide and
ammonia gases related to bacteria metabolism. Currently, research for
the integration of these two systems on a chip is being conducted for
the development of electronic nose module in a hand held system for
high sensitivity monitoring and rapid identification of gas species.
Our work involves the fabrication of polymer PEDOT :PSS -poly(3,4ethylene dioxythiophene):poly(styrene sulfonic acid) coated SWNT gas
sensors and subsequent characterization of their electronic properties
at room temperature .
The hybrid sensors displayed a change in resistance when exposed
to varying concentrations of analytes and hence showed promise as
conductometric sensors.
The underlying mechanism of sensing was also investigated by using
them as chemFET devices.
7646-17, Session 7
PEDOT :PSS coated SWNTs exhibited better , on average,sensitivity to
lower concentrations of a series of vapor phase analytes that were put
for sensing than pristine SWNT gas sensors .
Nanocalorimeter arrays for detection of
biohazard samples
7646-20, Session 7
L. Zuo, Stony Brook Univ. (United States)
Flexible strain sensor based on carbon
nanotube rubber composites
With the increased threat of biochemical terrorist attacks and concern
of environment pollution, it is necessary to identify small volume of
biohazards and provide early detection. The detection and analysis
of biohazard material are possible using biological thermodynamical
recognition in calorimetry. However, the long measurement times
and large sample requirements of the existing technology make it
difficult to screen the biohazard samples rapidly for early detection.
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I. Kang, J. H. Kim, K. T. Lim, Pukyong National Univ. (Korea,
Republic of)
Electrically conducting rubber composites (CRC) with carbon
nanotubes (CNTs) filler have received much attention as potential
materials for sensors. In this work, Ethylene propylene diene M-class
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Conf. 7646: Nano-, Bio-, Info-Tech Sensors and Systems
The low power integrated sensor system will be used to show the
variation of the power consumed for different resolutions of the
ADC. Since the designed ADC can be operated at three different
resolutions of 9, 12 and 14 bits by varying the oversampling ratios, the
power consumed by the integrated sensor system can also be varied
significantly. Hence, this system proves to be efficient and promising
for application of integrated sensor system in bio- and chemical
applications for wireless sensor networks.
rubber (EPDM)/CNT composites as a novel nano sensory material
were prepared to develop flexible strain sensors that can measure
large deformation of flexible structures. The EPDM/CNT composites
were prepared by using a Brabender mixer with multi-walled CNTs
and organo-clay. A strain sensor made of EPDM/CNT composite was
attached to the surface of a flexible beam and change of resistance of
the strain sensor was measured with respect to the beam deflection.
Resistance of the sensor was change quite linearly under the bending
and compressive large beam deflection. Upon external forces, CRC
deformation takes place with the micro scale change of inter-electrical
condition in rubber matrix due to the change of contact resistance, and
CRC reveals macro scale piezoresistivity. It is anticipated that the CNT/
EPDM fibrous strain sensor can be eligible to develop a biomimetic
artificial neuron that can continuously sense deformation, pressure and
shear force.
A. Srivastava and R. R. Anantha, “A Programmable Oversampling
Sigma-Delta Analog-to-Digital Converter,” 48th IEEE Midwest
Symposium on Circuits and Systems, vol. 1, pp. 539-542, 2005.
7646-23, Session 8
Probabilistic behavior and information
measures of sequential nanoICs
7646-21, Session 8
S. C. Lee, Univ. of Oklahoma (United States)
A digital logic nanowire for reliability
enhancement
Since the advent of nanotechnology, not only the size of the circuit
has been reduced to nanoscale but also the fundamental laws that
govern the circuit behavior have been changed: from the conventional
Kirchhoff’s voltage and circuit laws to the laws of quantum mechanics.
Due to high noise-to-signal ratio and the randomness nature of the
deterministic models, probabilistic models are used to model the circuit
behavior of nanocircuits. When the noise-to-signal ratio of a nanocircuit
is kept below a certain threshold, the circuit can still perform normally.
In order to design fault-tolerant computing nanomachinery, we must
first realize the importance of the understanding of the probabilistic
behavior of nanocircuits and then know how to extract their information
contents. The probabilistic behavior and information measures of
combinational nanoICs have recently been studied.
S. C. Lee, Univ. of Oklahoma (United States)
Due to the many random factors from thermal fluctuations to wave
interference, computational perfection in nanoICs is difficult to achieve.
Defects and faults arise from instability and noise proneness of
nanoICs, which lead to unreliable results. A probabilistic computational
model is needed to reduce such errors and to achieve more reliable
computation. The probabilities of the outputs of this model can be
calculated by the arithmetic expressions of the Boolean functions.
This paper presents a method for transforming a low reliability
nanocircuit made of unreliable nanogates into a high reliability
nanocircuit without the need of any special reliable nanogates. A class
of nanocircuits, called reliability enhancement nanocircuits (RENC)is
introduced. Each RENC is a simple logic circuit with a single input and
output. It is shown that with a proper setting of the “logic threshold
value” from the output probability function of RENC, which determines
logic value 0 or 1 for the input and output, the output reliability of
RENC can be higher than its input reliability. Thus, when an RENC is
connected to each output of a low reliability nanocircuit, the reliability
of the entire circuit can be enhanced. By cascading n numbers of
RENCs, we can form a reliability enhanced nanowire (RENW). It is also
shown that by connecting each output of a low reliability nanocircuit
with an RENW, the reliability of the nanocircuit can be raised to
any desirable level. Illustrative examples are given. This method is
applicable to any digital nanocircuit design using any nanotechnology.
The purpose of this paper is to investigate the probabilistic behavior
and information measures of sequential nanoICs which are in general
much more complex and have not been previously studied. Yet, it is
vitally important for the analysis and design of future fault-tolerant
nanocomputing machineray. To extract information from sequential
nanoICs in nanospace of a noisy environment, it is found that the most
appropriate measure of information is the measure of entropy. The
results of the study of probabilistic behavior and information measures
of various types of flip-flops and other sequential nanoICs such as
registers, counters, etc. in noisy nanospace are reported with detailed
illustrative examples.
7646-24, Session 8
Quantum state transition diagram: a bridge
from classical computing to quantum
computing
7646-22, Session 8
A programmable second order oversampling
CMOS sigma-delta analog-to-digital
converter for low power bio- and chemical
sensor interface electronics
L. R. Hook IV, S. C. Lee, Univ. of Oklahoma (United States)
Ever since Feynman’s paper (Simulating physics with computers,
Internat. J. Theor. Phys., 1982)suggesting the possible advantages
of a quantum computer, research into quantum computation has
received a lot of attention. Shor’s algorithms (Algorithms for quantum
computation: discrete logarithms and factoring. Symp. on Foundations
of Computer Sciences, 1994) showed that one could factor integers
with a quantum computer in polynomial time. More importantly, Shor’s
discovery proved a case where a quantum computer is more powerful
than a classical computer for specific and relevant algorithms. One of
the proposed architectures for the construction of a quantum computer
relies on quantum cellullar automata (QCA) which has recently been
accepted as the standard.
R. Soundararajan, A. Srivastava, Louisiana State Univ. (United
States)
In many sensor interface circuits used in biomedical, pharmaceutical,
wireless sensor networks or automotive, data conversion demands
great care and stringent requirement for power consumption. In this
work a programmable oversampling sigma-delta ADC has been
designed for effective use in low power interface electronics since the
resolution has a direct impact on the power consumption. A computer
simulated model of integrated sensor system consisting of carbon
nanotube field-effect transistor and a programmable oversampling
sigma-delta ADC will also be presented for low power bio- and
chemical sensing applications.
This paper proposes a new structure, a quantum analog to the classic
state diagram, called quantum state transition diagram (QSTD). In
QSTD, each node corresponding to each particular state has the
function of summing nodes and each transition link carries the value
of the original node, multiplied by a multiplier, M(i,j), where i and j are,
respectively, the destination and source nodes, which is determined
from the transformation matrix of the QCA. A general procedure for
constructing QSTD is presented with illustrative examples including
the constructions of QSTD for the Hadamard gate, the controlled-NOT
Recently, Srivastava and Anantha have reported a programmable
CMOS sigma-delta ADC using a first order modulator and second
order cascaded integrator comb filter. In this work, we have designed
a programmable oversampling sigma-delta ADC in 0.5 μm CMOS
process using a discrete-time 2nd order sigma-delta modulator and a
programmable 3rd order CIC decimator.
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Conf. 7646: Nano-, Bio-, Info-Tech Sensors and Systems
gate, the two-cell partitioned QCA and other QCA devices. The results
of this paper may provide computer scientists and engineers with a
useful design tool to construct molecular nanocomputers using QCAs
and, at the same time, serve as a bridge between classical computing
and quantum computing.
Langley Research Ctr. (United States)
Since many researchers have recently involved to develop bio-sensors
, it is critical to provide an alternative power source for the devices in
order to provide maneuverability and flexibility of the sensors. In these
applications, it is important to evaluate performance of rectennas
through humans or animals. In addition to that, biological effects of
humans and animals are critical issues as well.
7646-25, Session 9
In this paper, we designed various rectennas with different substrates,
and tested for evaluation of the performance. We studied the
influences of microwave on rectenna through a pig skin when we apply
this concept into sensors and devices under the skins for medical
applications.
Power beaming to a micro aerial vehicle
using an active phased array
H. Sawahara, A. Oda, A. Diallo, K. Komurasaki, Y. Arakawa, The
Univ. of Tokyo (Japan)
A power beaming system to a Micro Aerial Vehicle (MAV) using 5.8GHz
microwaves has been developed. With this wireless power system, a
battery on a vehicla is charged by receiving a microwave beam while
the vehicle is circling above a phased array transmitter. Then, it can
fly over the area struck by disaster, for example, continuously without
landing and take-off for recharging.
7646-28, Session 9
The schematic of the system developed in our laboratory consists
of three sub-systems; a pointing system, a tracking system, and a
receiving system. A microwave beam is pointed to the MAV using the
phase information of its pilot signal. Software retro-directive function
has been realized through a PC control. An electric motor for a
propeller is driven by the power received on a rectenna array.
Y. Liu, A. Srivastava, Louisiana State Univ. (United States)
Reliability considerations in switchable PLL
frequency synthesizers for wireless sensor
networks
A wireless sensor network is implemented by multiple sensor nodes
collecting analog information and communicating data between the
center control stations to each node. In wireless sensor system, a low
cost, wide frequency range and large bandwidth RF communication
system is required which uses phase-locked loop (PLL) as a frequency
synthesizer. A new strategy of switchable phase-locked loop frequency
synthesizer is designed and fabricated in 0.5 μm CMOS process to
analyze the chip reliability under hot carrier effect (HCE) and negative
bias temperature instability (NBTI). The switchable PLL frequency
synthesizer can work in a wide frequency range from 320 MHz to
1.15 GHz and can be integrated in RF transmitter and receiver of
the sensor systems. As device size shrinks and channel electric field
increases, interface and oxide traps play important roles affecting the
performances of devices and thus the reliability. HCE and NBTI are
known to be one of the critical reliability issues in sub-micron and
nanometer CMOS technologies. In this paper, jitter and phase noise
performances of both open loop VCO and PLL under HCE and NBTI
are investigated. The tuning frequency of open loop VCO decreases
about 200 MHz after 4 hour hot carrier stress and decreases about
140 MHz after 4 hour NBTI stress. The phase noise of PLL frequency
synthesizer increases about 1-2 dBc/Hz under both HCE and NBTI
stresses. The results will be extrapolated in better understanding and
design of reliable wireless sensor networks.
Steering of a 5.8GHz microwave beam was achieved by controlling
the phase of microwaves emitted from the multiple antennas called
phased array system, not by mechanical control of the antenna’s
attitude. Our phased array is composed of five horn antennas.
In the tracking system, three patch antennas receive the pilot signal
of 2.45GHz microwave sent from the MAV. Two pairs of patch antennas
were aligned in the x and y directions with the distance of . The
incident angle of the pilot signal is analyzed using a PC.
In the receiving system, a conventional patch rectenna array has been
replaced by an ultra-light and flexible rectenna array, which will be an
indispensable technology to realize real “micro” robots, such a MAVs.
7646-26, Session 9
Enhanced thermoelectric figure of merit in
nanostructured SiGe alloys
H. Kim, National Institute of Aerospace (United States); Y. Park,
George Washington Univ. (United States); G. C. King, NASA
Langley Research Ctr. (United States); K. Lee, Federal Highway
Administration (United States); S. H. Choi, NASA Langley Research
Ctr. (United States)
7646-29, Session 9
The application of wireless sensor system
on security network
Practical use of thermoelectric devices hinges on their performance
measured by the figure of merit. We focus on SiGe-based alloys for
high temperature application. DC and RF sputtering methods were
used to grow a SiGe layer and SiGe nanocluster-structured array on
c-plane sapphire substrate in various experimental conditions. In the
case of a SiGe layer, we were able to control the epitaxial growth to
make a [111]-oriented single crystalline SiGe layer or a [111]-oriented
highly twinned SiGe layer (60°-rotated crystal) on c-plane sapphire
which is baseline to lower the thermal conductivity for high figure
of merit. Also, we grew a SiGe array, which is composed of many
nanocluster-structures scaling up to several tens of micrometers.
Dense population of nanoclusters and nanorods is regarded enhancing
the scattering frequency of the phonons, thus reducing the thermal
conductivity and consequently increasing the figure of merit.
S. Oh, H. Kwon, H. Yoon, V. K. Varadan, Univ. of Arkansas (United
States)
In this research we developed wireless sensor system for security
network. We have used geophone to detect seismic signals which are
generated by footsteps. Geophones are resonant devices. Therefore,
vibration on the land can generate seismic waveforms which could
be very similar to the signature by footstep. The signals from human
footstep have weak signals to noise ratio and the signal strength is
subject to the distance between the sensor and human. In order to
detect weak signals from footstep, we applied 2-stage amplifying
circuit which consists of active and RC filters and amplifiers. The
bandwidth of filter is 0.7Hz-150Hz and the gain of amplifier is 1000. The
wireless sensor system also developed to monitor the sensing signals
at the remote area. The wireless sensor system consists of 3 units;
wireless sensor unit, a wireless receiver unit, and a monitoring unit. The
wireless sensor unit transmits amplified signals from geophone with
Zigbee, and the wireless receiver unit which has both Zigbee and Wi-Fi
module receives signals from the sensor unit and transmits signals to
the monitoring system with Zigbee and Wi-Fi, respectively. By using
both Zigbee and Wi-Fi, the wireless sensor system can achieve the low
power consumption and wide range coverage.
7646-27, Session 9
Rectennas performance based on
substrates for bio-medical applications
K. D. Song, F. Williams, Norfolk State Univ. (United States); S. Y.
Yang, J. Kim, Inha Univ. (Korea, Republic of); S. H. Choi, NASA
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Conf. 7646: Nano-, Bio-, Info-Tech Sensors and Systems
the nanorods were uniformly distributed and the gold nanostructures
were completely controlled. The results demonstrated that the
nanostructures and the composite display luminescent behavior and
the optical absorbance was enhanced by the gold nanoparticles in
the range of visible light owning to the surface plasmon resonance
phenomena in the gold nanoparticles. The composite of gold
nanoparticles attached ZnO nanorods may be utilized for biomedical
applications. The detail results will be discussed.
7646-30, Session 9
Software structure for broadband wireless
sensor network system
H. Kwon, S. Oh, H. Yoon, V. K. Varadan, Univ. of Arkansas (United
States)
This paper describes software structure for a wireless sensing system
using wireless LAN and Zigbee. The system has the benefit of Zigbee
sensor network measuring multiple sensors and the advantage of
wireless LAN with high data rate and broadband communication. This
system has three main software structures. The first part of software
structure comprises sensing data conversion and the second part is
to gather the sensor data through wireless Zigbee and to send the
data using wireless LAN. The second part consists of Linux packages
software based on Samsung2440 CPU, which has ARM9 core.
The Linux packages include bootloader, device driver, kernel, and
application. The applications are TCP/IP server program, wireless
Zigbee program, and wireless LAN program. The last part of software
structure was developed by using Visual C++ to communicate the
sensor data through TCP/IP client program and to display graphically
measured data; the sensor data is measured on 100Hz sampling rate
and the measured data has 10bit data resolution. The wireless data
transmission rate per each channel is 1.5kbps. Thus, the wireless data
transmission rate of this system that has 3 sensors is totally 4.5kbps.
7646-61, Poster Session
Simple theoretical analysis of the
thermoelectric power under strong
magnetic quantization in superlattices of
non-parabolic semiconductors with graded
interfaces
S. Singharoy, JIS College of Engineering (India)
The theoretical results of our paper can be used to determine the TPM
for SLs and the constituent bulk semiconductors in the absence of
magnetic field. It is worth remarking that this simplified formulation
exhibits the basic qualitative features of the TPM for the SLs and the
constituent materials respectively. Finally it may be noted that the aim
of the present work is not solely to investigate the TPM but also to
suggest the experimental determinations of the Einstein relation for the
diffusivity-to-mobility ratio, the Debye screening length and the carrier
contribution to the elastic constants for materials having arbitrary band
structures which, in turn, is again dimension independent.
7646-57, Poster Session
Micro-electronic circuit design for
amplification and modulation in a MEMs
human blood-pressure sensor
7646-62, Poster Session
J. A. Alvarez-Chavez, Ctr. de Investigación e Innovación
Tecnológica (Mexico); I. Quiñones, E. Vela, Instituto Nacional de
Rehabilitación (Mexico)
Dynamic behavior of double-walled carbon
nanotubes conveying viscous fluid based on
nonlocal elastic theory
In this paper the design and simulation of an integrated circuit for
electric signal amplification and digitalization from a MEMS human
blood pressure sensor is presented. The signal consists on a variable
voltage from 0 to 10 mV, 1 mA and frequency from 50 to 500 Hz. Its
simple but effective design consists on an operational amplifier (opamp) configured as a differential amplifier which amplifies the signal (up
to 3V and 10mA), originating from a Wheatstone bridge in the MEMS
sensor, and then this signal is digitalized and modulated via pulse width
modulation (PWM). The technology used in this circuit is MOSIS AMI
1.5 um. The circuit was designed with a two-stage Op-Amp used along
several stages of the system. The use of a differential amplifier, the
two-stage Op-Amp and the PWM simplifies the design and makes it
compact due to the use of fewer components (40 transistors). The use
of PWM facilitates processing of the signal in later stages. The result
is the design and simulation of the circuit. It consists in the schematic
diagram and layer diagram with all the rules specified in the process
MOSIS AMI 1.5 um. Electric and LTspice software were used in the
design and simulating of the circuit. A full description of the design
philosophy, design criteria, output traces and curves and results will be
presented.
Y. Zhen, B. Fang, T. Yang, Harbin Institute of Technology (China)
Because of perfect hollow cylindrical geometry and excellent
mechanical properties, the carbon nanotubes (CNTs) hold substantial
promise in nanobiological devices and nanomechanical systems
such as fluid storage, fluid transport, and drug delivery. Fluid flow
inside CNTs raises a significant and challenging research topic.
On the other hand, the influence of internal moving fluid on overall
mechanical behavior is another major topic. Based on the theory of
Euler-Bernoulli beam model, the instability of a free-free double-walled
carbon nanotubes (DWCNTs) conveying fluid is studied. The viscosity
of fluid and the nonlocal effect are incorporated in the formulation,
and the Galerkin discretization method is used to solve the coupled
equations of the motions. The critical flow velocities, associated with
divergence and restabilization, are obtained. As the increase of fluid
velocity, the system experiences stability, divergence, and restability
states. Numerical simulations show that the van der Waals (vdW)
interactions and the internal moving fluid play a significant role in the
natural frequency and the stability of DWCNTs. The critical velocities
with no vdW interactions are much smaller than those considering
vdW interactions. It means that the system is more stable with the vdW
interactions(Fig.1). The influence of viscosity, nonlocal effect, aspect
ratio and surrounding elastic medium are also analyzed in detail. Under
different dimensionless viscosities, there is no obvious difference with
the increase of fluid velocity until the dimensionless fluid velocity is
up to 14.20. The natural frequency of the DWCNTs decreases as the
fluid viscosity increased when the dimensionless velocity is greater
than 14.20 (Fig.2). As the nonlocal parameter increased, the natural
frequency decreases under the condition that the system is stable.
Also, the unstable region of velocity becomes greater when the
nonlocal parameter increased (Fig.3). The aspect ratio of DWCNTs
has important influence on the stability of the system. The system
gets more stable as the aspect ratio of the DWCNTs increased (Fig.4).
When the Winkler constant of the elastic medium is 1 KPa or 1Mpa, the
natural frequency and the stability of the system is almost the same.
When K=1GPa or 10GPa, the critical velocity of the system is greater
7646-58, Poster Session
Synthesis and characterization of composite
of gold nanoparticles attached ZnO
nanorods
K. Zhang, Norfolk State Univ. (United States)
Gold nanoparticles, ZnO nanorods and there composite were
synthesized through wet-chemical route at low temperature and
ambient pressure. The nanostructures and composite were examined
by X-ray diffraction, Scanning electron microscopy, transmission
electron microscopy, photoluminescence and UV-visible absorption
spectra. The gold nanostructures were tightly attached to the nanorods
surface of ZnO in the composite. The characterization showed that
96
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reserve of fossil fuels decrease. We describe a bio-photocatalyst
based on the iron storage protein ferritin. The ferritin protein
naturally sequesters ferrihydrite inside a spherical 12 nm protein
shell. Ferrihydrite is a semi-conductor material that functions as
a photocatalyst in aqueous solvents. Ferritin has been shown to
photoreduce Au(III) and Cu(II) ions in solution to form 10-30 nm Au(0)
and Cu(0) nanoparticles. Citrate acts as a sacrificial electron donor to
supply electrons for the photoreduction. We describe studies designed
to understand the mechanism of this catalyst in order to improve the
efficiency of the reaction. We have developed a spectrophotometric
assay to simultaneously illuminate the sample and kinetically
monitor the formation of products. We report that buffers containing
sulfur significantly increase the rate of the reactions. The absence
of salt can completely inhibit the reaction. Control reactions with
colloidal ferrihydrite nanoparticles do not catalyze the photochemical
reaction but produce a black magnetic precipitate indicating
that the protein shell has an important function in nanoparticle
formation. To substantiate this hypothesis, studies were done with
H and L homopolymers of ferritin. The results show that the H
homopolymers were more effective in nanoparticle formation than the
L homopolymers. Interestingly, the homopolymers were more efficient
than the natural heteropolymer of H & L ferritins found in horse spleen
ferritin. Finally, the sacrificial electron donor citrate appears to play an
additional role as an intermediate in the photochemical reaction.
than 1MPa. This implies that the surrounding elastic medium also plays
a role in the stability of DWCNTs (Fig.5).
7646-63, Poster Session
Analysis of the effect of both specimen size
and grain size on the tensile strength of the
polycrystalline metallic materials
B. Jung, H. Lee, H. Park, Pohang Univ. of Science and Technology
(Korea, Republic of)
A modified strain gradient plasticity theory is proposed based on
the mechanism-based strain gradient (MSG) plasticity. This study is
motivated by nonhomogeneity of polycrystalline materials. We believe
that the geometrically necessary dislocations (GND) are generated on
slip system as well as grain boundary to accommodate the deformation
shape with internal stress. The new theory differs from the MSG
plasticity in consideration of the GND on grain boundary and free
surface effect of polycrystalline materials.
Using the proposed model, an analysis of the effect of both specimen
size and grain size on the tensile strength of the polycrystalline
materials is carried out.
7646-31, Session 10
7646-64, Poster Session
Multi-walled carbon nanotubes covalent
bonded cellulose composite chemical vapor
sensor
Simple theory of the interband optical
absorption co-efficient in semiconductors
in presence of an electric field and its
dependence on a longitudinal magnetic field
S. Yun, S. Y. Yang, J. Kim, Inha Univ. (Korea, Republic of)
A cellulose solution is prepared by dissolving cotton pulp in LiCl/DMAc
solution. Functionalized multi-walled carbon nanotubes (MWCNTs)
are reacted with N, N-Carbonyldiimidazoles to obtain MWCNTsimidazolides. By acylation of cellulose with MWCNTs-imidazolides,
MWCNTs were covalently bonded on cellulose chains. Using the
product, regenerated cellulose with covalently bonded MWCNT
(RC-MWCNT) paper is fabricated with mechanical stretching to align
MWCNTs with cellulose. Finally, inter-digital (IDT) comb electrode is
formed on the paper via lift-off process. We expect that the presence
of alignment as well as covalent bonds of MWCNTs on RC-MWCNT
paper sensor will play an important role in remarkably changing chemoelectrical properties in response of absorption of the volatile vapors. As
exposing volatile chemical vapors corresponding to propanol, butanol,
methanol and ethanol, the chemo-electrical properties of RC-MWCNT
paper sensor will be analyzed with respect to selectivity, reproducibility
and stability.
S. Singharoy, JIS College of Engineering (India)
The oscillations in OAC is not due to “Stark” ladder (as claims
Callaway) but due to the consideration of -dependence of optical
matrix element (OME) in presence of electric field (Fig. 2c) as well as in
presence of electric plus parallel magnetic fields as it is obvious from
theoretical predictions.
In the case of the presence of Electric plus parallel magnetic fields,
the effect of electric field on OAC is more prominent than the case of
parallel magnetic field
7646-65, Poster Session
Thermal sensors based on nano porous
silicon
7646-32, Session 10
J. Lin, St. John’s Univ. (Taiwan); W. Tsai, National Cheng Kung Univ.
(Taiwan)
Integration of OLEDs in biomedical sensor
systems: design and feasibility analysis
Nano porous silicon (NPS), consisting of many nano pores and
high-aspect-ratio silicon (Si) pillars, was prepared by electrochemical
etching in a hydrogen fluoride (HF) and a potassium hydroxide (KOH)
solution. NPS can be designed to control heat transfer on its surface
and can lead to a better efficiency of thermal sensors because of the
high surface to volume ratio and considerable quantities of porosities
of NPS. In this study, the thermal sensors based on NPS were
explored. The size of the pores by adjusting process parameters like
the formation conditions of NPS and the sensitivities and responses of
thermal sensors were presented and discussed.
P. Rai, P. S. Kumar, V. K. Varadan, Univ. of Arkansas (United States)
Organic (electronic) Light Emitting Diodes (OLEDs) have been shown
to have applications in the field of lighting and flexible display. These
devices can also be incorporated in sensors as light source for
imaging/fluorescence sensing for miniaturized systems for biomedical
applications and low-cost displays for sensor output. The current
device capability aligns well with the aforementioned applications
as low power diffuse lighting and momentary/push button dynamic
display. A top emission OLED design has been proposed that can be
incorporated with the sensor and peripheral electrical circuitry, also
based on organic electronics. Feasibility analysis is carried out for an
integrated optical imaging/sensor system, based on luminosity and
spectrum band width. A similar study is also carried out for sensor
output display system that functions as a pseudo active OLED matrix.
A power model is presented for device power requirements and
thermal constraints. The feasibility analysis is also supplemented with
the discussion about implementation of ink-jet printing and stamping
techniques for possibility of roll to roll manufacturing.
7646-66, Poster Session
Ferritin as a photocatalyst in an artificial
photosynthesis system
R. J. Hilton, J. Keyes, R. K. Watt, Brigham Young Univ. (United
States)
Alternate fuel sources are becoming increasingly important as the
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Conf. 7646: Nano-, Bio-, Info-Tech Sensors and Systems
model nanocomposite. Calculated volume- temperature behavior and
X-ray scattering profiles were compared with experimental results. The
shrinkage of nanocomposite polymerized with POSS was showed to
be improved remarkably, declined from 3.53% to 2.18% at most. The
mechanical properties of novel nanocomposite were greatly increased,
for example, with only 2wt% POSS added, the nanocompsite’s
flexural strength increased 15%, compressive strength increased
12%, hardness increased 15% and uncommonly, even the toughness
of resins was obviously increased(+56%). Cohesive energy density
was calculated and found to be decreased with POSS copolymerized
and chain packing around the POSS cluster was evaluated through
radial distribution functions. The mobility of the POSS clusters was
determined via the mean square displacement. The mechanical
properties and shrinkage of light-curing dental nanocomposites
polymerized with POSS can be improved significantly. And their wear
resistance and service life were also increased greatly. The simulated
results implied that new nanocomposite system formed a netlike
distribution which may form a structural network holding the composite
together and resulting in increasing mechanical properties.
7646-33, Session 10
Cellulose polypyrrole-ionic liquid (CPIL)
nanocomposite for highly durable,
biomimetic electro-active paper actuator
S. K. Mahadeva, J. Kim, J. Kim, Inha Univ. (Korea, Republic of)
Cellulose has received much attention as a emerging smart material,
named as electro-active paper (EAPap), which can produce a large
bending displacement with applied external electrical field. In spite
of many advantages over other reported electro active polymers,
the material improvement as an actuator is required due to the poor
performance under ambient humidity condition and the degradation
of performance with actuating time. To improve the performance
and durability of EAPap, nano-layered PPy layer into cellulose
EAPap was formed by in-situ polymerization technique. CellulosePPy-IL nanocomposite based EAPap actuator showed nearly 100%
improvement of the actuator performance compared that of pure
cellulose based EAPap actuator systems. In present paper, we have
successfully developed the highly durable EAPap actuator working at
ambient condition with large displacement output.
7646-36, Session 11
Versatile smart optical material
characterizer
7646-34, Session 11
Y. Park, George Washington Univ. (United States); S. H. Choi,
NASA Langley Research Ctr. (United States); K. Lee, Federal
Highway Administration (United States)
Photoresponsive hydrogel microvalve
activated by bacteriorhodopsin proton
pumps
A versatile Smart Optical Material (SOM) characterization system
is constructed based on Michelson interferometer system. SOM
characterization system can measure not only the intensity of light
through materials but also deep properties of light such as phase
angle, polarization dependence, coherence, and so on. It can
characterize electro-optic materials including liquid crystal, non-linear
optical crystal, and electro-optic polymer, magneto-optic materials
with Faraday effect and Kerr effect, motion of MEMS devices,
thermal expansion coefficients, optical property changes by chemical
reaction and concentration, stress and strain coefficient, piezoelectric
coefficient, electro-chromism, and so on. Advanced software can
characterize not only one-point measurement, but also multi-pixel
measurement for array type devices as well. SOM characterization
system supports development of versatile optical materials and devices
for adaptive optics system, optical fiber communication, optical
display, and optical data storage system.
