PLENARY SESSION 1 Tuesday 10 June 2014 - 13.30-14.10 Professor Albano Cavaleiro

PLENARY SESSION 1  Tuesday 10 June 2014 - 13.30-14.10 Professor Albano Cavaleiro
16th Nordic Symposium on Tribology, Aarhus, Denmark
PLENARY SESSION 1
Tuesday 10 June 2014 - 13.30-14.10
Professor Albano Cavaleiro
Chair: Lars Pleth Nielsen
1
16th Nordic Symposium on Tribology, Aarhus, Denmark
Close to zero friction of sliding induced self-alignment of transition metal
dichalcogenides coatings
Albano Cavaleiro1, Tomas Polcar2,3
1
SEG-CEMUC - Department of Mechanical Engineering, University of Coimbra, Rua Luís Reis Santos,
3030-788 Coimbra, Portugal2n-CATS University of Southampton Highfield Campus
SO17 1BJ Southampton, UK
3
Department of Control Engineering Czech Technical University in Prague Technicka 2, Prague 6,
166 27 Czech Republic.
Abstract:
The reported possibility to achieve super low friction (friction coefficient less than 0.01) in particular
sliding conditions has been the driving force for extensive research studies performed in the field of
coatings tribology. In last decades, transition metal dichalcogenides (TMD) have been a potential solution
for this requirement due to their layered structure and weak inter-layer bonding allowing decreasing
friction in mechanical contacts. Unfortunately, two main drawbacks of these materials have hindered a
more extensive use in the field of low friction coatings, their high sensibility to moisture and their low
loading bearing capacity. Therefore, the main research studies in this field have been the alloying of TMD
in order to overcome those drawbacks. Our approach that goes beyond the state-of-the-art is to control the
deposition parameters, including the type and amount of alloying element, in order to tailor the structure
at nanometer level allowing a suitable self-adaption phenomenon at the contact surface. The scope is
twofold, (i) to increase the hardness and the capacity of the coatings to support increasing applied loads
on the contact and, (ii) to allow the formation of perfect aligned TMD basal planes parallel to the surface,
avoiding oxidation and guaranteeing very low friction in all atmospheres.
In this talk, we will present our approach that goes beyond the state-of-the-art, related to the deposition of
alloyed-TMD coatings by sputtering techniques. By varying the deposition parameters, including the type
and amount of alloying element, we intend to tailor the structure and microstructure of the coatings in
order to allow a suitable self-adaption of the material in the surface contact, either promoting
(re)crystallization of the material or the in depth reorientation of TMD crystals. With this procedure,
friction coefficients as low as 0.03 and 0.005 are possible to be achieved in humid and dry atmospheres,
respectively, under contact pressures higher than 1 GPa.
Keywords: self lubrication, low friction coatings, super low friction, sputtering
Biography:
Full Professor in the University of Coimbra, Portugal. In 1990, he received a PhD from Coimbra
University on the field of Mechanical Engineering. His field of research and publications is very
diversified as e.g. on materials and surface engineering, deposition and characterization of thin films,
tribology, nanocrystalline/nanocomposite materials. He participated in more than 30 research projects
(responsible in more than 20). He was invited for talks in about 30 international conferences on his field.
He supervised 14 PhD students and has an extensive evaluating activity for national and international
research agencies. He published more than 200 papers in international journals of SCI.
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16th Nordic Symposium on Tribology, Aarhus, Denmark
Tribo Chemistry
Chair: Sascha Louring
Tuesday 10 June 2014 - 14.20-15.20
Room: Suecia
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16th Nordic Symposium on Tribology, Aarhus, Denmark
1
Study the lubrication behavior of chemical mechanical polishing (CMP) of highly
boron-doped polysilicon at moderate and high polish velocities
Hamidreza Pirayesh, PhD student*, Dr. Ken Cadien, Professor
University of Alberta, Canada
*Corresponding author: Hamidreza Pirayesh ([email protected])
Chemical mechanical polishing is a critical step in microelectronic fabrication industry. It combines both
chemical and mechanical forces to polish the semiconductor surface and form the global planarization. It
has been shown that doping of polysilicon reduces the polish rate significantly. This is due to the
retardation of chemical reactions on the semiconductor surface after doping boron. In this study we tried
to improve the polish rate by studying the mechanical factors such as lubrication behavior during
polishing. It is shown that the mechanical forces are dominant in boron-doped polysilicon polishing. We
concluded that by reducing the slurry flow rate and increasing the polish velocity the lubrication regime
alters from boundary to dry lubrication. Increasing the polish temperature and friction force proved that
the lubrication and mechanical effects play the major role in this phenomenon. This helps improving the
polish rate even though less slurry was consumed in the process. In this study we also developed a model
explaining the interaction of chemical and mechanical forces to improve the polish rate. This model
shows that the polish rate increases by improving the polish friction at a constant flow rate or velocity.
Keywords: lubrication, Boundary lubrication, Dry lubrication, Chemical mechanical polishing (CMP)
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16th Nordic Symposium on Tribology, Aarhus, Denmark
62
Effect of normal load on multi-degradation mechanisms of super duplex stainless steel exposed to
tribocorrosive-fatigue environment
Amin H. Zavieh1,2)*, Nuria Espallargas2)
1)
NTNU, Faculty of Engineering Science and Technology, Dept. Engineering Design and Materials,
Tribology Lab. N-7491 Trondheim, Norway
2)
Department of Technology, Buskerud University College, Kongsberg, Norway
*
Corresponding author: [email protected]
Passive metals exposed to wear and fatigue in corrosive environment may suffer from multidegradation phenomena. It is not possible to approach the problem from the standpoint of tribology
exclusively or corrosion and fatigue solely to make any theoretically or experimentally valid assessment
of the damage, durability or limiting states of these passive alloys. Synergetic effects of this complex
scenario result in drastic reduction in the lifetime of systems in which any failure leads not only to
significant material losses, but puts people and eco-systems at risk. Board marine and offshore vessels
and installations are one of the main places that passive metals are exposed to multi-degradation. They are
typically involved in critical operations like mooring, material handling by cranes and hoisting systems,
riser tensioning, heave compensation and rotation equipment during drilling.
The complex multi-degradation mechanism has been first studied and proposed by von der Ohe et
al. with a first approach based on tribocorrosion experience and fatigue. However there is still a long way
to go to investigate the causes and micromechanisms of this type of material degradation for proposing a
model able to predict component failure and therefore for better designing structures.
In the present work, different types of stainless steels have been tested under multi-degradation
conditions by means of in-house developed lab scale multi-degradation (LSMD) test rig. This rig provides
4-point static or cyclic (fatigue) bend testing while applying reciprocating rubbing on the tensile loaded
side of the exposed test surface, in addition it includes arrangements for performing electrochemical
measurements to simulate saltwater (3.4wt% NaCl) with presence of hydraulic fluids. Consequently
samples are characterized and the mechanisms contribute in the processes of wear, corrosion and fatigue
will be studied.
Keywords: multi-degradation, tribocorrosion, super duplex stainless steel, fatigue
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16th Nordic Symposium on Tribology, Aarhus, Denmark
104
Neutron reflectometry of boundary films on DLC coatings
Rok Simič1, Mitjan Kalin1 *, Tomoko Hirayama2
1
2
Laboratory for Tribology and Interface NanoTechnology, Faculty of mechanical engineering,
University of Ljubljana, Bogišićeva 8, 1000 Ljubljana, Slovenia.
Department of Mechanical Engineering, Doshisha University, 1–3 Miyakodani, Tatara, Kyotanabe,
Kyoto 610-0394, Japan.
*Corresponding Author: Tel.: +386 1 4771 462. E-mail address: [email protected]
Adsorption is one of the key phenomena involved in the boundary lubrication since it determines the
formation and resistance of the boundary films. We used neutron reflectometry to study the adsorption
ability of alcohols and fatty acids from PAO oil solution onto several DLC coatings (a-C, a-C:H, a-C:H:F
and a-C:H:Si). We determined the thickness and the density of the adsorbed layers to reveal how the
coating composition and doping elements affect the adsorption ability. The non-hydrogenated a-C coating
proved to be the most inclined to adsorption, which is assumed to originate from the lack of hydrogen,
which is a well known surface passivation source. On the other hand, no adsorption layers were detected
on the F-doped DLC coating, which revealed the non-reactivity of the coating. To study the resistance of
the adsorbed films, the surfaces with the adsorbed molecules were cleaned ultrasonically in heptane and
analyzed by ToF-SIMS and XPS. We proved that the ultrasonic cleaning - irrespective of its duration does not affect the amount of adsorbed molecules with respect to rinsing, which reveals the good
resistivity of the adsorbed molecules to external influences. The obtained results show that the adsorption
on DLC is possible and presents a potential boundary lubrication mechanism for DLC coatings despite
their general non-reactivity.
Keywords: DLC, boundary films, adsorption, neutron reflectometry, alcohols, fatty acids.
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16th Nordic Symposium on Tribology, Aarhus, Denmark
Wear & Lubrication
Chair: Käti Valtonen
Tuesday 10 June 2014 - 14.20-15.20
Room: Dania
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16th Nordic Symposium on Tribology, Aarhus, Denmark
67
The Failure and Damage Mechanisms under Friction of Copper in the EHL and Mixed EHL
Regions
A. Moshkovich, I. Lapsker, A. Laikhtman, V. Perfilyev, L. Rapoport* Holon
Institute of Technology, Holon 5810201, Israel
[email protected]
Recently, friction and wear behavior of Copper (Cu)-steel pairs rubbed under different lubrication
conditions were studied. The Stribeck curve was used to identify the different regimes of friction of
copper with different virgin grain sizes the elasto-hydrodynamic lubrication (EHL), mixed lubrication
(ML) and boundary lubrication (BL) regimes. The aim of this work is the detailed analysis of the damage
evolution under friction in the EHL and mixed EHL regions. The effects of load on the friction and the
wear and damage mechanisms have been studied. The surfaces of Cu samples before and after friction
have been analyzed using SEM and AFM techniques as well as roughness and hardness measurements. It
was shown that the mechanisms of damage and failure of Cu samples under friction in the EHL region are
similar to the damage and failure mechanisms in Very High Cycle Fatigue. Friction in the EHL region is
accompanied by initiation and coalescence of pores and microcracks. The effects of the coalescence of
pores and microcracks observed in the EHL region are enlarged with a subsequent loading in the mixed
EHL region. The effect of the loading rate on the transition from the EHL to BL region has been studied.
It was shown that decreasing the loading rate increases significantly the load of the transition from the
EHL to BL region. The pore and microcrack coalescence remain the dominant damage mechanism under
friction in the mixed EHL region with the low loading rate while a lot of ploughing tracks, large
delaminated regions appeared on the surface of Cu sample after friction with the higher loading rate.
Keywords: Friction, Copper, Stribeck curve, Failure, Damage
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16th Nordic Symposium on Tribology, Aarhus, Denmark
134
Proposal of invariant precursor for boundary lubricated scuffing
Łukasz Wojciechowski , Thomas G. Mathia
Institute of Machines and Motor Vehicles, Poznan University of Technology, Poland
2
Laboratoire de Tribologie et Dynamique des Systèmes LTDS- C.N.R.S., École Centrale de Lyon,
France
1
One of the fundamental problems in Tribology is the prediction of finale performances and particularly
the longevity of lubricated frictional organs. In most cases the hydrodynamics, elastohydrodynamics
lubricated parts if load is too high or displacement of rubbing bodies is too slow the boundary lubrication
takes a place and prediction of performance becomes complicated because scuffing can appear [1,2]. The
authors try to shear their knowledge and contribute to better understanding of that transitional phase
dealing frequently with catastrophic wear. It can be the proposal one of new paradigm shift of today's
Tribology [3,4]. The paper presents the analysis of various features allowing the identification of starting
point to scuffing process. Authors present the topological paradigmatic approach to this problem in which
the key role plays the interaction between rheological, morphological and physicochemical properties of
contacting surface's layer [5]. For academic reasons specific tribological conditions are selected. The
results of scuffing test of different burnishing finishing process conditions offering various ground surface
properties in order to modify tribological wear performance of AISI 4130 cylinders-plane of ductile cast
irons counter bodies boundary lubricated with gear oil (extreme pressure EP additives) are discussed [5].
The interface rheological behavior based on micro-hardness and morphology measurements allowed
contact mechanics analysis in frame of plasticity index. Morphological investigations are consisted in the
analysis of areal field, functional and features parameters. The physicochemical part of investigations was
carried out on the basis of the residual stresses and wettability measurements with the surface free energy
and its components calculations [6,7]. Critical analysis of interfacial parameters for steady (burnished
cylinders) and transitional states up to the catastrophic wear (scuffed cylinders) is commented in order to
establish universal laws of shift from stable wear under boundary conditions to scuffing.
Taking into consideration the topological approach, the mutual interactions between analyzed parameters
in the context of scuffing were investigated and elucidated in order to propose invariant precursor
concept.
Keywords: boundary lubrication, scuffing, topological approach
Bibliography
1. Georges J.M., Jacquet M., Mathia T.G. "Quelques aspects de la lubrification limite", Congrès International de Chronométrie, Editeur: Herausgegeben von
der Deutschen Gessellschaft für Chronometric, e.V. Stuttgart, (1974).
2. Georges J.M., Meille G., Jacquet M., Lamy B., Mathia T.G. "Study of the durability of boundary films". Wear, Vol. 42, n° 2, 1977
3. Wojciechowski L., Mathia T.G., "Paradigmatic Approach to Limits of Boundary Lubrication" Actes des 25émes Journées Internationales Francophones de
Tribologie. Ecully, France 29-31 mai 2013
4. Wojciechowski L., Mathia T.G., "Conjecture and paradigm on limits of boundary lubrication" (presented at TriboLyon 2013 Conference, accepted in
Tribology International);
5. Mathia T.G., Louis F., Maeder G., Mairey D., “Relationship between surface states finishing processes and engineering properties”, Wear, 83, 2, 1982, 241250;
6. Wojciechowski L., Nosal S., “The application of surface free energy measurement to valuation of adhesive scuffing”, Maintenance and Reliability, vol. 45,
2010, 83-90;
7. Kubiak K.J., Wilson M.C.T., Mathia T.G., Carval P., “Wettability versus roughness of engineering surfaces", Wear, 271, 3-4, 2011.
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16th Nordic Symposium on Tribology, Aarhus, Denmark
118
Influence of Physical States of Amide Type Gel-Lubricants on Tribological and Rheological
Properties
Kazumi Sakai, Yuji Shitara
JX Nippon Oil & Energy Corporation
Presenting author: Kazumi Sakai
Amide type Gel-Lubricant (Gel-Lube) is a unique lubricant since Gel-Lube looks grease (gel) at low
temperature and changes to liquid at higher temperature. These physical state changes are repeatable. This
characteristic feature is attributed to the composition of Gel-Lube. Gel-Lube consists of liquid lubricating
oils and solid fatty amides. Fatty amides work as not only thickeners but also the oiliness agents.
Therefore, the oiliness effect provides Gel-Lube with the low friction properties. Gel-Lube could be
applied to various machinery lubrications for energy-saving.
Tribological properties of Gel-Lube compared with conventional oils and greases have been reported, for
instance, friction properties under boundary lubrication conditions. However, the understanding of
detailed tribological and rheological behaviors of Gel-Lube related to its physical state changes was not
sufficient. Therefore, these properties focused on physical state changes of Gel-Lube depending on
temperature were examined. As a result, liquid state Gel-Lube showed superior friction properties to gel
state. It is suggested that rheological property changes of Gel-Lube play important roles in addition to the
oiliness effect of fatty amides.
Keywords: tribology, rheology, gel-lubricant, low friction, lubricants
10
16th Nordic Symposium on Tribology, Aarhus, Denmark
Modelling 1
Chair: Kenneth Holmberg
Tuesday 10 June 2014 - 14.20-15.20
Room: Nortvegia
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16th Nordic Symposium on Tribology, Aarhus, Denmark
18
Atomistic origins of tribologically induced metallic surface folding
Nils Beckmann123, Pedro Romero124, Michael Moseler1345 and Peter Gumbsch124
1
Fraunhofer Institute for Mechanics of Materials IWM, Wöhlerstraße 11, 79108 Freiburg, Germany
Karlsruhe Institute of Technology, Institute for Applied Materials IAM, Kaiserstraße 12, 76131
Karlsruhe, Germany
3
University of Freiburg, Physics Department, Hermann-Herder-Straße 3, 79104 Freiburg, Germany
4
KIT-IWM MicroTribology Center µTC, P.O. Box 41 01 03, 76229 Karlsruhe, Germany
5
Freiburg Materials Research Center, Stefan-Meier-Straße 21, 79104 Freiburg, Germany
2
Tribology as the science of the interaction of surfaces in relative motion has many important
technological applications including machining, polishing and bearings. During tribological loading of
metallic surfaces, mechanically driven material intermixing processes induce quite complex phenomena,
such as plastic flow swirls that resemble Kelvin-Helmholtz instabilities or lamellar folding patterns,
which lead to debris particles reminiscent of flaky pastry. Especially atomistic simulations can yield
valuable insights into the evolution of surfaces because of the possibility of in situ analysis of the
intermixing processes and topographical evolution. In this contribution, we will reveal the emerging
patterns during shear deformation and surface generation on a nanocrystalline copper substrate by
molecular dynamics simulations. Besides the interplay between dynamic recrystallization and grain
growth, the disruption of laminar surface plastic flow and the formation of surface folds is observed. For
this specific topic, we will show that the polycrystalline bulk structure induces anisotropic material flow
behavior, depending on the crystallographic orientations of the grains. We demonstrate that folding can
lead to layered structures that act as precursors to lamellar wear particles.