K. M. Al-Aribe, G. K. Knopf, The Univ. of Western Ontario (Canada)
Light driven and optically controlled microfluidic chips have several
advantages over thermal, electrical or electromechanical designs.
Optical systems are free from current losses, resistive heat dissipation,
and friction forces that can greatly diminish the performance and
efficiency of the active microsystem components (eg. pumps and
valves). An organic photoelectric thin film that can control the
expansion and shrinkage of a pH sensitive hydrogel microvalve
is introduced in this paper. The organic film is fabricated from
bacteriorhodopsin (bR), a light sensitive protein found in the salt marsh
bacteria Halobacterium salinarium. The bR protein acts as proton
pump that transports hydrogen ions across the cell membrane when
exposed to visible light. However, for photon to ion flow efficiency, it is
necessary that all bR molecules are oriented in the same direction. In
this research, the directional proton pumps are self-assembled on gold
coated porous substrates using biotin and streptavidin for selective
molecular labeling and adsorption. The flow of ions from the photon
activated bR changes the pH value of the ionic solution around the
HEMA-AA hydrogel microvalve. The chargeable polymeric network
undergoes a geometric phase transition when the pH of the ionic
solution is shifted to the phase transition point pKa. Preliminary tests
show a measurable change in pH of the ionic solution (6.5 to 8.0) when
bR proton pumps were exposed to a 568nm light beam at 18mW for 20
minutes. Furthermore, the resultant pH gradient induced a 40% volume
change in the polymer microvalve.
7646-37, Session 11
Bioelectronic photosensing array for nonplanar imaging
G. K. Knopf, The Univ. of Western Ontario (Canada)
Omni-directional and wide field-of-view imaging systems require
complex optical assemblies to project time-varying spatial information
onto the flat surface of a CCD or CMOS sensor array. These optical
systems are often prone to geometric distortions, alignment errors,
vibrations, and thereby difficult to calibrate for field applications.
Biological vision systems, in contrast, use simple optics and numerous
highly-sensitive photoreceptors distributed in non planar arrays. A
novel imaging system that exploits the photoelectric signals generated
by dried bacteriorhodopsin (bR) films is described in this paper. The
dry bR thin film deposited on the microelectrodes respond to light
intensities over a wide dynamic range (ten orders of magnitude) and
exhibit a quantum efficiency of nearly 64%. By fabricating patterned
sensor arrays on flexible plastic substrates it is possible to develop non
planar imaging surfaces (eg. cylinder, sphere). In addition, the spatial
pattern and size of individual pixels can be modified prior to printing
the conductive electrodes on the PET plastic sheet. The flexible and
lightweight photosensor array is manufactured on an indium-tinoxide (ITO) coated plastic film using electrophoretic sedimentation
(EPS). Each sensor pixel is 1mmx1mm and arranged in a 16x16 array.
Experiments show that the peak spectral response occurs at 568nm
and is linear over the tested light power range of 200uW to 12mW. The
7646-35, Session 11
Synthesis and evaluation of novel lightcuring dental nanocomposite
X. Wu, Y. Sun, X. Song, Harbin Institute of Technology (China); W.
Xie, Harbin Medical Univ. (China)
A novel light-curing dental nanocomposite was explored to improve
the shrinkage and mechanical properties. Organic-inorganic hybrid
nanoscale multifunctional POSS (polyhedral oligomeric silsesquioxane)
was polymerized with composite resins to synthesize the new dental
nanocomposite. The structure of POSS-containing networks was
analyzed by FTIR, WAXD and DSC. Their properties were evaluated
including shrinkage, strength, elastic modulus, hardness and
toughness. Molecular dynamics simulations were performed to study
the effects of POSS with different loading levels on the properties of a
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bending test system to monitor the strain and resistance. Using
resistance as an index of the internal structure change, the reliability of
PEDOT:PSS can be revealed. The test system consists of force gauge,
linear stage and multi meter to measure the strain and resistance
change. Material testing system is controlled by National instrument
(NI) and Labview program.
photosensor response remains linear at the other tested wavelengths
but the amplitude is reduced. A bendable microlens assembly, with
discrete glass lenses, is used to focus the light onto the individual
elements. Suggestions for improvement are presented.
7646-38, Session 11
7646-40, Session 12
Can magnetotactic bacteria in multiple
optical traps be used to form magnetic
nanostructures?
Organic electronics based pressure sensor
towards intracranial pressure monitoring
D. Tierney, M. Henstridge, D. Engle, Xavier Univ. (United States);
W. Dultz, Johann Wolfgang Goethe-Univ. Frankfurt am Main
(Germany); H. Schmitzer, Xavier Univ. (United States)
P. Rai, V. K. Varadan, Univ. of Arkansas (United States)
The intra-cranial space, which houses the brain, contains cerebrospinal
fluid (CSF) that acts as a fluid suspension medium for the brain. The
CSF is always in circulation, is secreted in the cranium and is drained
out through ducts called epidural veins. The venous drainage system
has inherent resistance to the flow. Pressure is developed inside the
cranium, which is similar to a rigid compartment. Normally a pressure
of 5-15 mm Hg, in excess of atmospheric pressure, is observed
at different locations in side the cranium. Increase in Intra-Cranial
Pressure (ICP) can be caused by change in CSF volume caused by
cerebral tumors, meningitis, by edema of a head injury or diseases
related to cerebral atrophy. Hence, efficient ways of monitoring ICP
need to be developed. A sensor system and monitoring scheme
has been discussed here. The system architecture consists of a
membrane less piezoelectric pressure sensitive element, organic thin
film transistor (OTFT) based signal transduction, and signal telemetry.
The components were fabricated on flexible substrate and have been
assembled using flip-chip packaging technology. Material science and
fabrication processes, subjective to the device performance, have been
discussed. Capability of the device in detecting pressure variation,
within the ICP pressure range, is investigated and applicability of
measurement scheme to medical conditions has been argued for.
Magnetic bacteria have attracted attention for their ability to grow
single domain cuboctahedral iron oxide nanoparticles that can help
to align multiwalled carbon nanotubes during growth. This paper
describes a first experiment with helical, magnetic bacteria in optical
tweezers. Magnetosprillum Magnetotacticum cells, 4 to 5μm in length
with a diameter of 0.5μm were placed in solution, sealed between
microscope slides and placed in the focus of optical tweezers. Since
M. Magnetotacticum has a helical shape, it rotates when held in optical
tweezers due to the momentum transfer from the tweezing light.
Measurement of various M. Magnetotactica’s rotational speeds with
respect to photon flux showed linear results with speeds (1 to 13Hz)
comparable to small birefringent valerite crystals (diameter 5 to 7μm),
which are driven by spin angular momentum transfer from light [1].
Rotating bacteria could thus have a similar microfluidic flow of 200
μm3s-1 . It can thus be used as a micromotor for microfluidic flow
applications. We suggest using multiple traps to create a defined array
of M. magnetotacticum. In order to preorient the bacteria and their
dipole moments, a homogenous magnetic field can be applied. Several
line foci can then drag and orient the bacteria and their nanometer wide
dipoles into the required position.
[1] J. Leach, H. Mushfique, R. di Leonardo, M. Padgett, J. Cooper, Lab
Chip, 6, 735-739 (2006)
7646-41, Session 12
A bio-inspired flow sensor
7646-39, Session 12
X. Yu, Case Western Reserve Univ. (United States)
Flexible PEDOT:PSS strain gauge
Accurate measurement of the turbulent flow is an important step
to understand the mechanisms of many unknown phenomena.
The turbulent flow generally can not be easily measured without
significantly disturbing the original flow conditions. This paper
introduces the efforts to develop a bio-inspired sensor for monitoring
the turbulent flow. The sensor consists of an array of micro-pillar
or nano-pillar. It looks into the fluid sensing capability of carbon
nanotube bundles and its potential as the key sensing elements in
the construction of micro-pillar. The performance was evaluate for its
sensitivity as turbulence flow sensor.
W. Wang, Univ. of Washington (United States)
Organic electronics have emerged as an important technology in
the near future. The applications of it are being intensively studied
such as flexible display, electric label and organic energy harvesting
device. The developments of these organic devices create a trend
to shift the traditional hard material to soft material. Thus the termsoft electronics was created to describe the organic electronics. It is
apparent that the flexible conducting material plays a vital role in the
development of the organics device since the crack will be generated
in common metal such as silver or gold when cycling load is applied.
Among all the conducting polymer, poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate) abbreviated as PEDOT:PSS are known for its
high conductivity and processability because it can be dissolved in
water with low viscosity which is suitable for low cost inkjet printing
process. In this case, the mechanical property characterization of
PEDOT:PSS becomes important due its reliability issue when subjected
to cycling load. Recently, research shows that the stress and strain
curve of PEDOT:PSS highly depends on the environmental humidity
which reveal the instability issue of PEDOT:PSS when it is used as
an component or a sensor. Furthermore, the way of PSS distributed
in PEDOT structure will also affect the resistivity of the bulk material
especially when external polar solution is added into PEDOT:PSS.
7646-42, Session 12
Smart textiles with nanosensor array for
point-of-care soldier health monitoring in
real time
V. K. Varadan, Univ. of Arkansas (United States)
A new paradigm in healthcare, driven by cost and quality issues, is now
emerging, which enables continuous point-of-care (POC) monitoring
of soldier’s vital signs such as heart rate (ECG), respiration, body
temperature, galvanic skin response (GSR), and motion activities
(EMG) and sensing and monitoring of chemical and biological threats
and improve the survivability of soldiers in battlefields. The proposed
architecture is also useful for monitoring and control of neurological
and cardiovascular disorders for civilians at home. Real-time health
monitoring could ensure the effectiveness of therapy by providing
prevention, and early risk detection, which will significantly reduce
healthcare costs by avoiding unnecessary hospitalizations. Latest
advances in organic electronics have the ability to realize light and
In this paper, we present a reliability test of PEDOT:PSS conducting
polymer strain gauge to measure the bending motion of the rectangular
plate. Compare to commercial available strain gauge, the flexible
and piezo-resistive PEDOT: PSS strain gauge has benefit to measure
larger deformation without damaging itself. In our experiment,
PEDOT:PSS strain gauge is first made by molding PEDOT:PSS(Baytron
P, German) on Polyurethane(Bond Polymer, USA) and, then attach to
the rectangular acrylic plate. The sensor are further tested by 3-points
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Conf. 7646: Nano-, Bio-, Info-Tech Sensors and Systems
cost-effective smart fabrics with embedded electronics and sensors
combined with wireless communications. In this presentation, we
introduce several organic based sensor devices capable of measuring
temperature, strain, ph and potassium ion concentrations, each of
which will enable us to monitor the patient’s respiration rate, skin/
body temperature, and the onset of Acute Myocardial Ischemia and
neurological disorder triggered by chemical and biological species. It is
expected that these flexible organic sensors can easily fit on garment
with wireless instrument, and this sensory suit will be ideal for the
real-time monitoring of vital kinematics and signs at remote locations
for activity and location monitoring. Selected movies illustrating the
applications of both invasive and non-invasive wireless sensor systems
to patients and surgical procedures will be shown at the talk.
7646-45, Session 13
Characterization of micro-scale surface
features using partial differential equations
G. Gonzalez Castro, J. Sweeney, H. Ugail, B. Whiteside, R. Spares,
Univ. of Bradford (United Kingdom)
Micro-injection moulding (micromoulding) is an emerging technology
useful for mass production of devices and components with micro
and nano scale surface features and a complex three-dimensional
surface geometry for a range of applications including micro-optics,
couplings and life science applications. The process can be sensitive
to changes in processing variables such as the flow properties of
raw materials and machine fluctuations so it is therefore useful to
employ Quality Assurance techniques into the production cell to verify
product quality of each product following manufacture. Such systems
are usually required to perform three-dimensional measurements
of surface structures, and to this end, a range of techniques can be
adopted including Extended Depth of Field (EDOF) and White Light
Interferometry (WLI). However, such techniques generate measurement
datasets as regular Cartesian cloud point data which can be large
and unwieldy, particularly for large, high resolution scans and there is
a clear need for compression of the data required by picking out key
geometric feature properties which can be used as product quality
indicators. Therefore, the problem remains to represent the surfaces
thus generated, associated with large data sets, in an efficient way that
will facilitate their analysis and characterization.
7646-43, Session 13
Wave propagation and structural dynamics
in graphene nanoribbons
F. L. Scarpa, Univ. of Bristol (United Kingdom); M. Ruzzene,
Georgia Institute of Technology (United States); S. Adhikari, R.
Chowdhury, Swansea Univ. (United Kingdom)
Graphene nanoribbons (GNRs) are novel interesting nanostructures
for the electronics industry, whereas their state as metallic or
semiconductor material depends on the chirality of the graphene
structure. We model the natural frequencies and the wave propagation
characteristics of GNRs using an equivalent atomistic-continuum
FE model previously developed by some of the Authors, where the
C-C bonds thickness and average equilibrium length during dynamic
loading are identified during a nonlinear minimisation process of
the system Hamiltonian. We demonstrate that the thickness and
equilibrium lengths for the different dynamic cases are different from
the classical constant values used in open literature (0.34 nm for
thickness and 0.142 nm for equilibrium length), in particular when
considering out-of-plane flexural deformations. These parameters have
to be taken into account when nanoribbons are designed as nanooscillators.
The technique proposed here is based on the use of Partial Differential
Equations (PDEs) to describe the outer shell of the resulting surface
profiles from the raw measurement data. This technique has been
developed with the aim of identifying a number of parameters
responsible for determining the surface profile of a given product.
This set of parameters can then be compared with the theoretical
values associated with a particular surface profile (essentially the
mathematical functions which describe the mould cavity surface) and
therefore determine the quality of the produced parts by studying the
error between the two parameter sets. Ideally, a moulded product
should follow the form of the mould from which it was produced
exactly, therefore the error calculation provides a direct measurement
of the moulding deficiency.
7646-44, Session 13
Experimentally, the measurement data corresponding to the
manufactured pieces is obtained through WLI (Wyko NT1100 off-line
instrument and an in-process system designed and assembled at the
University). Such data is thus processed so that the cloud point data is
reduced to a set of boundary curves (reducing memory requirements)
and then, a PDE surface is computed which can be compared against
the ideal profile. Differences between the theoretical (mould) and
measured (product) surfaces can be evaluated against calculated
criteria such as height, surface area and volume. Moreover, a criterion
based on the coefficients associated with the analytic solution of a
given mould can be employed to implement quality assessments
of the manufactured components with low solution times, allowing
such systems to be easily integrated into the production process.
Additionally, this surface generation technique provides an analytic
expression for such a surface over a two-dimensional parametric
space, which could potentially facilitate the numerical solution of a
given mathematical model involving any of the physical properties
associated with the micromoulding process.
Effect of thickness on characteristics of ZnO
thin films prepared by sol-gel process
J. Nayak, K. S. Kang, Y. Chen, K. H. Yoo, J. Kim, Inha Univ. (Korea,
Republic of)
Among oxide semiconductors, ZnO is a subjected to numerous
extensive studies due to its potential applications in the field of
electronics, optoelectronics and information technology devices
including displays, solar cells and sensors. ZnO is a wide band gap
semiconductor (3.37 eV) and high excitation binding energy of 60
meV with unique properties including transparency in the visible range
and high infrared reflectivity, acoustic characteristics, piezoelectricity,
and excellent chemical and physical stability. We present our results
of characterization of ZnO thin films fabricated with sol-gel methods.
Thickness of the sol-gel based ZnO film was controlled by a multiple
coating process. Crystallization by annealing was performed over the
range at 750o C. The effects of thickness on the surface morphology,
microstructure and optical properties of the films were investigated.
The film thickness increased as the coating time increased. From the
XRD study, it is observed that the ZnO films with varying thickness
demonstrated wurtzite structure (002) and as the thickness increased
the intensity of (002) peak also amplified. Transmittance of the prepared
solution increased upon 24 h of aging, which might be due to formation
and gradual growth of crystals in the solution. Effect of thickness on
Schottky behavior was evaluated by current-voltage characteristics,
the undoped ZnO thin films with thickness of 132 nm exhibited perfect
Schottky characteristics with high rectification ratio.
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7646-46, Session 13
SERS from ellipsoidal nanoparticles
G. Mukhopadhyay, S. R. Puri, P. Mukhopadhyay, Indian Institute of
Technology, Bombay (India)
The mathematical formulation to determine enhancement factors of
Raman scattered light from molecules adsorbed on spherical and
spheroidal particles has been previously studied. But many applications
require that the particle on which a Raman active molecule is adsorbed
is not one of these simple shapes or the application might even require
the particle to be coated. In this paper we extend the established
mathematical technique to derive enhancement from molecules
adsorbed on an ellipsoidal particle having in general any number of
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Conf. 7646: Nano-, Bio-, Info-Tech Sensors and Systems
by specifying individual tools to be implemented.
coatings of other substances on it. We then use our formulae to study
enhancement of Raman scattering from molecules like pyridine and
CV from nanoparticles of gold and silver as well as their core-shell
structures with magnetic metal cobalt. The nanoparticles of these
metals are widely used in biomedical applications. We also present
results for the cases when the nanoparticle is covered with a monolayer
of Raman active molecules and dispersed randomly in a medium. Our
results can be of vital importance in medical technology.
Pars pro toto we introduce subsequently an environment for the
development of new processes to manufacture micro and nano
devices. The environment provides central data management for
manufacturing knowledge, handling the whole range of process related
information and their complex relationships. Specific tools supporting
the process management and design tasks like consistency check of
fabrication processes and process simulation have been implemented
based on the data management.
The development is currently carried out in an international multi-site
research project (CORONA - funded by the European Commission CPFP 213969-2).
7646-47, Session 13
Mathematical modeling for the design
of porous coronary stents: nano- and
microporous stents v. macroporous stents
7646-49, Session 14
A. Habib, Emory Univ. (United States)
Smart energy management system
Drug delivery polymers play a role in late in-stent thrombosis of first
generation drug-eluting stents (DES) via an inflammatory reaction.
To circumvent this problem, subsequent generation DES have
non-polymer based DES whose surface pores serves as a drug
reservoir. While drug elution for pores in the nanometer range have
been shown to be comparable to polymer-based DES in terms of
intimal suppression, how different pore sizes effect drug elution has
not been fully characterized. We hypothesized that drug elution can
be characterized with a mathematical model that takes into account
the pore size of the stents and molecular characteristics of the
eluted drug. Methods: Structural data from six porous, non-polymer
based stents were examined with pore size ranging from 5 nm to >
10 mm (1-Setagon Stent, Setagon Inc., Charlottesville, VA; 2-Yukon
stent, Translumina GmbH, Hechingen, Germany; 3-ESI Microporous
Stent, ESI Inc, Stillwell, KS; 4-Synergy Biomatrix, Medlogics Device
Corporation, Santa Rosa, CA; 5, 6- CoStar and Conor Stents, Cordis
Medsystems, New Brunswick, NJ). All stents eluted either Tacrolimus
or Sirolimus. We constructed a mathematical model based on mass
transport of molecules through a porous media. A dimensionless
number was derived characterizing molecular flux of the drugs through
a porous membrane. Results: Figure. 1 demonstrates that there was
exponential rise in molecular flux of the eluted drug with pore sizes
greater than 5 micrometers. The molecular characteristics of the eluted
drug did not affect the molecular flux. Conclusions: Stents in the nanoand microporous range will have similar drug elution profiles; while
macroporous stents will vary greatly. Careful attention to pore size may
significantly enhance the design and efficacy of microporous polymer
free stents.
A. A. Desai, J. J. Singh, La Trobe Univ. (Australia)
Peak and average energy usage in domestic and industrial
environments is growing exponentially and absence of detailed energy
consumption metrics is making systematic reduction of energy usage
very difficult. Smart Energy Management System aims at providing a
cost-effective solution for managing soaring energy consumption and
its impact on green house gas emissions and climate change.
The solution is based on seamless integration of existing wired and
wireless communication technologies combined with smart contextaware software which offers a complete solution for automation of
energy measurement and device control. The system can communicate
over existing power lines thereby allowing a low cost retro-fit model for
existing devices/appliances. The persuasive software presents users
with easy-to-assimilate visual cues identifying problem areas and time
periods and encourages a behavioural change to conserve energy.
The system allows analysis of real-time/statistical consumption
data with the ability to drill down into detailed analysis of power
consumption, CO2 emissions and cost. The system generates
intelligent projections and suggests potential methods (e.g. reducing
standby, tuning heating/cooling temperature, etc.) of reducing energy
consumption. The user interface is accessible using web enabled
devices such as PDAs, PCs, etc. or using SMS, email, and instant
messaging.
Successful real-world trial of the system has demonstrated the
potential to save 20 to 30% energy consumption on an average. Low
cost of deployment and the ability to easily manage consumption
from various web enabled devices offers gives this system a high
penetration and impact capability offering a sustainable solution to act
on climate change today.
7646-48, Session 14
Comprehensive design and process flow
configuration for micro and nano tech
devices
7646-50, Session 14
Implementation of capacitive RF MEMS
switches into a monolithic GaN on silicon
microwave technology
K. Hahn, T. Schmidt, M. Mielke, Univ. Siegen (Germany); D. Ortloff,
J. Popp, Process Relations GmbH (Germany); R. Brück, Univ.
Siegen (Germany)
A. Ziaei, M. Lebaillif, Thales Research & Technology (France)
The development of micro and nano tech devices based on
semiconductor manufacturing processes comprises the structural
design as well as the definition of the manufacturing process flow. The
approach is characterized by application specific fabrication flows, i.e.
fabrication processes (built up by a large variety of process steps and
materials) depending on the later product. Technological constraints
have a great impact on the device design and vice-versa.
The use of micro-machined switches for RF switching applications was
first demonstrated in 1979 . Since then, a large amount of research
effort has focused on the fabrication and the implementation of micromachined switches for various applications and specifications such
as reflect array antennas or phase shifters. Despite the differences in
designs, these switches have demonstrated the low insertion loss,
high isolation and low return loss (good impedance matching) at
microwave frequencies. Wide Band-Gap (WBG) Semiconductors are
being developed to replace GaAs based technologies. Some devices
has already reached specifications for applications .reports the
measured S-parameters in the 0-40 GHz frequency range, for the UP
state and DOWN state of the switch. For 40 GHz switching operation,
when the switch is in the UP state, the insertion loss (a) of the switch
is 0.3 dB with the return loss (b) better than 11 dB; when the switch
is switched to the DOWN state, the isolation (c) is 28 dB. The pulldown voltage ranges from 30 to 40 volts. (see geometrical Parameters
and microwawe characteristics of TRT shunt switch in Table1). The
In the first part of this paper we introduce a comprehensive
methodology for customer-oriented product engineering of MEMS
products. Micro and nano tech product development tailored towards
a distributed, networked operation between customers, designers
and semiconductor manufacturing partners are in the focus of this
methodology. The micro and nano device engineering process is
analyzed with regard to different business cases (e.g. IDM, fables
design houses etc.) taking into account application-specific procedures
and (data) interfaces. The results are used to develop and to enable an
appropriate CAD support either by incorporating existing CAD tools or
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Conf. 7646: Nano-, Bio-, Info-Tech Sensors and Systems
measurement of RF MEMS switches have been done at Thales
Research and Technology. If we want to join these capabilities, it is a
tricky point to show that GaN substrates present the same microwaves
losses as high-resistivity silicon substrate or Glass. Simulations and
measurements demonstrate RF-MEMS Switches on GaN on Silicon
substrate with metallic membrane possess low insertion loss and
good isolation at frequencies up into the millimeter-wave bands. A
further task will be devoted to the design, test specific fabrication and
RF characterisation of a Single Pole Double Throw (SPDT) RF-MEMS
switch and MMIC circuits for final demonstrator as active T/R module.
7646-53, Session 15
Thermal indicating paints for ammunition
health monitoring
J. L. Zunino III, U.S. Army Armament Research, Development and
Engineering Ctr. (United States); Z. Iqbal, New Jersey Institute of
Technology (United States)
Ammunition is often exposed to extreme temperatures and solar
radiation during transport and storage. This is of particular concern in
the present theater of operations. It was documented during Desert
Storm operations that temperatures inside munitions’ containers
exceeded 190oF degrees. This significantly exceeds the design limits of
145oF - 165oF. Currently there is no way to know what environmental
extremes fielded items have experienced. An easily readable indication
of the environmental exposure history of an item will enable troops
and munitions managers to readily identify ordnances that may have
been compromised. Furthermore, compromised munitions can be
screened out to ensure mission success and enhancing soldier safety.
Thermal chromic polymers that change color in response to external
stimuli are being tailored to paints and coatings to alert Army logistic
staff of dangerous temperature exposures. Irreversible indication
via color change in multiple thermal bands, 145oF-164oF, 165oF184oF and over 185oF, are possible with these thermal polymers. The
resulting active coating can be visually inspected to determine if safe
temperatures were exceeded. The coatings are comprised of costeffective and commercially available monomers of conjugated polymer
diacetylenes. The conjugated polymeric backbone of polydiacetylenes
(PDAs), undergo intriguing stress-, chemical- or temperature-induced
chromatic phase transitions associated with the disruption of the
backbone structure and shortening of the conjugation length. PDAs,
such as 10, 12 pentacosadiynoic acids (PCDA), form nanocomposites
and uniform blends with polymers. Cumulative time of exposure in
multiple temperature bands can be sensed and optically detected
by mixing small amounts of time-temperature sensitive diacetylene
monomers into coatings.
7646-51, Session 15
A very high Q-factor inductor using MEMS
technology
N. Khalid, La Trobe Univ. (Australia)
Quality (Q) factor is an important characteristic of a inductor which
significantly affects the performance of the radio frequency (RF) circuits
and systems such as gain/noise figure of the low noise amplifier (LNA)
and the phase noise of voltage controlled oscillator (VCO). Higher Q
inductors help minimise RF power loss, RF noise, phase noise and DC
power consumption of RF integrated circuits. High Q inductor design
and fabrication remain a challenge for designers to design components
that depend on passive components performance such as low phasenoise VCO, power amplifier (PA), LNA and mixers. The Q factor and
frequency limitations still limit RF front-end circuitry to a large number
of discrete passive components and make RF front-end module
integration very critical.
Currently, MEMS is actively being investigated and developed for high
performance RF circuits. MEMS is an enabling technology and can
replace most of the components in a receiver for RF applications. RF
MEMS technology enables the realisation of small communication
device elements or modules with high performance, lower insertion
loss, higher isolation, and better linearity than semiconductor devices
that are currently used.
7646-54, Session 15
7646-52, Session 15
Fabrication of UV-micro-patternable
permanent micro magnets for lab on a chip
and MEMS
Annealing temperature effect of GaN thin
layer Schottky diodes
K. H. Yoo, K. S. Kang, Y. Chen, N. Jyoti, J. Kim, Inha Univ. (Korea,
Republic of)
A. Khosla, B. L. Gray, D. B. Leznoff, Simon Fraser Univ. (Canada);
J. Herchenroeder, D. Miller, Magnequench International Inc. (United
States)
GaN is a wide band gap semiconductor, approximately 3.4 eV, and
has been widely used in various application fields including blue
and ultraviolet light emitting diodes, Schottky diodes, and other
electronic devices. For these applications, various techniques have
been employed, such as metal-organic chemical vapor deposition,
molecular beam epitaxy, vapor phase epitaxy, pulsed laser deposition,
and chemical solution deposition. Among these techniques, chemical
solution deposition has superior advantages due to the no requirement
of expensive equipments, no management cost for the expensive
equipments, wide area applications, doping capability, thermal stability,
and potential integration and used in this study. Ga(NO3)3 (0.3 g) has
been dispersed in ethanol (5 g). Acetic acid (3 ml) was added and
stirred for 24 h. Resulting solution was spin-coated onto a Si substrate
with spinning rate of 1000 rpm for 10 sec. Coated Si wafer was heated
in hotplate at 200 °C for 10min and these processes were repeated
three times. These resulting Ga2O3 layers annealed in tube furnace
with constant flow of NH3 gas at high temperature such as 700, 800,
900 °C. These films were investigated with x-ray diffractograms. To
investigate Schottky characteristics of the converted GaN layer, Al
electrode was deposited on top of the GaN layer, and current-voltage
characteristics were investigated.
102
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High quality permanent magnet materials are pivotal for development
of magnetic microsystems such as microscale sensors, micromotors,
actuators and power generators. One of the biggest advantages of
permanent micromagnets is that they can generate high forces over
comparatively long working distances, which is attractive for, among
other things, manipulation of fluids in micro total analysis systems that
require actuation to facilitate fluid transport and mixing. In this paper
we present fabrication of UV patternable permanent micromagnets
which are capable of generating large bi-directional forces with long
working lengths. We present UV patterned permanent micromagnets
fabricated at Micro-Instrumentation Lab (Simon Fraser University,
Canada) by ultrasonic agitation MQP- Spowder (manufactured by
Magnequench International Inc) in SU-8 which is a negative tone
photoresist. This powder is composed of spherical particles which
have a typical median size of 50 μm. It has a remanent induction (Br)
of 0.75 T , a theoretical density of 7.43 g/cm3 and an apparent density
of 4.2 g/cm3. It is an NdFeB based isotropic powder manufactured
by Magnequench Inc. The resulting composite was successfully
UV patterened down to the size of 500 μm x 300 μm with a height
of 200 μm. The fabricated micromagnets were magnetized with an
electromagnetic charger and tested using a Tesla meter and found to
have a magnetic field intensity of 0.7mT at the surface of the magnet.
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Conf. 7646: Nano-, Bio-, Info-Tech Sensors and Systems
7646-55, Session 15
Nanowire-organic thin film transistor
integration and scale up towards developing
sensor array for biomedical sensing
applications
P. S. Kumar, P. T. Hankins, P. Rai, V. K. Varadan, Univ. of Arkansas
(United States)
Exploratory research works have demonstrated the capability of
conducting nanowire arrays in enhancing the sensitivity and selectivity
of bio-electrodes in sensing applications. With the help of different
surface manipulation techniques, a wide range of biomolecules have
been successfully immobilized on these nanowires. Flexible organic
electronics, thin film transistor (TFT) fabricated on flexible substrate,
was a breakthrough that enabled development of logic circuits on
flexible substrate. In many health monitoring scenarios, a series of
biomarkers, physical properties and vital signals need to be observed.
Since the nano-bio-electrodes are capable of measuring all or most of
them, it has been aptly suggested that a series of electrode (array) on
single substrate shall be an excellent point of care tool. This requires an
efficient control system for signal acquisition and telemetry. An array of
flexible TFTs has been designed that acts as active matrix for controlled
switching of or scanning by the sensor array. This array is a scale up
of the flexible organic TFT that has been fabricated and rigorously
tested in previous studies. The integration of nanowire electrodes to
the organic electronics was approached by growing nanowires on the
same substrate as TFTs and flip chip packaging, where the nanowires
and TFTs are made on separate substrates. As a proof of concept,
its application has been explored in various multi-focal biomedical
sensing applications, such as neural probes for monitoring neurite
growth, dopamine, and neuron activity; myocardial ischemia for spatial
monitoring of myocardium; and field applications for detecting food
pathogens and gases.
7646-56, Session 15
Magnetic nanocomposites for drug delivery
with controlled release
L. Chen, J. Xie, V. K. Varadan, Univ. of Arkansas (United States)
In a typical targeted drug delivery, carriers transport and release drugs
to a target site, and it is highly desirable to eliminate undesirable
drug release before reaching the target site. Traditional stimuli, such
as electric signals, ultrasound and acidity, often require a physical or
chemical contact with the drug carriers to trigger the release. However,
triggering a drug release in such a manner is usually not practicable in
the human body.
We will report our work on the development of magnetic
nanocomposites that can be used as carriers for drug delivery with
controlled release. The magnetic nanocomposites we developed mainly
consist of magnetic nanomaterials and heat-responsive polymers.
The magnetic nanomaterials can be addressed and stimulated by
external magnetic fields in a noncontact and remote nature, and the
heat-responsive polymers are used as the host media. Such magnetic
nanocomposites are dual-responsive: the magnetic nanomaterials
respond to the external magnetic fields, and the polymers respond
to the heat produced by the magnetic nanomaterials. Due to this
dual-response characteristic, the drugs loaded in the magnetic
nanocomposites will be released in a way controlled by external
magnetic fields: magnetic fields cause heat-responsive polymer to
shrink, squeezing drugs out from the nanocomposites.
The self-recovery capability of nanocomposites is essential for
programmable drug release. Our work will concentrate on the
development of magnetic nanocomposite carriers with self-recovery
capability: after a burst-like drug release, the carriers can adjust their
structures, and the remaining drugs in the carriers can continue to be
released in a controllable way.
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103
Conf. 7647: Sensors and Smart Structures Technologies for Civil,
Mechanical, and Aerospace Systems
Monday-Thursday 8-11 March 2010
Part of Proceedings of SPIE Vol. 7647 Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2010
* Indicates papers that will also be presented in the NSF Poster Session
7647-03, Session 2a
7647-05, Session 2a
Feasibility of embedded wireless sensors for
monitoring of concrete curing and structural
health
Development of high-sensitivity sensor for
structural health monitoring
H. Jo, Univ. of Illinois at Urbana-Champaign (United States); J. A.
Rice, Texas Tech Univ. (United States); B. F. Spencer, Jr., Univ. of
Illinois at Urbana-Champaign (United States)
W. Quinn, G. Kelly, Cork Institute of Technology (Ireland)
When designing civil structures the objective is to design a cost
effective, reliable and durable structure. Many old structures are now
reaching the limit of their design life and are being replaced with
“smart” structures. These structures are self-monitoring and have
the ability to predict failure allowing steps to be taken to mitigate the
affects and in many cases save lives.
Structural Health Monitoring (SHM) system using smart sensors has
been a hot issue recently. State-of-the-art smart sensor technology
makes it possible to deploy dense array of sensors through a structure
because of the benefit of its cost-effectiveness, easy installation
and wireless communication so that a sensor network provides an
abundance of structural information. However, relatively low resolution
of MEMS sensors generally adopted in smart sensor puts a limitation
on the application to low-level vibration such as ambient vibration of
building structure. For extensive application of smart sensor network
to diverse structures, the limitation should be eliminated, and accurate
sensor should be available for the wireless smart sensor system. In
this study, as the possible solution to the limitation, the development
of high-sensitivity acceleration board for Imote2 platform is explored.
For this sensorboard, a low-noise accelerometer (SD1221 of Silicon
Designs Inc., capacitive sensor) is used, and several considerations
are implemented to reduce the noise effects from diverse components
including power source, resistors and ground plane. The capacity of
the high-sensitivity accelerometer board is verified through various
static and dynamic tests and compared with that of other MEMS
sensors. The high-sensitivity sensor can be used to measure low-level
ambient vibration and utilized as reference sensor to enhance the
accuracy of other sensors.
The aim of this project is to design a sensor which monitors the
concrete structure during the two stages of its life - the curing stage
and its subsequent service life. Monitoring the curing process of
concrete will ensure a durable structure is constructed while monitoring
of structural health will determine how the structure is performing.
A key research challenge for such a sensor is to determine if it
is feasible to embed wireless technologies within concrete. The
composition of concrete, with different sized aggregates and steel
reinforcement bars may have a significant affect on the attenuation of
electromagnetic waves from deep within the concrete and seriously
affect the functionality of wireless sensors. The sensor must also
withstand the aggressive environment within the concrete. Initial
tests were designed to determine the affects of reinforcement bars
and large aggregates had on data transmission. The subsequent
design and packaging of a prototype wireless sensor to monitor the
two main parameters which ensure concrete is curing completely internal relative humidity and temperature - is described along with
the response of the sensors when embedded in concrete over a time
period of 60 days.
7647-06, Session 2a
Structural health monitoring system of a
cable-stayed bridge using a dense array of
scalable smart sensor network
7647-04, Session 2a
The Smartbrick wireless sensor node for
high-resolution structural health monitoring
S. Cho, Korea Advanced Institute of Science and Technology
(Korea, Republic of); S. A. Jang, H. Jo, K. Mechitov, Univ. of Illinois
at Urbana-Champaign (United States); J. A. Rice, Texas Tech
Univ. (United States); H. Jung, C. Yun, Korea Advanced Institute
of Science and Technology (Korea, Republic of); B. F. Spencer,
Jr., Univ. of Illinois at Urbana-Champaign (United States); T.
Nagayama, The Univ. of Tokyo (Japan); J. Seo, Hyundai Motor Co.
(Korea, Republic of)
B. O. Banks, D. A. Lecko, S. Sedigh, Missouri Univ. of Science and
Technology (United States)
This paper introduces a wireless sensor node for the SmartBrick
platform, which provides a low-cost and autonomous method for
structural health monitoring. Design and testing of the SmartBrick base
station have been described in previous publications. The SmartBrick
sensor node presented in this paper leverages the Zigbee shortrange communication capabilities of the base station to increase the
monitoring range of the system. The primary function of the node is to
interface to humidity, temperature, tilt, strain, and vibration sensors and
transmit their values to the base station via Zigbee. The GSM modem
included in the base station has been omitted from the sensor node, in
order to reduce cost, form factor, and power consumption. Long-range
communication of data and alerts will be through the base station,
which serves as the gateway to the outside world, and relays remote
configuration and maintenance commands to the sensor nodes.
This paper presents a structural health monitoring (SHM) system
using a dense array of scalable smart wireless sensor network on a
cable-stayed bridge (Jindo Bridge) in Korea. The components of the
SHM system are Crossbow’s Imote2s, custom-designed multi-scale
sensor boards, base station computers, and Illinois Toolsuite for SHM
application. 70 sensors and two base station computers have been
deployed to monitor the bridge using an autonomous SHM application
with threshold exceeding events induced by wind and vibration. For
the deployment in situ for long-term monitoring, communication
parameters for the wireless sensor network have been optimized
considering the characteristics of the bridge and the communication
range of the sensors. The performance of the system has been
evaluated in terms of hardware durability, software stability, and power
consumption. 3-D modal properties were extracted from the measured
3-axis vibration data using output-only modal identification methods.
Tension forces of 4 different lengths of stay-cables were derived from
the ambient vibration data on the cables. For the integrity assessment
of the structure, multi-scale subspace system identification method is
One of the primary motivations behind development of the sensor node
is high-resolution monitoring of strain. Each wireless sensor node will
be able to measure strain from 16 different locations on a structure,
by multiplexing these gauges to the same signal conditioning circuit,
which drastically reduces the number of nodes required for monitoring
an area. Data collection can take place at regular intervals, or when
triggered by events of interest. Each sensor node includes sufficient
memory to store a day’s data, although the system default is to
transmit the collected data to the base station once per hour.
104
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Mechanical, and Aerospace Systems
The non-linear behavior of the base isolators is modeled by the
Bouc-Wen model. To simulate the structural damages during the
test, an innovative device, referred to as the stiffness element device
(SED), is proposed to reduce the stiffness of either the upper story of
the structure or the base isolator. Two earthquake excitations have
been used to drive the test model, including the El Centro and Kobe
earthquakes. Various damage scenarios have been simulated and
tested. Measured acceleration response data and the AEKF approach
are used to track the variation of the stiffness during the test. The
tracking results for the stiffness variations correlate well with that of the
referenced values. It is concluded that the AEKF approach is capable of
tracking the variation of structural parameters leading to the detection
of structural damages.
now under development using a neural network technique based on
the local mode shapes and the cable tensions.
7647-07, Session 2a
Issues of signal strength of wireless sensors
for civil infrastructure monitoring
L. S. Bryson, T. J. Lutz, A. Barnes, Univ. of Kentucky (United
States)
Research was conducted using simulated civil infrastructure system
conditions to evaluate issues pertaining to signal strength. This
research evaluated the performance of the wireless MICA2 sensor
motes developed by Crossbow Technology, Inc. The data collected is
intended to demonstrate how the motes would perform in a typical civil
infrastructure application when placed in a large network of sensors.
Specific to signal strength, the strength, quality, and reliability of the
signal originating from remote sensor was assessed as a function of its
distance from the Gateway Sensor. These experiments encompassed
several factors that relate to signal strength and distance such as single
motes, multiple motes, single hop, and multi-hop. Experimentation
was also performed to evaluate the mote performance for buried
applications. The results of the experimentation show that in all cases
the quality, reliability and strength of the transmitting signal is a function
the distance of the Gateway Sensor from the obstruction and the
amount of signal scattering caused by the material surrounding the
mote.
7647-09, Session 2b
Applications of a structural damage
detection method to experimental results
R. Li, L. Zhou, Nanjing Univ. of Aeronautics and Astronautics
(China); J. N. Yang, Univ. of California, Irvine (United States); Q. Yin,
Nanjing Univ. of Aeronautics and Astronautics (China)
An objective of structural health monitoring systems is to identify
the state of the structure and to detect the damage when it occurs.
Analysis techniques for damage identification of struc-tures, based
on vibration data measured from sensors, have received considerable
attention. Re-cently, new time-domain damage tracking approaches
have been proposed in the literature; how-ever, little experimental
tests were conducted for the verification purposes. To detect the local
structural damages quantitatively, such as the degradation of the
stiffness of an element, a finite-element formulation is required, which
results in a large number of degree-of-freedoms (DOFs) system and
thus requires a large number of sensor measurements. For practical
applications, it is highly desirable to install as few vibration sensors as
possible. Likewise, some vibration quanti-ties are difficult to measure,
such as the rotational acceleration at a nodal point. To reduce the
re-quired number of sensors, a method of reduced order system for
the finite-element formulation is presented. In this paper, the adaptive
damage tracking technique for structures recently proposed, referred to
as the adaptive quadratic sum-square error (AQSSE), and a reducedorder finite-element approach are used to identify the local damages of
structures. Experimental tests were conducted to verify the capability
of the proposed approach. A series of experimental tests were
performed using a scaled cantilever beams subject to different types
of excitations, including the white noise and sinusoidal excitations.
Based on the measured vertical acceleration data (without rotational
response measurements) using only a limited number of sensors, the
stiffness for all elements of the beam were identified. It is demonstrated
experimentally that: (i) the proposed fi-nite-element based adaptive
quadratic sum-square error approach is capable of detecting the
structural damages using only a limited number of sensors, and (ii) the
identification results for the stiffness of all finite-elements of the beam
are quite accurate.
7647-08, Session 2b
An experimental study on AEKF method
for damage detection of base-isolated
structures
Q. Yin, L. Zhou, Nanjing Univ. of Aeronautics and Astronautics
(China); J. N. Yang, Univ. of California, Irvine (United States)
An objective of a structural health monitoring system is to identify the
state of the structure and to detect the damage when it occurs. In this
regard, analysis techniques for damage identification of structures,
based on vibration data measured from sensors, have received
considerable attention. Various approaches for system identification
and damage detection have been proposed in the literature, including
literature reviews and structural health monitoring (SHM) benchmark
problems. When a structural element is damaged, such as cracking,
the stiffness of the damaged element is reduced. Hence, the structural
damage may be reflected by the changes of parametric values of
the damaged element. During a severe dynamic event, such as a
strong earthquake, a structure may be damaged, and the damage
events or the reductions of the stiffness of damaged elements will
be contained in measured vibration data. To identify the structural
damages using vibration data that contain damage events, system
identification techniques in time domain have been developed for
nonlinear and/or multi-degree-of freedom (MDOF) structural systems.
On the other hand, many civil engineering structures exhibit hysteretic
behavior when subject to severe dynamic loads, such as strong
earthquakes and sea waves. Hence, the modeling and identification of
nonlinear hysteretic systems are important for the damage detection
of structures. Recently, a new adaptive tracking technique, based
on the extended Kalman filter approach, has been proposed for the
damage identification and tracking of structures. Simulation and
experimental studies for linear structures have demonstrated that the
adaptive extended Kalman filter (AEKF) approach is capable of tracking
the variations of structural parameters, such as the degradation of
stiffness, due to damages.
7647-10, Session 2b
Coupling coefficient analysis in damage
detection using magnetic impedance
approach
X. Wang, J. Tang, Univ. of Connecticut (United States)
Impedance method has been explored for damage detection and
identification. Since the impedance information may be measured
at relatively high frequency range, it has been recognized that the
impedance method is sensitive to small-sized damage. Recently, the
magnetic transducer is introduced into the impedance approach.
Since it can be hung above the mechanical structure and move in
the horizontal plane, the magnetic transducer based impedance
approach may have many potential applications in online health
monitoring systems for structure with complex geometry. One
In this paper, an experimental study is conducted and presented to
verify the capability of the adaptive extended Kalman filter (AEKF)
approach for identifying and tracking the damages in nonlinear
structures. A base-isolated building model, consisting of a scaled
shear-beam type building model mounted on a rubber-bearing
isolation system, has been tested experimentally in the laboratory.
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Conf. 7647: Sensors and Smart Structures Technologies for Civil,
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crack development were quantified. It was shown that fatigue crack
detection and monitoring using both the low frequency guided waves
and higher frequency Rayleigh-like waves is possible. The sensitivity
and repeatability of the measurements were ascertained, having the
potential for fatigue crack growth monitoring at critical and difficult to
access fastener locations from a stand-off distance. Good agreement
was observed between the experimental results and predictions from
full three-dimensional numerical simulations of the scattering of the
ultrasonic wave at the fastener hole and crack. The robustness of the
methodology for practical in-situ ultrasonic monitoring of fatigue crack
growth was discussed.
important implementation issue is the weak magneto-mechanical
coupling between the transducer and the structure. Compared with
the impedance approach using piezoelectric transducer, the magnetic
impedance approach may be less sensitive to the damage induced
change of structural properties. In order to provide guidelines for
enhancing the coupling between the magnetic transducer and the
structure, the analytical model of magneto-mechanical coupling
coefficient is formulated in this research. Based on this model, it is
found that the coupling coefficient is closely related to the design
parameters of the transducer, such as the voltage excitation frequency
and the distance between the transducer and the top surface of the
structure, etc. The correlated numerical and experimental studies are
used to validate the modeling and analysis of coupling coefficient in
magnetic impedance approach.
7647-13, Session 3a
Embedded EMD algorithm within an FPGAbased design to classify nonlinear SDOF
systems
7647-11, Session 2b
Delamination detection using embedded
BOCDA optical fiber sensor
J. D. Jones, J. Pei, Univ. of Oklahoma (United States); J. P. Wright,
Weidlinger Associates, Inc. (United States); M. P. Tull, Univ. of
Oklahoma (United States)
S. Hasegawa, T. Yari, M. Toyama, K. Nagai, Mitsubishi Heavy
Industries, Ltd. (Japan); Y. Koshioka, RIMCOF (Japan)
Compared with traditional microprocessor-based systems, fast
growing field-programmable gate array (FPGA) technology offers a
more powerful, efficient and flexible hardware platform. An FPGA and
microprocessor (i.e., hardware and software) co-design is developed
to classify three types of nonlinearities (including linear, hardening and
softening) of a single-degree-of-freedom (SDOF) system subjected to
free vibration. This significantly advances the team’s previous work on
using FPGAs for wireless structural health monitoring.
Delamination is the most critical damage of the carbon fiber reinforced
plastics (CFRP), because such damages reduce its strength and
stiffness. In the aircraft structures, detecting such damage during
operation is very important issue. On the other hand, optical fiber
sensing technology has developed significantly. Especially, the Brillouin
optical correlation domain analysis (BOCDA) technology has been
enhanced its measuring capability. The BOCDA technology has the
unique characteristics; these are fully distributed strain measuring, and
dynamic strain measuring at arbitrary points along the optical fiber
sensor with high spatial resolution.
The classification is achieved by embedding two important
algorithms - empirical mode decomposition (EMD) and backbone
curve technique. With its implementation in both the FPGA and
microprocessor, numerous design considerations to embed EMD
are discussed. In particular, the implementation of cubic spline fitting
and the encountered challenges using both hardware and software
environments are discussed. The backbone curve technique is
fully implemented within the FPGA hardware and used to extract
instantaneous characteristics from the uniformly distributed data sets
produced by the EMD algorithm as presented in a precious SPIE
conference by the team. An off-the-shelf high-level abstraction tool
along with the MATLAB/Simulink environment is utilized to manage the
overall FPGA and microprocessor co-design.
In these surroundings, we conducted the feasibility study to detect
the delamination using the BOCDA measuring system. Firstly, we
selected the optical fiber sensor type to fit embedding into composite
structures. Embedding optical fiber sensor into CFRP structure causes
transmission loss of the optical fiber sensor increase, and has a critical
impact on the BOCDA measuring. So, we choose a low bending loss
optical fiber as sensor for the BOCDA method, i.e. hole-assist fiber and
high-delta optical fiber. These low bending loss optical fibers are low
influence than normal optical fiber (such as telecommunication fiber).
Secondly, we induced the artificial delamination damages to CFRP
plate. The BOCDA measuring data, strain distribution and/ or Brillouin
gain spectrum (BGS) shape, changed with artificial delamination
expanding. Therefore the BOCDA measuring system has the ability to
detect delamination damage of the CFRP structures.
Given the limited computational resources with an embedded system,
we strive for a balance between the maximization of computational
efficiency and minimization of resource utilization. The beauty of
this study lies far beyond merely programming existing algorithms
to hardware and software. Among others, extensive and intensive
judgment is exercised involving experiences and insights with these
algorithms, which renders processed instantaneous characteristics of
the signals that are well-suited for wireless transmission.
7647-12, Session 2b
Monitoring of fatigue crack growth using
guided ultrasonic waves
7647-14, Session 3a
B. Masserey, Univ. of Applied Sciences Fribourg (Switzerland); E.
Kostson, P. Fromme, Univ. College London (United Kingdom)
Development of a wireless artificial soil
particle sensor for monitoring particle
movement at soil-structure interfaces
Varying loading conditions of aircraft structures result in stress
concentration at fastener holes, where multi-layered components are
connected, possibly leading to the development of fatigue cracks.
Guided ultrasonic waves propagating along a structure allow in
principle for the efficient non-destructive testing of large plate-like
structures, such as aircraft wings. However, the sensitivity for the
detection of small defects has to be ascertained. This contribution
presents a study of the detection and monitoring of fatigue crack
growth using low-frequency guided ultrasonic waves and higher
frequency Rayleigh-like waves. Two types of structures were used,
single layer aluminum tensile specimens, and multi-layered structures
consisting of two adhesively bonded aluminium plate-strips. Fatigue
experiments were carried out and the sensitivity of the guided wave
modes to monitor fatigue crack growth at a fastener hole during
cyclic loading was investigated. Fatigue crack growth was monitored
optically and the changes in the ultrasonic signal caused by the
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B. Liea, K. J. Loh, Univ. of California, Davis (United States)
The load transfer and shaft capacities of civil infrastructure foundations
(e.g., axially-loaded piles) depend on the soil-structure interface’s
shearing and frictional behaviors. However, cyclic loading can
dramatically deteriorate the shaft resistance of these foundations to
cause catastrophic structural failure. Unfortunately, the mechanics of
soil-structure interactions and interface responses are yet to be fully
understood. In addition, although numerous tethered sensing systems
have been developed for gaining insight on properties of soil-structure
interfaces, the cables required to supply power and communicate with
sensors adversely affect the true soil-structure interaction behavior
during experimental investigations. In this study, a passive wireless
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Conf. 7647: Sensors and Smart Structures Technologies for Civil,
Mechanical, and Aerospace Systems
which is transmitted back to another photodiode located at the data
acquisition unit for diagnosis. The feasibility of the proposed power
and data transmission scheme has been experimentally demonstrated
at a laboratory setup. Since there is no need for a power supply
and a signal generator at the PZT transducer node, a self-sufficient
PZT transducer unit can be realized with little additional electronic
components.
sensor is proposed for measuring the absolute displacement of soils
at soil-structure interfaces. Wireless communications and power
transmission to the sensor is accomplished via electromagnetic
coupling between a portable reader and sensor. Here, the portable
reader is simply a coil antenna connected to an impedance analyzer,
and the sensor circuitry comprises a resistor, inductor (i.e., coil
antenna), and capacitor connected in series or parallel. The absolute
displacement of the embedded sensor can be easily measured by
correlating reader impedance changes with the reader-to-sensor’s
distances. By achieving wireless data acquisition and by designing the
sensor to be of a small form factor that is packaged in an epoxy mold
comparable to the size and shape of neighboring soil particles, the
device can be embedded within soil environments without disrupting
the interface response during cyclic loading. Preliminary experimental
results that characterize the passive wireless sensor’s absolute
displacement measurement performance are presented.
7647-17, Session 3a
Sandwich-Imote2 for wireless sensor
networks in bridge monitoring applications
S. N. Pakzad, L. Cheng, Lehigh Univ. (United States)
MIT Technology Review named wireless sensor networks consisting of
integrated sensing/communication/control devices as one of the ten
technologies that will change the world in the 21st century. Sandwichnode is a concept design to remedy the shortcomings of the previous
generation of integrated sensing/communication/control devices that
have been used for structural health monitoring applications. Based on
the popular Imote2 wireless sensor platform, we design and build such
sandwich nodes, each consisting of two control/communication motes
and a comprehensive sensor board, and enable them to support a
priority-ensured preemptive medium access control (PP-MAC) scheme
to realize a wirelessly preemptive sensing system. The first Imote2
(Imote2-1) is dedicated to providing an accurate and uninterrupted
clock to the ADC and performing digital filtering on the data on the fly
and on-board analysis of the data when it is not sampling; and it also
provides the control channel support for the PP-MAC. The second
Imote2 (Imote2-2) is in communication with the first Imote2 through the
circuitry on the sensor board to exchange command and data; and it is
responsible for communicating data with the network and supporting
the data channel of the PP-MAC. The new design may be applied to
a wirelessly preemptive sensing system for quasi-realtime earthquake
monitoring of bridges and traffic overload.
7647-15, Session 3a
Development of smart sensing system for
structural health monitoring
C. Loh, K. Lu, National Taiwan Univ. (Taiwan)
The objective of this paper is to upgrade a wireless sensing unit
which can meet the following requirements: 1) Improvement of
system powering and analog signal processing 2) Enhancement of
signal resolution and provide reliable wireless communication data, 3)
Synchronization on collecting of distributed data, 4) Enhance capability
for continuous long-term monitoring. Based on the prototype of
the wireless sensing unit developed by Prof. Lynch at the Stanford
University, the following upgrading steps are summarized:
1. Increasing the capacity of power and considering the powering of
sensor,
2. Reduce system noise by using SMD passive elements and
preventing the coupling digital and analog circuits,
3. Improve the ADC sampling resolution and accuracy with a higher
resolution Analog-to-Digital Converter (ADC): a 24bits ADC with
programmable gain amplifier.
7647-18, Session 3a
4. Improve wireless communication by using the wireless radio 9XTend
which supported with the router (Digi MESH) communication function
using 900MHz frequency band.
Embedded model updating and load
characterization of wind turbines using
wireless sensor networks
Based on the upgrade wireless sensing unit, verification of the new
wireless sensing unit was conducted from the ambient vibration
survey of an arch dam. This new upgrade wireless sensing unit can
provide more reliable data communication for continuous structural
health monitoring. Incorporated with the modified stochastic subspace
identification method the smart sensing system is developed.
R. A. Swartz, A. Zimmerman, J. P. Lynch, Univ. of Michigan (United
States)
The continued development of renewable energy resources is vital in
the current struggle to achieve sustainability and independence for our
nation’s energy production. Key to that effort are reliable generators
for sustainable energy sources that are economically competitive
with legacy (fossil fuel) sources. In the area of wind energy, a major
contributor to the cost of implementation is large uncertainty regarding
the condition of wind turbines in the field due to lack of information
about loading, dynamic response, and fatigue life of the structure
expended. Under favorable circumstances, this uncertainty leads
to overly conservative designs and maintenance schedules. Under
unfavorable circumstances, it leads to inadequate maintenance
schedules, damage to electrical systems, or even structural failure.
Low-cost wireless sensors can provide more certainty for stakeholders
by measuring the dynamic response of the structure to loading,
estimating the fatigue state of the structure, and even extracting
loading information from the structural response without the need of
an upwind instrumentation tower. This study presents a method for
using wireless sensor networks to estimate the spectral properties
of the loading that a wind turbine tower is exposed to based on its
measured response and some rudimentary knowledge of its structure.
Exact structural parameters are estimated via model-updating in the
frequency domain to produce an identification of the system. The
updated structural model and the measured output spectra are then
used to estimate the input spectra. Laboratory and field validation
results are presented.
7647-16, Session 3a
Development of a wireless power
transmission system for guided wave
generation and sensing via a laser
H. Park, H. Sohn, C. Yun, Korea Advanced Institute of Science
and Technology (Korea, Republic of); J. Chung, CyTroniq Co., Ltd.
(Korea, Republic of)
Guided waves based nondestructive testing (NDT) techniques
have attracted many researchers’ attentions for structural health
monitoring due to their relative long sensing range. These guided
waves in a structure can be generated and sensed by a variety of
techniques. This study proposes a new wireless scheme for PZT
excitation and sensing, where power as well as measured data can
be transmitted via laser. First, a generated waveform modulated by
a laser is wirelessly transmitted to a photodiode connected to a PZT
on the structures. Then, the photodiode converts the light into an
electrical signal and excites the PZT and the structure. The reflected
response signal received at the same PZT is re-converted into a laser,
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Conf. 7647: Sensors and Smart Structures Technologies for Civil,
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7647-19, Session 3a
7647-21, Session 3b
Wireless sensors for permanent monitoring
of heritage buildings
Noise reduction and analysis of two
time-based multi-output modal analysis
techniques
D. Zonta, M. Pozzi, H. Wu, Univ. degli Studi di Trento (Italy); M.
Ceriotti, Fondazione Bruno Kessler (Italy); P. Zanon, G. P. Picco, S.
V. Guna, Univ. degli Studi di Trento (Italy); A. L. Murphy, Fondazione
Bruno Kessler (Italy); L. Mottola, SICS (Sweden); M. Corrà, Tretec
S.r.l. (Italy)
K. X. D’Souza, B. I. Epureanu, Univ. of Michigan (United States)
Modal analysis is a well developed field with many applications. In
particular, forced response multi-output approaches are particularly
well suited for online damage detection because they use the natural
excitations the system undergoes during its normal operation. In
this work, two of these approaches, SOD and DSPI, are analyzed
and compared. SOD was originally developed as a tool for detecting
damage in chaotic dynamical systems. Recently it has been used as
a time-based multi-output modal analysis approach. SOD has been
demonstrated to work for the free vibration case and for random
excitations. DSPI was developed as a time-based multi-input multioutput approach. When the inputs are not measured, DSPI is very
similar to SOD and can handle both free vibrations and random
excitations. However, if the inputs are measured or known DSPI
can also handle arbitrary excitations. In addition to comparing and
analyzing these two methods, noise filtering algorithms are introduced
for both methods to improve upon the methods when using noisy
data. Numerical simulations are carried out on a variety of systems to
compare the methods and to show the effectiveness of the filtering
algorithms in improving frequency and mode shape extraction.
We report the outcomes of one year operation of a permanent
monitoring system based on wireless sensors deployed on a 31
meter-tall medieval tower located in the city of Trento. What makes
this monument worthy of attention is the “Cycle of the Months”, a set
of frescoes decorating the room on the second floor, that remarkably
represent one of most important International Gothic works in Europe.