Keywords: Tribology, Folding, Nanocrystalline, Machining, Molecular Dynamics, Plastic Flow
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16th Nordic Symposium on Tribology, Aarhus, Denmark
80
Combined consideration of qualitive and quantative factors in computer modeling of tribological
systems
Lev Evelson*, Mayya Rafalovskaya,
IT Department, Bryansk State Academy of Engineering and Technologies,
3 Stanke Dimitrov av., Bryansk, 241037 Russia
*- presenting author
Usually two main types of mathematical models are used for tribological systems. The first ones are analytic
models formed on a basis of natural laws known in Physics, Mechanics, Chemistry and so on. The second
ones are statistic models based on experiments realized either for the real objects or for some test benches.
The both above approaches have significant difficulties when qualitative factors take place together with
quantitative ones. However, such situation is usual for tribology. Soiling of contacting surfaces, shape of
wear particulars, etc. often take an important part comparable with pressure, sliding velocity and so on.
In this paper system approach and combination of mathematical and computer simulation are used to get
some hybrid model connecting controlled entrance factors and system response function. It’s like as
regression equation but real experiments are replaced on computer imitation and different ways of
estimation of model adequateness and model parameters are used here. In proposed approach statistical
models are replaced for fuzzy sets models. The general way of computer modeling is creation of tribological
integrated expert systems. They have “intelligent” part based on artificial intelligence technologies and
“traditional” part, which is developed by usual software development approaches. So, expert systems blocks
are working here together with data bases and calculation modules. In general, proposed integrated expert
system can be used as software supporting to make decisions regarding friction units design. It can also
take part of subsystem for CAD/CAE system. An important component of the software work is information
support. It’s proposed to develop multilevel information model of tribological system.
Proposed approach is presented with an example of complicated tribological system including interaction
between wheel and rail. The multilevel information model is formed as a result of analysis of a great amount
of various information resources. A method of systematization of tribological knowledge is presented. The
method is based on development of knowledge base as a set of production rules. Every rule has an universal
structure including parts “IF”, “THEN”, “insurance factor”. The last part is the fuzzy set belonging function
value. Specific method of estimation of that factor is presented in this paper.
Proposed approach can be used for modeling of friction and wear in tribological systems. It can be used
also within CAD/CAE systems for computer modeling of machines including friction units.
Keywords: tribological system, computer modeling, qualitative and quantitative factors, expert systems,
information model
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16th Nordic Symposium on Tribology, Aarhus, Denmark
Machine Elements
Chair: Ronald Larsson
Tuesday 10 June 2014 - 15.40-17.00
Room: Suecia
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16th Nordic Symposium on Tribology, Aarhus, Denmark
17
Rolling Contact Fatigue Of Hydrogen Infused Bearing Surfaces Under An Applied Hoop Stress
And EHL Conditions
Shravan Janakiraman1*, Ole West1, Peder Klit1, Niels Jensen1
1
: Technical University of Denmark, Department of Mechanical Engineering, Nils Koppels Alle,
Kgs. Lyngby, Denmark 2800
* : Presenting author
Rolling element bearings are used in the gear systems found in the gearbox of wind turbine drive-trains.
The bearings are mounted on the shaft using a interference fit, thus imparting a hoop stress and radial stress
to the bearing inner ring. High pressures and temperatures can be generated in the lubricant film between
the non-conformal contacts of the roller and the inner ring. It has been suspected that, hydrogen, potentially
from the lubricant diffuses into the bearing elements. It is however hard to verify the presence of hydrogen
in the metal, because it diffuses out at room temperature. The presence of hydrogen increases the
susceptibility of the bearing material to rolling contact fatigue failure.
Experimental conditions were created to closely resemble the mounting stresses and loading conditions as
experienced in the field. Rolling contact fatigue tests were conducted, where two rings, simulating the nonconformal contact in the bearings, were run against each other with continuous lubricant supply at the
contact at steady state. The regime of lubrication was Elastohydrodynamic lubrication (EHL). The rings
were made from standard 100Cr6 SKF bearing steel,. The rings were immersed in a solution of Ammonium
Thiocyanate for 48 hours to introduce hydrogen in them, before mounting. The rings were mounted on
shafts with a conical interference fit. The rings were loaded against each other at high loads, corresponding
to large maximum Hertzian contact stresses. There was minimal slip between the two rings in the contact
zone. The experiments were conducted to study the mode of failure and number of cycles to failure for each
ring pair tested. The number of cycles to failure for each ring pair was plotted on a Weibull graph.
The results indicated that the crack initiated near the surface. After the fatigue crack propagation a final
brittle fracture occurred. The plane of fracture was perpendicular to the direction of the hoop stress. Surface
pitting was observed in all the rings tested. The fracture mechanisms were compared to the fracture
mechanisms observed in other hydrogen infused bearing surfaces, but not under the influence of any applied
Hoop stress.
Keywords: elastohydrodynamic lubrication, fatigue, rolling contact fatigue, hoop stress, hydrogen
infused surfaces
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16th Nordic Symposium on Tribology, Aarhus, Denmark
19
On the Running-In Behaviour of Lubricated Line Contacts
Thomas Lohner1 (Presenting Author), Josef Mayer1, Klaus Michaelis1,
Bernd-Robert Höhn1, Karsten Stahl1
1
Forschungsstelle fuer Zahnraeder und Getriebebau (Gear Research Centre) – FZG, Technische
Universitaet Muenchen, Boltzmannstrasse 15, D-85748 Garching, Germany
Running-in corresponds to a conditioning process of the contacting surfaces of rolling and sliding
elements during the first operating hours and is usually associated with surface roughness smoothing.
Thereby, the selected operating conditions are usually within the mixed lubrication regime in order to
provoke asperity contact of the rough surfaces. As the running-in of machine elements can be seen as a
transient tribological system, the surface topography is modified by wear and plastic deformation until a
steady state condition is reached. This condition can be defined by a steady coefficient of friction or a
steady wear rate. The running-in also strongly influences the formation of tribofilms, particularly if
additive-containing lubricants are used. Therefore, a well-designed running-in procedure has large
potential to increase the load carrying capacity and efficiency of machine elements without any effort in
terms of element design.
The intention of this study is to offer further insights into the running-in behaviour of lubricated line
contacts in discs and gears (both made from case-carburized steel and cross ground) with particular
attention to the correlation between running-in parameters, surface roughness, pre-damages and
measureable parameters during running-in time. Thereby, experimental investigations are performed at a
model test rig (FZG twin-disc machine) and at a gear test rig (FZG back-to-back test rig). Parameter
variations include the initial surface roughness, lubricant additive and the lubricating condition defined by
the applied load, oil temperature and circumferential speed.
The work packages are as follows: First, running-in experiments are performed at a twin-disc test rig
characterized by simple test part geometry and excellent reproducibility. Second, the results obtained
from the twin-disc-machine are transferred to the path of contact of the specified test gears by a local
analysis in order to define different running-in conditions for test gears. Thereby, a specific parameter is
introduced to describe the relative surface loading during running-in. Third, extensive experiments are
performed at the FZG efficiency back-to-back test rig in order to have the possibility to measure the mean
coefficient of friction during running-in time. For each running-in for discs and gears, the friction
coefficient, the surface roughness and the close-surface material condition is properly investigated. For
the twin-disc experiments, additionally the bulk temperature of the discs is measured.
Results show that the additive package has major influence on the solid state friction coefficient, on the
characteristics of touching surface asperities, on the tribofilm formation and therefore on the entire
running-in process. The applied load has the most significant influence on surface roughness reduction.
Besides very limited “micro-cracks” on the surface, no clear pre-damages are found for any parameter
configuration on discs after running-in. For gears, when load is increased above a critical level, clear predamages characterised by cracks, micropitting and profile deviations are identified. Depending on the
running-in condition, significant advantages in terms of gear efficiency and in terms of the scuffing load
carrying capacity of gears are found.
Keywords: running-in, mixed-lubrication, asperity contact, tribofilm formation
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16th Nordic Symposium on Tribology, Aarhus, Denmark
106
In situ surface characterization of running-in of involute gears
MSc. Mario J. Sosa, Dr. Stefan Björklund, Dr. Ulf Sellgren, Prof. Ulf Olofsson
Dept. of Machine Design, Royal Institute of Technology, Stockholm, Sweden
Gear life and operation are in large part determined by the properties of the contacting surfaces, and these
inevitably change over its life. The initial topography transformation, often referred to as running-in, is of
pronounced importance. The focus of this paper is how running-in of the surface topography can be
characterized and also what methodology can be used to characterize it. To characterize running-in gears
were run in a FZG back-to back-test rig utilizing a Form Talysurf Intra in situ. This enables the system to
stay unchanged, and as well as permitting the same gear tooth surface to be measured and with enough
precision to study the same surface at different stages. The separation of roughness from the form and
waviness has been achieved through surface roughness measurement. The gear tooth surface was
measured as manufactured, after a standard running-in procedure, and after different operational
conditions, varying load, speed and temperature. Running-in is characterized both qualitatively by
plotting of roughness profiles, and quantitatively by analyzing a selected set of roughness. Conclusions
from this paper show that the summits of the asperities were worn off at the initial running-in stage;
roughness, waviness and form can be separated utilizing a carefully chosen polynomial fit and a Gaussian
filter; surface topography can be studied initially, after running-in, and after operation in situ; and
complete wear of the initial surface can be demonstrated in some circumstances.
Keywords: gear, running-in, surface topography
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16th Nordic Symposium on Tribology, Aarhus, Denmark
102
A study on surface influence on gear efficiency and lubricant temperature
Martin Andersson, Phd Student Machine Design, Ulf Olofsson, Professor Machine Design, Stefan
Björklund, Associate Professor Machine Design
Kungliga Tekniska Högskolan, Stockholm, Sweden
Losses in a vehicle gearbox influence the fuel consumption. These losses can be divided in to load
dependent and speed dependent losses and they occur in the gears, bearings, seals and auxiliaries such as
pumps. One way of reducing the speed dependent losses in gearboxes is to lower the lubricant level. In
this way the amount of oil that is splashed around by the gears and bearings dipping in to the oil is reduced.
On the other hand, a certain amount of oil is necessary to dissipate heat away from the contact. Furthermore
oil is necessary for the transport of additives to build up a protective tribo layer between the contacting
gears.
In this study the energy losses in a gearbox are measured together with lubricant and gear temperature
to study the influence of initial gear surface roughness and PVD coated gear surfaces in parallel with
different oil levels in the gearbox. The tests were performed in a back-to-back gear test rig, in this case an
FZG efficiency test rig, modified to measure the temperature of the contacting gear pairs. Gears with
different surface manufacturing methods, grinded and polished, as well as coatings on the polished gears
were tested against each other. Lubricant temperature, gear bulk temperature and torque loss was measured
for a set of speeds and lubricant levels while the contact pressure was kept constant.
The load and speed dependent losses for the gears are obtained for the different test conditions by using
analytical expressions for the losses in seals and bearings together with the measured torque loss.
The main findings for all lubricant levels are that a higher efficiency in the gear contact is obtained both
for smoother and coated gears, as well as a slightly lower lubricant and gear temperature. As expected,
speed dependent losses are significantly reduced with a lower lubricant level while the load dependent
losses increase with a lower level. Thus, the results indicate that it is possible to find an optimal lubricant
level for a given degree of surface roughness that minimizes the losses while fulfilling the need of
lubrication and cooling.
Keywords: gears, efficiency, temperature
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16th Nordic Symposium on Tribology, Aarhus, Denmark
Texturing
Chair: Klaus Pagh Almtoft
Tuesday 10 June 2014 - 15.40-17.00
Room: Dania
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16th Nordic Symposium on Tribology, Aarhus, Denmark
3
Effect of counterface roughness on adhesion of mushroom-shaped microstructure
Haytam Kasem*, Michael Varenberg
Dept. of Mechanical Engineering, Technion – Israel Institute of Technology, Haifa 32000, Israel
*Corresponding author: [email protected]
To elucidate the effect of the substrate roughness on adhesion of mushroom-shaped microstructure, we
have replicated topography of 12 different surfaces and, using replicas made of the same material, measured
pull-off forces of microstructured and smooth samples. It was found that classical roughness parameters,
such as average roughness Ra and others, cannot be utilized to explain topography-related variation in pulloff force. This has led us to the development of an integrated roughness parameter capable of explaining
results of pull-off measurements. Using this parameter, we have also found that there is a critical roughness,
above which neither smooth, nor microstructured surface could generate any attachment force, which may
have important implications on design of both adhesive and anti-adhesive surfaces.
Keywords: biomimetic, fibrillar adhesives, pull-off force, surface topography
22
16th Nordic Symposium on Tribology, Aarhus, Denmark
41
The effect of oil pockets array on tribological behaviour of sliding elements
Slawomir Wos1, Waldemar Koszela1 and Pawel Pawlus1*
1)
Department of Manufacturing Technology and Production Engineering, Rzeszow University of
Technology, Poland.
*
Presenting author, email [email protected]
The introduction of specific textures on sliding surfaces, including micropits (or holes, dimples, cavities,
oil pockets) is an approach to improve the seizure resistance of sliding elements. Those micropits may
reduce friction by acting as a reservoir for lubricant, improving seizure resistance. Holes can also serve as
a micro-trap for wear debris in lubricated or dry sliding. Various techniques can be employed for surface
texturing including machining, ion beam texturing, etching techniques and laser texturing. Surface
texturing has been shown to provide tribological benefits in terms of friction reduction in conformal contact.
A lot of experiments were done using pin-on-disc testers. On the basis of literature review it is possible to
select parameters of textured surfaces like pit-area ratio (oil pockets density), dimple depth, width and
surface roughness in areas free of dimples. However the effect of oil pockets array (layout) on tribological
behavior of sliding elements has not been explained yet. It is usually selected based on intuition of
researchers.
In this work the attempt was done in order to explain mechanism of influence of selected oil pockets array
on tribological properties of contacting elements. Experiments were carried out using pin-on-disc tester in
conformal lubricated contact for different sliding speeds. Surface texturing was done using abrasive jet
machining with application of laser cut mask. In order to eliminate the effect of different input variables,
in all the experiments pit-area ratio and sizes of oil pockets were very similar. Five types of oil pockets
arrays were tested:





radial,
concentric,
spiral,
of square arrangement,
of random arrangement.
The experiments were also made for untextured polished disc. During tests the friction force was monitored
as a function of time. Before and after tests, disc surface topography was measured using a white light
interferometer Talysurf CCI Lite with 0.01 nm height resolution.
The beneficial effect of surface texturing was obtained for spiral array of dimples on disc surface. The
presence of radial array of oil pockets resulted in the worst tribological properties of tribological assemblies
containing textured discs.
Keywords: textured surfaces, pin-on-disc, friction force
23
16th Nordic Symposium on Tribology, Aarhus, Denmark
108
Application of fractal analysis to diagnose contact interaction of frictional solid objects
A.M, Pashayev, A.Kh. Janahmadov, N.G. Javadov, M.Y. Javadov
Azerbaijan Engineering Academy
The additional quantitative research tools are developed to examine the surface roughness: the
fractal dimension of bearing surface curvature and the fractal dimension of profilograms. These values are
used to classify the contact interaction modes of the frictional metal elements and to diagnose the type of
contact according to the fractal dimension scale by describing the main three types of contacts: elastic,
elastic-plastic, plastic.
Keywords: friction, roughness, bearing surface curvature, fractal analysis, diagnostics, contact interaction
mode
24
16th Nordic Symposium on Tribology, Aarhus, Denmark
Modelling 2
Chair: Ulf Olofsson
Tuesday 10 June 2014 - 15.40-17.00
Room: Nortvegia
25
16th Nordic Symposium on Tribology, Aarhus, Denmark
10
Simulation of a Hydraulic Rod Seal with a Micro-Patterned Rod
Yuli Huang and Richard F. Salant*
Georgia Institute of Technology,Atlanta, Georgia 30332-0405, USA
* Presenting author [email protected]
A numerical model of a hydraulic rod seal operating with a micro-patterned rod has been constructed to
determine if such a rod can reduce seal friction without increasing leakage.
The motivation for this work is the high friction forces measured on the rod and seal by manufacturers,
and the fact that micro-patterned surfaces have been successfully applied to other machine elements like
journal bearings, piston rings and mechanical seals to reduce friction.
The numerical model is comprised of a fluid mechanics analysis of the flow through the fluid film, a
contact mechanics analysis, and a deformation analysis of the seal. These three components are coupled
so an iterative computational procedure is used.
The finite element analysis for the static contact mechanics and static deformation has been the greatest
challenge in this project. While the maximum axial width of the sealing zone is about 2.5 mm and the rod
diameter is 44 mm, the characteristic dimensions of the triangles are in the 5 to 80 micron range. So a
very fine mesh near the sealing surface must be used. Therefore, for a complete 3D model of this seal one
would need about 109 elements. This is a huge number, when compared to the 104 elements typically used
for a 2D model. So it is clear such a 3D model is not practical.
In the present study a new unique FEA approach for the static contact and static deformation analyses has
been developed. It is based on the fact that the material in the seal lip above 100 microns from the sealing
surface is unaffected by the rod surface features, like micro-cavities. Therefore, a 3D FEA is performed
on a model of only the lower layer of lip material, divided into 6 axial segments. The displacement
boundary condition on the upper boundary of the layer is obtained from an axisymmetric 2D FEA of the
entire seal with a smooth rod. The 3D models of the 6 segments are used to compute the static contact
pressure distribution and the static deformation.
The above numerical model has been used to generate friction and leakage data over a range of operating
speeds.
Keywords: hydraulic seal, rod seal, reciprocating seal, micro-pattern.
26
16th Nordic Symposium on Tribology, Aarhus, Denmark
53
Roughness Evolution in Mixed Lubrication Condition due to Mild Wear
G. E. Morales Espejel(1,2), V. Brizmer* (1)
* Presenting author
(1)
(2)
SKF Engineering and Research Centre, Nieuwegein, The Netherlands
Université de Lyon CNRS INSA-Lyon, LaMCoS UMR 5259 F-69621 Villeurbanne France
Modelling of surface roughness evolution in time, as a function of the lubrication condition and other
operating parameters (i.e. load, sliding/rolling ratio, and initial roughness of both contacting surfaces) is
very important for understanding and prediction of various surface damage modes, such as surface distress,
wear, and scuffing. Moreover, it is one of the key points in understanding friction and running-in
phenomena.
In the present study, a previously developed model for partial micro-elastohydrodynamic lubrication
conditions is combined it with a local Archard-type wear model to describe the surface topography
evolution during the operation of a rolling/sliding lubricated contact.
The model has been compared with a series of experimental results showing good agreement.
Keywords: surface roughness, mild wear, running-in, mixed lubrication.
27
16th Nordic Symposium on Tribology, Aarhus, Denmark
135
Model for Contact Area between Finger and Sinusoidal Plane to Evaluate Adhesion and
Deformation Component of Friction
K. Duvefelt1*, U. Olofsson1, C.M. Johannesson1, L. Skedung2
1
2
Machine Design, Royal Institute of Technology (KTH), Brinellvägen 83, SE-100 44 Stockholm, Sweden.
SP Chemistry, Materials and Surfaces, SP Technical Research Institute of Sweden, Box 5607, SE-114 86
Stockholm, Sweden.
* Kenneth Duvefelt ([email protected]).
One of the main parameters affecting finger friction, friction induced vibrations in the finger and
consequently tactility is surface topography. Different peaks, amplitudes and spatial distributions affect for
example contact area and adhesion forces, the deformation and generated vibrations into the finger.
Earlier Skedung et.al. made subjective tests and objective finger friction measurements on fine controlled
surfaces. These surfaces were sinusoidal with a wavelength between 0.27 and 98.8 µm and amplitude
between 0.007 and 6 µm. To examine the variations in friction an analytical model that calculated the
contact ratio for one finger ridge was used. This model showed a correlation between the contact ratio and
the friction coefficient.
Expanding this model to cover the whole contact area together with the adhesion and deformation
component of friction would give further understanding of the contact between the finger and rough
surfaces. The finger print is modelled as trapezoid shaped ridges in a circle formation and the test surface
as a sinusoidal plane. With data for the different surfaces and normal forces can the deformations and
contact area be calculated which give the adhesion and deformation component of friction force.
Furthermore, this model can be used to see how the different surface parameters influence the friction and
also estimate the level of friction before manufacturing of a surface.
Keywords: finger friction, model, real contact area, adhesion, deformation.
28
16th Nordic Symposium on Tribology, Aarhus, Denmark
9
Theoretical Analysis of the Local Load Situation of Rough Surfaces
Jun.Prof. Dr.-Ing. Balázs Magyar, Prof. Dr.-Ing. Bernd Sauer
University of Kaiserslautern, Institute of Machine Elements, Gears and Transmissions
D-67663 Kaiserslautern, Gottlieb-Daimler-Str. 42,
E-mail: [email protected], [email protected]
The real contact conditions of machine elements influence their life time. The modern simulation
techniques can be help to understand the fatigue mechanism, started from the surface region of machine
elements. Based on such numerical solutions the rough surface topography can be optimized.
This paper will present a complex calculation method to determine the local load situation in the dry contact
of rough surfaces. First of all the generation method of rough surfaces and their analysis are presented. In
the next step the calculation of the contact pressure and the deformation on the basis of the half space theory
and the finite difference method are described. Taking into account of the calculated contact pressure
distribution the sub surface stresses and the three dimensional temperature distributions also can be
computed. The first based also on the half space theory and the second on the numerical solution of the
differential equation of the heat conduction. After this analysis the mechanical and thermal load situation
in the contact is known.
Finally a parameter study shows the effect of the load on the pressure, stress and temperature distribution.
Keywords: generation of rough surface, contact calculation, temperature calculation, stress under the
surface
29
16th Nordic Symposium on Tribology, Aarhus, Denmark
PLENARY SESSION 2
Wednesday 11 June 2014 - 08.40-09.20
Professor Martin Priest
Chair: Svend Stensig Eskildsen
31
16th Nordic Symposium on Tribology, Aarhus, Denmark
Friction and Durability of the Piston/Cylinder Interface in Reciprocating Engines
Martin Priest
School of Mechanical Engineering, University of Leeds, Leeds, LS2 9JT, United Kingdom
Abstract:
The tribology of the reciprocating piston in an engine is crucial to its overall performance as the interface
it forms with the cylinder wall is the largest source of friction power loss in an engine, has a high potential
for wear and strict control of lubricant flow in this region is essential for limiting oil consumption and
unwanted exhaust emissions. Recent advances in engine hardware to increase powertrain efficiency have
exposed the piston, the piston rings and the cylinder wall to more extreme operating conditions and made
the control of friction and wear ever more difficult. Furthermore, the lubricant in this region is subjected
to high levels of contamination by fuel (including bio-fuel components), water and combustion products
and is degraded at the elevated local temperatures, primarily by oxidation and nitration.
This presentation will provide a review of a large body of experimental research by the author and coworkers into the tribology of this crucial sub-system of the engine. A specific single cylinder gasoline
research engine, of modular design but importantly using a standard commercial piston and piston rings,
was chosen to provide a consistent, accessible and realistic environment to study the tribology and its
response to changing operating conditions and the degradation of the engine lubricant with time. Results
for lubricant film thickness, lubricant degradation, lubricant flow, friction and wear have been obtained for
a wide range of lubricant and fuel formulations. Greater insight has been gained into the tribology of the
piston/cylinder interface and how it evolves as the lubricant ages. The results also provide a comprehensive
data set to validate and enhance mathematical models for the tribology of the piston, piston rings and
cylinder wall.
Biography:
Jost Professor of Engineering Tribology at the University of Leeds and Chairman of the Leeds contribution
to the Leeds-Lyon Symposium on Tribology, now in its 41st year. He is associate editor of the journal
Tribology Transactions and an editorial board member for several other journals in the field. His research
interests encompass fundamental studies of lubrication, friction and wear; application of tribology to the
lifecycle of engineering systems and the tribology of internal combustion engines.
Keywords: film thickness, lubricant, degradation, tribology, wear
32
16th Nordic Symposium on Tribology, Aarhus, Denmark
Abrasion
Chair: Jørgen Jakobsen
Wednesday 11 June 2014 - 09.40-11.20
Room: Suecia
33
16th Nordic Symposium on Tribology, Aarhus, Denmark
125
Erosive and abrasive wear resistance of carbide free bainitic steels
Esa Vuorinen1*, Christoph Rau1, Christian Gahm2
1Dept.
of Engineering Sciences and Mathematics, Luleå University of Technology, Sweden
2
LKAB, Produktion Teknik, SE-98381 Malmberget, Sweden
* E-mail: [email protected] , Phone: +46 920 493449, Fax: +46 920-491084
Steels with fine ferritic-austenitic lath microstructure with high strength and toughness have also shown
to have good sliding and sliding-rolling wear resistance. In this work has one of these so called carbide
free bainitic (CFB) steels been tested in two heat treated conditions and compared with currently used
quench and temper (QT) steel in an industrial application subjected to a complex mixture of erosion- and
abrasion-wear in combination with impact resistance. In addition have these steels been subjected to
abrasive laboratory test.
The wear resistance has been determined by the specific wear rate for the laboratory tested samples and
by measuring the volume and weight losses in the field tests. The microstructural changes in the steels
have been investigated by optical- and scanning electron-microscopy. The hardness and hardness changes
of the different steels have been investigated.
The results show that the abrasive wear rate of the CFB steel is up to 50 % lower in comparison to the QT
steel in the laboratory tests. The field tests show that the volume and weight loss of the CFB steel in the 2
tested conditions is less than 10 % in comparison with that of the currently used QT steel. The improved
wear resistance of the CFB steel can be explained by the higher hardness and higher increase of the
hardness in the surface layer of the CFB steel.
Keywords: carbide free bainite, erosion, abrasion, wear resistance
34
16th Nordic Symposium on Tribology, Aarhus, Denmark
74
Influence of hardness and microstructure on the mechanisms of deformation and wear of cemented
carbides for rock drilling
Jannica Heinrichs1, Karin Yvell2, Mikael Olsson1,2, Staffan Jacobson1
1
Ångström Tribomaterials Group, Uppsala University, Sweden
2
Materials Science, Dalarna University, Sweden
The combination of high toughness and high hardness makes cemented carbides the most widely used
material for the rock crushing parts of rock drills. As indicated by the name, cemented carbides are
composites, most often comprising tungsten carbide grains cemented together by a cobalt binder phase.
This combination of a hard ceramic phase in a ductile metallic binder phase makes the material hard
enough to avoid excessive deformation against the rock, while also being tough enough to minimise
brittle fracture. These mechanical properties often result in low wear rates and wear mechanisms that
operate on a very small scale. The properties can be fine tuned by adjusting two main parameters, the
grain size of the hard phase and the fraction of ductile binder. Additionally, the binder phase material as
well as the carbide material can be varied.
The present investigation employs a newly developed laboratory technique to study the influence from
the microstructure of the cemented carbide on the mechanisms of its deformation against a scratching
rock tip. The selected microstructures include two cemented carbide grades that are commonly used in
rock drilling but also grades spanning a much wider interval of carbide sizes and binder fraction.
Moreover, cemented carbides including alternative binder phases are used for comparison. This wide
range of cemented carbides is used to gain fundamental insights into the relations between microstructure
and micro-scale deformation and wear, in contact with rock materials.
The initial micro-scale deformation of polished cemented carbide surfaces is studied by micro scratching
with rock materials tips, nano scratching with diamond tips, and also by instrumented nano indentation
(hardness testing). The deformation is evaluated on the submicrometer scale using high resolution FEGSEM with EBSD, FIB cross sectioning and AFM. The results are discussed with respect to their
significance for wear of cemented carbides in rock drilling operations.
Keywords: cemented carbides, microstructure, scratching, deformation, wear, rock drilling
35
16th Nordic Symposium on Tribology, Aarhus, Denmark
28
Abrasive wear of CVD α-Al2O3 and Ti(C,N) coatings
at room and elevated temperature
Mikael Fallqvist* and Rachid M´Saoubi
Seco Tools AB, R&D Materials and Technology Development
Fagersta SE-73782, Sweden
*presenting author
Abstract
In the present study the wear resistance of three CVD α-Al2O3 coatings with different growth textures, i.e.
(001), (100) and (012), and a CVD Ti(C,N) coating were investigated by using micro abrasion test and
high temperature pin-on-disc test, respectively. Micro cutting and micro chipping were found to be the
dominant wear mechanisms and the latter does strongly control the wear rate of the coatings. Also,
differences in superficial plastic deformation and adhesive wear have an influence. Of the three Al2O3
coatings the (001) texture shows the best wear resistance in micro abrasion test using small abrasives at
room temperature (RT) and in the pin-on-disc test at both RT and 450°C. In general the Ti(C,N) shows a
better wear resistance, due to its higher hardness, as compared to the Al2O3. The results obtained are
discussed in relation to the dominant wear mechanisms of the coatings identified using scanning electron
microscopy.
Keywords: abrasive wear, CVD coating, elevated temperature, Al2O3, coatings texture
36
16th Nordic Symposium on Tribology, Aarhus, Denmark
30
Nanotribological simulations of multi-grit polishing and grinding
A. Pauschitz*, S.J. Eder1, D. Bianchi1, U. Cihak-Bayr1, A. Vernes1,2, and G. Betz2
1
Austrian Center of Competence for Tribology,
Viktor-Kaplan-Straße 2, 2700 Wiener Neustadt, Austria
2
Institute of Applied Physics, Vienna University of Technology,
Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria
*presenting author
A quantitative molecular dynamics (MD) study of nanoscopic wear under dry grinding and polishing
conditions with multiple abrasive grits is presented. The initial topography of the monocrystalline iron
surface has a pseudo-random Gaussian height distribution, and the sixteen rigid abrasive grits have cuboid
or spherical geometries. The grinding and the polishing process are differentiated via the kinematic
constraints imposed on the abrasive grits. A post-processing scheme based on advection velocity
dynamically identifies atoms as either part of a wear particle, the substrate, or the sheared zone between
the two. The knowledge of each atom's zone affiliation and a time-resolved grid-based evaluation of the
substrate topography lead to a break-down of the asperity volume reduction into its constituents: pit fillup volume, individual wear particles, shear zone, and sub-surface substrate compression. The time and
pressure dependence of the wear volume contributions as well as the roughness parameter Sq and the
surface levelling are presented for selected systems.
Keywords: molecular dynamics simulations, abrasion, atomistic wear
37
16th Nordic Symposium on Tribology, Aarhus, Denmark
60
Microstructure refinement effect on two-body abrasion resistance of white cast irons
Jimmy Penagos1,*, Fernando Satoshi1, Amilton Sinatora1, Eduardo Albertin2
1
Surface Phenomena Laboratory, Department of Mechanical Engineering, University of Sao Paulo, Sao
Paulo, Brazil
2 Instituto
de Pesquisas Tecnológicas - IPT, Cidade Universitária, 5508-901 São Paulo, Brazil.
E-mail
address:
[email protected] (Jimmy Penagos)
[email protected] (Fernando Satoshi)
[email protected] (Amilton Sinatora)
[email protected] (Eduardo Albertin)
In this study, the effect of microstructure refinement on the wear of white cast iron was investigated.
Abrasive wear tests using a pin on garnet paper (whit mean size between 60 mm and 66 mm and hardness
of 1453±85 HV) configuration were carry out employing a PLINT TE 79 machine at a normal load of 4.6
N as prescribed in the ASTM G132 standard.
In order to create a temperature gradient effect, the samples were melted placing a metal plate at the bottom
of the sand mold. Subsequently abrasive wear samples of 3 mm diameter were cut (using wire electrodischarge machining.) at three different heights from the chill thereby obtaining four levels of refinement;
with the following mean free path: 6.6±1, 15.2±2, 22.9±3 and 27.3±3 μm and with a constant carbide
volume fraction about 22 percent.
Further microstructural characterization was performed by optical microscopy and X-ray diffraction
(XRD). After wear tests the worn surfaces were examined by scanning electron microscope (SEM) in order
to identify the wear mechanisms.
The results show that the mass loss increases linearly whit the increase in mean free path until the critical
mean free path (about 23 μm). After the critical mean free path is reached, the rate of mass loss of the WCI
increases at a lower linear rate. Finally, the study led to the conclusion that there is a special condition in
which a particular abrasive size is critical value for a space between solidification carbides and this
condition is dependent on the abrasive grain size.