The sensors and power system were specifically selected and
deployed to record expected structural response and environmental
effects, and to operate unsupervised for a period of one year and more.
Strain sensors include prototypes of new fiber-optics gauges in view
of their long-term stability and durability. Customized hardware deals
efficiently with high-volume vibration data. Dedicated software services
provide: i) data collection, to efficiently reconcile the diverse data rates
and reliability needs of heterogeneous sensors; ii) data dissemination,
to spread configuration changes, enabling remote tasking; iii) time
synchronization, with low memory demands. System operation
requires techniques for processing the large amount of data acquired
to develop information on the risks to the structure. The general
approach used for identifying damage is based on Bayes’ principle.
This methodology allows us to deal flexibly with all the uncertainties
involved in the problem: measurement noise, uncertainness on the
model and inaccurate prior information. In the specific case, the result
of the simulated day by day risk analysis shows that the identification
algorithm can highlight a hazardous condition many days in advance
with respect to the actual occurrence of damage.
7647-22, Session 3b
An active vibration control system for
spacecraft in launch vehicles
A. Shah, B. Chen, O. Abdelkhalik, Michigan Technological Univ.
(United States)
Launch vehicle vibrations’ impact on the payload continues to be a
major concern for the Launch vehicle providers as well as spacecraft
manufacturers. To control these unwanted vibrations, active vibration
control is studied. Active vibration control systems are closed-loop
control systems and mainly based on piezoelectric transducers.
Currently, the most common active vibration control systems use data
acquisition boards such as dSPACE, which is connected to a PC.
The large size and weight of such control systems would not make it
effective for a spacecraft launch vehicle. We propose to employ an
embedded computer with an integrated sensing and actuation control
board for active vibration control in spacecraft launch vehicles.
7647-20, Session 3b
* Design of a mobile gait monitoring system
and its experimental results
J. Bae, K. Kong, M. Tomizuka, Univ. of California, Berkeley (United
States)
Currently, rehabilitation treatments for gait disorders are performed
by physical therapists in a clinical setting. Although an array of
equipment, such as motion capture devices and multi-directional
force plates, has been devised to provide the physical therapists
with more objective diagnostic data, restriction of the time and space
limits the effective use of such devices. To overcome this limitation,
various wearable sensors for patients to directly monitor their health
conditions anywhere at anytime have been studied in recent years. We
have proposed a monitoring system for this purpose, which includes
smart shoes. The smart shoes measure the ground contact forces by
air-pressure sensors connected to air-bladders embedded in shoes.
The sensing performance (e.g., linearity and accuracy) and practicality
(e.g., durability) of the smart shoes have been verified in a laboratory
environment. In this paper, a mobile gait monitoring system (MGMS)
is introduced, which integrates the smart shoes and the monitoring
algorithms in a mobile microprocessor. The mobility of the MGMS
allows patients to take advantage of the gait monitoring device in
their daily lives. The monitoring algorithms embedded in the MGMS
observe various physical quantities useful for objective gait diagnoses,
such as the gait phases, the center of ground contact forces, and the
deviation of ground contact forces from a standard pattern. By the
visual feedback information displayed on the LCD screen, the patients
can self correct their walking patterns. The preliminary results of clinical
verification are also given.
Finite element analysis was used to find the modal frequencies and
the modal shapes of the cantilever beam. The optimal placement
locations for the piezoelectric sensor and actuator were found by
comparing where the mode shape and its derivative had the same
trend. It was also necessary to view where the areas of zero strain
were located; this was found by taking the second derivative of the
mode shapes. If an actuator is place where an area of zero strain is
located the force produced by the actuator will be decreased. To meet
the two conditions, the actuator was placed near the fixed end of the
cantilever beam. A cantilever beam with a shaker was set up for the
experimentation study. The cantilever beam had a piezoelectric sensor
and actuator bonded on the beam to control the vibrations.
7647-23, Session 3b
* Fast estimation of bifurcation conditions
using noisy response data
S. W. Shaw, N. J. Miller, M. I. Dykman, Michigan State Univ. (United
States); K. L. Turner, Univ. of California, Santa Barbara (United
States)
Dynamic bifurcations often correspond to dramatic changes in system
response that can be utilized for sensing purposes. This is conveniently
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applicable in micro- and nano-scale resonators that are subjected
to harmonic excitation. Of interest here is the case of parametric
resonance, in which the system response is essentially at the noise
floor, except in a resonance zone that occurs at nearly twice the device
natural frequency. These subharmonic resonance bifurcations are
currently being developed for use in MEMS mass sensors and rate
gyros. Depending on the level of noise present and the sweep rate,
the response jump can be premature or delayed relative to the actual
bifurcation point. A fundamental issue that must be addressed is the
determination of the bifurcation parameter condition from a collection
of response jump parameter values, obtained from parameter sweeps.
The purpose of the proposed work is to provide a quantitative estimate,
and confidence information, for the bifurcation parameter value from
this data. We use tools from stochastic nonlinear dynamical systems
to examine this problem in terms of noise-activated escape from a
diminishing potential, and we attack the general problem by solving
a Fokker-Plank equation for the escape problem with a parameter
sweeping through the bifurcation. It is shown that nonadiabatic
sweeping can provide more accurate and faster measurements than
adiabatic (quasi-static) sweeping, and an optimal sweep strategy is
derived. The theory is applied to a model and experimental data for a
parametrically forced microbeam.
also enables the microcontroller to perform system identification
and monitor the mechanical eigenfrequencies of the structure. This
information is subsequently used for updating the parameters of the
algorithm mimicking the inductor-resistor shunt. The performance of
the electronic circuit is evaluated on a homogeneous rectangular glass
plate with a C-F-C-F boundary condition, i.e. two opposite edges either
clamped or free. The plate is equipped with a piezoelectric patch which
is placed in the center of the plate to influence damping of the 1-n plate
eigenmodes with n being an odd number. Excitation of the plate is
achieved by an acoustic source and plate vibrations are recorded with
a Laser scanning Doppler vibrometer. Simulation and experimental data
along with analyses on the adaptation of the software parameters with
respect to variations in the mechanical eigenfrequencies are presented.
7647-27, Session 4a
Integrated PZT/FBG guided wave generation
and sensing system using a single laser
source
H. Lee, H. P. Park, H. Sohn, Korea Advanced Institute of Science
and Technology (Korea, Republic of); I. Kwon, Korea Research
Institute of Standards and Science (Korea, Republic of)
7647-24, Session 3b
One of the key factors limiting the application of miniature directional
microphones is the noise. In this article, a theoretical investigation is
conducted to compare the three approaches to construct a directional
microphone, including a conventional microphone pair, a pressure
gradient (first-order) microphone combined with a pressure sensor,
and a mechanically coupled directional microphone inspired by the
superacute ear of the parasitoid fly Ormia ochracea. Given the same
detection method to measure the diaphragm deflection and same
noise floor, it is found out that the mechanically coupled design can
achieve much higher resolution than the other two methods. Numerical
simulation also demonstrates that this bio-inspired design is able to
accommodate much lower signal-to-noise ratio in the incident acoustic
signals. This work provides an indirect evidence explaining how the fly
ear achieves directional sensitivity comparable to the human ears while
it has sub-millimeter interaural separation and much fewer number
of neuron cells. It also serves as a theoretical support for applying
the fly ear mechanism to the development of miniature directional
microphones.
Guided waves based structural health monitoring (SHM) techniques
have been of great concern to many researchers. Among various
kinds of SHM devices, lead zirconate titanates (PZTs) and fiber Bragg
gratings (FBGs) have been widely used for guided wave generation
and sensing. To utilize their merits, integration of PZT-based actuation
and FBG-based sensing has been developed by many researchers.
This integrated PZT/FBG system is widely known as a technique
that enables the decoupling of actuation and sensing channels to
prevent electromagnetic interference (EMI). For wide application of
this technique, this study proposes an integrated PZT/FBG system
using a single laser source. Since this system is based on optic
devices such as a tunable laser and fiber optics, it is possible to
avoid technical problems regarding the electrical power cablings
such as complicated cabling setups, and power attenuations. Also,
simultaneous measurement of multiple parameters is possible by
using FBG sensors which are good for multiplexing. The experimental
procedure for the proposed system is as follows. First, a tunable laser
is used as the common power source for guided wave generation and
sensing. Then, one laser beam is modulated and amplified to actuate
the PZT. The other laser beam is used with the FBG sensor to measure
high-speed strain changes induced by guided waves. The feasibility
of the proposed technique has been experimentally demonstrated
using an aluminum plate. The results show that the proposed system
could properly generate and sense the guided waves compared to the
conventional methods.
7647-25, Session 3b
7647-28, Session 4a
Adaptive damping of piezoelastic structures
via digital implementation of inductorresistor shunts
Laser induced highly nonlinear solitary
waves for structural NDE
* A new approach to tackle noise issue in
miniature directional microphones: bioinspired mechanical coupling
H. Liu, M. Yu, Univ. of Maryland, College Park (United States)
X. Ni, R. Garden, P. Rizzo, Univ. of Pittsburgh (United States); C.
Daraio, California Institue of Technology (United States)
T. Rittenschober, J. Korak, A. Dantele, Profactor
Produktionsforschungs GmbH (Austria)
This paper describes the generation and detection of highly nonlinear
solitary waves (HNSWs) in a chain of steel beads excited by using laser
pulses. Ablative generation of mechanical stress was induced on the
bead at one end of the chain in order to enhance the amplitude of the
stress waves generated. Compared to the use of a mechanical striker,
the laser-based generation of stress waves is fully non-contact and
allows for the broadest energy spectrum. In this study the amplitude,
duration, and velocity of the solitary waves propagating along the
chain of beads as a function of the laser pulse energy is investigated.
Moreover the effect of chain pre-compression induced by means of an
electromagnet is presented and discussed. Finally the application of
HNSW as a pulse generator for the NDE of bulk structures is shown.
This contribution is concerned with adaptive damping of plate-like
structures equipped with a piezoelectric patch. It is well known in the
literature that damping of mechanical modes can be accomplished
by connecting an electrical impedance, e.g. an inductor-resistor
shunt, at the terminals of the piezoelectric patch. The electrical circuit,
however, needs to be tuned quite exactly to achieve good damping
performance around the desired mechanical eigenfrequency. Also,
mechanical structures are exposed to varying environmental conditions
which lead to a non-negligible shift in mechanical eigenfrequencies
and de-tuning of the resonant circuit. The authors, hence, propose
the algorithmic implementation of the electrical behavior of the
inductor-resistor shunt on a microcontroller. The digital approach
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pollution. The biggest challenge for developing this type of sensors is
that the sensors have to sustain at extreme environments in turbine
engines, such as high-temperatures (> 800oC) and oxidation/corrosion
surroundings. In this paper, we describe a certain class of sensors
made of polymer-derived ceramics (PDCs) for such applications. PDCs
have the following advantages over conventional ceramics, making
them particularly suitable for these applications: (i) micromachining
capability, (ii) tunable electric properties, and (iii) high-temperature
capability. Here, we will discuss the materials and their properties in
terms of their applications for high-temperature micro-sensors. In
addition, we will also discuss two types of micro-sensors: (i) heat-flux
sensor and (ii) pressure sensor, which are made from polymer-derived
ceramics.
7647-192, Session 4a
Magnetic Nanoparticle (MNP) enhanced
biosensing by Surface Plasmon Resonance
(SPR) for portable devices
J. L. Wang, Z. Z. Zhu, A. Munir, S. H. Zhou, Worcester Polytechnic
Institute (United States)
The use of magnetic nanparticles in microfluidic systems is emerging
and is receiving growing attention due to the synergistic advantages
of microfluidics and magnetic nanoparticles. Biomagnetic separation
techniques based on magnetic nanoparticles are becoming increasingly
important with a wide range of possible applications. However, the
separation products are difficult to be detected by general method
due to the small size of MNPs. Here, we demonstrate magnetic
nanoparticles can greatly enhance the signal of surface plasmon
resonance spectroscopy (SPR). Features of MNPs-aptamer conjugates
as a powerful amplification reagent for ultrasensitive immunoassay are
explored for the first time. Our results confirm that MNPs is a powerful
sandwich element and an excellent amplification reagent for SPR
based sandwich immunoassay and SPR has a great potential for the
detection of magnetic nanoparticles-based separation products.
7647-32, Session 4b
* Non-contact torque measurement using
rolled single crystal-like Galfenol patches
D. Douglas, S. Na, A. B. Flatau, Univ. of Maryland, College Park
(United States)
Galfenol is an iron-gallium alloy that exhibits magnetostrictive behavior
up to approximately 400ppm. It has been shown that Galfenol exhibits
a linear response in strain that follows commercially available strain
gauges when a magnetic bias field is placed near the Galfenol patch
in a bending test. In this study we extend these results to use of a
Galfenol patch for measuring torque. The benefits of Galfenol-based
torque sensors over existing strain sensors for measuring torque
are (1) the potential for use of stray magnetic fields for non-contact
torque measurement; (2) ease of integration and/or retrofit of the
proposed torque measuring capability into existing hardware; and (3)
an inexpensive yet mechanically robust alternative to torque sensors
that require slip rings or wireless signal transmission. This Research will
show that when placed on a circular shaft at ± 45o relative to the shaft
axis Galfenol will exhibit a linear response to shear strain on the shaft.
By showing that measurement of shear strain is possible it is evident
that the torque on the shaft can also be determined. A hall sensor will
be rigidly attached to a non-rotating component of the measurement
frame supporting the shaft, and used to determine the change in the
magnetic field above the patch. While the shaft is rotating the response
from the hall sensor is monitored to determine the torque load on the
shaft.
7647-30, Session 4b
Optical fiber sensors for high temperature
harsh environment applications
T. Wei, X. Lan, Y. Zhang, H. Duan, H. Xiao, Missouri Univ. of
Science and Technology (United States)
Sensors for harsh and extreme environments demand non-reduced
accuracy and supreme robustness. Optical fiber sensors (OFS), with
their all glass nature, small size, corrosion resistance, electromagnetic
immunity, and high resolution, are considered a promising candidate for
various sensing applications in high temperature hash environments.
This paper summarizes our recent research progresses in developing
various harsh environment sensors for various engineering applications.
High-temperature tolerant long period fiber gratings (LPFG) and
core-cladding mode interferometers (CCMI) were developed to
monitor and assess the structural condition of critical buildings in an
earthquake-induced fire environment. Both sensors were fabricated
by controlled CO2 laser irradiations for operation in high temperature
environments. Their axial strain measurement properties were studied
at high temperatures (up to 700ºC). Investigations have also been
conducted to use these sensors for simultaneous temperature and
strain measurements.
7647-33, Session 5a
* Smart pavement sensor based on
thermoelectricity power
Fiber inline Fabry-Perot interferometers (FIFPI) were fabricated
by femtosecond (fs) laser micromachining for temperature, strain
and dynamic pressure measurements in high temperature harsh
environments. The sensor had a high-quality interference fringe and
survived temperatures upto 1100 C. A diaphragm based FIFPI sensor
was designed and fabricated for in situ monitoring of the dynamic
pressures inside an auto-ignited combustion engine. The sensor probe
was packaged and tested inside an engine operating at a temperature
around 800ºC. The sensitivity and frequency response were evaluated
experimentally. Structural parameters of the FIFPI sensor such as the
diagram diameter and thickness were investigated to optimize the
sensor performance.
X. Yu, Case Western Reserve Univ. (United States)
The aging infrastructure requires a proactive strategy to ensure their
functionality and performance. Innovative sensors are needed to
develop infrastructures that are intelligent and adaptive. A power
supply strategy is among the crucial components to reduce the
instrument cost and to ensure the long term function of these
embedded sensors. This paper introduces the results of a preliminary
study on using thermo-electricity generation to power sensors. This
presents an innovative strategy for long term monitoring of pavement
performance.
7647-31, Session 4b
7647-34, Session 5a
* Micro-machinable polymer-derived
ceramics sensors for high-temperature
applications
Experimental investigation of a smart FRPconcrete composite bridge superstructure
Y. Wang, Dalian Univ. of Technology (China); Q. Hao, Harbin
Institute of Technology (China); J. Ou, Dalian Univ. of Technology
(China)
J. Liu, C. Xu, L. An, Univ. of Central Florida (United States)
Micro-sensors are highly needed for on-line temperature/pressure
monitoring in turbine engines to improve their efficiency and reduce
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superstructure is a type of newly developed structure. It behaves
brittle failure at its peak strength, and so the health monitoring of the
FRP part is essential for the life-cycle safety of the structure. Optical
fiber Bragg grating (FBG) sensor is broadly accepted as a structural
health monitoring device for FRP materials by either embedding into
or bonding onto the structures. Herein, a new kind of smart FRPconcrete composite bridge superstructure, which consists of FRP box
sections combined with a thin layer of concrete in the compression
zone, was developed by using eight embedded FBG sensors in the
top and bottom flanges of FRP box sections at mid-span section along
longitudinal direction, respectively. Fabrication process of the proposed
smart FRP-concrete composite bridge superstructure was introduced.
The flexural behavior of the smart composite bridge superstructure was
experimentally studied in 4-points loading. The longitudinal strains of
the FRP box sections were recorded using the embedded FBG sensors
as well as the surface-bonded electric resistance strain gauges.
Test results indicate that the FBG sensors can faithfully record the
longitudinal strain of the FRP box sections in tension at bottom flange
or in compression at top flange, as compared with the surface-bonded
strain gauges. The proposed smart FRP-concrete composite bridge
superstructure can reveal its true internal strain over the entire load
range, and will have wide applications for long-term monitoring in civil
engineering.
nickel particles can induce field emission and tunneling effects, which
leads to highly sensitive responses to compressive stress/strain.
A constitutive model relating the change in the electrical resistivity
to the applied compressive stress of cement-based composites
containing nickel powders with needle-like surfaces is also developed.
This model incorporates the field emission effect and the inter-particle
separation change of nickel powders in composites within elastic
regime under uniaxial compression. The model is used to predict the
piezoresistive characteristic behavior of cement-based composites
containing nickel powders with different particle sizes. The predicted
results are compared with the experimental data obtained on three
kinds of composites, and good agreements are obtained.
7647-37, Session 5b
Multifunctional sensor network for structural
state sensing
X. P. Qing, R. Ikegami, S. J. Beard, D. Zhang, S. Das, S. Banerjee,
Acellent Technologies, Inc. (United States)
In order to take full advantages of composites and enable future
composite structures to operate at their physical limits rather than
limits predetermined from computational design assumptions and
safety factors, there is a need to develop an embeddable sensing
system to allow a structure to “feel” and “think” its structural state.
In the paper, the concept of multi-modal sensing capabilities using
a network of multifunctional sensors integrated with a structure in
developed. Utilizing this revolutionary concept, future structures
can be designed and manufactured to provide multiple modes of
information that when synthesized together can provide capabilities for
intelligent sensing, environmental adaptation and multi-functionality.
To demonstrate the feasibility of multi-modal sensing capabilities with
built-in sensor network, one single type of piezoelectric sensor was
selected to perform the measurements of dynamic strain, temperature,
damage detection and impact monitoring. The uniqueness of the
sensing system includes (1) Ultra-thin film, flexible, multifunctional
sensor networks for integration with any type of unitized composite
structural component, (2) Scalable sensor network for monitoring of a
large composite structure, (3) Reduced number of connecting wires for
sensors, (4) Hybrid diagnostics with multiple sensing capabilities, (5)
Sensor network self-diagnostics and self-repair for damaged sensor
system.
7647-35, Session 5a
Foot angle determination using conductive
polymer sensors
L. M. Castano, Univ. of Maryland, College Park (United States)
A study was carried to assess the possible monitoring of joint angles,
foot posture and foot motion through the use of conductive polymer
sensors. The sensors are composed of a carbon polymer coating on
an elastic fabric and they present a strain gauge behavior. A hinge
was used as an angle generator and a sensor strip was clamped
longitudinally across the hinge. An electrogoniometer was used to
monitor the angle spanned by the two wings of the hinge. Series of
simultaneous measurements of angle and resistance were conducted
at different speeds. Results indicate that a range of resistance
differentials can be assigned to an angle span regardless of speed. The
amplitude of the Fourier transform of the resistance measurements also
had a defined range for each angle span i.e. 10 to 20, 10 to 40, etc...
degrees. This would imply that the angle span could be determined
at any flexing speed based on resistance measurements, enabling
real time monitoring. Four carbon sensors were then applied on socks
and were placed on different locations of maximum strain on the foot.
Different sets of sensor locations were assessed for a better sensor
response. A correlation was found among the waveforms of the
resistance signals outputted by each of the sensors for different types
of foot motion. This was also characterized by wavelet analysis of each
set of resistance measurements for short periods of time. The smart
socks intend to aid in the gait detection and rehabilitation of patients
with walking disabilities.
7647-38, Session 5b
SMART composite high pressure vessels
with integrated optical fiber sensors
P. Gasior, W. Blazejewski, J. Kaleta, Wroclaw Univ. of Technology
(Poland); A. Czulak, Technische Univ. Dresden (Germany)
In this paper application of integrated Optical Fiber Sensors for strain
state monitoring of composite high pressure vessels is presented.
The composite tanks find broad application in many areas such as:
automotive industry, aeronautics, rescue services, etc. In automotive
application they are mainly used for gaseous fuels storage (like CNG
or compressed Hydrogen). In comparison to standard steel vessels,
composite ones have many advantages (ie. high mechanical strength,
meaningful weight reduction, etc).
7647-36, Session 5a
Smart composite based on field emission
and tunneling effects and its piezoresistive
characteristic model
In the present work a novel technique of vessel manufacturing,
according to this construction, was applied. It is called braiding
technique, and can be used as an alternative for winding method.
During braiding process, between GFRC layers, two types of optical
fiber sensors were installed: point sensors in form of Fiber Bragg
Gratings as well as interferometrical sensors with long measuring arms
(SOFO®). An integrated optical fiber sensors create a nervous system
of the pressure vessel and are used for its structural health monitoring
(SHM). OFS register deformation areas and detect construction
damages in its early stage (ensure a high safety level for users). Applied
sensor system proved also a possibility of strain state monitoring even
during vessel manufacturing process.
B. Han, J. Ou, Harbin Institute of Technology (China)
A highly sensitive piezoresistive inorganic composite fabricated from
cement-matrix and nickel powders is reported. The electrical resistivity
of such composite decreases 69.00% under uniaxial compression
(the electrical resistivity decreases 62.61% within the elastic regime).
The sensitivities of this composite to compressive stress and strain
are higher than 0.05/MPa and 895.45 respectively. These extremely
high piezoresistive properties are attributed to the unique needle-like
surface morphology of nickel powers. Comparing to the normal smooth
spherical nickel particles, the needle-like features of spiky spherical
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A survey of the literature shows the importance and the large number
of applications for sensors. Several applications deal with detecting the
presence of proteins, mercury vapor, etc., using either one or arrays
of cantilever resonator sensors. Recent papers presented an interest
in developing biosensors arrays that are based on micro-fabricated
resonators coated with molecular recognition chemistry. The ultimate
goal was to integrate hundreds of miniature resonators within a single
chip for detection of biological species. Microresonator sensors were
used to detect virus particles, bacteria, gas, and vapor. Mercury vapor
in the air was detected using microsensors coated with a thin gold film.
OFS sensors can be inbuilt in the structure of composite material
without changing its mechanical properties. Moreover, OFS sensors
are spark less and resistant against electromagnetic disturbance.
They have large range of measurements and well collaboration with
other electric systems of cars, enabling tank’s on-line or periodical
monitoring.
7647-40, Session 5b
Magnetostrictive unimorph transducer
network model
7647-41, Session 6a
U. Marschner, Technische Univ. Dresden (Germany); S. Datta, C.
Mudivarthi, Univ. of Maryland, College Park (United States); E.
Starke, G. Pfeifer, W. Fischer, Technische Univ. Dresden (Germany);
A. B. Flatau, Univ. of Maryland, College Park (United States)
Distributed wireless sensor network
for structural health monitoring using
embedded piezoelectric transducers
A new rotational magnetomechanical transducer network model for
a magnetostrictive unimorph is presented. Such a magnetostrictive
unimorph structure reacts with bending to an appropriate directed
magnetic field and can be used as actuator. A forced bending of the
unimorph changes the magnetic properties of the magnetostrictive
layer which is the basis for sensor and energy harvesting applications.
A transducer setup defines often an operating point about which
the mechanical, magnetic and electrical quantities show only small
variations which can be linearized. Taking the component geometries
into consideration a lumped parameter circuit representation of the
magnetomechanical and electromechanical system can be derived.
It is a useful tool for understanding and explaining the behavior of
systems involving different physical domains. It is shown that the
magnetomechanical transduction coefficient in actuation direction,
which is obtained via classical laminated plate theory, holds also for
the sensing relation. The magnetomechanical model can be combined
with electromagnetic coil models to include the electrical domain. The
electromagnetic and the magnetomechanical transducer are connected
by a magnetic voltage divider which takes the spatial magnetic field
distribution into account. The presented models can be used for a
fast analysis of existing systems and also for the optimization of new
designs. The resulting circuit description can be simplified, e.g. to
a single impedance, by transforming network elements into other
domains. Both the actuation and sensing behavior of a laminated
magnetostrictive Al-Galfenol composite are experimentally investigated
and the transduction coefficient is determined.5EYX
P. Li, C. Olmi, G. Song, Univ. of Houston (United States)
Piezoceramic based transducers are widely researched and used for
structural health monitoring (SHM) systems due to the piezoceramic
material’s inherent advantages of dual sensing and actuation ability.
Wireless sensor network (WSN) has the benefit of easy and flexible
installation, low system cost and increased robustness over wired
system. However, piezoceramic based wireless SHM systems still faces
drawback as they require relatively high computational capabilities for
calculating damage information, on the other hand battery powered
WSN sensor nodes have strict power consumption limitation and
hence limit computational power. Although commonly used centralized
processing networks can provide sufficient computational capability,
it requires wireless sensors to transmit all data back to the network
coordinator for analysis, which is neither energy efficient nor robust.
In this paper, we aimed to solve these problems with a distributed
wireless sensor network for piezo-base SHM systems. Instead of
sweep sine excitation that was used in early research, several sine
frequencies were used in sequence to excite the concrete structure.
The wireless sensors record the sine excitations and compute the time
domain energy for each sine frequency locally to detect the energy
change. By comparing the data of the damaged concrete frame with
the healthy data, we are able to find out the damage information. A
relative powerful wireless microcontroller was used to carry out the
distributed data processing in real-time. The distributed wireless
network dramatically reduced the data transmission between wireless
sensor and the wireless coordinator, which in turn reduced the power
consumption of the overall system.
7647-193, Session 5b
On electrostatically actuated microsensors
7647-42, Session 6a
D. Caruntu, The Univ. of Texas-Pan American (United States); M.
Knecht, Univ. of Texas-Pan American (United States)
The combined use of low-cost smart
sensors and high accuracy sensors to
apprehend structural dynamic behavior
This paper deals with electrostatically actuated mass sensing cantilever
resonators. Nonlinear parametric resonances are present in the system.
The principle of mass detection resonator sensors is the change
in frequency due to mass deposition. Resonator sensitivity used in
this work is defined as the fraction of change in frequency per unit
mass. The hypotheses of this work are: 1) the sensor is a coated with
molecular recognition chemistry Euler-Bernoulli cantilever beam, 2)
the thickness of the deposited film is constant, 3) the thickness of the
deposited film is very small compared to any of the beam dimensions,
4) the deposition occurs on all sensor lateral surfaces, and 5) the film
mass it is small but not negligible compared to the total mass of the
sensor-film system, and 6) the sensor is electrostatically actuated
(nonlinear parametric force).
T. Nagayama, M. Ushita, Y. Fujino, The Univ. of Tokyo (Japan); M.
Ieiri, N. Makihata, JIP Techno Science Corp. (Japan)
Wireless smart sensors equipped with computational and wireless
communication capabilities are expected to provide rich information
for structural health monitoring (SHM); inexpensive nature of
sensors nodes and wireless communication allows dense sensor
instrumentation over structures. While dense measurement is
advantageous with regard to spatially characterizing structural dynamic
behaviors, limited sensing accuracy of inexpensive wireless sensor
nodes possibly bounds applications. For example, small ambient
vibration may not be captured by smart sensor nodes. Weakly excited
modes may not be well captured. Though the use of better accuracy
sensors might be considered obvious solution, the increase in sensor
node cost abates one of merits of wireless smart sensor usage, i.e.,
inexpensiveness.
Analytical results are obtained by applying the method of multiple
scales directly to the differential equation of motion. The original
boundary value problem results into two simpler boundary value
problems to be solved. The first problem consists of a homogeneous
partial differential equation along with its boundary conditions. The
second problem consists of a nonhomogeneous partial differential
equation and boundary conditions that provides the influence of the
deposited mass on the nonlinear parametric resonance of the sensor.
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This paper proposes a combined use of low-cost smart sensors
and high accuracy sensors for dynamic measurement of a bridge to
alleviate the influence of this limitation. In addition to inexpensive smart
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Conf. 7647: Sensors and Smart Structures Technologies for Civil,
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sensor nodes densely instrumented on structures, a smaller number
of high accuracy sensors are installed. Signals from these two sets of
sensors are analyzed together to take advantage of the dense sensor
arrangement and high accuracy sensors. Numerical simulation shows
the effectiveness of this approach. The use of two sets of data is then
applied to vibration measurement of a full-scale cable-stayed bridge.
This field application demonstrates the potential capability of smart
sensors to capture dynamic behavior of structures in detail.
However, as opposed to wired sensor networks in which centralized
data acquisition and processing are a common practice, the WSSN
requires decentralized approaches due to the limitation associated with
wireless communication; to date implementation of such approaches
in the WSSN are limited. This study presents a decentralized data
aggregation scheme implemented in the WSSN employing Crossbow
Imote2 sensors. Rather than collecting sensor data centrally, the
onboard processing unit is utilized to obtain two commonly used data
in the structural identification: (1) correlation function of the Natural
Excitation Technique and (2) pseudo impulse response function of the
Random Decrement Method. The efficacy of the decentralized data
aggregation scheme in the WSSN is experimentally verified.