Keywords: abrasive wear; microstructure refinement, white cast iron; second phase
material.
38
16th Nordic Symposium on Tribology, Aarhus, Denmark
IC Engine
Chair: Svend Stensig Eskildsen
Wednesday 11 June 2014 – 09.40-11.00
Room: Dania
39
16th Nordic Symposium on Tribology, Aarhus, Denmark
128
Experimental Investigation of the Tribological Behaviour of Cylinder Liner – Piston Ring Contact
with High Pressure Difference Across Ring Pack
Peder Klit1, Anders Vølund2
1Technical
University of Denmark, Department of Mechanical Engineering, Solid Mechanics,
Nils Koppels Allé , Building 404, 2800 Kgs. Lyngby
2
MAN Diesel & Turbo SE, Teglholmsgade 41, 2450 København SV
Abstract
The tribological interface between piston rings and the cylinder liner is a highly complex system. In order
to study isolated effects a test rig was used and equipped with sensors. Experiments with varying running
speeds, loading and geometry of the piston ring segment are conducted. The test rig is a scale model of a
real engine. The cylinder liner – piston ring contact is studied in the test apparatus where the cylinder
diameter is Ø160mm. The test apparatus consists of a frame structure in which cylinder liner, piston,
piston rings and connecting rod from a L16/24 MAN engine is utilized. The piston has been modified
such that up to four piston rings can be mounted in the piston. The pressure drop across rings is obtained
by injecting high pressure air between the rings. The maximum injecting pressure is 60bar. The operation
of the device is made using a crank mechanism in order to ensure engine-like operation. The frictional
force between the liner and the piston rings is recorded. Furthermore sensors for evaluation of oil film
thickness are installed.
Keywords: piston ring, friction, lubrication, experiment
40
16th Nordic Symposium on Tribology, Aarhus, Denmark
120
The lubricity of diethyl ether (DEE)
*Sivebaek I. M., Jacobsen J.
Technical University of Denmark, Mechanical Engineering. DK-2800 Lyngby, Denmark
*Presenting and corresponding author.
Dimethyl Ether is known as a green fuel capable of giving high efficiency to diesel engines without
forming particulate matter in the exhaust. While the combustion qualities of this fuel are excellent, its low
lubricity and viscosity cause the fuel injection equipment to break down prematurely due to wear. A
minor drawback is the low boiling point of the fuel which implies pressurisation to obtain a liquid.
The Medium Frequency Pressurised Reciprocating Rig (MFPRR) has been developed to establish the
lubricity of DME [1]. As mentioned above the lubricity is very low but it can be redressed by commercial
lubricity additives in moderate proportions, below 1000 ppm.
Diethyl Ether (DEE) is also an excellent fuel for diesel engines. It is an important part of arising diesel
fuels so its lubricity property becomes important. The lubricity of neat DEE is of the same order as that of
DME but it only responses very weakly to the addition of lubricity additives. Commercial additives in
proportions of 5000 ppm do not even increase the lubricity to the kerosene level.
A number of liquid and solid additives have been mixed to DEE and after many trials an acceptable
lubricity level has been reached. It was not foreseen that DEE would present more serious lubricity issues
than DME the molecule being larger and thereby offering a better separation of the surfaces.
1. Sivebaek, I.M., Sorenson S.C. “Dimethyl Ether (DME) – Assessment of Lubricity Using the
Medium Frequency Pressurised Reciprocating Rig Version 2 (MFPRR2).” SAE* Paper 2000-012970. 2000.
Keywords: Diethyl Ether (DEE), Dimethyl Ether (DME), lubricity, additives
41
16th Nordic Symposium on Tribology, Aarhus, Denmark
105
Testing scuffing resistance of materials for marine 2-stroke engines
– Difficulties with lab scale testing of a complex phenomenon
Petra Olander*, Svend S. Eskildsen#, Jesper Weis Fogh#, Patrik Hollman*
and Staffan Jacobson*
* Ångström Tribomaterials Group, Uppsala University, Box 534, 751 21 Uppsala, Sweden
# Combustion Chamber Parts, R&D, MAN Diesel & Turbo, Teglholmsgade 41, 2450 Copenhagen,
Denmark
How can a complex phenomenon that is not well understood be tested? Scuffing in the cylinders of
engines is a catastrophic type of wear that has been quite investigated through the years. However, there
is still no agreement on what the mechanisms behind scuffing are. The catastrophic nature of scuffing
implies a very high wear rate, which means that the cylinder liner has to be changed, and this is costly.
The incentives for optimising the sliding materials and lubricating oil to reduce the risk for scuffing are
therefore large. Especially, development towards higher power output and cleaner fuel aggravates the
tribological situation, leading to higher risk for scuffing if no counteractions are made.
Here, experiences of scuffing in marine two-stroke engines are presented. These are accompanied by
results from simple lab tests aimed for testing scuffing resistance of piston ring materials, to highlight the
inherent difficulties of simulating the scuffing process in a lab test. The materials tested were grey iron
and a plasma sprayed cermet coating, both used in engines today. In different tests, the tribological
situation was aggravated by simulating starved lubrication and stepwise load increase, respectively. The
influence of different appearances of the sliding surfaces on the scuffing resistance is also presented.
The ranking of the materials differed between the different types of tests and also between the tests and
the experiences from real engines. The possible mechanisms between these differences are discussed.
Further, mechanisms for avoiding scuffing as well as for initiating scuffing in different tests and in the
engine are discussed and compared. Special emphasis is given to the different roles of the contacting
materials, their surface topographies and their propensity to retain a small lubricant volume active in the
contact.
Keywords: scuffing resistance, cylinder, piston ring, materials, marine two-stroke engine
42
16th Nordic Symposium on Tribology, Aarhus, Denmark
140
Investigation on friction properties of nickel ceramic electrodeposits
Io Mizushima1, Per Møller2 and Anette Alsted Rasmussen1
1
2
IPU, Denmark
Technical University of Denmark, Denmark
Low friction engine coating has been demanded for reducing CO2, NOx and other emissions from
combustion engines and increasing fuel efficiency of vehicles. Reduction of friction taking place between
piston, piston ring and cylinder is critical, as more than half of the vehicle power loss is related to the
friction.
Nickel ceramic coating based upon silicon carbide for internal cylinder walls has been popular for 40
years, since the coatings have good properties for immobilising an oil film on the cylinder wall causing
lower friction, giving better wear resistance against adhesive wear and lower fuel consumption. More
knowledge about functions of the ceramic particles in low friction coating combined with self-lubricating
particles can contribute to reduction of energy consumption.
In this work friction properties and oil affinity of nickel co-electrodeposits containing different particles
such as SiC, BN, CaF2 and diamond were investigated. The oil affinity was evaluated with measurement
of the contact angle of the engine oil to the deposits. Friction measurement was performed with a
tribometer (CSM Instruments SA) both in air and in engine oil. Wear resistance was estimated with
profile measurement of worn samples after friction measurement.
The Ni-ceramic coatings have similar property with respect to hardness. The friction coefficient in air of
the Ni-SiC coating is higher than the ones of all other coatings, even higher than the one of pure Ni. The
wear resistance upon the dry friction measurement of the Ni-SiC is a little worse than the one of the Ni
coating. BN has a lower friction coefficient, but less wear resistance than the Ni-SiC coating has. The Nidiamond coating has the lowest friction coefficient and the best wear resistance. The co-deposits have
better oil affinity and a lower friction coefficient in engine oil than the pure nickel has. Especially BN has
a good oil affinity. The wear resistance of the co-deposits upon the tribometer test in oil is higher. The
particles are likely to work for improvement of lubricant property and besides CaF2 and diamond can
improve wear resistance of deposits.
Keywords: cylinder wall coating, friction, wear, lubricant, oil affinity
43
16th Nordic Symposium on Tribology, Aarhus, Denmark
Adhesion & Friction
Chair: Janne Juoksukangas
Wednesday 11 June 2014 – 09.40-11.00
Room: Nortvegia
45
16th Nordic Symposium on Tribology, Aarhus, Denmark
22
Integrated surface chemistry and roughness characterization to study wetting and adhesion
behavior
Jyrki Korpela*, Susanna Laurén and Maiju Pykönen
Biolin Scientific, Tietäjäntie 2, 02130 Espoo, Finland
*Corresponding/presenting author: [email protected]
1. Introduction
Wetting and adhesion behavior needs to be optimized in many applications. Wettability is usually studied
by measuring contact angles using the well-known Young equation.
𝛾𝑠𝑣 = 𝛾𝑠𝑙 + 𝛾𝑙𝑣 𝑐𝑜𝑠𝜃𝑒
(1)
The interfacial tensions, γsv, γsl and γlv, form the equilibrium contact angle θe of wetting. The Young
equation assumes that the surface is chemically homogenous and topographically smooth. This is
however not true in the case of real surfaces, which instead of having one equilibrium contact angle value
exhibit range of contact angles. To define the equilibrium value, surface roughness should be taken into
account. Relationship between surface roughness and wettability was defined by Wenzel who stated that
adding surface roughness will enhance the chemical wettability of the surface [1].
Until now, it has not been possible to directly combine the surface roughness and contact angle
measurements. Here we describe the equipment where these two measurements can be done together. In
addition, example measurements will demonstrate the importance of separating the effect of surface
chemistry and surface roughness.
2. Measurement
principle
In the presented instrument, an optical tensiometer is integrated with an optical topography module.
This enables measurement of the surface roughness on the same sample spot as the following contact
angle measurement. Roughness measurement is based on the principle of fringe projection phase shifting
in which a structure illumination pattern of sinusoidal intensity is projected on a surface. 3D contours of
the surface modulate the phase of the fringe pattern seen from the camera’s point of view. By calculating
the phase shift caused by this modulation the 3D shape of the surface can be determined [2]. With this
topography module it is possible to measure the 2D roughness parameters, such as Rq root-mean-square
roughness but also its 3D equivalents Sq. The software will automatically measure the contact angle in the
same area and calculate the surface roughness corrected contact angle values.
3. Conclusions
Measuring surface roughness together with the contact angle makes it possible to separate the influence of
the surface chemistry and the surface roughness on wetting and adhesion behavior. This is especially
important when working with different types of surface modifications where both surface chemistry and
surface topography are altered. This abstract presents for the first time, integrated surface roughness and
optical tensiometer equipment which enables the measurements to be done on the same sample location.
4. References
[1] Wenzel, R.N., “Resistance of solid surfaces to wetting by water”, Industrial and engineering chemistry, 28, 8, 1936, 988- 994.
[2] Zhang, S. and Huang, P., “High-resolution, real-time 3D shape acquisition”, Conference on computer vision and pattern recognition
workshop 2004 (CVPRW ’04).
46
16th Nordic Symposium on Tribology, Aarhus, Denmark
Keywords: surface roughness, wetting, contact angle, topography, surface chemistry
47
16th Nordic Symposium on Tribology, Aarhus, Denmark
97
The effect of surface roughness and carbon coatings on the friction performance in rolling contact
H. Ronkainen1, L. Kilpi1, S. Varjus1, O. Elomaa2, J. Koskinen2, T. Jaatinen3, J. Toikkanen3,
1
VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT, Finland
2
3
Aalto University, Espoo, Finland
Moventas Gears Oy, Vesangantie 1, FI-40101 Jyväskylä, Finland
Optimizing the friction and wear performance of high-load contact surfaces improves efficiency and
provides longer lifetime for different applications. All of these lead to cost reductions and improved
competitiveness. In this study the friction and wear performance in the rolling contact situation was
studied by using the twin disc test device.
In Twin Disc tests a set surface finishing procedures providing different surface roughness values on test
discs were evaluated with two different types of surface coatings. The surface finish grades represented
the ground surface, and two polishing procedures providing surface roughness values of Ra 0.615 µm,
0.128 µm and 0.030 µm in average. The surface coatings were two carbon based coatings with a
thickness of 1 to 2 µm. The Twin Disc test parameters were selected to represent the contact parameters
in the gear contact. The contact load was increased stepwise in a similar way to FZG tests. The maximum
contact pressure applied was 1.7 GPa and the surface velocities of the discs 1.05 m/s and 1.5 m/s for the
upper and lower disc, respectively. The slide-to roll-ratio was thus about 30 %. The friction was measured
during the tests and the wear performance of the discs was evaluated after the tests. Optical microscopy,
scanning electron microscopy, nanoindentation and 3D profilometry were used for contact surface
characterization.
The test results showed that high surface roughness induced micropitting of uncoated contact surfaces.
With polished surfaces no micropitting or severe wear for the uncoated contact surfaces were observed.
Hard carbon containing coatings deposited on rough surfaces were delaminated when high loads were
applied on the contact. On the other hand, on polished surfaces the carbon containing coatings improved
the wear performance and load carrying capacity compared to uncoated case.
The surface roughness had the major effect on friction performance, since the friction reduction in the
range 11 to 18 % was provided by the smoother surface finish. Also the use of carbon containing surface
coatings reduced friction by 1 to 10 % depending on the roughness of the surface.
Keywords: rolling contact, surface roughness, carbon coatings, friction
48
16th Nordic Symposium on Tribology, Aarhus, Denmark
87
Integrated characterisation and functional testing of friction-locking surfaces
Matthias Gräfensteiner1, Erhard Leidich2
1
M.Eng., research assistant, corresponding author, 2 Prof. Dr.-Ing., head of department,
2
Chemnitz University of Technology, Department of Engineering Design,
Reichenhainer Str. 70, 09126 Chemnitz, Germany
Tel.: +49371 / 531 39289, Fax: +49371 / 531 23319, Email: [email protected]
Frictional engaged surfaces can be found in several powertrain applications. At the dimension equations
of bolt, shrink-fitted and flange joints the static friction coefficient acts as a linear actuating variable. Low
Scatter of friction and a high static friction coefficient are functional requirements for a secure force
transmission at friction locking surfaces. At the same time the technical specification of frictional surfaces
is rarely function-oriented.
In this study, the friction locking material pairs are
characterized with respect to surface geometry as well as
material microstructure and boundary layer. The frictional
properties of conventional, uncoated (milled, grinded and
turned) surfaces were characterized under torsional and lateral
force loading. Based on these results a methodological approach
for the characterisation of friction characteristics and the
definition of the static friction coefficient will be presented. The
adhesion model developed by Kragelski was used and evaluated
in order to investigate the adhesion of the specimen materials.
Furthermore the potential of friction enhancing surface modifications (e.g. laser structuring and PVD
coatings) were investigated experimentally under static and dynamic load regimes. Reassembly of the
friction surfaces and the influence of intermediate medium were also considered. Observed differences
among the results are discussed and design guidelines for the engineering design process will be
enunciated.
References:


Leidich, E.; Gerlach, M.; Bartel, D.; Zimmer, O.; Exner, H.: Gecko. AiF/DFG-Gemeinschaftsvorhaben, laufend. www.haftreibwerte.de
Berger, L.-M.; Spatzier, J.; Gräfensteiner, M.; Vidner, J.; Leidich, E.; Schiefer, S.; Gröger, S.; Gerlach, M.: Investigation of HVOF-Sprayed
Hardmetal Coatings for Static Friction Applications. Proceedings of the International Thermal Spray Conference 2013, Busan, Republic of Korea,
13-15 May 2013
Keywords: static coefficient of friction, frictional engaged joints, friction enhancing surface
modifications
49
16th Nordic Symposium on Tribology, Aarhus, Denmark
99
Friction property of DLC films in low-pressured hydrogen condition
Hikaru Okubo1, Hirochika hukuda1, Ryo Tsuboi2, Shinya Sasaki2
1
Graduate School, Tokyo University of Science, 6-3-1 Niijuku, Katusika-ku, Tokyo, 125-8585, Japan, 2 Tokyo
University of Science, Japan
Corresponding author: [email protected]
Diamond-like Carbon (DLC) film is a thin film of amorphous carbon which has sp2 and sp3 hybrid
orbital. It is expected to be applied in various industrial applications because of their excellent tribological
properties. Previous works showed that extremely low friction coefficient appeared in the case that
hydrogenated DLC film pairs were slid in hydrogenated condition. However, the detailed mechanisms of
the extremely low friction have not been clarified yet. In this study, the effects of surrounding hydrogen gas
for the friction behavior of DLC films were investigated by varying the hydrogen pressure during friction
tests.
Friction tests were carried out using the ball-on-disk tribotester which could change the test environment.