7647-43, Session 6a
SHMTools: a new embeddable software for
SHM applications
7647-45, Session 6a
E. B. Flynn, S. Kpotufe, D. Dondi, Univ. of California, San Diego
(United States); E. F. Figueiredo, Los Alamos National Lab.
(United States); T. Mollov, M. D. Todd, T. Simunic Rosing, Univ. of
California, San Diego (United States); S. G. Taylor, G. Park, C. R.
Farrar, Los Alamos National Lab. (United States)
* Validation of a wireless sensor network
using local damage detection algorithm for
beam-column connections
S. N. Pakzad, L. Cheng, Lehigh Univ. (United States)
This paper introduces a new software tool for various structural
health monitoring (SHM) applications. The SHM paradigm has been
cast in the framework of statistical pattern recognition, promoting
data driven damage detection approaches. To reflect this paradigm
in SHM and to allow user-friendly analyses of data, new software,
referred to as “SHMtools” is developed. This software is a set of
standardized modules of MATLAB code covering the four categories
of statistical pattern recognition as applied to SHM: data acquisition,
data normalization, feature extraction, and feature analysis for damage
identification. Input and output parameters are standardized so that
custom SHM processes are easily assembled by merely specifying a
set of functions from each of these modules. The detection algorithms
are an embeddable subset of an open source package designed to
facilitate the assembly of custom SHM processes. The embeddable
subset consists of functions which can be cross-compiled into generic
“C” programs. Embedding the algorithms onto hardware then consists
of compiling the embeddable subset into executables using a “C”
cross-compiler optimized for the targeted hardware. The software is
also designed to accommodate multiple sensing modalities, including
piezoelectric active-sensing, which has been widely used in SHM
practice.
There has been a rapid advancement in wireless sensor network
(WSN) technology in the past decade and its application in structural
monitoring has been the focus of several research projects. The
evaluation of the newly developed hardware platform and software
system is an important aspect of such research efforts. Although much
of this evaluation is done in the lab and using generic signal processing
techniques, it is important to validate the system for its intended
application as well. In this paper the performance of a newly developed
accelerometer sensor board is evaluated by using the data from a
beam-column connection specimen with a local damage detection
algorithm. The sensor board is a part of a wireless node that consists
of the imote2 control/communication unit and an advanced antenna
for improved connectivity. A scaled specimen of a steel beam-column
connection is constructed in ATLSS center at Lehigh University and
densely instrumented by synchronized networked systems of both
traditional piezoelectric and wireless sensors. The column ends of the
test specimen have fixed connections, and the beam cantilevers from
the centerline of the column. The specimen is subjected to harmonic
and white noise excitations in several test runs and its accelerometer
response is collected by both systems. The collected data is then used
to estimate two sets of system influence coefficients with the wired one
as the reference baseline. The performance of the WSN is evaluated
by comparing the quality of the influence coefficients and the rate of
convergence of the estimated parameters.
One of the hardware designed to embed the SHMtools is a custom
wireless embedded system, referred to as SHiMmer. SHiMmer is
a stand-alone platform capable to perform active-sensing SHM
measurement. SHiMmer system comprises three independent
components: a Digital board for data analysis and communications
running a custom Linux-based OS, an Analog board that manages 16
channels connected to piezoelectric sensors for SHM measurements,
and a power manager module.
7647-46, Session 6b
The details of this embeddable software and hardware will be
discussed, along with several example processes that can be used for
guidelines for future use of the proposed technology.
Compact sensitive piezoelectric mass
balance for measurement of unconsolidated
materials in space
7647-44, Session 6a
S. Sherrit, A. Trebi-Ollennu, R. Bonitz, Y. Bar-Cohen, Jet Propulsion
Lab. (United States)
Decentralized data aggregation in wireless
smart sensor network
In many in-situ instruments information about the mass of the sample
could aid in the interpretation of the data and portioning instruments
may require accurate sizing of the mass before dispensing the sample.
In addition, on sample return missions a method to directly assess
the collected sample quantity is required to determine if the sampler
can return or needs to acquire another sample. In an effort to meet
these requirements we have developed piezoelectric balances using
flextensional actuators which are capable of monitoring the addition
of mass using two methods. A piezoelectric balance can be used to
measure mass directly by monitoring the voltage developed across the
piezoelectric which is linear with force or it can be used in resonance
to produce a frequency change proportional to the mass change. If
a small mass is added to the balance the resonance frequency shifts
down proportionally to the mass. By monitoring the frequency shift the
mass can be determined. This approach allows for two independent
measurements of the mass. In microgravity environments spacecraft
S. Sim, B. F. Spencer, Jr., Univ. of Illinois at Urbana-Champaign
(United States)
Wireless Smart Sensor Networks (WSSN) facilitates a new paradigm
to structural identification and monitoring for civil infrastructure.
Conventionally, wired sensors and central data acquisition systems
have been used to characterize the state of the structure, which is quite
challenging due to difficulties in cabling, high equipment cost, and
long setup time. The WSSN offers a unique opportunity to overcome
such difficulties. Recent advances in sensor technology have realized
low-cost, smart sensors with on-board computation and wireless
communication capabilities, making deployment of a dense array
of sensors on large civil structures both feasible and economical.
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Conf. 7647: Sensors and Smart Structures Technologies for Civil,
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spatial resolution sensor including the challenges. Preliminary sensor
designs and test results will be presented in this paper.
thrusters could be used to provide acceleration in order to produce
the required force in the first technique or to bring the mass into
contact with the balance in the second approach. In addition, the
measuring actuators could be driven at higher voltages to fluidize
the powder to aid sample movement. In this paper, we describe our
design considerations and present the results obtained using prototype
balances that we developed.
7647-49, Session 6b
Multipoint fibre optic voltage sensor
Z. Brodzeli, H. K. Bal, F. Sidiroglou, S. F. Collins, Victoria Univ.
(Australia); V. G. Chigrinov, A. Murauski, F. Fan, Hong Kong Univ. of
Science and Technology (Hong Kong, China)
7647-47, Session 6b
* Mechanisms of sliding friction studied with
an array of industrial conical piezoelectric
sensors
In this paper we propose a new approach to fibre optic voltage
sensors via a voltage-controlled Liquid Crystal (LC) cell, which would
allow direct measurement of up to 400 kV/m electric fields at multiple
points along a power line. The voltage applied to the cell is harvested
by probe (antenna) from the electric filed created by high voltage
transmission lines.
G. McLaskey, S. D. Glaser, Univ. of California, Berkeley (United
States)
In this study, we use a new design of high-fidelity nanoseismic sensors
to detect the stress waves produced at the initiation of sliding during
stick-slip friction. The reported experiments are designed to provide
insights that may be applicable to both fault scales and micro contact
junctions. The sensors used are packaged in a hardened steel case
to facilitate their use in the field. The transducer’s small size (15 mm
threaded body, 30 mm long) permits a dense population of sensors
to be installed on laboratory-sized samples, or surrounding localized
centers of damage on structural applications. The piezoelectric sensors
can detect radiated waves just a few pm in amplitude in the frequency
range of 10 kHz to over 2 MHz, and therefore have the ability to identify
load drops down to about 10 mN. The closely spaced sensor array
facilitates the localization of individual load releases from tiny asperities
on a cm-scale frictional interface. At the same time, the broadband
response of the conical piezoelectric sensors makes possible the study
of source dynamics using theory developed for the study of Earthquake
source mechanisms via radiated seismic waves.
7647-50, Session 6b
Study on in-line fiber-optic sensor using
near-infrared spectroscopy
H. Wang, Y. Peng, South China Univ. of Technology (China)
A methodology for monitoring extrusion process using in-line fiberoptic near-infrared spectroscopy is present in this paper. Fiber-optic
sensor and sensing system are also designed. Predictive calibration
models of NIR spectra are developed for monitoring of polymer
composition and concentration by using multiple linear regression
techniques and artificial neural networks. It is important to study
nucleation of microcellular plastics.
7647-51, Session 7a
7647-48, Session 6b
Structural health monitoring for ship
structures using time series models
Direct measurement sensor of the boundary
shear stress in fluid flow
C. R. Farrar, G. Park, M. Anghel, M. Bement, Los Alamos National
Lab. (United States); L. W. Salvino, Naval Surface Warfare Ctr.
Carderock Div. (United States)
M. Badescu, Y. Bar-Cohen, X. Bao, Z. Chang, Jet Propulsion Lab.
(United States); K. Kerenyi, Federal Highway Administration (United
States); S. Lih, S. Sherrit, B. P. Trease, S. Widholm, Jet Propulsion
Lab. (United States)
Currently the Office of Naval Research is supporting the development
of structural health monitoring (SHM) technology for U.S. Navy ship
structures. This application is particularly challenging because of the
physical size of these structures, the widely varying and often extreme
operational and environmental conditions associated with these ships’
missions, lack of data from known damage conditions, limited sensing
that was not designed specifically for SHM, and the management of
the vast amounts of data that can be collected during a mission even
with this limited sensing. This presentation will discuss ship structure
SHM challenges in the context of applying various SHM approaches
to sea trials data measured on an aluminum multi-hull high-speed
ship, the HSV-2 Swift. In particular, linear and nonlinear time series
models are shown to be a very effective tool for modeling the sensors’
response during sea trials, establishing correlation between widely
distributed sensors and identifying anomalous conditions.
The flow fields and boundary erosion that are associated with scour
at bridge piers are very complex. In particular, scour development
is complicated by the important effects of large scale turbulence
structures (macro-turbulence) that markedly characterize pier flow
fields. The role that such turbulence structures play in scour has only
been partially appreciated. It is a role that needs to be very wellunderstood when investigating scour at bridge piers. Turbulence
structures, together with local flow convergence / contractions around
the fronts and flanks of piers, or between piles of complex pier
configurations, are erosive flow mechanisms of primary importance.
The interactions of macro-turbulence structures with converging
flows are of key significance in illuminating how pier geometry affects
sediment entrainment and thereby scour morphology and maximum
scour depth. Direct measurement of the boundary shear stress and
boundary pressure fluctuations in experimental scour research has
always been a challenge and high spatial resolution and fidelity have
been almost impossible. Most researchers have applied an indirect
process to determine shear stress using precise measured velocity
profiles. Laser Doppler Anemometry and Particle Image Velocimetry
are common techniques used to accurately measure velocity profiles.
These methods are based on theoretical assumptions to estimate
boundary shear stress. In addition, available turbulence models
cannot very well account for the effect of bed roughness which
is fundamentally important for any CFD simulation. The authors
have taken on the challenge to advance the level at which direct
measurements of the shear stress in water flow can be performed.
This paper examines the development of a higher accuracy and small
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7647-52, Session 7a
Corrosion monitoring of reinforcing steel in
concrete by electrochemical sensors
G. Qiao, Harbin Institute of Technology (China)
Health degradation by corrosion of steel in civil engineering, especially
in rough environment, is a persistent problem. A novel all solid statecurrent confined corrosion sensor has been developed to provide
the platform for corrosion monitoring of the steel bar in concrete
beam by electrochemical method. Finite element method has been
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used to optimize the geometric configuration of the corrosion sensor.
The numerical results show that the corrosion sensor can effectively
confine the current in the fixed area which is 45mm×π×Dsteel bar.
Then the sensors have been used in the concrete beams to monitor
the corrosion of the steel bar. The monitoring results of the sensors
show that the magnitudes of the corrosion rate of the steel bar are
from 10-7μA/cm2 to 10-5μA/cm2 before and after corrosion. It can be
concluded that the optimized corrosion sensor can confine the excited
current effectively and monitor the corrosion condition of the steel bar
accurately. The multi-point distribution and in-situ corrosion monitoring
can be realized by using the corrosion sensor in the field.
pavement length could be found obviously. The experimental results in
this paper also confirmed that the bar would give good strengthening
in the beam, especially after the steel bar’s yielding, and control the
development of cracks due to the concrete shrinkage well. All the
results confirm that this new self-sensing BFRP bar will show not only
good sensing performance but also mechanical performance in the
concrete structures.
7647-55, Session 7a
Coordinated sensing and autonomous repair
of pressure vessels and structures
7647-53, Session 7a
D. R. Huston, D. H. Hurley, K. Gollins, A. Gervais, The Univ. of
Vermont (United States)
Prestress-force monitoring of PSC girder
bridges using wireless impedance sensor
nodes
This paper discusses coordinated sensing and autonomous self-repair
of structural systems. The underlying principle of autonomous repair
techniques is to embed redundant capability into the structural system
and to then use the redundant capability to repair and carry the load
of the damaged components. Self-healing materials in the form of
self-sealing fluid containment vessels have been used in man-made
structures for millennia. Engineered self-healing materials have been
in use in applications such as tires and airplane fuel tanks for over
a century. The bulk of these techniques have the damage initiate
the repair response in the material directly without any intermediate
sensing and control. This research expands and demonstrates
the enhancement of autonomous repair techniques through the
coordinated damage sensing and directed repair activities with test
bed pressure vessels and structural panels that have been damaged
by puncture and drilling of holes. Acoustic emission, embedded optical
and capacitance sensors detect the damage. Electrorheological, shear
thickening and thermoplastic repair techniques are initiated upon
repair detection and localization of damage. Autonomous leak repair in
pneumatic pressure vessels and panels with perforations up to 3 mm
upon detection and localization of the damage are demonstrated.
J. Park, J. Kim, Pukyong National Univ. (Korea, Republic of)
To date, many prestressed concrete (PSC) girder bridges have been
constructed since the compressive prestress makes more economical
use of the concrete. Therefore prestress force in tendon is an important
parameter that should be secured for its safety against external
loadings and environmental conditions. Recently, electro-mechanical
impedance-based health monitoring has shown the promising
success to detect minor changes in structural integrity. While the
impedance-based health monitoring is efficient, the costs associated
with installation and maintenance of the impedance-based monitoring
system can be very high. The high costs of the system can be greatly
reduced through the adoption of wireless sensor node. However, the
wireless impedance sensor node has measurable range with narrow
frequency band which is relatively smaller than commercial impedance
analyzers.
In this study, a technique using wireless impedance sensor nodes is
proposed to monitor prestress-force in PSC girder bridges. In order
to achieve the goal, the following approaches are implemented.
Firstly, a wireless impedance sensor node is designed for automated
and cost-efficient prestress-loss monitoring. Secondly, a prestressloss monitoring technique using an interface plate is proposed to
overcome limitations of the wireless impedance sensor node such
as measureable frequency ranges with narrow band. Thirdly, an
impedance-based algorithm is embedded in the wireless impedance
sensor node for autonomous structural health monitoring. Finally, the
feasibility and applicability of the proposed technique are evaluated in a
lab-scaled PSC girder model for which several prestress-loss scenarios
are experimentally monitored by the wireless impedance sensor node.
7647-56, Session 7a
Structural identification of progressive
damage states in concrete columns subject
to seismic excitations
Z. Wu, A. P. Adewuyi, Ibaraki Univ. (Japan); S. Xue, Kinki Univ.
(Japan)
The traditional post-seismic visual inspection of structures, though
provides knowledge about the vulnerability of structural systems
and mechanisms of failure, they are often unreliable for effective
maintenance-based monitoring against major earthquakes. In recent
years, significant efforts have been devoted to developing nondestructive techniques for damage identification in structures. Prompt
monitoring and accurate measurement structural characteristics are
very essential for reliable condition evaluation and early detection,
localization and estimation of severity of damage in structures. This
paper investigates the application and evaluation of structural health
monitoring (SHM) techniques for concrete columns subject to ground
motions. The progressive damage states of the structure is studied
based on the structural dynamic response of the eccentrically loaded
reinforced concrete columns of square cross-section of side 150
mm and overall height 1200 mm mounted on a shaking table and
subjected to different seismic excitations of increasing intensities. The
dynamic responses to different excitations were measured using longgage fiber Bragg grating (FBG) sensors, dynamic strain gauges and
piezoelectric accelerometers installed on the two adjacent surfaces of
the columns. An array of six long-gage FBG sensors of gauge lengths
200 mm were installed on each face in a distributed manner, while the
number of accelerometers and conventional strain gauges on each
face is three. The excitations included the sine, sine-sweep and the
Niigata earthquake excitations. The changes of the structural dynamic
characteristics of the columns due to excitations and progressive
damages were investigated based on the general principle that
7647-54, Session 7a
Application of self-sensing BFRP bars into
concrete structures
Y. Tang, Southeast Univ. (China); Z. Wu, Ibaraki Univ. (Japan); C.
Yang, G. Wu, L. Zhao, S. Song, Southeast Univ. (China)
In this paper, a new type of self-sensing basalt fiber reinforced polymer
(BFRP) bars was buried into some concrete structures to investigate
the sensing performance with using the Brillouin scattering-based
distributed optical fiber sensing technique, while the mechanical
performance was paid attention as well. First, one of the smart bars
was applied to strengthen a 2m long concrete beam with a 4-points
static loading model in the laboratory. During this experiment, the
bar measured the inner strain changes well, especially caught the
randomly distributed cracks. With the distributed strain information
along the bar, the distributed deformation of the beam and moments
of each cross area can be calculated, therefore, the structure health
can be evaluated. Then, the two smart bars with a length of about
70m were embodied into a concrete airfield pavement reinforced all
by long BFRP bars. In this field test, all the optical fiber sensors in the
smart bars survived the whole concrete casting process and worked
healthily. From the measured data, the concrete shrinkage along all the
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The problem of estimating the configuration of a robotic system
relative to a known (static or dynamic) environment is known as robot
localization. Several algorithms for localizing robotic systems have
been developed in the literature, for example, the Extended Kalman
Filter localization (EKF) algorithm. These algorithms use noisy sensor
data to estimate the relative position and configuration of the robot
with respect to the surrounding environment. In this article, the effect
of different levels of sensor noise on the performance of several
localization algorithms is studied and relevance of this work to the use
of mobile sensor platforms in applications such as oil storage tanks is
discussed.
vibration measurements prior to and after a damage scenarios should
give information damage occurrence. The performances of the sensors
for structural identification are also comparatively discussed.
7647-57, Session 7a
Detection and assessment of wood decay in
glulam beams using a decay rate approach
H. L. Reis, A. Senalik, Univ. of Illinois at Urbana-Champaign (United
States); F. C. Beall, Univ. of California, Berkeley (United States)
7647-60, Session 7b
A glulam beam retired from the field and without visible indications
of wood decay was used. Towards detection and assessing wood
decay, X-ray computer tomography and ultrasonic measurements
were carried out. It was observed that decrease in mass density with
increasing levels of wood decay affects x-rays attenuation and allows
radioscopy to detect and assess wood decay. To detect and assess
decay when only one lateral side of the beam is available, a modified
impulse-echo is presented. The modified impulse-echo approach
is based on observing the dynamic response of each lamina in the
glulam beam to the drop of a steel sphere onto a steel plate coupled
to the glulam beam lamina and upon a decay rate analysis of the
corresponding time domain signal in a frequency band of interest. The
selection of the frequency band of interest only requires knowledge
of the nominal transverse dimensions of each lamina in the beam and
of the corresponding wood species. It was observed that decay rate
analysis allows detection and assessment of wood decay. The decay
rate approach leads to a 5.7% probability of false negative calls (i.e.,
decayed wood assumed to be sound wood) and to a 3.5% probability
of false positive calls (i.e., sound wood assumed to be decayed),
with an overall rate of false calls of 7.2%. Considering the variability
that exists in wood including the presence of splits, orientation and
thickness of growth rings, etc., this relative low rate of false calls makes
this approach very attractive. Results show that results from both
X-ray computer tomography and impulse-echo decay-rated based
measurements are consistent with each other and can be used to
detect and assess wood decay in structural lumber.
Systematic decision-support in damage
assessment: an evidential reasoning
approach
I. Lopez, N. Sarigul-Klijn, Univ. of California, Davis (United States)
In real-world applications, sensory data is often incomplete and
imprecise. Structural health monitoring is an information-based
engineering application that is a data and knowledge intensive
application with unique requirements from engineering information
modeling. Due to structural complexity and rich semantic requirements,
damage assessment analysis needs to incorporate modeling of
imprecise and uncertain information. Structural sensory data is subject
to random disturbances, and the environment in which structural
system operates is often precisely unpredictable. We develop an
expert supervisory strategy based on evidential reasoning to deal
with uncertain decision knowledge in multi-attribute decision-making
with both quantitative and qualitative information sources. In this
paper, we begin by showing that a Dempster-Shafer inference learning
system can be used to adapt nominal damage assessment system
to compensate for data uncertainty. In addition, we show that the
performance in damage assessment can be significantly enhanced by
exploiting damage detection and identification information to achieve
an “adaptive” damage assessment approach depending on the type
of damage that occurred. The robustness of the damage detection
approach to uncertainty in the input data is investigated using
probabilistic-based confidence bounds of prediction accuracy. This
approach is illustrated with publicly available fault detection datasets
and laboratory experiments.
7647-58, Session 7b
* An emerging time-domain sensing
technique for large scale, multi-function
fiber optic sensor networks
7647-61, Session 7b
C. Wang, C. Herath, Mississippi State Univ. (United States)
* Intelligent fault detection, diagnosis and
prevention (iFDDP) technology for the
design of smart outlets in healthy and safe
homes
Power losses, light intensity fluctuations, and high terminal equipment
costs are important issues in development of a large scale, multifunction fiber optic sensor systems or sensor networks. Fiber loop
ringdown (FLRD), a uniform time-domain sensing scheme, has potential
to help address the three key issues in the development of fiber
optic sensor networks for simultaneously sensing multiple quantities,
including pressure, temperature, strain, chemical species, etc. with fast
response, high sensitivity, and significantly reduced costs. Performance
and design of a cluster of individual FLRD-based fiber optic sensors
for pressure, force, temperature, strain, chemical compounds, etc. are
presented. Multiplexing those individual FLRD sensor units into a large
scale sensor system for multi-function sensing is proposed. System
configuration, operation, and advantages compared with the peersensors based on current sensing schemes are discussed.
I. M. Kao, Stony Brook Univ. (United States)
In the paper, we will present the ongoing study to significantly
reduce various types of electrical fire and injury hazards at home
by developing a smart outlet, using innovative sensors and sensing
system with an intelligent fault detection, diagnosis, and prevention
(iFDDP) technology. This study can improve a very important device
of our existing infrastructure in our daily lives, and provide a better
quality of life for all. In this paper, we will present the study from the
perspectives of mechanisms, sensing, fingerprints, diagnosis, and
prevention of serial arcing, a very common but serious safety hazard
to homes. A fingerprint study with pattern recognition of the serial
arcing on experimental results has been conducted by examining the
wavelet components. The analysis indicates that typical “W” or “M”
fingerprints are recurring when the high-frequency serial arcing takes
place in the detailed components of wavelet. Such characteristics
occur at the transition of the intermittent electrical connection through
arcing. Experimental data also suggest that such arcing will increase
the temperature rapidly, causing degradation in the outlet and further
aggravating the condition. The integrated sensor and sensing system
7647-59, Session 7b
Noise effects on mobile sensor platform
localization
N. Chopra, B. Balachandran, Univ. of Maryland, College Park
(United States); H. Karki, The Petroleum Institute (United Arab
Emirates)
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with signal analysis will also be presented. Another benefit of the
ongoing research study is the capacity of real-time monitoring of the
energy use of individual appliances to save energy and power usage.
The new iFDDP technology can potentially revolutionize the usage of
outlets in homes and provide a healthy and safe home environment for
better quality of life.
are simulated. Here, those signals are super-posed with a white noise
signal and are used for reconstruction of the full dynamic state of the
structure. The influence of different uncertainties or disturbances like
measurement noise, low order of considered modes or variance of
sensor position to the accuracy of the reconstruction is examined and
compared with each other. As a quality criterion for efficiency of filtering
and to evaluate uncertainties, the mean square error and the coherence of simulated and reconstructed vibration and loads is used.
7647-62, Session 7b
This work shows that uncertainties in any load-carrying system can be
reduced when knowing the real load condition of the system as well as
any possible disturbances any-time and anywhere during its lifetime.
Object identification by multispectral fusion
and Haar classification
A. Manohar, F. Lanza di Scalea, Univ. of California, San Diego
(United States)
7647-156, Poster Session
Mechanical monolithic tiltmeter for low
frequency measurements
An approach to identify and classify objects in real time by
multispectral imaging, image registration, wavelets based fusion,
and Haar classification is presented. The specific object of interest
is a cardboard box placed on the roadside. The proposed approach
involves capturing a scene in the visible and infra red spectrum.
Fusing the spectra is performed by using the wavelet transform after
the images are spatially registered. Further, Haar training is performed
using sample positives and negatives prior to classification. The
presented approach is tested to work in real time with very good
accuracy. If successful, the method will be applied to the detection of a
variety of anomalous objects placed at the roadside.
F. Acernese, Univ. degli Studi di Salerno (Italy); R. De Rosa, G.
Giordano, Univ. degli Studi di Napoli Federico II (Italy); R. Romano,
Univ. degli Studi di Salerno (Italy); F. Barone, Istituto Nazionale di
Fisica Nucleare (Italy)
The paper describes the application of a monolithic folded pendulum
(FP) as a tiltmeter for geophysical applications, developed at the
University of Salerno. Both the theoretical model and the experimental
results of a tunable mechanical monolithic FP tiltmeter prototype are
presented and discussed. Some of the most important characteristics,
like the possibility of tuning its resonance frequency to values as low
as 70 mHz and its measured resolution of 0.1 nrad at 100 mHz, are
detailed. Among the scientific results, earth tilt tides have been already
observed with a monolithic FP tiltmeter prototype.
7647-63, Session 7b
A survey of the reduction of uncertainties by
comprehensive monitoring of load-carrying
structures
7647-157, Poster Session
J. Koenen, Technische Univ. Darmstadt (Germany); R. Platz,
Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit
(Germany); H. Hanselka, Technische Univ. Darmstadt (Germany)
Low frequency seismic noise acquisition
and analysis in the Homestake Mine with
tunable monolithic horizontal sensors
Long Abstract:
During the design process of a load-carrying structure, the real
operational loads are unknown in most times. Thus, the loads to
estimate the durability during design are taken from experiences with
calculations, numerical simulations or real experiments. However,
even an experiment represents just a partial cutout of all possible
load scenarios. In contrast, monitoring systems offer the possibility
to measure and reconstruct loads and vibra-tions during the usage of
any structure out in the field. What is more, those measurements are
influenced by uncertainties such as measure- or system-noise, signals
from misplaced sensors, fatigue of sensors or changes in system
dynamics.
F. Acernese, Univ. degli Studi di Salerno (Italy); R. De Rosa, Univ.
degli Studi di Napoli Federico II (Italy); R. DeSalvo, Califonia
Institute of Technology (United States); G. Giordano, Univ. degli
Studi di Salerno (Italy); J. Harms, V. Mandic, Univ. of Minnesota,
Twin Cities (United States); F. Barone, Istituto Nazionale di Fisica
Nucleare (Italy)
In this paper we describe the scientific data recorded along one
month of data taking of two mechanical monolithic horizontal sensor
prototypes located in a blind-ended (side) tunnel 2000 ft deep in
the Homestake (South Dakota, USA) mine chosen to host the Deep
Underground Science and Engineering Laboratory (DUSEL). The
two mechanical monolithic sensors, developed at the University of
Salerno, are placed, in thermally insulating enclosures, onto concrete
slabs connected to the bedrock, and behind a sound-proofing wall.
The main goal of this experiment is to characterize the Homestake
site in the frequency band 10^-4 - 30 Hz and to estimate the level of
Newtonian noise, providing also the necessary preliminary information
to understand the feasibility of underground gravitational-wave
interferometers sensitive at 1 Hz and below.
Today, current methods analyse the dynamics and damages of loadcarrying structures. For example, with the Finite Element Analysis (FEA)
static and dynamic behaviour of structures could be calculated. UsageMonitoring-Systems offer information about loads and vibrations,
Structural Health Monitoring (SHM) show position and size of damages.
With methods of damage accumulation we can calculate the level of
fatigue [4, 5, 7].
The monitoring method presented in this paper combines these
methods to a compre-hensive monitoring system which is represented
in an information processing chain. Sev-eral influences of uncertainty
that affect the quality of state identification are analyzed, figure
1. Stochastic signal processing is used to reduce the effects of
probabilistic influences, adaptive filtering allows observing changes in
system parameters within time. Those changes can be used to update
the model parameters online [6]
7647-159, Poster Session
Study on the fatigue reliability of optical
fiber based on distributed optical fiber strain
sensing technique
....
Numerical simulations of a simple beam are performed to verify the
applicability and accuracy of the proposed methods, figure 2.
S. Song, Southeast Univ. (China); Z. Wu, Ibaraki Univ. (Japan); C.
Yang, G. Wu, S. Shen, Southeast Univ. (China)
The simulation of the dynamic responses is conducted with a high
order model. For the reduced number Nred DOF measured signals
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Conf. 7647: Sensors and Smart Structures Technologies for Civil,
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coefficients and then corrects the wavefront through driver commands
sent to the deformable mirror in terms of Zernike profiles. We have
implemented and tested an experimental Prototype of the AO System
in our laboratory at the University of Salerno. The results confirm
effectiveness and robustness of the control which performs significant
reduction of the first and second order laser beam geometrical
fluctuations. In particular we have measured the decrease of
astigmatism and defocus modes of 60 dB at low frequency below 1 Hz
and of 20 dB up to 200 Hz, which at the best of the present technology
fulfils the requirements for noise reduction of the interferometric GW
detectors.
for damage identification of important civil infrastructures bearing
long-term fatigue loads, such as bridges and prestressed steel
structures. In this paper, based on the distributed optical fiber strain
sensing technique of pulse-prepump Brillouin Optical Time Domain
Analysis(PPP-BOTDA), three types of optical fiber, i.e. single-mode
optical fiber with Jacket (Type-A), UV resin-coated optical fiber (Type-B)
and optical fiber with improved strain sensitivity (Type-C), were selected
to study on the monitoring reliability in low cycle fatigue experiment
with different initial strain and amplitudes. Three kinds of optical
fibers were tested in direct tension at certain cycle numbers. Initial
experimental results show that the strains of the Type-A and Type-B
drift more with cycle numbers, while the Type-C show little deviation
with the true value. It is indicated that the monitoring data of Type-A
and Type-B was not reliable with fatigue loading, because of the fatigue
damage accumulation of the optical fiber, while there is little effect
in Type-C. As a result, optical fibers with improved strain sensitivity
can be used in the long-term monitoring of important structures
bearing long-term fatigue loads such as bridges and prestressed steel
structures.
7647-162, Poster Session
Piezoelectric sensor system for
simultaneous detection of local and global
damages in structures
Y. Roh, H. Kwon, J. Kim, B. Kim, Kyungpook National Univ. (Korea,
Republic of)
7647-160, Poster Session
This paper presents the feasibility of a sensor system consisting of
piezoelectric oscillator sensors to detect local damages and ultrasonic
sensors to detect global damages in a structure. The oscillator sensor
is composed of a feedback oscillator circuit and a piezoceramic lateral
mode vibrator to be attached to a structure. Damage to the structure
causes a change in the resonant frequency of the vibrator. The
oscillator circuit instantly detects the frequency change and configures
the damages. However, the response of the oscillator sensor is limited
to the area around the sensor, thus local measurement. The ultrasonic
sensor generates Lamb waves and the waves traveled over a long
distance are received by the piezoceramic patch used in the oscillator.
The received wave form reflects all the defects encountered during
the propagation, thus global measurement is possible. The two sensor
types are combined as a sensor network, and its operation system is
developed as a portable unit for practical applicability. Performance of
the sensor system was verified with a sample aluminum plate where
artificial cracks of different lengths and number were imposed in
sequence. Performance of the sensor was quite promising, responding
accurately and reliably to the crack configuration.
Structural health monitoring of a composite
wind turbine blade using fiber Bragg grating
sensors
H. Bang, H. Shin, Y. Ju, Korea Institute of Energy Research (Korea,
Republic of)
This paper describes implementation of FBG (fiber Bragg grating)
sensors to monitor the composite manufacturing process as well as
load bearing condition of down scaled 3.5m wind turbine rotor blade.
At first, wavelength division multiplexed 5 point FBG sensors were
embedded between the unidirectional layer of carbon spar and we
measured the internal strain during oven curing process. We made
blade skin with glass fiber materials by resin infusion molding process
in air temperature, and the box spar structures were made by oven
curing process using carbon fiber prepreg. Because the unwanted
residual compressive strain can cause early delaminations between
the glass skin and carbon spar, the residual strain level in the carbon is
need to be known after the high temperature oven curing process.
After the monitoring the manufacturing process, these embedded
FBG sensors were used to measure the strain condition of the blade
in structural performance tests. Impact modal tests and flap and
edgewise static tests were performed using 5 FBG sensors. In the
modal tests, we made a comparative study of FBG test result with
that of conventional accelerometers and FE analysis. In the static load
test, measured strain result of electric strain gage and FBGs were
compared.
7647-163, Poster Session
7647-161, Poster Session
EMAT which is based on magnetostrictive effects was employed to
detect internal flaws in an inspected sample with surface oxide scaling.
EMAT is a contact-free NDT method and can quickly scan over the
inspected sample’s surface. It is also more suitable for rough surfaces
of inspected samples than conventional piezo-elastic transducers.
This study seeks to derive internal 3D-images of sample. As a target
sample, chromium molybdenum steel (SCM415) was annealed at 600
˚C to 900˚C for two to eight hours and subjected to EMAT to survey
its signal properties. The sample annealed at 875 ˚C for two hours
produced clear EMAT signals good enough to recognize internal flaws.
The data derived from these samples were compared to data from
an actually used sample. The EMAT signal derived from the actual
sample was found too noisy to detect and identify internal flaws and
to reconstruct flaw images in a computer. The noise was thought to
come from the Barkhausen effect and can easily be removed from
the inspected samples by averaging EMAT signals. However, it is
impossible to average EMAT signals while quickly scanning a sample’s
surface. There is another method to remove noise from EMAT signal.
Because the frequency of Barkhousen (BH) noise is much higher than
the EMAT’s resonance frequency, most of BH noise can be removed
numerically by a low-pass filter but such a low-pass such a filter
produces its own noise. This study proposes to remove the noise
Development of NDT system with image
reconstruction capabilities of flaws using
EMAT
Y. Nishimura, A. Sasamoto, T. Suzuki, National Institute of
Advanced Industrial Science and Technology (Japan)
Adaptive optics system for fast automatic
control of laser beam jitters in air
S. Grasso, Univ. degli Studi di Roma Tre (Italy); F. Acernese, R.
Romano, Univ. degli Studi di Salerno (Italy); F. Barone, Istituto
Nazionale di Fisica Nucleare (Italy)
In this paper we present an Adaptive Optics (AO) System properly
developed for the fast automatic control of laser beam jitters on first
and second order Hermite Gauss (HG) modes. This research has
been driven by the necessity of suppressing laser beam geometrical
fluctuations in the interferometric Gravitational Waves (GW) antennas.
In fact, it is demonstrated that oscillations of higher order Hermite
Gauss modes in the laser source couple with the interferometer
asymmetries and give rise to additional noise that limits the antenna
sensitivity below the value of 10^-23 1/sqrt(Hz) . In the paper we
demonstrate the feasibility of a novel AO System performing effective
laser jitters suppression in the bandwidth up to 200 Hz. In particular
we describe an innovative AO System that extracts error signals as HG
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compression test. Also, the FBG sensors were used to measure strain
of asphalt concrete beams. Linearity and repeatability of the sensors
are quit well and measured strains are quite believable. So, we can say
that due to bond and deformation compatibility between packaged
material and FBG, FBG sensor and measured material, especially low
modulus of packaging materials, strain of asphalt pavement can be
monitored by the kind of sensors.
by maximizing the likelihood of signals including BH noise in all the
sampled signals based on the probability distribution of BH noise. To
derive 3D internal images of sample, a high-speed 3D-scanner driven
by linear motors with a positioning precision of 0.5 for each directions
(x, y, z) and having a scanning speed of 1m/s was developed. A time
series of data consisting of 16,000 samples for each position, was
sampled by an A/D converter (400MHz) at 1024x1024 positions within
a 5cmx5cm area. The signals were subjected to Hilbert transformation
to derive curve envelopes that coincide with the distribution of a
reflection coefficient in the inspected sample. The time series of data
was arranged in each scanning line meaning (X direction), and 3D
internal-images of the sample were successfully reconstructed and
depicted.
7647-166, Poster Session
Decentralized semi-active structural control
system with wireless sensing and control
network
7647-164, Poster Session
Y. Lei, Xiamen Univ. (China)
Oblique excitation of nearly-longitudinal
waves in thick plates
Decentralized Semi-active Structural Control System with Wireless
Sensing and Control Network
Y. Ying, J. H. Garrett, Jr., D. W. Greve, I. J. Oppenheim, L.
Soibelman, Carnegie Mellon Univ. (United States)
Ying Lei*, Y. K. Mao and D.T. Wu
Previous research has studied the generation of nearly-longitudinal
waves in thick plates by edge excitation at relatively high frequencythickness products. These nearly-longitudinal waves, also well known
as trailing pulses, are promising for flaw detection due to their shorter
wavelength and the capability of retaining the pulse characteristics
after scattering from defects. However, in the real world, the edges of
the structures may not be accessible due to construction design or
environmental constraints. Therefore, we propose to excite ultrasonic
waves with a wedge transducer in oblique incidence at the plate
surface. We use finite element simulations to examine the generation of
nearly-longitudinal waves in a thick plate. Experiments are conducted
to validate this wave behavior when a wedge transducer is applied.
The good agreement between the simulation and experiments shows
that uniformly spaced trailing pulses, with the initial arrival traveling at
the speed of a longitudinal bulk wave, are produced in a thick plate
by wedge excitation. The received signals, however, are weaker than
those when an edge-mounted transducer is used. In this paper, we
theoretically investigate the dependency of the strength of nearlylongitudinal waves on the incidence angle to choose optimal wedge
angle for energy transmission. Consistent simulations and experimental
results are presented. Furthermore, we employ the nearly-longitudinal
waves excited by a wedge transducer for flaw detection. The
correspondence among theory, simulation and experiment demonstrate
that nearly-longitudinal waves by oblique incidence excitation are a
good alternative for infrastructure inspection, especially for plates
permitting only surface access.
ABSTRACT
School of Architecture and Civil Engineering, Xiamen University,
Xiamen, China, 361005
In the past decades, structural control technologies have received
great attention for hazard mitigation; however, traditional structural
control techniques are centralized in nature. As structural control
systems grow in size, there are many problems with the centralized
control architectures. Recently, a novel decentralized structural control
method based on substructure and LQG control algorithm has been
proposed by the authors. The decentralized control algorithm is
suitable for implementation on a control system of densely distributed
sensors and actuators. In this paper, application of this method
with experimental verification by a new sensing and control network
developed by the authors is studied. The sensor and control network
consists of active sensing units in which actuation interface is to allow
commanding semi-active variable dampers in a structural control
system. The decentralized control algorithm is embedded into the
computational core of each active sensing unit. A large size structure
is divided into substructures. The distributed active sensing units in
a substructure are grouped into a cluster to collect measurements,
transmit data with wireless communication, determines control forces
using computational resource, and command structural actuators at a
specified time interval, all in real-time. Therefore, structural control can
be performed by local controllers in different substructures concurrently
with parallel computing or even independently. Considering the
practical case that measurements at the substructure interface are not
available, active sensing units in a substructure needs to communicate
with limited information with those in the surrounding substructures.
To assess its efficacy in practice, the proposed technique is
experimentally verified by application to decentralized semi-active
control of a 6-story steel-frame building using MR dampers. The
building is excited at its base by shaking table, two MR dampers are
located on the first and the fourth floor, and limited accelerometers are
installed. By evaluating the control performance, the feasibility of the
decentralized wireless sensing and control network is discussed.
7647-165, Poster Session
The development and performance study of
polypropylene packaged FBG strain sensor
for monitoring on asphalt pavement
Keywords: decentralized structural control; wireless sensing and
control network; LQG control algorithm; Semi-active control, MRdamper
Q. Hu, C. Wang, J. Ou, Harbin Institute of Technology (China)
Modulus of asphalt concrete is very low, so ordinary FRP or Steel
packaged sensors can not measure its strain accurately. In view
of this problem, one kind of optical fiber Bragg sensor based on
polypropylene, one kind of thermoplastic resin, was proposed in
this article. Firstly, a conveniently installed and dissembled steel die
was designed and fabricated. Then, after characteristics study of
polypropylene during heating and repeatedly tries, a reliable grouting
technique was formed. After this, real-time monitor of the entire
sensor packaging process was performed with demodulator, and
then the sensor mechanics performance, the microscopic structure
and properties were studied thoroughly. Results of SEM indicate
that interface of optical fiber and polypropylene is considerable
tight. Measured strain during sensor making is reasonable. Then, the
FBG sensors were buried into concrete columns to measure their
strain during continuously 7 day-long early-times solidification and
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* Corresponding Author: Professor Ying Lei, Department of Civil
Engineering, Xiamen University, Xiamen 361005, Fujian, China. E-mail:
[email protected]
7647-167, Poster Session
An optimal design of magnetostrictive
material (MsM) based energy harvester
J. Hu, F. Yuan, North Carolina State Univ. (United States); F. Xu,
Donghua Univ. (China) and North Carolina State Univ. (United
States); A. Q. Huang, North Carolina State Univ. (United States)
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Mechanical, and Aerospace Systems
The objective of this research is to design an optimized energy
harvesting system based on a magnetostrictive material (MsM) to
power the Wireless Intelligent Sensor Platform (WISP), developed
by North Carolina State University. Compared to the piezoelectric
material based harvester, MsM is more flexible, has an inherent low
resonance frequency, and it provides almost unlimited number of
vibration cycles. Without a dense mass, the cantilever beam with two
Metglas 2605SA1 (cast) layers laminated on a steel substrate has the
first order resonance frequency lower than 70Hz. Several important
considerations in designing the optimal MsM generator are explored,
including the coil and cantilever beam optimization, load matching,
and efficiency. The coil and the geometry of the MsM cantilever beam
are optimized to maximize the output power using MATLAB Sequential
Quadratic Programming method under the constraint that the whole
device size including the coil is 1cm3. From the measurement, the
open circuit voltage is 1.26V when the MsM device is working at the
2nd order resonance frequency 342Hz. The output power is 1.2mW.
An optimized energy harvesting circuit for maximum power transfer
from a Magnetostrictive Material (MsM) vibration generator has also
been designed. Since the MsM device has low open circuit output
voltage characteristics, a full-wave quadrupler was designed to boost
the rectified output voltage because of its better load regulation,
lower ripple and faster settling time. To implement complex conjugate
impedance matching, a discontinuous conduction mode (DCM)
buck-boost converter was designed to charge a rechargeable battery.
Compared to the previous work done by Lei Wang, at least 2 times
higher power is obtained at a lower frequency with a lower coupling
coefficient MsM material. The power density is 4 times higher than the
work done by Lei Wang using his power density calculation method.
X. Li, T. S. Yun, L. Cheng, S. Pamukcu, Lehigh Univ. (United States)
The effective in-situ characterization and hazard monitoring in geoengineering practice are key issues that can be addressed by use of
wireless sensor networks. The conventional methods deployed in geoengineering practice for in-situ characterization experience limitations
in acquisition of spatially localized and/or temporally discrete data.
We propose the idea of functional signal that address such limitations.
The concept of functional signal advocates that the variation of the
link quality between wireless transceivers can be used as an effective
sensing mechanism which reflects characteristics of geo-media
subjected to various geo-events. This novel method makes a wireless
signal network as a global geo-media measurement system that
performs the geotechnical characterization in a spatial and temporal
continuous fashion with embedded wireless sensors in distributed
configurations. This not only enables to evaluate and visualize entire
geo-system but also helps develop knowledge of functional-signal map
to benchmark such continuums through spatiotemporal calibrations
of wireless link quality. Simulation and experiment results show that
this new idea can provide simple and robust sensing methodology
to identify and evaluate indiscriminate geo-events and evolution of
geophysical conditions in geo-media.
7647-170, Poster Session
Low-cost self-cleaning room temperature
tin dioxide thin film gas sensor on polymer
nanostructures
M. Shen, H. Huo, F. Yan, C. Wang, H. Ren, Univ. of Massachusetts
Lowell (United States)
7647-168, Poster Session
Coupling of ab-initio and bifurcation
techniques for martensitic transformations
in transition-metal materials
We have successfully fabricated tin dioxide (SnO2) thin film CO
gas sensors on nanospiked polyurethane (PU) polymer surfaces
that are replicated with a low-cost soft nanolithography method
from nanospiked silicon surfaces formed with femtosecond laser
irradiations. The sensors show sensitive responses to the CO gas at
room temperature because of the high area/volume ratio and sharp
structures of the nanospikes. This is much different from the sensors
of SnO2 thin film coated on smooth surfaces that show no response
to the CO gas at room temperature; the operating temperatures of
the sensors must be above 150 degree C. To make the nanostructure
sensor surface behave self-cleaning like lotus leaves, we deposited
a silane monolayer on the surface of the SnO2 thin film sensors in a
vacuum chamber with the 1H,1H,2H,2H-perfluorooctyltrichlorosilane
(PFOTS). The contact angle measurement conducted on the
PFOTS monolayer-coated SnO2 gas sensors indicates that a superhydrophobic surface formed on the nanospike sensor. The CO gas
response sensitivity of the PFOTS-coated SnO2 sensors is almost the
same to that of the as-fabricated SnO2 sensors without the PFOTS
coating. Such a super-hydrophobic surface can protect the sensors
exposed to moisture and heavy particulates, and can perform cleaningin-place operations to prolong the lifetime of the sensors. These results
show a great potential to fabricate thousands of identical gas sensors
at low cost. The identical gas sensors also decrease the calibration
cost greatly. In addition, the sensors operating at room temperature
greatly decreases the electrical power consumption of the sensors.
R. S. Elliott, M. Cococcioni, D. B. Ghosh, Univ. of Minnesota
(United States)
The technologically important properties of transition-metal materials
such as shape memory alloys (SMAs) and magnetic SMAs (MSMAs)
are due to solid-to-solid martensitic phase transformations (MPTs)
which result from an instability of the material’s crystalline structure.
Ab-initio simulations are currently capable of providing accurate
predictions of material behavior, but methods such as molecular
dynamics or monte carlo simulation are computationally too expensive
to comprehensively explore a material’s MPT behavior.
This work aims to couple a state-of-the-art electronic density functional
theory (DFT) software package capable of ab-initio predictions of
materials behavior with a branch-following and bifurcation (BFB)
software package capable of efficiently and comprehensively mapping
out the MPTs exhibited by any given material. BFB techniques map
out a curve or branch corresponding to the evolution of a material’s
equilibrium configurations as a parameter (such as temperature or
applied magnetic field) is varied. Following the natural evolution of
the material’s behavior allows for significant computational savings
over other methods. Often the branches of two different crystalline
structures cross. The point of intersection is called a bifurcation
point. These bifurcation points allow for the systematic discovery and
exploration of many material phases.
7647-171, Poster Session
The coupled DFT-BFB computational system will be described and
its features demonstrated for some simple materials of interest. The
results indicate that DFT simulations coupled with BFB techniques
have the potential to provide new insights on why certain materials
exhibit technologically useful MPTs and others do not.
Classification of damage in structural
systems using time series analysis and
supervised and unsupervised pattern
recognition techniques
7647-169, Poster Session
P. Omenzetter, O. R. de Lautour, The Univ. of Auckland (New
Zealand)
In-situ geo-characterization using wireless
functional signals
Developed for studying long, periodic records of various measured
quantities, time series analysis methods are inherently suited and
offer interesting possibilities for Structural Health Monitoring (SHM)
120
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Conf. 7647: Sensors and Smart Structures Technologies for Civil,
Mechanical, and Aerospace Systems
applications. However, their use in SHM can still be regarded as an
emerging application and deserves more studies. In this research,
Autoregressive (AR) models were used to fit experimental acceleration
time histories from two structural systems, a 3-storey bookshelf-type
laboratory structure and the ASCE Phase II SHM Benchmark Structure,
in healthy and several damaged states. The coefficients of the AR
models were chosen as damage sensitive features. Preliminary visual
inspection of the large sets of AR coefficients to check the presence
of clusters corresponding to different damage severities was achieved
using Sammon mapping - an efficient nonlinear data compression
technique. Systematic classification of damage into states based on
the analysis of the AR coefficients was achieved using three supervised
classification techniques: Back-Propagation Neural Networks (BPANNs) Nearest Neighbour Classification (NNC) and Learning Vector
Quantisation (LVQ), and one unsupervised technique: Self-Organising
Maps (SOM). This paper discusses the performance of AR coefficients
as damage sensitive features and compares the efficiency of the four
classification techniques using experimental data.
7647-66, Session 8a
Adaptive noise variance identification
for data fusion using subspace-based
technique
Z. Li, C. Chang, Hong Kong Univ. of Science and Technology
(Hong Kong, China)
Displacement response of civil structures is of great importance
for condition monitoring and evaluation of these structures.
Current displacement measurement techniques such as the global
positioning system and the image-based approach however suffer
from low sampling rate as well as measurement noise. To circumvent
these problems, the Kalman filter is commonly employed to fuse
displacement measurement with acceleration which can be easily
and accurately obtained. Although the Kalman filter can mitigate the
aforementioned limitations, the performance of data fusion however
depends on the accurate estimation of noise variances in the
displacement and acceleration measurement. Typically, noise variances
are estimated empirically a priori and are assumed to be invariant
throughout the fusion which may lead to large estimation error. In this
study, an adaptive subspace-based technique is developed to identify
time-varying noise variances in the measured response. The proposed
method estimates the variances of acceleration and displacement
independently and can ensure the positive definite of noise variances.
Furthermore, the proposed technique can be performed in on-line
fashion; hence, it can be incorporated into an adaptive Kalman filter. A
numerical example and a laboratory test are conducted to validate the
proposed approach
7647-64, Session 8a
Detecting seismic response signals using
singular spectrum analysis
C. Loh, C. Mao, C. Chen, National Taiwan Univ. (Taiwan)
Singular Spectrum Analysis (SSA) is a novel non-parametric technique
based on principle of multivariate statistics. The original time series
is decomposed into a number of additive time series, each of which
can be easily identified as being part of the modulated signals, or as
being part of the random noise. It provides trend extraction involves
a decomposition of a time series into low-frequency trends and
high-frequency variability. It shows that the embedding dimension m
of a dynamical time series can be conducted by the Singular Value
Decomposition (SVD) experiments. This SVD scheme was used
to detect low-dimensionally dynamic signals and the residuals. In
this study SSA and nonlinear identification are used to measure the
nonlinear seismic responses of reinforced concrete structures and
to elucidate residual deformation. Then, damage feature extraction
is conducted using the high-frequency variability of SSA, the Holder
exponent and the Level-1 detail of the discrete wavelet component.
Five reinforced concrete frame test data collected in response to
various degrees of seismic excitation are used to study the severity of
damage.
7647-67, Session 8b
* Design and fabrication of a sensor
integrated MEMS/nano-skin system for
human physiological response measurement
Y. Lin, Northeastern Univ. (United States)
Human state in human-machine systems highly affects the system
performance. Human state should be monitored to enhance humanmachine interaction, optimize the system performance, and derive the
accident risk and cost. After literature review, this study revealed that
physiological cues are suitable for monitoring human state in humanmachine system. This study was focused on developing a new sensing
system, i.e. MEMS/Nano-Skin, to non-intrusively measure physiological
cues at human-machine contact surfaces, and then assess human
state in human-machine systems.
7647-65, Session 8a
* Support vector machine for abnormality
detection of a cable-stayed bridge
The first part was to analyze the characteristics of human-machine
contact, and find the appropriate physiological cues for monitoring
human state. Human-machine contact usually happen between
human skin and machines, and is dynamic. Generally, heart rate,
skin conductance, skin temperature, gripping force, blood alcohol
concentration, sweat rate, and electromyography have close relation
with human state. These physiological cues can be measured from
human skin to evaluate human state in human-machine systems.
The measurement of physiological cues does not add constrains to
humans, does not affect human normal state, and is non-intrusive. The
non-intrusive measurement of physiological cues is essential to find the
real reason for the change of human state in human-machine systems,
and then activate appropriate response of machines.
D. M. Vines-Cavanaugh, Y. Cao, M. L. Wang, Northeastern Univ.
(United States)
The Support Vector Machine (SVM) is an algorithm used for solving
data classification problems. It is a machine learning technique,
and therefore, rather than having an explicit methodology, it relies
on learning how to classify data from examples given in a training
process. This characteristic is highly beneficial as it allows the SVM to
have broad applications ranging from image recognition to leukemia
diagnosis. The focus of this paper is on the SVMs application to the
field of structural health monitoring; specifically, its use in detecting
structural abnormalities from a cable-stayed bridge’s health monitoring
system (HMS) data. An inherent complexity of this application is the
acquiring of training data, representing structural abnormalities, from
a structure that is unable to be damaged. Accordingly, this issue is
resolved by developing a finite element model and using it to simulate
each abnormality that is to be detected. Regarding the application’s
success, this paper compares SVM results to those from another, more
established, health monitoring technique. In accomplishing this, the
SVM is tested to see that it can detect some abnormal expansion joint
behavior, 10-20% fixity in the longitudinal direction, that was previously
found using a finite element updating technique.
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The second part was to select appropriate sensing methods to
measure the human physiological cues from the human-machine
contact surfaces. The physiological signals are weak, and should
be acquired using sensors with high sensitivity. Due to the dynamic
human-machine contact, the physiological signals may be
discontinuous. A sensor network will cover the human-machine contact
surfaces to measure physiological cues, and ensure the consistence
and continuity of measurement. The sensor network needs sensors
with small sizes and low energy-consumption. This study reviewed and
compared the common sensors, MEMS sensors, and NANO sensors. It
was found that MEMS sensors and NANO sensors can achieve higher
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monitoring sensors for such systems.
sensitivity, smaller sizes, and lower energy-consumption than common
sensors. Both of them can offer unique contributions to humanmachine contact based non-intrusive measurement of physiological
cues.
While many technologies for UAV and SHM systems can be, and
have been, adapted from those currently available in large manned
aircraft; cost, weight, and size constraints have prevented mini UAVs
from including many of the robustness mechanisms common to larger
aircraft. Moreover, the ubiquitous nature of the sensing requirements for
SHM systems has limited their uptake, due mainly to the same issues
of cost, weight and size.
The third part was to discuss the design and manufacture of MEMS/
Nano-Skin system. The system generally involves four components,
the flexible substrate, sensors, special integrated circuit, and
connecting circuits between sensors and special integrated circuit.
The flexible substrate is used to fix the sensors, special integrated
circuit, and connecting circuits between them, and protect them. The
functions of special integrated circuit include power supply to sensors,
signal acquisition, signal conditioning, and signal transmission. The
connecting circuits between sensors and special integrated circuit
consist of two networks, one network for power supply to sensors
and another network for signal acquisition. The MEMS/Nano-Skin is
flexible, and can be attached to any curved surfaces of machines.
Except the special integrated circuit, this study investigated the
manufacture of the flexible substrate with sensors and connecting
circuits.
This paper details the design of a reconfigurable multivariable MEMS
(Micro Electro Mechanical System) array to address these issues. This
array is comprised of multiple instances of identical sensors, which can
be dynamically reconfigured to achieve the desired measurand(s) with
tradeoffs against accuracy. The available measurands include such
items as; accelerations, rotational rates, magnetic fields (all in X, Y and
Z directions), temperature and pressure. The full paper will present the
design of a reconfigurable multivariable MEMS sensor array together
with simulation and measured results.
After a prototype MEMS/Nano-Skin was produced using MEMS
and NANO technologies, experiments were designed to verify the
measurement accuracy in human physiological responses. It is feasible
to use this MEMS/Nano-Skin to measure physiological cues from
human-machine contact surfaces to monitor human state in humanmachine interactions.
7647-70, Session 9a
7647-68, Session 8b
Piezoelectric wafer active sensors (PWAS) are well known for its dual
capabilities in structural health monitoring, acting as either actuators
or sensors. Due to the variety of deterioration sources and locations of
bridge defects, there is currently no single method that can detect and
address the potential sources globally. In our research, our goal of the
PWAS based sensing has the novelty of implementing both passive (as
acoustic emission) and active (as ultrasonic transducers) sensing using
a single PWAS network. The combined schematic is using acoustic
emission to detect the presence of fatigue cracks in steel bridges
in their early stage since methods such as ultrasonics are unable to
quantify the initial condition of crack growth since most of the fatigue
life for these details is consumed while the fatigue crack is too small to
be detected. Hence, combing acoustic emission with ultrasonic active
sensing will strengthen the damage detection process. The integration
of passive acoustic emission detection with active sensing will be a
technological leap forward from the current practice of periodic and
subjective visual inspection, and bridge management based primarily
on history of past performance.
Steel bridge fatigue crack detection with
piezoelectric wafer active sensors
L. Yu, V. Giurgiutiu, P. H. Ziehl, Univ. of South Carolina (United
States); D. Ozevin, Physical Acoustics Corp. (United States)
Carbon nanotube sensors on CMOS
circuitry for environmental monitoring
Y. Liu, C. Chen, M. R. Dokmeci, M. L. Wang, Northeastern Univ.
(United States)
Single-walled carbon nanotubes (SWNTs) with their large surface area,
high aspect ratio are one of the novel materials which have numerous
attractive features amenable for high sensitivity sensors. Several
nanotube based sensors including, gas, chemical and biosensors
have been demonstrated. Moreover, most of these sensors require
off chip components to detect the variations in the signals making
them complicated and hard to commercialize. Here we present a
novel complementary metal oxide semiconductor (CMOS) integrated
carbon nanotube sensors for portable high sensitivity chemical sensing
applications. Multiple zincation steps have been developed to axcertain
proper electrical and mechanical connectivity between the carbon
nanotubes and the foundry made CMOS circuitry. The SWNTs have
been integrated onto (CMOS) circuitry as the feedback resistor of a
Miller compensated operational amplifier utilizing low temperature
Dielectrophoretic (DEP) assembly process which has been tailored to
be compatible with the post-CMOS integration at the die level. Building
nanotube sensors directly on commercial CMOS circuitry allows
single chip solutions eliminating the need for long parasitic lines and
numerous wire bonds. The carbon nanotube sensors realized on CMOS
circuitry strong response to various vapors including methanol and
dinitrotoluene. The remarkable set of attributes of the SWNTs realized
on CMOS electronics chips provides an attractive platform for high
sensitivity portable nanotube based bio and chemical sensors.
In this study, extensive laboratory investigation will be performed
supported by theoretical modeling analysis. A demonstration system
will be presented to show how piezoelectric wafer active sensor is used
for acoustic emission. Specimens representing different structures
are tested and compared with the finite element model predictions.
The results will also be compared with traditional acoustic emission
transducers to identify the application barriers.
7647-71, Session 9a
Monitoring concrete by means of embedded
sensors and electromechanical impedance
technique
7647-69, Session 8b
V. G. M. Annamdas, P. Rizzo, Univ. of Pittsburgh (United States)
Reconfigurable multivariable MEMS sensor
array
This paper describes the use of embedded and surface bonded
piezoelectric transducers PZTs) to monitor concrete by means of the
electromechanical impedance (EMI) method. The main objective of the
present study is the design and utilization of a rugged and embeddable
sensing system capable to monitor curing, stress and damage in
concrete structures. Three concrete cylinders with these designed
sensors were cast and tested. Surface bonded PZT were also used
to compare the response of conventional PZT patch to the response
of the embedded system. After the conventional 28-days curing, two
cylinders were subjected to a compression test and the third cylinder
was subjected to induced damage. The EM signatures were processed
S. P. van der Velden, Defence Science and Technology
Organisation (Australia) and La Trobe Univ. (Australia); J. Singh, La
Trobe Univ. (Australia)
Research into operational aspects of mini unmanned aerial vehicles
(UAV) and structural health monitoring systems (SHM) is being
conducted at the Defence Science and Technology Organisation and
La Trobe University. A fundamental area of interest is investigating the
problems associated with miniaturisation of the control and health
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using a statistical index and a slope gradient. The results show that
the sensing system and the EMI method are suitable to monitor curing
progression and to detect applied stress, damage onset, and damage
propagation.