The test conditions were at a load of 2.5 N, a rotation radius of 5 mm and a rotation speed of 6 rpm. The
hydrogen pressure was varied with increment of 0.5 kPa from 0.5 kPa to 5.0 kPa every three minutes. After
the hydrogen pressure reached 5.0 kPa, it was varied with decrement of 0.5 kPa to 0.5 kPa every three
minutes. The test specimens were steel disks (24 mm × t7.9 mm, ISO100Cr6) and balls (4 mm,
ISO100Cr6) covered with DLC films, respectively. The coating methods were CVD and PVD. The
hydrogen contents of the CVD-DLC and the PVD-DLC were 30 at.% and free, respectively. The
combinations of specimens were CVD-DLC / CVD-DLC and PVD-DLC / PVD-DLC.
The relationship of the hydrogen pressures and average friction coefficients was shown in Fig.1. The results
of PVD-DLC tests in Fig. 1(a) showed that the average friction coefficients changed linearly with the
varying of the hydrogen pressure. In the case of CVD-DLC in Fig 1(b), extremely low friction coefficient
less than 0.01 was observed when the hydrogen pressure reached at 5.0 kPa. In addition, the hysteresis was
shown in the relationship between the friction coefficients and the hydrogen pressure. From these results,
it is considered that hydrogen contents of the DLC films and varying of the ambient hydrogen pressure
influenced the specific decreasing of the friction coefficients. Further investigation using chemical analysis
will be performed to clarify the mechanisms of the low friction phenomena.
Friction coefficient
0.15
ta−C/ta−C:Increase
Increase
ta−C/ta−C:Decrease
Decrease
0.10
0.1
0.15
a−C:H/a−C:H:Increase
Increase
a−C:H/a−C:H:Decrease
Decrease
0.10
0.1
0.05
0
(b)
Friction coefficient
(a)
0.05
2500
0
5000
2500
Hydrogen Pressure [Pa]
Hydrogen Pressure[Pa]
5000
Fig. 1 Effect of hydrogen pressure on average friction coefficients of (a) PVD-DLC and (b) CVD-DLC
Keywords : tribology, diamond-like carbon, hydrogen, vacuum.
50
16th Nordic Symposium on Tribology, Aarhus, Denmark
Wear
Chair: Martin Priest
Wednesday 11 June 2014 – 11.40-13.00
Room: Suecia
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16th Nordic Symposium on Tribology, Aarhus, Denmark
23
Rolling-sliding wear of nodular cast iron rollers against wire ropes
Ville Oksanen*1, Kati Valtonen1, Peter Andersson2, Antti Vaajoki2, Anssi Laukkanen2, Kenneth
Holmberg2, Veli-Tapani Kuokkala1
1
Tampere Wear Center, Department of Materials Science, Tampere University of Technology,
P.O.Box 589, FI-33101 Tampere, Finland
2
VTT Technical Research Centre of Finland, P.O.Box 1000, MK6, FI-02044 VTT (Espoo), Finland
*Corresponding author: Ville Oksanen ([email protected])
Simplified laboratory wear tests are frequently used for producing comparable data to represent materials
in different contact conditions. However, in order to obtain deeper knowledge about the wear behavior of
a material in a specific application, component wear tests should be performed. By comparative
characterization of wear test samples and actual field-service components, a correlation between the wear
test results and the field-service operation findings can be established.
The present work describes wear test results and characterization findings for nodular cast iron in contact
with steel wire samples and wire ropes. Grooved nodular cast iron roller components were tested employing
a wire-rope bend tester. The contact motion between the roller and the wire rope consists of rolling and
sliding perpendicular to the rolling direction, caused by a rotation of the wire rope around its axis. In
addition, twin-disc friction and wear tests were carried out with a steel-wire-coated counter-disc. The
characterization results for the component and twin-disc test samples were compared to the findings on the
wear behavior of a field-service component sample. The wear characterization was carried out by optical
microscopy, electron microscopy, and statistical analysis of fatigue wear cracks.
In the component wear test, the higher rope force resulted in higher wear rates and the wear surface showed
more severe macroscopic damage. The wear process in the component test samples had advanced in the
subsurface region by plastic deformation and internodular crack growth under conditions of contact fatigue.
This process resulted in deformation tongues oriented perpendicularly to the rolling direction, and the
formation of shallow pits in the wear surface. The twin-disc test produced similar deformation tongues, but
in the rolling-sliding direction. In comparison with component wear test samples and the field samples, the
twin-disc test sample discs from cast iron revealed material removal in the shape of deeper and larger spalls.
This indicates that in the twin-disc tests the fatigue process proceeded by more brittle fracturing than in the
case of the field-service and the component test samples. Moreover, in the twin-disc sample, the fatigue
cracks extended deeper into the material than in the roller component samples.
The findings indicate that the component wear tests very well simulate the wear behavior of the fieldservice sample. The contact conditions in the twin-disc test are slightly more severe, but the wear
mechanism is quite close to that of the roller samples. The findings will be utilized in the modelling of the
rolling-sliding wear mechanisms of nodular cast iron rolls against wire ropes.
Keywords: nodular cast iron, wear mechanism, rolling-sliding, wire rope
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16th Nordic Symposium on Tribology, Aarhus, Denmark
84
Initiation of wood defibration, tribology at the fiber level
Magnus Heldin1*, Urban Wiklund1, Per Isaksson2, Staffan Jacobson1
1
Ångström Tribomaterials group, Department of Engineering Sciences, Uppsala University
2
Applied Mechanics, Department of Engineering Sciences, Uppsala University
* Corresponding and presenting author, mail: [email protected]
Mechanical wood pulping is widely used to create fibers to be used in many types of papers. One of the
mechanical processes is called stone grinding. In this process a log is ground against a wheel with a
surface containing an abrasive, alumina is common. This process consumes lots of energy, amounting to
GJ/ton pulp produced. Though commonly used,the exact mechanisms which wear the wood into pulp has
not been extensively analyzed,a trial and error approach is most commonly used. In an attempt to design
tools that consumes less energy, an understanding of the basic mechanisms is needed.
This work investigates the cell deformation and early fiber separation that initiate the defibration process.
An X-ray tomograph (µCT), equipped with a miniature tensile stage, was used to monitor the mechanical
behavior of the microstructure in wood when a hard tip was pressed into it step by step.
Subsequent digital image correlation analysis was used to estimate the strain field in the region around the
indented tip.The information on regions of high strain—where cracking and fiber separation may
initiate—is then compared with images of wood scratched with a diamond tip to simulate a single asperity
contact in the industrial tool. From the high strain region numerical stress and strain analyses are made
using high-resolution discrete finite element models. This is done to be capable of capture large
deformations and rotations and to describe the mechanical behavior on the heterogeneous microscale up
to the macroscale. The single tip scratched wood surfaces are also compared with surfaces formed by the
industrial grinding process.
Keywords: µCT, defibration, wood-fiber deformation, wood scratching, FEM modeling, wood strain
54
16th Nordic Symposium on Tribology, Aarhus, Denmark
56
Sliding Wear of Quartz and Granite Surfaces
V. Heino*, K. Valtonen, V.-T. Kuokkala
Tampere Wear Center, Department of Materials Science, Tampere University of Technology
P.O.Box 589, FI-33101 Tampere, Finland
*Corresponding author: Vuokko Heino ([email protected]).
One key element in reducing wear is to include in the analysis the entire wear environment, i.e., more
comprehensive solutions are required. Abrasives are usually considered as the third body in wear related
phenomena. Nevertheless, understanding the variables and the effects that the abrasives have on wear can
affect the outcome of the materials selection processes quite dramatically. Previously we have conducted
studies related to natural abrasives and wear [1-3]. We found that the effect of abrasives changes
significantly when the subject of wear is varied. For example, in WC-Co materials quartz causes more wear
than granite, but for steels granite is more abrasive than quartz. Moreover, it was concluded that embedded
quartz in the sample surface increases friction and affects the further wear rate of certain materials.
The aim of this study was to characterize the properties of two natural abrasives, quartzite and granite, using
the ball-on-disc test set-up. For testing, quartzite and granite particles were mounted in a resin and the
surfaces of the resulting test pieces were ground. In the ball-on-disc tests, these abrasive surfaces were
regarded as the discs, and the balls were made from different steels, zirconia and WC-Co hard metal. These
tests were performed using both constant and continuously increasing forces. By increasing the contact
force during sliding it was possible to identify different regions from crack generation to delamination. The
contact points of the balls were also characterized to see the differences in the minerals attachment to the
surfaces. Surface characterizations were done with optical and scanning electron microscopes. In addition,
an optical profilometer was used to determine the surface topographies.
The results showed that the highest friction values for both rock surfaces were obtained when the hardness
values of the rock and the ball were similar. Moreover, the characterization of the wear tracks provided
information about the mineral behavior under a point-like slider and about the material transfer from the
ball to the mineral surface.
Keywords: granite, quartzite, ball-on-disc, sliding wear
[1] V. Heino, et al.,”Wear Reducing Effect of Embedded Quartz Abrasives in the Crushing-Pin-On-Disc Test Method”, Tribology Online
7(3):179-183(2012), 10.2474/trol.7.179
[2] V. Heino, et al.,”Characterization of the effects of embedded quartz layer on wear rates in abrasive wear”, Wear, in press,
http://dx.doi.org/10.1016/j.wear.2013.06.01
[3] V. Heino, et al.,”Tribological Properties of Quartz and Granite Abraded Wear Surfaces”, International Tribology Symposium of IFToMM,
19.-21.3.2013, Luleå, Sweden
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16th Nordic Symposium on Tribology, Aarhus, Denmark
68
The effect of stick-slips on the dislocation structure of LiF single crystals
A.Moshkovich, I. Lapsker, A. Laikhtman, V. Perfilyev, L. Rapoport
Holon Institute of Technology, Holon 5810201, Israel
[email protected]
The effect of sliding velocity and the direction of sliding have been studied using single crystals of
Lithium Fluoride (LiF). The sliding velocity was changed in the range of 1 µ/s – 1 mm/s. Stick-slip tests
were performed using ball-on-flat arrangement. Dry friction tests were conducted using a linear ball-onflat device at room temperature in air (relative humidity 55 ± 5%). The diamond indenter with the radius,
R=0.2mm, was slid against a plate of LiF. In order to provide stick-slips the spring with low stiffness was
chosen, k = 15 N/m. In order to compare stick-slip motion with sliding, stiff spring was also used, k =
2400 N/m. The friction force and the displacement of indenter relative to LiF plate were measured. The
amplitude (A), the difference between the maximum and minimum values of the friction force and the
kinetic (average value) of the friction force were chosen for description of stick-slip phenomenon.
Dislocation structure around the wear track was revealed by etching of samples before and after friction.
The zones of sleep, creep and stick have been revealed for the tracks obtained at different friction
conditions. Sticks and creeps are accompanied with expansion or bending of the track. The surfaces after
friction were analyzed using optical microscope, scanning electron microscope (SEM) and atomic force
microscope (AFM). It has been found that the dislocation structure around the track is associated with
stick-creep-slip phenomena. The dislocation structure depends on the sliding velocity and the stiffness of
spring. Good correlation between real contact conditions and stick-creep-slip behavior was observed.
Keywords: friction, stick-slip, dislocations, structure, single crystal
56
16th Nordic Symposium on Tribology, Aarhus, Denmark
Test Methods 1
Chair: Bjarke Holl Christensen
Wednesday 11 June 2014 – 11.40-13.00
Room: Dania
58
16th Nordic Symposium on Tribology, Aarhus, Denmark
13
The use of high temperature nanomechanics in designing coatings with improved wear resistance in
high-speed machining
Ben Beake*, Adrian Harris and Mike Davies, Micro Materials Ltd., UK
German Fox-Rabinovich, McMaster University, Canada
* Presenting author. E-mail address: [email protected]
Frictional heating results in very high operating temperatures in ultra-high speed machining (e.g. 1000 ºC
or more). To extend tool life and operate at higher cutting speed coatings must provide mechanical and
thermal protection. Nanoindentation tests used to evaluate the mechanical properties of novel
multifunctional PVD coating systems designed for extreme environments such as high speed cutting of
hard-to-cut hardened steels or Ni-based aerospace alloys are invariably performed at room temperature. If
nanomechanical measurements are to be used reliably in the optimisation of coatings then it is much
better that the measurements are performed at the relevant temperature.
This is achieved using a patented method to separately actively heat and control the temperatures of
indenter and sample resulting in minimal/no thermal drift during the high temperature indentation. The
instrumentation allows reliable nanomechanical testing (e.g. nanoindentation, nano-scratch, micro-pillar
compression, micro-cantilever bending) to 750C and above. To achieve higher temperatures without
indenter or sample oxidation an ultra-low drift high temperature vacuum nanoindentation system capable
of testing to 1000 C has been developed.
In this presentation high temperature nanoindentation data for a wide range of multifunctional nitridebased hard coatings on cemented carbide are used to develop robust design rules enabling coating
optimisation for different machining applications. Subtle compositional tuning of the coatings resulted in
large differences in how their hardness, modulus and H/E vary with increasing temperature [1]. The
interrelationship between the high temperature mechanical properties and the coating system’s adaptive
behaviour and tribo-film formation and ultimate performance is investigated. Overall, the high
temperature nanoindentation data show excellent correlation to coating life under severe high speed
machining applications.
[1] Why can TiAlCrSiYN-based adaptive coatings deliver exceptional performance under extreme frictional conditions? BD
Beake et al, Faraday Discussions (2012) 156, 267-278.
Keywords: nanomechanics, high-speed machining, multifunctional coatings, adaptive behaviour
59
16th Nordic Symposium on Tribology, Aarhus, Denmark
42
Introduction of a novel AC²T tribometer especially designed for harsh environment scratch-,
adhesion- and hardness investigation up to 1000°C
M. Varga1)*, M. Flasch1), S. Paar1), E. Badisch1)
1)
*
AC²T research GmbH, Viktor-Kaplan-Straße 2, 2700 Wr. Neustadt, Austria
Corresponding author. Tel.: +43 2622 81600 132. E-mail address: [email protected]
Wear of materials at high temperatures is a very challenging issue, implying many different mechanisms
occurring in the tribocontact. Increasing temperature often leads to microstructural change of materials as
well as loss of hardness. At high temperatures oxidation is one of the major damaging processes,
additionally corrosion has to be taken into account if aggressive media are present. An abrasive environment
further complicates the acting mechanisms. While wear can be increased due to hardness loss also beneficial
effects like the formation of mechanically mixed layers, which can increase wear resistance are known.
In order to gain fundamental knowledge of these phenomena a high temperature test device was designed
operating up to 1000°C (Fig. 1). The test takes place in vacuum to avoid oxidation and the normal load
range is 1 - 500 N. So it is possible to gain hardness progress in a wide temperature and load range and
monitor possible microstructural modifications. For characterisation of single abrasive phenomena on a
very fundamental level scratch tests at variable loads are proposed. Furthermore, the implementation of
application’s abrasives will be an important issue in the future.
The interaction of sliding surfaces can be simulated by adhesion testing. Thereto an application specific
counterbody can be moved over the sample surface at variable loads. In order to simulate forming
conditions the counterbody can be cooled and the temperature difference between workpiece and tool can
be simulated in this lab-scale test.
In future, pre-worn samples e.g. after abrasive or erosive loading entailing mechanically mixed layers, will
be analysed in order to gain information on the potential of wear reducing mechanisms. Additionally, the
influence of corrosion products, for example gained by defined high temperature corrosion tests, on
tribological behaviour will be a focus of scientific research.
Finally, it can be claimed that this newly designed HT-HET offers an enormous potential for deeper
understanding of fundamental wear phenomena occurring at high temperature.
Fig. 1: Schematic view on High Temperature – Harsh Environment
Tribometer (HT-HET)
Loading unit
Load measurment
Y-Actuator
Indenter
unit
X-Actuator
Keywords:
high temperature, hardness, abrasion, adhesion, tribology
Vacuum chamber with
heating system and
sample holder
60
16th Nordic Symposium on Tribology, Aarhus, Denmark
14
Extreme nanomechanics:
overcoming the challenges in vacuum nanoindentation to 1000 ºC
Ben Beake*, Mike Davies and Adrian Harris,
Micro Materials Ltd., UK
* Presenting author. E-mail address: [email protected]
Elevated temperature mechanical and tribological properties are much more relevant for practical wear
situations than corresponding measurements at room temperature. However, high temperature
nanomechanics and tribology is highly challenging experimentally. To overcome these challenges we
have developed instrumentation (the NanoTest) with (1) active heating of the sample and the indenter (2)
horizontal loading to avoid convection at the displacement sensor (3) patented stage design (4) patented
thermal control method. By separately actively heating and controlling the temperatures of indenter and
sample there is minimal/no thermal drift during the high temperature indentation and measurements can
be performed as reliably as at room temperature.
A range nanomechanical and tribological tests such as nanoindentation [1-2], nano-scratch, nano-wear,
micro-pillar compression [2], nano-friction [3], creep, micro-cantilever bending can be performed to 750
C or more. Above 500 C it is necessary to use Argon purging to limit oxidation of samples and the
diamond indenter although the efficiency of this decreases over 750 C.
To achieve higher temperatures without indenter or sample oxidation an ultra-low drift high temperature
vacuum nanomechanics/tribology system capable of testing to 1000 C has been recently developed [4].
This presentation describes the development of the high temperature vacuum system and its use at high
temperature on a wide range of metals, alloys, ceramics and coatings.
[1] Mechanical properties of solid oxide fuel cell glass-ceramic seal at high Temperatures, J. Milhans, D.S. Li, M. Khaleel, X.
Sun, Marwan S. Al-Haik, A. Harris, H. Garmestani, Journal of Power Sources 196, (2011) 5599–5603
[2] High temperature microcompression and nanoindentation in vacuum, S.K. Korte, R.J. Stearn, J.M. Wheeler and W.J. Clegg,
J. Mater. Res. 27, (2012) 167-176.
[3] Nanoscale Friction Measurements Up to 750 ºC, J.F. Smith, V.M. Vishnyakov, M.I. Davies and B.D. Beake, Tribol Lett
(2013) DOI 10.1007/s11249-013-0102-5.
[4] The NanoTest Xtreme. www.micromaterials.co.uk
Keywords: nanomechanics, high temperature tribology, vacuum nanoindentation
61
16th Nordic Symposium on Tribology, Aarhus, Denmark
76
Effect of temperature control in high temperature tribology
Kirankumar P. Jayananda1, Anshuman Dube1, Amit Ganguly1, Deepak H.Veeregowda2
1
Ducom Instruments Pvt. Ltd., 477/A, 12th cross, 4th Phase, 560058 Peenya Industrial Area,
Bangalore, KA, India
2
Ducom Instruments Europe B.V, Center for Innovation, L. J. Zielstraweg 2, Groningen, 9713 GX, The
Netherlands
Contact Email: [email protected]
Friction and wear is measured in an environment where both the articulating parts are subjected to high
temperature. Although, in some applications like metal forming (extrusion, die casting) only one
articulating surface is at 900 deg C or higher. It is important for the bench top testers to atleast mimic the
temperature difference occurring during the metal forming process. Here, we have developed a friction
and wear testing method using Ducom high temperature ball on disc tester that can control the ball and
disc temperature independent of each other within 5 deg C error. Alumina ball was loaded on an unidirectionally sliding inconel 625 disc, ball and disc heating was controlled independently upto 900 deg
C using induction coil heating. Coefficient of friction was acquired during variable heating patterns
i.e. heating only inconel disc and both inconel disc and alumina ball at the rate of 11 deg C/ min upto
900 deg C.. Coefficient of friction was the lowest when only inconel disc was subjected to heating i.e.
0.2 and it was 2 times lower then coefficient of friction when both alumina and inconel was heated. Post
wear analysis using white light interferometry indicates 6 times lower wear on inconel disc when only
inconel disc is heated compared to both alumina and inconel is heated. This suggests that controlled
variable heating patterns of the ball and disc is important for high temperature tribology.
Keywords: metal forming, high temperature, inconel, heating pattern, coefficient of friction, wear
62
16th Nordic Symposium on Tribology, Aarhus, Denmark
Bio Tribology
Chair: Lars Pleth Nielsen
Wednesday 11 June 2014 – 12.00-12.40
Room: Nortvegia
64
16th Nordic Symposium on Tribology, Aarhus, Denmark
7
The influence of diamond like carbon coated surfaces on friction and film thickness to a bovine
ceramic lubrication condition
Dipankar Choudhury, Fadi Ali, Martin Vrbka, Ivan Krupka, Martin Hartl
Faculty of Mechanical Engineering, Brno University of Technology, Technická 2896/2, 616 69 Brno, Czech
Republic
#Corresponding Author: E-mail: [email protected], TEL: +420 541 143 323, FAX:
+420 5 4114 3231
Issues: Diamond like carbon (DLC) is a promising material in many engineering interfaces due to its
excellent tribological performance. Very recently, it has been extensively tested as biotribological surfaces,
and reported to have very lower friction and wear. However, very little studies have been carried out
identifying its lubrication mechanism (film thickness) under a bovine serum lubrication mechanism.
Therefore, the aim of the study is to understand the lubrication mechanism of DLC to a simulated hip joints
condition.
Method: A spherical head was manufactured to a diameter of 25 mm from a stainless steel bar, and polished
to a mirror type surface finishing. Then, these have been coated with DLC by using a physical vapour
depositing. Hardness, elasticity, wettability and surface roughness profiles were measured prior to the
tribology test. In the tribology test, the DLC coated ball rubbed against Cr coated glass disk, where 25%
bovine serum was used a lubricant and temperature was maintained at 370 C. Film thickness and a frictional
force was measured by a An optical interferometry and a torque sensor respectively. Experiment was
repeated with reciprocating motions, and different contact pressures. The outcomes were compared with
lubrication film thickness and friction coefficient measured at similar conditions to a bearing steel ball.
Results and conclusion: Loads and speeds were found to be influencing factors to film thickness and friction
coefficient of both materials. Moreover, DLC produced lower and consistence friction coefficient profiles
compared to steel at all of the experiment conditions. Film thickness was fluctuated to both materials,
however most cases, thicker to DLC surface. Since the contact pressure was relatively high, the disk
material was severely damaged by DLC within few minutes of experiment, whereas both ball and disk
surfaces were severely damaged in case of steel ball. Moreover, DLC surfaces were found to be delaminated few spot. Therefore, DLC has better tribological performance in both boundary and mixed
lubricant regime compare to steel. However adhesion of DLC need to be improved and its courterface
material should be carefully chosen.
Keywords: Diamond like carbon, bovine serum, friction coefficient, film thickness
65
16th Nordic Symposium on Tribology, Aarhus, Denmark
86
Studying Water Based Lubricant Behavior in Mini-Channel
1
Alaleh Safari*1,Maria Pau Ginebra2, Nazanin Emami*1, Michel J. Cervants,3,4
Biotribology group, Division of Machine Element, Luleå University of Technology, 97187, Luleå, Sweden.
Biomaterials, Biomechanics and Tissue Engineering Group, Dept. of Materials Science and Metallurgy,
Technical University of Catalonia, Barcelona, Spain
3
Division of Fluid and Experimental Mechanics, Luleå University of Technology, 97187, Luleå, Sweden.
4
Water Power Laboratory, Norwegian University of Science and Technology, Norway.
2
Oral presentation
* Presenting author: Alaleh Safari ([email protected]).
Keywords: TJR, joint lubricant, wear particles, micro-PIV
Abstract
One of the most common causes of failures in total joint replacements is the generation of wear
particles within the joint that leads to the micro separation at the implant-bone interface. This
contributes to bone lost aseptic loosening of the implant, requiring eventually its replacement.
Many studies have been carried out to improve the wear characteristics of bearing surfaces in total
joint replacement (TJR). From lubrication point of view the friction behavior of surfaces and rheology
of the joint lubricant (Synovial fluid) were extensively studied. However, not much attention was paid
to the interaction between the lubricant and the bearing surfaces. The aim of this study is to develop a
methodology for studying the behavior of water based lubricant in a micro-channel. For this purpose,
Micro-PIV (Particle Image velocimetry) was used in order to characterize the lubricant behavior.
Experimental models made of relevant materials such as ultra high molecular weight polyethylene,
Cobalt-Chromium-Molybdenum alloy and Titanium-Aluminum-Vanadium alloy with 1 and 1.5 mm
width, 45 mm length and 2 mm depth experimentally investigated.
16th Nordic Symposium on Tribology, Aarhus, Denmark
Wear & Fretting
Chair: Sergei Glavatskih
Wednesday 11 June 2014 – 14.00-15.20
Room: Suecia
68
21
Computational multiscale modelling concept and supporting experimental testing
procedures for material wear behaviour under severe environments
Anssi Laukkanen1, Päivi Kivikytö-Reponen1,*, Antti Vaajoki1, Richard Waudby1, Tom Andersson1,
Marjaana Karhu1, Marian Apostol2, Kati Valtonen2, Veli-Tapani Kuokkala2
1
2
VTT Technical Research Centre of Finland, Espoo, Finland,
Tampere Wear Center, Department of Materials Science, Tampere University of Technology, Tampere, Finland
Abstract: Sustainable design is a growing trend driven by resource scarcity, safety and
environmental aspects, and volatile prices of energy and raw materials. Traditionally materials for
severe industrial conditions, such as wear, corrosion, or elevated temperatures, have been designed
based on the material performance and cost issues, largely by trial and error. For process
optimization and material life cycle estimating purposes computational modelling aided material
design is applied to improve and accelerate the design procedures. Moreover, it is challenging to
mimic in laboratory conditions realistic operational environment during abrasive, erosive, and impact
type wear, and modelling can be applied as a tool for transferability material properties and
performance measures.
This paper presents a computational multiscale modelling concept and supporting experimental
testing procedures for elastomer materials designed for severe environments, such as applications
involving repeated impacts of hard abrasive particles on surfaces at high or moderate strain rates.
The approach was to model behaviour and carry out lifetime predictions by studying different types
of single and erosive impacts between hard particles and an elastomer surface. The model was
verified by experimental testing procedures using high velocity particle impactor, surface scratch
testing and centrifugal accelerator with various impact angles.
Keywords: modelling, material testing, impact, wear, severe environments
*Corresponding
author Päivi Kivikytö-Reponen ([email protected]).
16th Nordic Symposium on Tribology, Aarhus, Denmark
37
Effect of the contact angle on the impact-sliding wear of nitrided stainless steel at 400˚C
Takahiro Yamazaki1) *, Junichi Yoshihisa2), Jean-Christophe Abry3), Gaëton Bouvard3), Vincent
Fridrici3) and Philippe Kapsa3)
1
Fundamental Research Engineering Department, IHI Corporation,
1,Sin-nakahara-cho, Isogo-ku, 235-8501 Yokohama, Japan;
2
Machine Element Department, IHI Corporation,
1, Shin-nakahara-cho, Isogo-ku, 235-8501 Yokohama, Japan
3
Laboratoire de Tribologie et Dynamique des Systèmes, Ecole Central de Lyon, CNRS, 36 Avenue Guy
de Collongnue, 69134 Ecully Cedex, France
*
Presenting author: [email protected]
In the sliding parts of the industrial machines, unexpected vibrations generated from external parts could
lead severe abnormal wear. In most of case, it might be caused by impact-sliding wear. In order to find the
solution for it, it is important to understand the mechanism of impact-sliding wear. So far, authors have
reported the effect of impact energy and number of cycles on wear by using impact-sliding wear test rig.
In this study, focusing on the effect of the contact angles on wear, we conducted the impact-sliding wear
test at 400˚C in air.
The impact-sliding wear tests were conducted by using cross-cylinder type. Cylindrical specimens (10mm
of diameter and 10mm of length) were used for the test. Specimens were made of stainless steel 310S.
Two kinds of nitriding treatments were treated on the specimens: gas nitriding and ion nitriding. Both
nitriding were used in combination as a pair. Test conditions were shown in Table1.
One of the test results is shown in figure 1. Wear volumes shows sum of the pair of specimens. It showed
the tendency of decrease with the contact angles increase. It is due to the difference of contact condition
between both specimens and elimination of the wear debris on the sliding surfaces.
Table 1 Test conditions
400
4
5×105
16
45, 60, 90
Wear Volume (mm3)
Temperature ˚C
Impact energy mJ
Number of cycles
Frequency Hz
Contact angle ˚
0.70
0.60
0.50
45˚
0.40
60˚
90˚
Contact angle
0.30
0.20
0.10
0.00
20
40
Figure 1
60
Contact Angle (˚)
Keywords: impact-sliding wear, contact angle, nitriding, stainless steel
70
80
100
Wear volume to the contact angles
16th Nordic Symposium on Tribology, Aarhus, Denmark
49
Applying the digital image correlation method to fretting contact
J. Juoksukangas1*, A. Lehtovaara1, A. Mäntylä2
1
Engineering Design, Tampere University of Technology, P.O. Box 589, 33101 Tampere, Finland
2
Research & Development, Wärtsilä Finland Oy, P.O.Box 244, 65101 Vaasa, Finland
*Corresponding and presenting author: Janne Juoksukangas ([email protected]).
Fretting occurs between contacting parts that undergo small relative oscillatory movement. It can cause
serious damage to machine components, either by decreasing fatigue life (fretting fatigue) or by wearing
the contacting parts (fretting wear). The relative movement, i.e. slip, between contacting parts and the
friction coefficient are both important fretting parameters. Numerical fretting contact models are used to
calculate quantities, such as slip, contact tractions and further stresses in contacting bodies for fatigue life
calculations. In the models, using the proper friction coefficient as an input value is of utmost importance.
However, experimental measurement of the friction coefficient from fretting contacts is not
straightforward: neither is the measurement of the micrometer-level motion between the contacting parts.
In this study, the digital image correlation (DIC) method is applied to a fretting contact. A DIC system,
consisting of a digital camera extended with a long-distance microscope, is implemented into an in-house
complete contact fretting test device. Complete contact means that the contact size is independent of the
applied normal load, i.e., the contact has ‘sharp’ edges. Theoretically, this leads to singular contact
traction field. The material used here is quenched and tempered steel. DIC is employed to measure the
local displacement field at the contact edge. The size of the slip regime and the micrometer-level slip
amplitude can be directly determined. The experimental system allows displacement field measurement at
specified time intervals during an entire fretting fatigue test, consisting of several million loading cycles
of the test specimen. This makes it possible to establish the development of the slip amplitude and the slip
regime size throughout a fretting test.
Keywords: fretting, complete contact, slip, digital image correlation, DIC.
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16th Nordic Symposium on Tribology, Aarhus, Denmark
54
Fretting wear behaviour of MoS2 dry film lubricant
K. Barman1*, K.T. Voisey1, P.H. Shipway1, G.A. Pattinson2
1
Faculty of Engineering, The University of Nottingham; 2 Rolls-Royce Plc
*presenting author
Dry film lubricants (DFL) are used as palliative coatings to prevent fretting wear. In this work
fretting tests are carried out on coated Ti6Al4V cylinders on coated flat samples under dry sliding
conditions, using an amplitude of 300mm, 2.5Hz frequency and 575N normal load. During the tests
the coefficient of friction (CoF) was monitored with time, with tests being terminated when the
coefficient of friction reached 0.7. Wear scars were analysed by profilometry and SEM to elucidate
wear mechanisms. Results show that CoF initially increases rapidly to 0.4, this is then followed by
a plateau region that finishes in a sudden step decrease in CoF following which CoF rises
steadily. This behaviour is shown to be characteristic and interrupted tests are presented to allow
elucidation of the wear scar at different stages in the lifetime and thus aid an understanding of the
mechanisms of degradation which control the tribological behaviour.
Keywords: fretting, friction, tribology, solid lubricant coating, dry sliding wear
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16th Nordic Symposium on Tribology, Aarhus, Denmark
Test Methods 2
Chair: Dirk Drees
Wednesday 11 June 2014 – 14.00-15.20
Room: Dania
74
16th Nordic Symposium on Tribology, Aarhus, Denmark
36
Film thickness measurements in a running hydrostatic swash plate type unit using ultrasound
Sünje Marsch*1, Lars Leonhard1, Marc Diesselberg1, Phil Harper2, Rob S. Dwyer-Joyce3
1
Danfoss Power Solutions GmbH & Co. OHG, Neumünster, Germany
Tribosonics Ltd, Sheffield, United Kingdom
3
University of Sheffield, Department of Mechanical Engineering, Sheffield, United
Kingdom
2
*Corresponding author: Contact by phone +49 4321 971 901 or by email [email protected]
The present work describes the measurement of the oil film thickness in the range of a few micrometers
in an operating hydrostatic unit using ultrasound. The investigated tribological system consists of a rotating
steel cylinder block and a stationary bi-metal valve plate under static and hydrodynamic lubrication. The
film thickness has been recorded in a wide range of operating conditions, pressure between 100 to 300 bar
and rotational speed between 500 and 3000 rpm, to support a deeper understanding of the system.
Temperature sensors were implemented next to the ultrasound sensors to compensate the ultrasound signal
amplitude and phase change due to temperature dependent impedances. To confirm the results, especially
the presence of purposely intended zero-film conditions, wear profiles of the running surface were taken.
In contrast to past measuring methods, the ultrasound technique shows a significant improvement in
resolution allowing the real-time observation of film thickness oscillations with cylinder block and piston
frequency. Steady-state measurements confirm the system behavior observed in transient operation and
zero-film conditions with respect to hardware configuration were detected. The findings will be utilized to
support current development activities and to improve simulation models used for film thickness
predictions.