Fatigue induced damage is often progressive and gradual in nature.
Structures subjected to large number of fatigue load cycles will
encounter the process of progressive crack initiation, propagation
and finally fracture. Monitoring of structural health, especially for
the critical components, is therefore essential for early detection of
potential harmful crack. Conventional structural health monitoring
(SHM) techniques such as ultrasonic wave propagation technique have
been employed to detect incipient crack. Despite the accuracy of crack
length measurement offered by these techniques, various drawbacks
exist such as the necessity of frequent inspections which are tedious,
laborious, potentially hazardous and cost intensive.
7647-72, Session 9a
Identification of delamination between steel
bars and concrete using wavelet packet
analysis
Recent advent of smart materials such as piezo-impedance transducer
has ushered a new era in the field of SHM. Commonly available
techniques such as the electromechanical impedance (EMI) technique
and wave propagation technique are well proven to be effective
in incipient damage detection and characterization. Exceptional
advantages such as autonomous, real-time and online, remote
monitoring may provide a cost-effective alternative to the conventional
SHM techniques.
G. Ou, The Univ. of Western Australia (Australia); X. Zhu, Univ. of
Western Sydney (Australia); H. Hao, The Univ. of Western Australia
(Australia)
The interface between steel bar and concrete plays an important role
in retaining the strength of reinforced concrete under loading. When
the interface is damaged, such as crack and de-bond between the
two materials, it will lead to significant degradation of the structural
performances. In this study, wave propagation on several steel bars
embedded in two concrete plates is tested in order to identify the
delamination between steel bar and concrete. Piezoelectric actuators
and sensors are attached to steel bars for gathering input and response
signal. This paper adopts wavelet transform combined with wavelet
packet decomposition, component energy and Shannon entropy to
analyse the experimental results. Damage features including energy
distribution, damage index, entropy distribution and relative entropy are
provided. The results demonstrate that both damage index and relative
entropy are sensitive to the existence of damage and alter linearly with
debonding length in single debonding test, while energy and entropy
distribution is largely influenced by the property of the excitation signal.
In multiple delaminations test, damage index and relative entropy have
no such clear tendency.
In this study, the main focus is to investigate the feasibility of
characterizing a propagating fatigue crack in a structure using the EMI
technique as well as estimating its remaining fatigue life using the linear
elastic fracture mechanics (LEFM) approach. Uniaxial cyclic tensile load
is applied on a lab-sized aluminum beam up to failure. Progressive shift
in admittance signatures measured by the Piezo-impedance transducer
(PZT patch) corresponding to increase of loading cycles reflects
effectiveness of the EMI technique in tracing the process of fatigue
damage progression. With the use of LEFM, prediction of the remaining
life of the structure at different cycles of loading is possible.
7647-75, Session 9b
7647-73, Session 9a
Life cycle structural health monitoring of
airframe structures by strain mapping using
FBG sensors
Monitoring bond performance between steel
rebar and concrete by electro-mechanical
impedance approach
I. Takahashi, K. Sekine, M. Kume, H. Takeya, Mitsubishi Electric
Corp. (Japan); Y. Iwahori, Japan Aerospace Exploration Agency
(Japan); N. Takeda, The Univ. of Tokyo (Japan); Y. Koshioka,
RIMCOF (Japan)
R. Tawie, H. Lee, Korea Advanced Institute of Science and
Technology (Korea, Republic of)
The purpose of this research is to develop the structural health
monitoring system for composite airframe structures by strain
mapping through their life cycles. We apply FBG sensor networks to
CFRP pressure bulkheads and monitor the strain through their life
cycles: molding, processing, assembly, operation and maintenance.
Damages, defects and deformations which occurred in each stage are
detected using the strain distribution. To establish this SHM system,
we worked to develop life cycle monitoring technology and highly
reliable diagnostic technology. At first, we monitored the strain of
CFRP laminates during molding and processing with FBG sensors. As
a result, not only the thermal strain on curing process but also strain
changes due to demolding and trimming was measured precisely. In
addition, we analyzed the damages and accidental deformation of
pressure bulkhead in operation and calculated the strain distributions.
On the basis of these results, the location of FBG sensors suitable for
the detection of damages and accidental deformation was investigated.
Moreover, we developed an optical fiber implementation system using
unidirectional prepreg and verified the durability and reliability of the
optical fibers with FBG sensors mounted on CFRP by this system. As a
result, it was confirmed that the optical fiber sensor system has enough
durability and accuracy required for strain monitoring. Furthermore, we
developed a small, lightweight optical measurement system suitable
for implementation to aircrafts and evaluated its reliability under various
temperature conditions.
The bond between steel reinforcing bar and concrete is critical to
the effectiveness of steel in reinforced concrete structures. The bond
strength between the steel rebar and concrete can be evaluated
experimentally by pull-out test. It would be very useful to develop
a technique to evaluate the bond performance of reinforcing bar in
concrete by non-destructive way since pull-out test is labor-intensive
and not easy to conduct. In this study, the feasibility of the impedance
approach utilizing piezoceramic patches to evaluate bond performance
between steel rebar and concrete is investigated. The impedance
approach based on the electro-mechanical coupling of piezoelectric
materials has been successfully demonstrated by many researchers
for detecting damage in structures using high frequency excitations.
The test results in the present study show that the bond performance
of reinforcing bar is influenced by the quality of concrete. It is
apparent that sufficient compaction is important to maximize the bond
strength of the reinforcing bar in hardened concrete. In conclusion,
this preliminary study shows that it is possible to determine the bond
performance of steel rebar in concrete by a non-destructive method
based on the electro-mechanical impedance approach.
7647-74, Session 9b
Estimation of fatigue life using
electromechanical impedance technique
Y. Y. Lim, C. K. Soh, Nanyang Technological Univ. (Singapore)
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Conf. 7647: Sensors and Smart Structures Technologies for Civil,
Mechanical, and Aerospace Systems
strip. The results of finite element analyses on the design parameters
for a comb transducer strip will be presented.
7647-76, Session 9b
In situ determination of stress intensity
factors for the prediction of fatigue crack
growth using piezoelectric polymer coatings
7647-78, Session 10a
Autonomous smart sensor network for fullscale structural health monitoring
A. Ricoeur, Univ. Kassel (Germany); D. Bäcker, M. Kuna,
Technische Univ. Bergakademie Freiberg (Germany)
J. A. Rice, Texas Tech Univ. (United States); K. Mechitov, B. F.
Spencer, Jr., G. Agha, Univ. of Illinois at Urbana-Champaign (United
States)
Technical structures like aerofoils, wind energy plants or civil
engineering structures are mostly exposed to complex stochastic load
configurations. The uncertainty of loading assumptions in connection
with complex geometries and joints makes numerical analyses of
stresses inaccurate. Thus, concepts of structural health monitoring
are valuable means for the assessment of reliability and durability of
vulnerable constructions. In particular, fatigue crack growth rates must
be estimated in order to determine inspection intervals.
The demands of aging infrastructure require effective methods
for structural monitoring and maintenance. Wireless smart sensor
networks offer the ability to enhance structural health monitoring (SHM)
practices through the utilization of onboard computation to achieve
distributed data management. Such an approach is scalable to the
large number of sensor nodes required for high-fidelity modal analysis
and damage detection. While much of the technology associated with
smart sensors has been available for nearly a decade, the number of
full-scale SHM applications has been limited. This slow progress is
due, in part, to the complex network management issues that arise
when moving from a laboratory setting to a full-scale monitoring
implementation. This paper presents flexible network management
software that enables continuous and autonomous operation of
wireless smart sensor networks for SHM applications. The software
components combine sleep/wake cycling for enhanced power
management with threshold detection for triggering network wide
tasks, such as synchronized sensing or decentralized modal analysis,
during periods of critical structural response.
Polyvinylidene fluoride (PVDF) is a transparent elastic polymer
exhibiting piezoelectric properties. Connecting the polymer coating to
a shell-like structure which is deformed by any kind of loading, electric
potential differences are monitored at electrodes applied to the polymer
surface at different locations. Solving an inverse problem, stresses
acting on the surface of the structure can be calculated from these
data.
In a cracked body, stress intensity factors can be calculated from the
electrode signals. In contrast to classical procedures using mostly
one or two resistance strain gauges applied close to the crack tip, the
concept presented in this paper is based on a continuous piezoelectric
polymer layer which is applied at the zone of the estimated crack path.
A large number of electrodes distributed all over the PVDF coating
delivers a variety of signals, which are interpreted to determine Mode-I
and II stress intensity factors, T-stresses and the position of the crack
tip. These quantities emerge from an inverse optimization problem
drawn upon a redundant number of electric signals. Compared to a
small number of resistance strain gauges, more signal information is
available, the spatial resolution is higher, the location of the crack tip is
variable and an external power source is dispensable.
7647-79, Session 10a
Discovery of emerging patterns with
immune network theory
The paper presents theoretical work, analytical calculations and
numerical simulations to demonstrate the efficiency of the new
sensor concept, to investigate possible design options, to provide the
fundamentals for the solution of the inverse problem and to optimize
essential parameters.
B. Chen, C. Zang, Michigan Technological Univ. (United States)
This paper presents an unsupervised structure damage pattern
recognition based on the immune network theory. The immune network
method provides more flexible learning tools than neural networks and
clustering technologies. With a neural network, a network structure has
to be defined first, and the network is only as good as its initial design.
The immune networks allow their components to change and learn
patterns by changing the strength of connections between individual
components.
7647-77, Session 9b
* Continuous piezoelectric health monitoring
systems based on ultrasonic guided waves
The goal of the presented computational model for unsupervised
structure damage pattern recognition is to dynamically construct a
network of antibodies (feature vectors) to represent the internal image
of the damage patterns presented in the structure. The connection of
antibodies depends on the affinity among them. The clonal immune
response is initiated by each presented antigenic pattern. The newly
generated antibodies with high affinities to the antigen will be recruited
into the network. The antibodies with low affinities to the antigen will
be eliminated from the network to change affinities of representative
antibodies. The continuous recruitment and elimination of antibodies
not only provides a competition mechanism to control the survival of
antibodies in the network, but also offers great potential to discover
and reinforce the beneficial ones, which are able to bind with
unpredictable invaders.
C. J. Lissenden, S. Li, J. L. Rose, The Pennsylvania State Univ.
(United States)
Aircraft, the civil, mechanical, power generation and distribution
infrastructures are all aging and becoming less reliable. Inspection
and off-line nondestructive evaluation are expensive in many ways.
Structural health monitoring (SHM) and condition based maintenance
(CBM) are keys to shifting the paradigm to cost effective operation and
maintenance of reliable systems. A new research project investigates
continuous comb transducer strips to generate ultrasonic guided
waves for structural health monitoring of plate and shell structures
(pipelines, pressure vessels, storage tanks, airframes). A theoretically
driven approach, based on the application of wave mechanics
principles, is used to research and design a network of strip sensors.
Fibrous piezoelectric composites will be considered for the comb
elements, widely expanding the design space of these elements
to include fiber orientation and volume fraction in addition to size,
configuration, and location/size of the electrodes. Piezoelectric and
mechanical material properties for these innovative sensor designs will
be researched. The system will be capable of active interrogation with
Lamb waves upon demand, as well as passive monitoring of acoustic
emissions with low power. This paper presents results from wave
propagation studies of continuous strip actuators composed of aligned
piezoelectric fibers having different orientations with respect to the
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The presented immune network-based unsupervised structure
damage pattern recognition approach has been validated using a
benchmark civil structure. The test result shows the feasibility of using
the presented method for the unsupervised structure damage pattern
recognition.
7647-80, Session 10a
Multi-functional wireless impedance sensor
nodes for structural health monitoring
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Conf. 7647: Sensors and Smart Structures Technologies for Civil,
Mechanical, and Aerospace Systems
Because of their low installation costs and autonomous data
processing capabilities, wireless sensing networks have recently made
it possible to intelligently instrument large civil structures with dense
arrays of sensors. The data collected by these sensing networks can
then be used to monitor the behavior and health of these structures
over time. Perhaps the most important characteristics that can be
measured by a network of wireless sensors are the dynamic (or
modal) properties of a structural system. Modal frequencies and mode
shapes, as well as modal damping ratios, can all be used to validate
analytical models, improve design concepts, and detect and locate
damage within a structural system. As such, it has become important
to develop autonomous, in-network methods of determining the
modal properties of a structure. In this study, an agent-based method
is developed in which a network of wireless sensors autonomously
organize themselves in order to compute modal properties through
the use of the Frequency Domain Decomposition (FDD) method.
The methodology developed herein uses market-based principles to
create an optimal computing environment with respect to constraints
on computational speed, FDD accuracy, communication bandwidth,
and network power consumption. The proposed approach is validated
through a series of modal tests performed using a network of wireless
sensing prototypes.
J. Min, Korea Advanced Institute of Science and Technology
(Korea, Republic of); S. Park, Sungkyunkwan Univ. (Korea,
Republic of); C. Yun, Korea Advanced Institute of Science and
Technology (Korea, Republic of); B. Song, Korea Electronics
Technology Institute (Korea, Republic of)
This study presents the development of a low cost, but multi-functional
wireless sensor node for the impedance-based SHM. The bottom
line is to provide multifunctional wireless sensor nodes for excitation/
sensing, structural damage detection/sensor self-diagnosis using
embedded algorithms, temperature/power monitoring, and energy
scavenging. A miniaturized impedance measuring chip is utilized
for low cost and low power structural excitation/self-sensing. Then,
structural damage detection/sensor self-diagnosis are executed on
the on-board microcontroller. Moreover, it can use the harvested
power from solar energy to measure and analyze the impedance data.
It can also monitor temperature and power consumption. A series of
experimental validation studies have been carried out for detecting
loose bolts and crack damages on a lab-scale steel structure as well as
on real bridge/building structures. It has been found that the proposed
wireless impedance sensor nodes can be effectively used for local
health monitoring of structural components and for constructing a
low-cost and low-power but multifunctional SHM system as “place and
forget” sensors.
7647-83, Session 10b
Pressure adaptive honeycomb: a
new adaptive structure for aerospace
applications
7647-81, Session 10a
* Flexure-based mobile sensor design
with application in structural damage
identification
R. Vos, Delft Univ. of Technology (Netherlands); R. M. Barrett, The
Univ. of Kansas (United States)
D. Zhu, X. Yi, J. Guo, Y. Wang, K. Lee, Georgia Institute of
Technology (United States)
A novel adaptive aerostructure is presented that relies on certified
aerospace materials and can therefore be applied in conventional
passenger aircraft. This structure consists of a honeycomb material
which’ cells extend over a significant length perpendicular to the plane
of the cells. Each of the cells contains an inelastic pouch (or bladder)
that forms a circular tube when the cell forms a perfect hexagon.
By changing the cell differential pressure (CDP) the stiffness of the
honeycomb can be altered. Using an external force or the elastic force
within the honeycomb material, the honeycomb can be deformed such
that the cells deviate from their perfect-hexagonal shape. It can be
shown that by increasing the CDP, the structure eventually returns to
a perfect hexagon. By doing so, a fully embedded pneumatic actuator
is created that can perform work and substitute conventional lowbandwidth flight control actuators.
Wireless sensing techniques have been widely explored for structural
health monitoring in recent years, due to the advantages in reducing
installation cost and time. Limitations of current wireless sensors
have been identified in terms of power supply, communication
bandwidth, communication range, computing power, etc. To address
these limitations, mobile sensor networks may be adopted as a
transformative change to wireless sensor networks. A mobile sensor
network contains sophisticated mobile nodes with capabilities of
sensing, wireless communication, and embedded computing. The
sensor nodes may be passive for collecting structural response data,
and/or active for applying excitation to a local area of the structure.
Compared to conventional sensors with static configuration, mobile
sensor networks can offer measurements with flexible deployment and
high spatial resolution.
A comparison of pressure adaptive honeycomb to other active
materials shows that it belongs to the group showing the highest
strains (in excess of 50%). For a pressure adaptive honeycomb that
relies on compressed bleed air from the jet engine, a mass-specific
energy density of 12.4J/g was calculated (on the par with SMA).
In this paper, we propose the design concept of a flexure-based
mobile sensor. The flexure-based mobile sensing node is capable of
maneuvering on ferromagnetic structures using motorized magnetic
wheels. A compliant spring steel beam is mounted on the mobile
sensing node for attaching/detaching an accelerometer onto/from the
measurement location. Meanwhile, infrared sensors and Hall effect
sensors are equipped to ensure the safety and reliability of the mobile
sensing node. To validate the performance of the mobile sensing
system, laboratory experiments are conducted with a steel portal
frame. In the experiments, two flexure-based mobile sensing nodes are
adopted to collect acceleration data for the damaged and undamaged
structure under modal hammer excitation. Transmissibility function
analysis is employed to identify the damage by comparing data from
the undamaged and damaged structure.
Pressure adaptive honeycomb was embedded into a 35%c adaptive
flap on a NACA2412 wing section with a chord of 1.08m. Wind tunnel
tests at a Reynolds number of one million demonstrated a shift in
the cl-alpha curve upwards by an average of 0.3, thereby increasing
the maximum lift coefficient from 1.27 to 1.52. This successfully
demonstrated the application of pressure adaptive honeycomb
embedded in a morphing aircraft structure.
7647-84, Session 10b
Detailed studies on the formation of
piezoelectric β-phase of PVDF at different
hot-stretching conditions
7647-82, Session 10a
* Agent-based computational topology
formation for automated modal analysis in
dense wireless sensing networks
A. Jain, J. Kumar, National Aerospace Labs. (India); D. Roy
Mahapatra, Indian Institute of Science (India); H. Kumar, Defence
Research and Development Organisation (India)
A. Zimmerman, J. P. Lynch, Univ. of Michigan (United States)
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Poly (Vinylidene Fluoride) or PVDF is promising material for transducer
applications. PVDF exists in four crystalline phases viz., alpha, β,
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Conf. 7647: Sensors and Smart Structures Technologies for Civil,
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of this work is to examine the micro-nanoscale deformation and
thermal induce recovery behavior of shape memory polymer. The
copolymer shape memory material is synthesized by our Smart
Materials and Structures Laboratory with certain percentages of epoxy
and condensate. Instrumented nanoscratching is used to examine
ambient temperature deformation of the epoxy SMP below their glass
transition temperature. Temperature induced shape recovery of the
scratching is studies using atomic force microscopy. The scratched
surface is toweled at above Tg of the material and cooled down to
ambient temperature. Then a scan of the surface profile is performed
as a function of the increasing temperature from room temperature to a
temperature above Tg until the scratch is fully recovered. Full recovery
of mar has been recorded. The difference in height during temperature
induced recovery is also recorded. Dynamic mechanical analysis
is used to acquire the recovery behavior of the polymer with the
function of recovery temperature and recovery time, which are critical
for the development of the SMP-based applications. Furthermore,
the difference between temperature induced shape recovery of the
indentation and scratch is studied. The study will also provide insight
on application of SMP in nanoscale through the investigation of the
elastic, plastic and recovery deformation response of the SMP.
gamma, and delta. The apolar alpha-phase is most stable and polar
β-phase exhibits piezoelectric properties. In the present work, alphaphase PVDF films have been converted to β-phase by hot stretching
using a specially designed setup. The effect of stretching
temperature and stretching ratio on the evolution of β-phase has been
studied from x-ray diffraction patterns, Line profile analysis of (110)
reflection from β-phase indicates that grain size increases from 6 to
17 nm and micro strain decreases from 0.026 to 0.014 as stretching
temperature increases from 50-80 degree C. Films prepared at different
conditions have also been characterized for mechanical, thermal and
surface features. In addition, Raman and infrared spectroscopy (IR) has
also been used at various stages.
It is found that β-phase is achieved at all temperatures and stretching
ratios. The conditions to achieve the beta phase have been optimized
by checking the 2θ value corresponding to (110) reflection. Hotstretching at 80°C with a stretching factor of 4 gave 20.8degree for 2θ
of (110) reflection of β-phase. This value agrees well with the standard
value quoted in the literature. For further studies, these stretching
conditions are used to prepare the β-phase. These films give a value in
the range 13-15 pC/N for d33.
To evaluate the performance of the sensor made out of this film, the
vibration modes of cantilever have been simultaneously recorded
with PVDF and PZT sensors. A comparison of the two sets of signals
indicates the excellent performance of PVDF sensors.
7647-87, Session 10b
Novel fabrication technology for threedimensional high surface area pyrolized
structures
7647-85, Session 10b
Thermodynamic modeling of martensitic
phase transformations
V. Ho, G. S. Bisht, L. Kulinsky, M. J. Madou, Univ. of California,
Irvine (United States)
V. S. Guthikonda, R. S. Elliott, Univ. of Minnesota (United States)
High specific surface area structures are used in a variety of
applications including the production of highly sensitive biosensors,
fabrication of separation membranes, in high throughput catalytic
processing, and for the efficient electrodes in batteries and fuel cells.
In many electrochemical applications (i.e. sensors, batteries) it’s also
critical to have good conductive properties of the fabricated high
surface area structures.
The unusual properties of shape memory alloys (SMAs) are due to
solid-to-solid martensitic phase transformations (MPTs) which result
from an instability of the material’s crystalline structure. Accurate
models of MPTs based on the material’s atomic composition and
crystal structure are currently not available. However, models of this
type are required to computationally discover new SMAs.
Careful design of surface-to-volume ratio of the electrode surface is
important for electrochemical energy generation such as in batteries
and fuel cells. Although high surface area of electrodes facilitates
better electrochemical reaction rate, it also increases the overall
internal resistance of the cell. Thus more intelligent design of electrode
geometries is required that maximizes current exchange while
minimizing the resistance path for the current. One such geometry is
ubiquitously existent in nature in the form of fractal structures.
This work aims to develop a lattice-dynamics model using a “firstorder self-consistent approach” capable of capturing MPT behavior. In
particular, atomic interactions are modeled using empirical potentials
(the Morse pair potential is used as an example). In general, these
potentials are determined from first-principles calculations such
as electronic density functional theory simulations. The effects
of atomic vibrations on the material properties are captured by
computing the renormalized frequencies of atomic vibration using
a set of self-consistent equations. A key feature of this approach is
that the renormalized frequencies depend on both configuration and
temperature. The model is, thus, able to capture “entropiclly stabilized”
transformations such as those found in SMAs.
We have invented a novel fabrication technology for creating high
surface area, three-dimensional conductive structures based on the
deposition and subsequent processing of the electroactive polymers
(EAP). Further methods have been considered to exploit the fabrication
technique in achieving fractal scaling of the electrode structures. The
proposed fabrication technique is capable of fast and inexpensive
production of high surface area structures with the designed geometry,
porosity, and conductivity.
The model is demonstrated for a one dimensional bi-atomic chain.
Morse potentials are chosen to illustrate the desired behavior and the
capabilities of the self-consistent approach. The resulting model is
evaluated by generating a stress-free bifurcation diagram consisting
of the material’s equilibrium states as a function of temperature. The
bifurcation diagram reveals the existence of a hysteretic temperatureinduced MPT. The ability of the model to predict temperature-induced
MPTs indicates that it has the potential for use as a computational tool
to discover new SMAs.
7647-88, Session 11a
Pavement roughness monitoring method
using fiber optic vibration sensors
K. S. Kim, Hongik Univ. (Korea, Republic of); I. K. Yoo, Y. Baek,
Korea Institute of Construction Technology (Korea, Republic of)
7647-86, Session 10b
Characterization of strain recovery
behavior of shape memory polymer by
nanoscratching test
Main purpose of pavement of the highway is to provide the safe
and efficient surface of the road to the vehicles. In order to achieve
the safe and efficient surface of the road, overall investigations after
construction and every year inspection are performed. For maintenance
of the pavement, inspections with 7.6 profilermeter or ARAN(Automatic
Road Analyzer) are used, but they are not suitable for local in situ
monitoring of the roughness of pavement while they are widely used for
long range roughness of pavement.
H. Zhang, Y. Liu, J. Leng, Harbin Institute of Technology (China)
The nanoscaled operation of polymers is particularly challenging
due to their significant compliance and low hardness, viscoelastic
or viscoplastic response, and apt to destroy probe tip. The objective
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Fiber optic sensor system, which is not corrosible semi-permanent,
no influence by electromagnetic waves, and able to multiplex, can
be expect to take an important part to assess the safety and residual
estimate the life span of the highway pavement structure.
7647-91, Session 11a
Monitoring of stress distribution along a
ground anchor using BOTDA
In this research, as in situ monitoring of roughness of pavement, we
propose the vibration monitoring method using fiber optic sensors.
We designed and produced prototype fiber optic vibration sensor
packages. Laboratory impact tests with the sensors were performed.
The sensors showed very good responsibility to the impact and nice
damping shape like other ordinary accelerometers. Actual road tests
with the prototype vibration sensor were also performed. The ambient
vibration by the vehicles was used for the experiment.
M. R. Iten, A. M. Puzrin, ETH Zürich (Switzerland)
The determination and monitoring of the stress distribution along a
loaded ground anchor rod is essential for the understanding of the
bearing behavior of this geotechnical structure. Thus, lots of interest
has been put into measuring strain at distinctive points along anchor
rods by various means of sensors, such as conventional strain gauges
and, more recently, fiber Bragg gratings. Other approaches are based
on elongation measurements in a very limited amount of rod sections.
This can be basically seen as long-gauge strain sensors. Monitoring
anchor rods, which offer strain readings in up to 4 sections are
commercially available and are regularly used in constructions.
7647-89, Session 11a
Development and laboratory validation of a
low-cost time-of-fly fiber optic sensor
In this paper, a novel monitoring ground anchor using embedded
optical fibers for the continuous strain assessment along the anchor
rod is proposed and results from laboratory and field testing of such
anchor rods are presented. Continuous strain along the embedded
fiber cable is measured by Brillouin Optical Time Domain Analysis
(BOTDA) through a commercially available measurement unit.
G. Fontana, G. Soncini, Univ. degli Studi di Trento (Italy); M. Corrà,
Tretec S.r.l. (Italy); M. Pozzi, D. Zonta, Univ. degli Studi di Trento
(Italy)
This paper presents a novel elongation sensor based on direct
measurement of the Time of Flight of short laser pulses in an optical
fiber circuit. The technology was developed with the idea of producing
very low cost fiber optic measurement systems with a single-channel
Interrogation Unit (IU), and we employ ordinary and inexpensive
electrical components: a nanosecond laser pulser, a photo-diode and
a Pulse Width Modulation electronic circuit. For the same reason, the
optical circuit consists only of bare fiber. In more detail, the optical path
is divided into two lines, permitting intrinsic thermal compensation:
one measuring fiber is attached to the structure, while the other is
kept loose for reference. The system was developed in a number of
prototypes and tested in the laboratory to validate its performance.
The model of IU tested generates 1ns pulses at a frequency of 30kHz.
Two optical arrangements were investigated: the first is a 100m long
optical fiber coil, designed for a measurement base of about half a
meter, the second is a 15 meter gauge-length sensor. Test results show
that response of the system is almost linear and precision is of the
order of 20-60 . A model of this sensor was embedded in a laboratory
prototype of smart reinforced concrete beam, while other models have
been installed in-situ in a historic building as part of the instrumentation
of a pilot wireless monitoring system.
In a first step, different techniques of optical fiber integration into rods
of 1.2m to 3.3m length have been carried out. Thereafter, the rods
where strained stepwise in a tensile testing apparatus and optical
strain measurements were taken at each load step. The optical strain
was compared with independently acquired strain data. The evaluation
of the laboratory testing led to the design and development of an
8m long monitoring ground anchor for field application. In 2009, this
anchor has been integrated into a wall supporting an excavation pit
and subsequently, anchor pull testing was performed. The optical strain
data led to the successful monitoring of the stress profile in the 5.75m
grouted section of this anchor. Additionally, the data could be used
for the calculation of the applied pull out load in the free length of the
anchor and the anchor head displacement. These results contribute
towards the proof of serviceability for distributed fiber optic sensors in
these kinds of practical approaches.
7647-92, Session 11a
Study on the reliability of distributed optical
fiber sensors under fatigue load
S. Song, C. Yang, Southeast Univ. (China); Z. Wu, Ibaraki Univ.
(Korea, Democratic Peoples Republic of); S. Shen, Southeast Univ.
(China)
7647-90, Session 11a
Measures for identifying cracks within
reinforced concrete beams using BOTDR
It is significant to improve the fatigue reliability of strain measurement
for damage identification of important civil infrastructures under
long-term fatigue loads, such as bridges and prestressed steel
structures. In this paper, based on the distributed optical fiber strain
sensing technique of pulse-prepump Brillouin Optical Time Domain
Analysis(PPP-BOTDA), three types of optical fibers, i.e. single-mode
optical fiber with Jacket (Type-A), UV resin-coated optical fiber
(Type-B) and optical fiber with improved strain sensitivity (Type-C),
were selected to study the monitoring reliability in low cycle fatigue
experiment with different initial strain amplitudes. Three kinds of optical
fibers were tested in unidirectional tension at certain cycle numbers.
Preliminary experimental results show that the strains of the Type-A
and Type-B drift much with cycle numbers, while the Type-C show little
deviation from the true value. It is indicated that the monitoring data
of Type-A and Type-B was not reliable under fatigue loading because
of the fatigue damage accumulation of the optical fiber, while Type C
had little effect on its reliability. As a result, optical fibers with improved
strain sensitivity can be used in the long-term monitoring of largescale structures under long-term fatigue loads such as bridges and
prestressed steel structures.