Keywords: ultrasound, hydrostatic swash plate unit, oil film thickness, cylinder block, valve plate
75
16th Nordic Symposium on Tribology, Aarhus, Denmark
38
Validation of a New Tribological Test Bench for Lightweight Hydraulic Components
M.Sc. Markus Blust (IPEK), Dipl.-Ing. Benoit Lorentz (IPEK)
M.Sc. Markus Blust (oral presentation)
Karlsruhe Institute of Technology, IPEK – Institute of Product Engineering, Kaiserstraße 10
76131 Karlsruhe, Germany; email: [email protected]
In mobile systems, and especially for automotive applications, reducing moving masses becomes even more
relevant. Reducing moving masses decreases the energy consumption and consequently the CO 2 emission
of the overall mobile systems.
Present paper focuses on tribological contacts occurring in “lightweight” hydraulic systems, often subject
to oversizing, leading to unnecessary high masses of the systems and contributing to high costs. As
demonstrator, the main component of a hydraulic power train (here an axial piston variable pump) is taken
under investigation. A possible strategy to reduce the overall mass of an axial piston variable pump may
consist in replacing steel-components with polymeric material or hybrid design components. This way
induces changes of tribological properties of the system as polymeric or hybrid design components in such
tribological contacts are still unknown yet.
To improve scientific understanding of these tribological contacts between cited lightweight materials, a
test bench was developed at the IPEK – Institute of Product Engineering. The test bench enables analyzing
the tribological behavior of a typical contact occurring in the axial piston variable pump: contact between
cylinder and control plate. The developed test bench reproduces real tribological conditions observed in the
tested system and aim at establishing the tribological behavior of the contact observed in the real system.
A description of the modeling as well as a validation of the test bench are presented in the proposed paper.
Additionally, first results of the friction behavior will be shown as well as measured wear rates.
Keywords: hydraulic components, tribology of materials, system tribology
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16th Nordic Symposium on Tribology, Aarhus, Denmark
39
Test rig for drag force measurements
Bihotz Pinedo, Jose Mª Seara, Joseba Arana, Raquel Bayon, Amaya Igartua*
IK4-Tekniker, C\ Iñaki Goenaga 5, 20600, Eibar, Spain
*Presenting author
Ships’ performance is affected by the drag force at the underwater hull. This drag force depends on the
physical and biological hull roughness. If the former can be controlled by the manufacturing process and
by means of opportune anti-corrosive surface treatments, the latter needs several developments for
avoiding bio fouling. In order to test these developments at laboratory scale a test rig has been designed
and assembled.
It consists of a 200 mm diameter stationary cylinder fixed to a frame through a torque meter and sank into
a rotating tank of marine water. The measuring device is uncoupled from the actuation part allowing a
precise recording of the drag force. The gap between the stationary test cylinder and the tank can be
decided changing the tank inner diameter, therefore, both Couette and turbulent flow can be reproduced.
Precise measurements of the drag force in two ranges 0-1 Nm and 0-10 Nm can be carried out. The
opportune dimensioning of the system allows reaching velocities up to 30 knots for a rotating speed of
1500 rpm. The performances of the test rig and its limits are herein illustrated.
Keywords: drag force, tribometer, turbulent flow, hull roughness
77
16th Nordic Symposium on Tribology, Aarhus, Denmark
94
Surface plasmon resonance measurements of adsorbed films under fluid lubrication conditions
Satoru Maegawa, Anna Koseki, Fumihiro Itoigawa, Takashi Nakamura
Nagoya Institute of Technology, Japan.
Recently, the in-situ observations of surface chemical structures based on surface plasmon resonance
(SPR) phenomenon have been focused on due to their high sensitivity, high time resolution and simple
construction. In several situations, using SPR signals from the surfaces, the adsorbed film thickness, surface
coverage, or surface concentrations, etc., are estimated.
The aim of this study is to introduce the SPR measurement technique for monitoring the adsorption
processes of fatty acids in fluid lubrication systems. The experimental apparatus used in this study employs
a fluid-lubricated contact between a flat surface of a semicylinder prism (made of polycarbonate) and a
metal roller (made of SAE4135). The clearance between them was set to be 50 m, i.e, thickness of fluid
lubrication film: 50 m. In order to generate SPR signals, the Ag SPR sensing film (thickness:
approximately 50 nm) was deposited onto the prism surface. In the test, base oil (Hexadecane) and a small
amount of additive (0.1 and 1 mass% Oleic acid) are dropped into the clearance space.
Figure 1 shows the change in SPR signal curves under static conditions (i.e., without rolling). It means
that the method can measure the small change of the permittivity resulting from the increased concentration
of Oleic acids; the dependence of adsorption properties on the concentration of additive can be qualitatively
observed by measuring SPR signals. Figure 2 shows time changes SPR signals under dynamic condition
(i.e., with rolling). This result shows some of adsorption characteristics of fatty acids in fluid lubrication
conditions. The adsorbed film of oleic acid is developed on a time scale of 10 minutes, and the growth rate
depends on the concentration of oleic acid. In addition, it is suggested that mechanical shearing is an
important factor to promote the ability of forming adsorbed layers. Through the experimental test, it was
found that the SPR measurement technique have a high potential for monitoring adsorption processes of
fatty acid films under lubrication conditions.
1.5
0.1%
1%
4
3
1.45
Intensity
Intensity
Base oil: Hexadecane
Additive: Oleic acid
2
0%(base oil)
0.1%
1%
65
Oil thickness: 50 m
1.4
Additive: Oleic acid
1.35
Oil thickness: 50 m
1.3
0
70
75
Incidence angle(deg)
Base oil: Hexadecane
10
Time(min)
20
Velocity: 78.5 mm/s
Fig. 2 Time changes of Ireflect under the dynamic test.
Fig. 1 SPR curves under the static test.
Keywords: surface plasmon resonance, in-situ observation, adsorbed film, and fluid lubrication.
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16th Nordic Symposium on Tribology, Aarhus, Denmark
Modelling 3
Chair: Kristian Tønder
Wednesday 11 June 2014 – 14.00-15.20
Room: Nortvegia
80
16th Nordic Symposium on Tribology, Aarhus, Denmark
16
Cavitation analysis of a journal bearing - Finite Element modelling and experimental studies
1
C.K. Christiansen1*, P. Klit1, J.H. Walther1, A. Vølund2
Department of Mechanical Engineering, Technical University of Denmark, Nils Koppels Allé, bld. 404,
2800 Kgs. Lyngby, Denmark.
2
MAN Diesel & Turbo, Teglholmsgade 41, 2450 Copenhagen SV, Denmark.
*Corresponding author: Christian Christiansen ([email protected]).
This paper will present a two-sided approach to establish understanding of the cavitation phenomenon in a
dynamically loaded journal bearing, more specifically the engine bearings of a large two-stroke marine
diesel engine. Journal bearings are used in a wide range of applications due to their simplicity and derived
low cost but also a reasonable load carrying capacity. On the other hand, one of the most often mentioned
disadvantages of the journal bearing is the converging-diverging geometry making it prone to cavitation. A
typical area of application for journal bearings is combustion engines. Here the journal bearing plays a vital
role especially as main and crosshead bearings transmitting the combustion forces. Those forces vary highly
during one combustion cycle which is further influencing the load carrying capacity. For machinery
operating at low RPM’s such as large two-stroke marine diesel engines, as featured in this work, this is
critical. Reynolds equation is solved numerically using Finite Elements incorporating a cavitation algorithm
and dynamic coefficients. To the author’s knowledge this particular combination is novel. Validation of the
results is done against the Ruston–Hornsby 6 Veb-X Mk III engine. Besides the numerical investigations a
cavitation test rig has been developed. With this rig it has become possible to generate cavitation under
controlled conditions in terms of load/eccentricity and rotational speed. The development of cavitation in
time in terms of position and distribution can be visually recorded. The obtained numerical results are
compared with the experimental results.
Keywords: cavitation, journal bearing, Finite Element, filling ratio, test rig
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16th Nordic Symposium on Tribology, Aarhus, Denmark
83
Dynamic and tribological analysis of a toroidal CVT
Keith Philpot and Romeo Glovnea
Department of Engineering and Design, University of Sussex
Continuously variable transmissions (CVT) are mechanical transmission, which unlike ordinary gearboxes
offer seamless change of the transmission ratio through a theoretically infinite range. There are many design
configurations of these transmissions however they all have in common the continuous change of a length
or angular dimension which results in an adjustment of the velocity of the output element. Most CVT
designs include tribological contacts which can transmit power while changing the geometrical
configuration of the contacting elements. A distinct kind of CVTs includes devices in which the tangential
force between rotating elements is transmitted through a thin lubricant film, known as traction drives, where
the lubricant film works in the elastohydrodynamic (EHD) regime of lubrication. Of these, the toroidal
design is best known, probably because of the devices of this type used in automotive applications. The
working principle and calculations of a toroidal-type CVT capable of automatically adjusting the
transmission ratio function of the resistive torque was presented in a number of papers by the authors. A
schematic of the device is shown in Figure 1.
Output disc
F
Coupling
T
Input discs
Figure 1
The main elements of the traction drive are the input discs, one conical and the other toroida,l with a conical
output disc, between which a convenient number of spherical elements are placed. The power is transmitted
from the input to the output discs through the shearing of the EHD film formed in the contacts between
these discs and the intermediary spherical elements. The toroidal disc rotates with the input shaft but is free
to move axially, thus when a torque is applied to the output shaft, the coupling between this and the output
disc displaces axially the later which in turn forces the balls to move in radial direction and consequently
change the transmission ratio. In the present study an analysis of the relative kinematics on the contact areas
between the discs and balls is carried out. The relative motion between these elements consists of spin and
side slip imposed over the longitudinal slip. The later is obviously the motion used to transmit power while
the former are parasitic motions. Understanding this kinematics is important for the design and modelling
of the CVT because these relative motions cause shear of the EHD film and provide the tangential force
which drives the elements. The lubricant is modelled as a non-Newtonian fluid using a multi-grid multilevel method to calculate the traction force on the contacts. These are subsequently used to evaluate the
dynamic response of the CVT to a rapid variation of the input/output parameters.
Keywords: CVT, EHD, traction, modelling, dynamics
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16th Nordic Symposium on Tribology, Aarhus, Denmark
24
Comparison of Four Numerical Methods of EHL Modeling
Shravan Janakiraman1*, Peder Klit1
Technical University of Denmark, Department of Mechanical Engineering, Nils Koppels Alle, Kgs. Lyngby, Denmark
2800
* : Presenting author
Several methods to model Elastohydrodynamic Lubrication in non-conformal contacts have been presented
over the years. Two of the more commonly used methods are the Finite Difference method by Houpert and
Hamrocka and the multigrid method by Lubrechtb. These two numerical methods can obtain convergence
of the pressure and film thickness curves for high input loads. A finite element model for low loads has
been developed as part of the current work and its advantages and limitations compared to the models by
Houpert & Hamrock and Lubrecht are studied. The Finite Difference model by Houpert and Hamrock is
extended to study slip in EHL contacts at low loads. The advantages and limitations of this model is
compared to the previously mentioned three models.
The Finite Difference approach by Houpert and Hamrock to model EHL in isothermal, non-conformal
contacts by applying the Newton Raphson method to solve the highly coupled, non-linear Reynolds
equation and the elasticity equation is a popular method to obtain the pressure and film-thickness curves at
high loads. Input loads corresponding to a maximum Hertzian pressure of 2 GPa have been applied using
this method. This method of solution has been extended by Houpert and Hamrock to solve the EHL
equations for slip at low loads and slide-roll ratios. At high loads or slide-roll ratios, the high temperature
at the contacts limits this isothermal model in its use.
A finite element model using 4 node quadrilateral elements was used to solve Reynolds equations at low
loads. The finite element model does not converge for high loads. The advantages and limitations of this
model are discussed.
Lubrecht used a multigrid method to resolve convergence problems in the EHL model at high loads. The
coarse mesh in the multigrid method eliminates the low frequency errors, while the fine mesh eliminates
the high frequency errors. This interpolation of data between grids of varying number of elements and
elimination of errors at each level leads to faster convergence of the pressure and film thickness curves at
high loads. Input loads corresponding to a maximum Hertzian pressure of 4 GPa have been solved using
this method. The multigrid method has been further extended to study the EHL behavior in contacts where
one of the surfaces in contact is textured. The advantages and limitations of this method in relation to the
other methods are discussed.
a
– Houpert L.G and Hamrock B.J. ., “Fast Approach for Calculating Film Thicknesses and Pressures in Elastohydrodynamically Lubricated
Contacts at High Loads,”(1986)
b
– Lubrecht A.A., “Numerical Solution of the EHL Line and Point Contact Problem Using Multigrid Techniques,” PhD Thesis, (1987)
Keywords : elastohydrodynamic lubrication, multigrid method, finite element method, finite difference
method
83
16th Nordic Symposium on Tribology, Aarhus, Denmark
92
A Non-Newtonian THD Lubrication Model for Journal Bearings
Shiuh-Hwa Shyu, 1 Shen-Min Liang,2 Tz-Ting Chiou3 and Jyun-Jye Liao4
1
Graduate School of Opto-Mechatronics and Materials, WuFeng University, MingHsiung, ChiaYi,
Taiwan 621, ROC
2
Department of Computer Application Engineering, Far East University, Hsin-Shih, Tainan,
Taiwan 744, ROC
3
Department of Aeronautics and Astronautics Engineering, National Chung Kung University, Tainan,
Taiwan 701, ROC
4
Department of Mechanical Engineering, WuFeng University, MingHsiung, ChiaYi, Taiwan 621,ROC
Presenting author: Shiuh-Hwa Shyu
A general lubrication model was developed for laminar and turbulent thermohydrodynamic (THD) journal
bearings with non-Newtonian effects. The Navier-Stokes and energy equations were solved with the
molecular viscosity modeled with the power law and as a function of temperature. A Legendre collocation
method was used in the cross-film direction while the axial direction was discretized with a staggered
system. The model was validated by comparing with the Reynolds equation and a study in the literature.
A parametric study was conducted to find that the load capacity, friction coefficient and the THD effects
on the load capacity increase with the power-law index.
Keywords: non-Newtonian fluid, turbulent flow, thermohydrodynamic, journal bearing, Legendre
collocation, Navier-Stokes equations
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16th Nordic Symposium on Tribology, Aarhus, Denmark
PLENARY SESSION 3
Thursday 12 June 2014 - 08.40-09.20
Professor Mathew Mate
Chair: Ion Sivebæk
85
16th Nordic Symposium on Tribology, Aarhus, Denmark
Improved Understanding of Lubrication at the Molecular level and its Impact on
Technology
Dr. C. Mathew Mate
HGST, a Western Digital company, San Jose, California, USA
Abstract:
The past thirty years has seen a tremendous increase in the number of experimental results
elucidating how lubricants work at the molecular scale to reduce friction and wear. Over the same
period of time, major advances have also occurred in computer modeling of lubricant behavior
over a wide range of length scales: from atomic-scale molecular dynamic (MD) simulations to
macroscale computational fluid dynamics (CDF) modeling.
In this talk, I will review the progress that has been in improving our molecular level
understanding of lubrication from these modern experimental techniques, simulations, and
theory. I will also discuss how these advancements in molecular level understanding have led to
major technological advances, with a particular emphasis on the tribological advances achieved
by the disk drive industry that I work in. Finally, I will discuss opportunities for achieving
advancements in other technologies and for even enabling entirely new technologies through
better molecular level understanding of friction, lubrication, and adhesion.
Keywords: lubrication, disk drive tribology
Biography:
Bachelor in Engineering Science from the University of California at Berkeley in 1981 and PhD
in Physics from the same university in 1986. Afterwards he began to work at the IBM Almaden
Research Center in the area of tribology research. When IBM sold its disk drive business to
Hitachi in 2003, his research organization became part of Hitachi Global Storage Technologies;
and, then when Hitachi sold this business to Western Digital in 2012, it became part of HGST, a
Western Digital company. Dr. Mate's research interests at IBM, Hitachi, and HGST have focused
on understanding how friction and lubrication occur at the atomic and molecular levels. Initially,
this work has involved pioneering the use of the atomic force microscope to study tribological
phenomena. He has also conducted seminal studies on the physical properties of molecularly thin
polymer films that are important for lubrication. More recently, this research has centred on
understanding friction, lubrication, and wear of recording heads flying over disk surfaces inside
of disk drives. In 2001, he was awarded the MRS Medal from the Materials Research Society in
recognition of his pioneering studies of friction at the atomic and molecular level; and, in 2012,
he received the International Award from the Society of Tribology and Lubrication Engineers.