A. Klar, Y. Goldfeld, Z. Chares, Technion-Israel Institute of
Technology (Israel)
BOTDR is one of the strain measurement technologies that is suitable
for smart monitoring of civil engineering infrastructures, such as
bridges. While the technology has the advantage of supplying spatially
distributed data, it is currently limited to a spatial resolution of about
1m. This infers that the technology may lack the ability to identify
the exact type and source of damage; that is, different geometrical
configurations of cracking within a concrete beam may lead to similar
BOTDR readings, and hence the exact nature of cracking might not be
resolved by the BOTDR.
This study suggests different cracking indicators, and examines,
both analytically and experimentally, their correlation with BOTDR
readings of damaged reinforced concrete beams. The analytical part
entails statistical analysis of thousands of cracking cases in fractured
reinforced concrete beams and their effect on the simulated BOTDR
readings. The analysis is conducted within COMSOL-Multiphysics,
and is aimed to understand the correlation between the different
cracking indicators and the beam curvature as would be obtained by
the BOTDR. The experimental part consists of a controlled load test
of a reinforced beam instrumented by BOTDR fibers, and is aimed to
validate the analytical findings.
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127
Conf. 7647: Sensors and Smart Structures Technologies for Civil,
Mechanical, and Aerospace Systems
7647-93, Session 11a
P. L. Alvarez, R. Aragonés, J. Oliver, Univ. Autònoma de Barcelona
(Spain); C. Ferrer, Univ. Autònoma de Barcelona (Spain) and CNMIMB (CSIC) (Spain)
Development of an optical fiber sensor
to monitoring the formation of cracks in
concrete structures
It is well-know that continuous revisions of aerospace structures
are necessary to detect damage on aircraft. Therefore, developing a
preventive maintenance in aircraft ensures higher security and cost
reduction. In this work, a modeling and simulation environment of
Heterogeneous Electronic System is described. This system helps
to identify high risk damage areas which have been produced by
environmental conditions. This smart solution include: a three axis
accelerometer, capacitive humidity sensor, low voltage temperature
sensor, pressure sensor, and stress-strain. Signal acquisition
techniques based on voltage to frequency converters, capacitance to
frequency converters and frequency to code conversion has been also
used.
K. Rodriguez Carmona, A. M. Lucero, Ctr. de Investigación en
Materiales Avanzados, S.C. (Mexico)
Many times when a fissure in a concrete structure is discovered it is
too late because the fissure has already propagated. Because of this, a
fiber optic sensor for detecting fissures at their origin was sought to be
developed. The goal of developing such a sensor was to monitor the
formation of fissures in their initial stages before they propagate and
by this way avoid the failure of a structure. The functionality of such
sensor was demonstrated and was able to detect fissures early (from
their origin) in any part of the structure. This sensor is innovative due to
the fact that it can monitor the condition of a structure in a distributed
way and not at points.
The behavioral modeling is performed on the environment MATLAB®/
SIMULINK® with target of translate it into a structural VHDL-AMS
code able to be co-simulated with VHDL descriptions for digital signal
processing circuitry. The model has a user interface for easy interaction
that permits inputs parameters, which are sensing, access to visual
indicators, graphics of response time and frequency.
Interest in the supervision of structures in civil engineering has been
growing constantly in order to improve the durability and safety of
structures. Because of this, development of fiber optic sensors has
been researched for a number of engineering applications. One of
these applications is the continuous supervision of concrete structures.
A mathematical model for each sensor is implemented within
simulink block diagrams. When the sensors are modeled, besides
the conversion, there are multiples factors that influence in their
performance each as: noise density, temperature, supply voltage,
frequency that are simulation in real time allowing the output
signals more precise and reliable. The values of the supply voltage,
and current, and scale factor for the sensors are intended for this
application over the specific range.
This type of continuous supervision has many advantages when
compared to visual inspection. This is because visual inspections
sometimes cannot detect fissures inside a structure unless these
fissures propagate to the surface, which many times cause irreparable
damage. The continuous supervision of optical sensors allows the
permanent monitoring of the condition of a structure. These sensors
are recommended for structures that have variable loads such as
bridges and dams. The ability to permanently monitor a structure has
been recognized as an important development in the supervision of
civil infrastructure.
An excellent way to acquire a complete range of signals presenting
low nonlinearly effects and high accuracy are frequency acquisition
techniques. The output signal of each sensor is different, so that
the system performs analogue signals conversion to the frequency
dominium. Concretely four signals to frequency converters are
employed in this work: the CMOS differential oscillator (relaxation
model of one channel), relaxation model of two channel, resistance to
voltage converters, and voltage controlled oscillator (VCO). Good noise
immunity, high output voltage range, a widest dynamic range, and an
acquisition circuitry reduction are some advantage of this frequency
data acquisition method. Furthermore the system performs frequency
to code conversion based on indirect count method (ICM), and the
dependent count method (DCM).
7647-94, Session 11a
Development of a wireless node for fiberoptic sensing
S. Taylor, E. A. Moro, Univ. of California, San Diego (United
States) and Los Alamos National Lab. (United States); A. Puckett,
Los Alamos National Lab. (United States); M. D. Todd, Univ. of
California, San Diego (United States)
One important aspect of the design methodology is the co-simulation
of circuitry. For analogue signals to frequency converters have been
performed a mathematical model of which output frequency varies
as a result of changing the transduction value, providing symmetrical
and wide range frequency outputs. Therefore is necessary to force
the output oscillation signal to +VDD converting it in to square signal
employing a pulses generator. Power supply rejection ratio (PSRR),
phase noise (PNoise), output spectrum (PSS), and current consumption
(RMS) are parameters to be considered in order to estimate the
environment of oscillator.
Structural health monitoring (SHM) is a developing field of research with
a variety of applications including civil structures, industrial equipment,
and machine process monitoring. The first and most important
stage of any SHM system is the design of the sensing architecture,
which is traditionally composed of transducers that measure some
physical response at discrete points. Distributed fiber-optic sensing
methods have a significant advantage over traditional discrete sensing
systems, in that they can be used to obtain continuous measurements
along the length of an optical fiber to provide real-time monitoring
data. However, fiber-optic sensing equipment is often heavy, bulky
and difficult to install in situ. Furthermore, physical access to the
structure being monitored may be limited, as is the case for rotating
blades or unmanned aerial vehicles, motivating the need for wireless
transmission of sensor readings. This paper presents a first step in
the development of a compact wireless node for fiber-optic sensing,
with which light intensity measurements are used to obtain a firstorder strain approximation. Experimental results from a wind turbine
blade are compared with those obtained using conventional fiber-optic
sensing equipment.
7647-96, Session 11b
On the combination of asymptotic and direct
approaches to the modeling of plates with
piezoelectric actuators and sensors
Y. M. Vetyukov, M. Krommer, Johannes Kepler Univ. Linz (Austria)
The paper presents a novel complex approach towards mathematical
modeling of the performance of thin structures integrated with
strain-type sensors. Namely, we analyze the response of a plate with
piezoelectric patches under mechanical and electrical loads.
7647-95, Session 11b
We consider a two-dimensional material surface with particles having
five mechanical degrees of freedom (translations and rotations) and one
electrical (potential difference between the surfaces). The variational
principle of the direct approach provides both the system of equations
and the expressions of the local strain measures, on which the total
enthalpy in the cross-section depends.
Modeling and simulation of heterogeneous
electronic system based on smart sensors
for aerospace structures health monitoring
128
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As the expression of enthalpy cannot be derived in the framework of
the direct approach, the asymptotic analysis of the three-dimensional
problem is an essential part of the research. We consider the complete
system of equations for a piezoelectric plate with the material
properties, varying over the thickness. Condition of compatibility of
strains plays a central role in the analysis. Looking for the solutions
varying slowly in the plane of the plate, we find the terms, which
dominate as the thickness tends to zero. The relation to the direct
approach is established with the help of the expression of the virtual
work of internal forces. The integrated total enthalpy of the threedimensional model complements the two-dimensional formulation.
was a linear distribution across the thickness, further more they
assumed that the strain distribution across the structure could be a
linear Bernoulli-Euler type or a uniform extensional strain.
Although the solution of Crawley and Luis is only valid at low values
of the frequency-thickness product (i.e., where the axial and flexural
wave approximation holds), this solution has been subsequently used
by other authors for describing the shear-lag transfer at ultrasonic
frequencies where the axial and flexural approximation to the S0 and
A0 modes no longer holds and where more than these two fundamental
modes may be present.
The present paper will present the extension of the work of Crawley
and deLuis for the case of two modes at high frequency and it will
introduce the problem of deriving the interfacial shear stress between
PWAS and structure for two or more wave modes present.
A finite element scheme was implemented based on the suggested
model, and successful comparison with full-scale three-dimensional
solutions was performed. The results serve as a basis for the analysis
of geometrically nonlinear shell structures as well as for model-based
health monitoring and optimal sensor placement.
7647-99, Session 11b
7647-97, Session 11b
Conductor width independence case of the
self-resonance quality factor of semiadditive
planar coils on a magnetoelastic substrate
* Acoustic emission detection and energy
transduction with piezoelectric wafer active
sensors
U. Marschner, E. Starke, C. Wenzel, U. Merkel, A. Jahn, N. Liu,
Technische Univ. Dresden (Germany); A. B. Flatau, Univ. of
Maryland, College Park (United States); W. Fischer, Technische
Univ. Dresden (Germany)
B. Lin, V. Giurgiutiu, Univ. of South Carolina (United States)
Structural health monitoring (SHM) is important for reducing
maintenance costs while increasing safety and reliability. Acoustic
emission (AE) occurs due to stress waves generated when there is a
rapid release of energy in a material, or on its surface. Piezoelectric
wafer active sensors (PWAS) used in SHM applications are able to
detect structural damage in both active and passive mode. PWAS are
small, lightweight, unobtrusive, and inexpensive and achieve direct
transduction between electric and elastic wave energies.
A magnetostrictive bending sensor with rectangular planar coil is
investigated. Its purpose is to measure contactlessly mechanical
quantities of non-vibrating structures using an alternating magnetic
field. The coil turns are electrodeposited by pattern plating on top of a
magnetostrictive Galfenol layer and a thin magnetron sputtered SiO2
insolation layer.
The achievable conductor height depends on the photoresist and
conductor width and gap using standard semiadditive technology.
Therefore a large conductor height, e.g. 20..100 μm, reduces the
number of turns and the coil resistance but is more time consuming
during manufacturing. For this reason the coils investigated in this
paper were manufactured with a constant height h = 10 μm and gap
and variable width.
This paper starts with a literature review of the state of the art on the AE
detection method and AE detection using PWAS. Numerical verification
of AE event and wave propagation in steel and aluminum substrates
was simulated by finite elements method. The energy transduction
of PWAS and substrate was considered. The experimental result and
numerical simulation shows the trends in energy flow behavior during
AE events. This indicates that PWAS can be used as an AE sensor and
with proper adaption; it can replace the bulk traditional AE sensors for
SHM applications, e.g. steel bridge health monitoring.
The sensor is operated near its electrical self-resonance between 5 and
40 MHz and requires a high quality factor. It determines the number of
periods in the impulse response and the bandwidth of the resonance
circuit. FEM-simulations show that the quality factor is almost
independent on the conductor width under the design restrictions when
skin and proximity effects are included.
7647-98, Session 11b
Shear lag solution for structurally attached
active sensors
It could be confirmed by measurements obtained from sensors with
three different turn numbers and conductor widths depending on the
turn number that the self-resonance quality factor is almost constant
when a semiadditive technology is used to manufacture the coil
turns. This is a contradiction to the low frequency properties of the
quality factor. The reason is mainly the displacement of the electrical
current by the proximity effect. An effective conductor width could be
determined.
G. Santoni-Bottai, V. Giurgiutiu, Univ. of South Carolina (United
States)
In nondestructive evaluation (NDE) applications, induced strain
actuators are embedded in structure elements to control the structural
deformation. Piezoelectric wafer active sensors (PWAS) have been
used as actuators in application with beams, plate, and truss elements.
Under electric excitation, the PWAS undergoes oscillatory contractions
and expansions which are transferred to the structure through
the bonding layer and thus excite Lamb waves into the structure.
The transducer is bonded to the plate with an adhesive layer. The
contractions and expansion of the PWAS is transmitted to the material
through the bond layer. Due to the reciprocity of the piezoelectric
properties, the PWAS can be also used to detect Lamb waves and
transform them to electric signals.
7647-100, Session 11b
Electromechanical network modeling
applied to magnetoelastic sensor design
U. Marschner, Technische Univ. Dresden (Germany); J. Yoo, Univ. of
Maryland, College Park (United States); E. Starke, Technische Univ.
Dresden (Germany); F. Graham, C. Mudivarthi, Univ. of Maryland,
College Park (United States); W. Fischer, Technische Univ. Dresden
(Germany)
Crawley and deLuis developed an analytical model of the mechanical
coupling of segmented piezoelectric actuators to the dynamic of
the structural member. The configuration they studied was of two
piezoelectric elements bonded by a finite bonding layer to an elastic
structure. The solution proposed was the classic shear lag solution.
They showed that when the shear lag goes to zero, the solution
reduces to the simpler model of the perfectly bonded piezoelectric.
They assumed that the strain distribution in the piezoelectric actuator
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Electromechanical network models are used in this paper to analyze a
prototype micro-gyro sensor that employs the magnetostrictive alloy
GalFeNOL for transduction of Coriolis induced forces into an electrical
output at a given rotational velocity. The concept takes advantage
of the principles employed in vibratory gyro sensors and the ductile
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129
Conf. 7647: Sensors and Smart Structures Technologies for Civil,
Mechanical, and Aerospace Systems
trace gases species in high temperature gases using nanomaterials
coated silica optical fibers as transducers. This paper describes the
OFCS developed in the author’s laboratory for monitoring trace NH3,
H2S, H2, CH4 in high temperature gas samples.2,3 In addition, the
challenges in developing OFCS for monitoring HTP reactions related to
clean energy processes will also be discussed.
attributes of GalFeNOL to target high sensitivity and shock tolerance.
The sensor is designed as a tuning fork structure which reacts with
vibration of the prongs in tangential direction due to an excited
vibration in redial direction. A GalFeNOL patch attached to the ax.-rad.surface changes its permeability depending on the bending. When it is
surrounded by a solenoid coil and a constant electrical current creates
a magnetic field then this field fluctuates with the prong vibration. The
induced voltage is used as sensor output and the sensor sensitivity
calculated. A rotational velocity being effective on the tuning fork
structure causes an amplitude modulation of the excitation frequency
which is the carrier frequency.
Reference:
1. Z. Dardas, M. G. Suer, Y. H. Ma, W. R. Moser, Journal of Catalysis,
159 (1996) 204-211.
2. S. Tao, J. C. Fanguy, TVS Sarma, IEEE Sensors Journal, 8 (2008)
2000-2007.
The prongs are modeled as dynamic bending beams which are
surrounded by a solenoid coil. A circuit representation of the
electromechanical system is derived, which enables an understanding
and explanation of the behavior of thiss system involving different
physical domains, as well as fast analytical and numerical calculations,
e.g. with pSpice.
3. Q. Yan, S. Tao, H. Toghiani, Talanta, 77 (2009) 953-961.
7647-101, Session 12a
Modeling and analysis of hybrid energy
storage systems for wireless sensor
networks
In first experiments the magnetic field at the end of the sensing prong
was measured using a the GMR-sensor. In the frequency spectrum
predicted sidebands of the adjusted 20 Hz rotation can clearly be
recognized.
H. Yang, Y. Zhang, Georgia Institute of Technology (United States)
7647-191, Session 11b
Ambient energy harvesting has been employed to extend the lifetime
of wireless sensor networks. However, the network lifetime is still
limited by the cycle life of rechargeable batteries. Alternatively,
supercapacitors have extremely long cycle life - on the order of
millions of cycles. A hybrid energy storage system (HESS) that
leverages the complementary strengths of rechargeable batteries
and supercapacitors can significantly increase the lifetime of wireless
sensors. To provide design guidelines for the hybrid storage system,
the HESS model is developed and the storage system performance
is evaluated under different situations. The HESS model consists of
five components: energy source, energy consumer, supercapacitors,
rechargeable batteries and switch control module. The performance
of HESS is evaluated in terms of two metrics: wireless sensor lifetime
and energy conversion efficiency. Different HESS configurations are
investigated with varied energy source and energy consumer profiles.
The results indicate that the HESS performance strongly depends on
the characteristics of energy source (power and duration of an energy
pulse, timing sequence and energy ratio between different pulses) and
energy consumer (whether it is time critical and its relative magnitude
compared with the energy source). A tradeoff is usually observed
between the two performance metrics. However, under certain
circumstances a specific HESS configuration can outperform the
rechargeable battery only storage system in terms of both metrics. The
results also suggest that an adaptive HESS that dynamically configures
the storage devices based on the energy source and consumer
profiles may have better performance comparing with a fixed HESS
configuration.
Optical fiber chemical sensors with sol-gel
derived nanomaterials for monitoring high
temperature/high pressure reactions in
clean energy technologies
S. Tao, West Texas A&M Univ. (United States)
Optical spectroscopy is an ideal technique to indentify the existence,
and measure the concentration of chemical compounds in samples
due to the existence of figure-print absorption spectrum of chemical
compounds. In order to interrogate a sample, techniques must be
developed to send a probing light beam into the sample, collect light
transmitted or reflected from the sample, and detect the intensity of
light being transmitted or reflected at specific wavelength. Presently,
the application of optical spectroscopic techniques for interrogating
heterogeneous samples is still a tough challenge. This is especially
true for the high temperature/high pressure (HTP), corrosive reaction
systems in clean energy industrial processes, such as coal or bio-oil
gasification, syngas reforming and cleaning. The samples in such
reaction systems contain corrosive gaseous molecules, liquid droplets
and solid particles, which not only cause optical interference, but also
damage the optical windows which are in contact with the sample.
Total internal reflection spectroscopy (TIRS) is one of the advanced
optical spectroscopic techniques could be used for analyzing such
heterogeneous reaction system.1 In TIRS, the interrogating light is
guided inside a waveguide. The interaction of the evanescent wave
(EW) of light guided inside the waveguide with species on the surface
of the waveguide is monitored. Therefore, the TIRS technologies avoid
the interferences of a continuous changing scattering signal when
used to analyzing heterogeneous samples. Present state-of-the-art
TIRS uses prisms or planner waveguides for bringing light to interact
with samples. These optical elements are not corrosion resistant,
and their optical properties deteriorate with time when deployed into
a corrosive HTP reaction system. In addition, the sensitivity of EW
absorption techniques is not as high as traditional optical absorption
spectroscopy, and it is difficult to detect the intrinsic optical absorption
signal of most compounds with traditional TIRS.
7647-102, Session 12a
Power harvesting from microbial fuel cell
P. Frank, C. McFadden, X. Yu, Case Western Reserve Univ. (United
States)
Microbial Fuel cells (MFCs) are batteries driven by bacteria. MFCs
have the potential of powering small sensors in remote areas and
disposing of organic waste safely as they harvest the energy stored
in the waste products. From previous research in this field, a few
important factors for MFC performance have been identified. These
include the internal resistance of MFC, the surface area of anode with
catalyst for the biofilm development, the type and number of bacteria,
and the abundance of nutritional supplies to the bacteria. With internal
resistance as the focus of this MFC research, this experiment uses
previous discoveries to develop and optimize the single chambered
fuel cell for large-scale applications.
In an optical fiber light is guided via total internal reflections, and
therefore, optical fibers are appropriate to perform TIRS. The silica
optical fibers are robust, corrosive resistant, and can work at
temperatures up to 1000 oC. In addition, a chemical reagent can be
coated on the surface of a silica fiber in order to introduce chemical
reactions, which convert optically insensitive species to optically
sensitive compounds for detection with fiber optic TIRS. These features
make optical fiber TIRS very attractive for observing HTP reactions
in clean energy processes. The author’s group has been developing
optical fiber chemical sensor (OFCS) technologies for monitoring
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A variety of methods were applied to improve MFC efficiency. Mainly,
the researchers employed design techniques to increase the surface
area of the electrodes, so that more of the generated electrons could
be transported to the anode. In addition to that, several other measures
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0.1 - 10 Hz. Finally, hypotheses are made on further developments and
improvements of monolithic sensors.
were implemented to reduce the internal resistance, namely, adding
ionic content, as well as introducing conductive particles such as
carbon powder. These resulted in findings crucial to MFC technology.
7647-105, Session 12b
7647-103, Session 12a
A combination of energy harvesting
methods to power wireless sensor networks
efficiently
Mechanism governing surface stress
development associated with hybridization
of monomolecular DNA film and formation
of alkanethiol SAM on gold surfaces
C. U. Grosse, M. Krueger, Univ. Stuttgart (Germany); S. D. Glaser,
Univ. of California, Berkeley (United States)
K. Kang, Y. Zhao, P. Shrotriya, Iowa State Univ. (United States)
Surface stress changes associated with hybridization of surface
immobilized DNA molecules and formation of alkanethiol SAM
are measured and a multiscale model is developed to identify
the mechanisms underlying the measured response. A novel
interferometry technique employing two adjacent micromachined
cantilevers a sensing/reference pair is used to measure the surface
stress development. Experimental results indicate that surface stress
develops only on exposure to complimentary strands (specific binding)
and is not affected by exposure to other single strand DNA (nonspecific binding).The surface stress change as a function of analyte
concentration is used to determine the disassociation constant
associated with hybridization reaction. Calculated value of the
disassociation constant agrees well with independent measurements
performed using isothermal titration calorimetry (ITC). Measured
surface stress changes and disassociation constants are used in
a multiscale analysis of monomolecular film in order to estimate
the interaction potentials between hybridized DNA. Experiments
on alkanethiol SAM formation show that the adsorption of the selfassembled monolayers (SAMs) on a gold surface induces surface
stress change that cause a deflection or deformation of underlying
substrate. Molecular dynamic (MD) simulations are applied to study
the mechanism behind the phenomenon. Two different potential
applications, embedded atom method (EAM) and surface embedded
atom method (SEAM), are used in the MD simulations separately.
Quantum chemical calculations are used to modify the potentials
for gold atoms to model the reported surface reconstructions. The
simulation results show that the surface energy due to gold-sulfur
interaction is the dominant part of the phenomenon.
Since there is a growing demand in wireless monitoring techniques,
an efficient, long-term, power source for sensor nodes becomes more
and more necessary. This is especially true for nodes recording highly
dynamic data like acoustic emissions or vibrations.
A sensor network system is presented measuring pseudo-static (e.g.,
temperature, humidity or strain) and in concert with dynamic data from
acoustic emissions and vibrations. A pre-processing of the data from
the different sensors is done in the node. Moreover, clusters of sensor
nodes are formed within a sub-network to compare the pre-processed
data. All these efforts are made to limit the data transfer effort
through the network and to the sink. Since a long sensor node life is
required conventional power solutions need to be supported by novel
techniques. In particular, this paper deals with the implementation of
hybrid energy sources to sensor nodes. A mix of batteries and super
capacitors are augmented by techniques consisting of solar cells or
modules harvesting energy using the Seebeck effect.
The paper describes the efficiency of the different harvesting methods
as a function of various environmental conditions. The amount of
energy harvested using the Seebeck effect is closely related to
the mounting-surface materials (e.g. steel, stone or concrete), the
materials’ albedo, and air flow conditions.
7647-104, Session 12b
A new architecture for the implementation
of tunable mechanical monolithic horizontal
sensors
7647-158, Session 12b
F. Acernese, Univ. degli Studi di Salerno (Italy); R. De Rosa, Univ.
degli Studi di Napoli Federico II (Italy); G. Giordano, R. Romano,
Univ. degli Studi di Salerno (Italy); F. Barone, Istituto Nazionale di
Fisica Nucleare (Italy)
Development of nano-based sensors for the
detection of improvised explosive devices
B. Zientek, Univ. of Illinois at Chicago (United States) and Argonne
National Lab. (United States); H. Wang, Argonne National Lab.
(United States); E. Indacochea, Univ. of Illinois at Chicago (United
States)
This paper describes a new mechanical version of the monolithic
tunable folded pendulum, developed at the University of Salerno,
configurable both as seismometer and, in a force-feedback
configuration, as accelerometer. Typical application of the sensors
are in the field of geophysics, including the study of seismic and
newtonian noise for characterization of suitable sites for underground
interferometer for gravitational waves detection. The sensor, shaped
with precision machining and electric-discharge-machining, like the
previous version, is a very compact instrument, very sensitive in the
low-frequency seismic noise band, with a very good immunity to
environmental noises. Important characteristics are the tunability of
the resonance frequency and the integrated laser optical readout,
consisting of an optical lever and an interferometer. The theoretical
sensitivity curves, largely improved due to a new design of the
pendulum arms and of the electronics, are in a very good agreement
with the measurements. The very large measurement band (10-6
Hz - 10 Hz) is coupled to a very good sensitivity (10^-12 m/sqrt(Hz)
in the band 0.1 - 10 Hz), as seismometer. Prototypes of monolithic
seismometers are already operational in selected sites around the
world both to acquire seismic data for scientific analysis of seismic
noise and to collect all the useful information to understand their
performances in the very low frequency band (10^-6 - 10^-3 Hz). The
results of the monolithic sensor as accelerometer (force feed-back
configuration) are also presented and discussed. Particular relevance
has the sensitivity that is better than 10^-11m/s^2/sqrt(Hz) in the band
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Tragic world events have called for a need for fast, reliable, and more
deployable methods of detection of improvised explosive devices
(IED) than trained canines and visible detection by x-ray screening
technologies. Anodized Aluminum Oxides (AAO) are ideal substrates
for chemical sensor developments. The nano-porous structure provides
small pore-to-pore distance and large surface area. These unique
qualities allow optical interference in the visible spectrum when the
film thickness is in the proper range. By coating the nano-wells of
the oxide surface first with a thin film of a noble metal followed by a
monolayer of a target-specific chemical, detection of trace amounts
of explosive materials becomes possible. Research has shown that
the carboxyl group of 6-mercaptopyridine-3-carboxylic acid (6-MNA)
has an attraction to the nitro groups of TNT while the thiol group of
6-MNA creates a self-assembled monolayer on the substrate. By
utilizing these chemical properties together, UV-vis spectrometry can
detect a shift in the visible spectrum on the coated AAO substrate
as the 6-MNA structure attracts trace amounts of TNT particles. The
sample characterization with use of AFM, Raman, the interference
measurements, and IED detection will be presented.
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131
Conf. 7647: Sensors and Smart Structures Technologies for Civil,
Mechanical, and Aerospace Systems
updating procedure. Based on updated results, the baseline model of
the Wondongcheon railway bridge is identified.
7647-107, Session 12c
Damage detection based on nonlinear
prediction model to large-span bridges
7647-109, Session 12c
G. Liu, Z. M. Huang, Chongqing Univ. (China)
Application of nonlinear observer in
hysteretic model updating
A new method based on volterra nonlinear model is proposed in
this paper to detection the damage in large-span bridges. Random
decrement technique is used to acquire free attenuation signals from
stochastic excitation responses and associative neural network is
used to obtain normalization vehicle excitation response signals, thus,
output-only information is need in this method and more information
can be utilized when there is the same amount of sensors. The
nonlinear prediction model is built using volteera model, which can
capture accurately the nonlinear character in the response signal,
the method to choose the delay time and embedding dimension is
discussed. The volteera model is built up using signals obtained from
the health bridge and the prediction error between the theoretical
prediction time history values and the measurement signals is treated
as damage detection index (DDI). The threshold of DDI is get from the
statistical value when the bridge is health. If a new DDI, calculated
from unknown condition of the bridge, exceed the threshold, damage
may occur. Different damage cases are simulated to a five span
continuous beam and a large-span bridge respectively. Results show
that the nonlinear prediction model can not only detect whether there
is a damage or not , but also can detect the damage location at some
degree.
W. Song, S. J. Dyke, Purdue Univ. (United States)
The use of model updating have been widely applied in structural
health monitoring, FE model validation and refinement, material
identification from vibration testing, FE model reduction, and so on. So
far, the essential assumption that updating model is based upon, is that
the linear dynamic model of the investigating structure. However, with
the need of the identification of structural systems exhibiting nonlinear
hysteretic behavior, usual linear dynamic system assumption collapse
and the commonly used modal analysis tools can no longer be applied.
In the recent years, several observer-based nonlinear hysteretic
modeling techniques have been developed (Smyth). Considering the
random nature of ambient loading condition, extended Kalman filter
(EKF) has also been introduced into structural model identification
(Yang). However, the deterministic observers usually demand a welldevised mathematical adaptive model a priori, and the optimization
process sometimes involves results in a local solution. For the EKF,
since the basic assumption is the linearization of the nonlinear model at
each observing data point, for highly nonlinear models, it is difficult to
obtain an accurate solution within a small time frame.
In this paper, an adaptive stochastic observer-based model updating
scheme has been proposed to identify the key parameters of a certain
type of structural hysteresis. This technique is applicable to both linear
and nonlinear structures under random excitations. A steel frame model
with nonlinear hysteretic joints is presented as a numerical example.
With the simulation results for tracking the parameters of the nonlinear
model, the accuracy and efficiency of the proposed method can be
well demonstrated. The updated nonlinear structure model can be used
not only for damage localization and quantification, more importantly, it
could be used for predicting the future structural behavior.
7647-108, Session 12c
Field vibration tests-based model update
for system identification of Wondongcheon
railway bridge
D. Ho, J. Kim, J. Park, D. Hong, K. Nguyen, Pukyong National Univ.
(Korea, Republic of)
During the last decade, the development of methodology for
accurate and reliable condition assessment of civil structures has
become increasingly important. In structural engineering analysis
and design, the finite element (FE) analysis is a powerful and useful
tool to simulate the behavior of real structure. Hence, an accurate
FE model is prerequisite for civil engineering applications such as
damage detection, health monitoring and structural control. However,
it is not easy to generate the accurate FE model