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16th Nordic Symposium on Tribology, Aarhus, Denmark
Coatings 1
Chair: Helena Ronkainen
Thursday 12 June 2014 – 09.40-11.20
Room: Suecia
87
16th Nordic Symposium on Tribology, Aarhus, Denmark
142
Tribological and mechanical properties of Cr2N-11Ag – coatings deposited on Cr-V
ledeburitic steel
Pavel Bílek1, Peter Jurči1, Michal Novák1,2, Mária Hudáková1, Ľubomír Čaplovič1,
1
Institute of Materials Science, Faculty of Materials Science and Technology in Trnava, Slovak University
of Technology in Bratislava, Paulínská 16, 917 24 Trnava, Slovak Republic.
2
Institute of Materials Research, Slovak Academy of Sciences, Watsonova 47, 04001, Košice, Slovak
Republic
4.7 μm thick Cr2N-Ag nanocomposite coatings, containing 11 wt.% Ag solid lubricant, were
deposited on substrate made of Cr-V ledeburitic tool steel Vanadis 6 by reactive magnetron
sputtering, at a deposition temperature of 500 oC, using pure Cr and Ag targets, in a composite low
pressure N2/Ar atmosphere. The nanohardness of the Cr2N-11Ag film was 17.86 ± 0.79 GPa, e.g.
it was slightly higher than that of the pure Cr2N, Cr2N-3 wt.% Ag and Cr2N-7 wt.%Ag coatings,
respectively. The Young modulus was 280 ± 7 GPa, e.g. it was not influenced negatively by
elevated silver content, also. The Cr2N-11Ag film exhibited good adhesion on the substrate – the
first critical loads, related to the first indications of side flaking of the films, established by scratchtesting method, ranged between 34 and 40 N. Tribological testing using a pin-on-disc apparatus
has been realized at ambient and elevated temperatures: 300, 400 and 500 °C, respectively. The
balls made of Al2O3 and 100Cr6, respectively, have been used as counterparts. Wear tracks after
pin-on-disc testing were analyzed by scanning electron microscopy and microanalysis. The selflubricant effect is dependent on transport of lubricious Ag within the Cr2N matrix to the surface of
coatings. The experiments have shown the strong dependence of tribological properties on the
temperature. At ambient temperature, the friction coefficient μ against alumina was 0.70 and it was
reduced to 0.34 when tested at temperatures of 400 °C and 500 °C, respectively. The reduction of
μ makes of about 52 %. Compared to the films with lower silver content, the reduction of the
friction coefficient was found to be similar with increasing temperature. The friction coefficient of
Cr2N-11Ag film against 100Cr6 was 0.57, e.g it was practically the same than that of Cr2N-7Ag.
Obtained results infer that there is good opportunity to design the Cr2N-Ag film for specific
tribological applications, through proper choice of both the deposition temperature and the silver
addition into the basic Cr2N coating.
Keywords: Vanadis 6, PVD, chromium nitride with silver, pin-on-disk, nanohardness, scratch-test.
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16th Nordic Symposium on Tribology, Aarhus, Denmark
6
Friction investigation with thermally sprayed Fe-based coatings for application on cylinder
running surfaces in combustion engines
Beate Schleif, Dipl.-Ing.1, Wolfram Wagener, Dr.-Ing.2, Ludger Deters, Prof. Dr.-Ing.3
1
BMW Group, Hufelandstraße 4, D-80788 München, [email protected]
BMW Group, Ohmstraße 2, D-84030 Landshut, [email protected]
3
Institute of Machine Design, Otto-von-Guericke-University Magdeburg. Universitätsplatz 2
D-39106 Magdeburg, [email protected]
2
Modern combustion engines for automobile applications are demanded to show improved
performance resulting in higher loads and requirements, e.g. for the cylinder running surface. To
ensure an unproblematic operation over the whole life time of the component, the running surface
needs to be resistant against scuffing and wear. Therefore, the current BMW four-cylinder gasoline
engine has a ferrous coating applied on the aluminium crank case by wire-arc spray. This coating
reduces the weight and thermal deformations of the cylinder bores in operation compared to gray
cast iron liners while having higher wear resistance and scuffing load capacity than hypereutectic
aluminium liners. In addition, the reduction of frictional losses is aimed for in order to reduce CO2emissions. The tribological system cylinder liner / piston is one of the main focuses for optimization
because it contributes the largest part to the total engine losses. On the one hand, the chemical and
structural composition of thermal spray coatings is dependent on the coating process. Due to the
lamellar structure containing pores and oxidized phases, such coatings do not behave like the cast
alloys when exposed to friction. On the other hand, heterogeneous materials can be applied in a
way that the phases serve different tasks in the function of the coating, e.g. resulting in lower
friction. Therefore, selected metallic materials are applied on cylinder bores by wire-arc spray and
their behaviour in boundary friction is evaluated in an oscillating tribometer. Subsequent analyses
determine the character of the coatings and the built tribo-layers.
Keywords: thermal spray coating, wire-arc spray, cylinder bore, boundary friction
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16th Nordic Symposium on Tribology, Aarhus, Denmark
50
Friction and wear resistance of plasmapolymeric coatings applied on elastomers
Dominik Paulkowski, Stefanie Karpinski, Klaus Vissing
Fraunhofer-Institut für Fertigungstechnik und Angewandte Materialforschung
Using plasmapolymeric coatings on flat elastomer plates as well as on dynamic sealing
components a significant reduction of friction and wear was determined in the past1,2,3.
Quantifying the improvement of wear resistance enhanced lifetime tests were performed as a
function of the applied film thickness.
The flat elastomer plates were coated with a plasmapolymeric film (SiOxCyHz) in a plasma
enhanced chemical vapour deposition (PECVD) process. The film thickness was varied from 0.66
to 3.9 µm. The investigated substrate type was acrylic rubber (ACM).
The friction of elastomers was investigated using an Universal Material Tester (UMT3) system
with oscillating Pin-on-plate contact geometry. The counterpart in the tribological tests was a
100Cr6 steel ball with a diameter of 10 mm. The tribological tests were runned dry in ambient
conditions with a velocity of 200 mm/s, a stroke length of 11 mm, and normal force of 4.7 N. The
used normal force represents an initial Hertzian pressure of 1.5 MPa. The oscillating
measurement setup was chosen to save test time subjecting premature wear. In spite of that fact
the tests were performed 24, 60, and more hours.
It was found that the set in of the wear depended on the film thickness. The set in of wear was
detected at the steep rise of the coefficient of friction. The wear resistance decreased with
increasing film thickness. A minimum film thickness is required.
The beneficial wear resistance of the thinnest 0.66 µm film depicts the improved lifetime in
combination with reduced friction at low costs due to short film deposition time. In contrast to the
uncoated sample the coated ones exhibited only a polished like wear track. The counterparts
revealed heavy wear at increased coating thickness on the elastomers. The results at the
investigated dry contact demonstrate emergency running properties. The coefficient of friction
was in the range of 0.15 to 0.17. It revealed that the coefficient of friction was independent on the
film thickness.
Keywords: plasmapolymeric coating, elastomer, rubber, friction reduction, wear resistance,
energy saving, CO2 saving
Dominik Paulkowski, Klaus Vissing, Tribological improvement of elastomers using plasmapolymeric coatings,
15/1-15/14, Proceedings of Tribologie Fachtagung 2011, GfT, Göttingen, Germany
2
Dominik Paulkowski, Klaus Vissing, Reduction of elastomeric friction in lubricated contact using plasmapolymeric
coatings, Tagungsband 2, 52/1-52/9, Proceedings of Tribologie Fachtagung 2012, GfT, Göttingen, Germany
3
Dominik Paulkowski, Klaus Vissing, Plasmapolymeric coatings improve radial shaft sealing on application, 87/187/11, Proceedings of Tribologie Fachtagung 2013, GfT, Göttingen, Germany
1
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16th Nordic Symposium on Tribology, Aarhus, Denmark
65
Evaluation of Durability of SOG-layers on Steel Surfaces by Wear and Scratch Tests
Z. Dimkovski1, G. Kofod2, S. Rebeggiani1*, B.-G. Rosén1
1
Halmstad University, Sweden; 2InMold Biosystems, Denmark
*[email protected]
Steel moulds with high precision surfaces are being used in various branches. Process aspects, like
tool life and tribological properties, as well as design issues are of great importance. This work
summarises experimental studies performed to test durability properties of SOG (spin-on-glass)layers on steel surfaces. This coating technique is based on a newly developed method for surface
preparation of tools which has been demonstrated to be durable for more than 66.000 replications
in injection moulding processes without loss of surface fidelity. The procedure allows surface
roughness reduction from approximately 200 nm Ra down to some few nm for high gloss
applications, as well as easy transfer of large-area functional nanostructures on complex 3D
surfaces.
Three different types of surfaces were investigated: SOG-layered metal surfaces with three
different layer thicknesses, one ingot casted and one electro slag remelted material (with hardness
level of 950 and 2500 MPa, respectively). The metal surfaces were ground and polished to mirrorlike finishes.
Three circular samples of each type were rubbed against a hard steel ball of 6.35 mm radius on a
commercial pin-on-disk tribometer. To resemble the molding process a sliding speed of 2 mm/s
and a load of 8 N were chosen. The tests were performed with 5 minutes intervals until the first
damage on the surface were observed. In parallel, scratch tests were performed in the same
tribometer. The surfaces were measured in-situ by a portable microscope and a stylus, and
afterwards by a white light interferometer and scanning electron microscope to evaluate the size of
the wear/scratch traces.
The surface type with the longest time to damage and/or smallest wear/scratch traces was
considered to be the most durable one.
Keywords: mirror finish, tribometer, ball-on-disk, scratch-test, SOG-layers
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16th Nordic Symposium on Tribology, Aarhus, Denmark
Industrial Tribology 1
Chair: Hector Torres
Thursday 12 June 2014 – 09.40-11.20
Room: Dania
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16th Nordic Symposium on Tribology, Aarhus, Denmark
143
Three – body abrasion behavior of selected commercially available polymer materials
Vladimir Pejaković1,*, Robin Jisa1, Friedrich Franek1
1
AC²T research GmbH, Wiener Neustadt, Austria *Corresponding author: Vladimir Pejaković;
AC²T research GmbH; Viktor Kaplan Straße 2; 2700 Wiener Neustadt; Austria. E-mail:
[email protected]; Telephone: +43(0)2622 81600-144
The aim of this investigation was to examine several types of commercially available
polymers for potential application in machine elements of conveyors or rotary feeders which are
exposed to three body abrasion. Abrasion resistance of selected materials was evaluated on
abrasion G 65 test rig with rubber and steel wheel setup, using the quartz sand (SiO 2) as an
abrasive, with the average grain size of particles in range of 0.8 – 1.6 mm. Experiments have been
performed under the dry conditions, and at room temperature, under the load of 50 N, with wheel
rotation of 200 rpm, and testing time of 90 minutes. The best performing samples have been
selected and further investigated on longer sliding distances, with corresponding testing times of
180, 270, and 360 minutes respectively. Results of testing on G65 test rig, as well as following
surface topography analysis revealed the strong influence of polymer hardness and elasticity, as
well as abrasive particle embedment on the wear behavior.
Keywords: abrasion, G 65, polymers, particle embedment
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16th Nordic Symposium on Tribology, Aarhus, Denmark
27
New tribo-systems for sheet metal forming of advanced high strength steels
and stainless steels
E. Ceron1, N. Bay2
1
2
GRUNDFOS A/S, Poul Due Jensens Vej 7, 8850 Bjerringbro, Denmark
Dept. Mech. Ehng. Technical University of Denmark, Produktionstorvet 425, 2800 Kgs. Lyngby,
Denmark
Testing of new tribo-systems in sheet metal forming is nowadays an important issue, since new
legislations push industry to replace current, hazardous ones. The present paper summarizes the
work done in a PhD project at the Technical University of Denmark. The project focused on
development of a new methodology for off-line testing of new tribo-systems for advanced high
strength steels and stainless steels. The methodology is first presented and applied to an industrial
case, where different tribo-systems are tested. For the purpose a new, Universal Sheet Tribotester
was developed, which can run automatically, repetitive Bending Under Tension test. Tests on a
lean duplex material reveal that the particular surface texture is very sensitive to hydrodynamic
effects. The overall results show that the methodology ensures satisfactory agreement between
laboratory and production tests, although disagreement can occur, if tribological conditions are not
the same in both cases.
Keywords: tribo-system, galling
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16th Nordic Symposium on Tribology, Aarhus, Denmark
78
Development of diffusion couple method to study chemical interactions between cemented
carbide and difficult to machine materials
L. v Fieandt1*, R. M’Saoubi2, B Jansson2, M. Schwind2, C. Århammar3
1
Department of chemistry, Uppsala University, Ångström laboratory, Box 538 Uppsala Sweden,* presenting author
2
Seco Tools AB, Björnbacksvägen 2, SE-737 82 Fagersta, Sweden
3
Sandvik Coromant, Lerkrogsvägen 13, SE-120 80 Stockholm
In the present investigation, a diffusion couple method has been developed to study the chemical
interactions between cemented carbide cutting tools and difficult to machine materials (Ferrous
alloys, Ti and Ni based alloys). The method is relatively simple and consists of pressing a rod of
the desired work material into the hole of a cemented carbide tool and further heating of the toolwork material couple in a high temperature furnace at 1100°C for 2 hours under inert gas
atmosphere.
Polished cross sections of the diffusion couple specimens were investigated using different
experimental techniques, including light optical microscopy (LOM), scanning electron
microscopy (SEM), energy and wavelength dispersive spectroscopy (EDS/WDS) and electron
back scattered diffraction (EBSD).
The results obtained indicate clearly that chemical interactions have occurred between the
different alloys and the cemented carbide. In particular, the formation of a thick layer of titanium
carbide was observed at the cemented carbide /Ti alloy interface while the formation of a distinct
compound (η-phase) was observed at the cemented carbide /Fe alloy interface. The observed
TiC-formation is supported by the small solubility range of carbon in bcc-Ti and the strong
driving force for fcc-TiC1-x formation even at low carbon contents. In the Fe-C system, the
solubility of carbon in fcc-Fe stretches up to 8 mol% at 1100 °C, wherafter graphite is formed.
Keywords: cemented carbide, difficult alloys, diffusion couple, chemical interactions.
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16th Nordic Symposium on Tribology, Aarhus, Denmark
95
Design of an axially concave pad profile for a large turbine tilting-pad bearing
Prof. Dr-Ing. B. Bender, *Nico Buchhorn, M.Sc. Dipl.-Ing. Sebastian Kukla
Ruhr-University Bochum, Germany
*Presenting Author: Nico Buchhorn
To improve operational safety and/or achieve higher load capacity of large turbine tilting-pad
bearings an axially concave pad profile is presented. The thermal and mechanical stress of the
loaded pads of a test bearing in load between pads configuration has been analyzed in detail. The
bearing with a double tilting support is lubricated by spray-bars and can be described by the
following specifications: Five pads, 0.23 nominal preload, 60% offset, 56° pad arc angle, 500 mm
inner diameter, 350 mm pad length and 1.28 per mille relative bearing clearance. Both film
thickness and pressure distribution have been measured in a very high resolution. Pad temperatures
are measured by the means of 100 thermocouples which are located 5 mm behind the sliding
surface. The test procedure and test rig are described in detail. A fluid film calculation program in
combination with a finite-element program is used to simulate the deformation of a single pad
under high circumferential speeds. In this context, the axial and tangential heat transfer coefficients
of the pad surface, which act as boundary conditions for the calculation of the 3D temperature
distribution, are determined using an optimization process. Herein, the match of predicted and
measured pad temperatures is the goal. It can be shown that there must be a huge difference in heat
transfer in axial and tangential direction in order to match the large measured temperature gradient
in circumferential direction. Based on the measured deformed profile the code is used to derive a
concave pad profile, which will result in an axially non-arched sliding surface under the expected
thermal load. Therefore, an iterative simulation procedure is used.
By decreasing the axial arching of the pad and thus the large film thickness at the axial ends using
an improved profile designed for a specific operation point, the minimum film thickness and
maximum pad temperature can be influenced beneficially. Hereby, either better operational safety
or higher load capacity of the bearing can be achieved.
The comparison of measurement data and calculation results shows very good agreement regarding
the pad deformations. The results indicate that by axially concave profiling of the loaded pads of a
large tilting-pad bearing for a specific operation point, the static characteristics in the form of
temperature, film thickness and load capacity can be improved.
Keywords: thermal deformation, compensation, tilting-pad, profiling
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16th Nordic Symposium on Tribology, Aarhus, Denmark
Lubrication 1
Chair: Peder Klit
Thursday 12 June 2014 – 09.40-11.20
Room: Nortvegia
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16th Nordic Symposium on Tribology, Aarhus, Denmark
77
Adsorption of ATF additives on wet clutch friction interfaces under water
contaminated lubricant conditions
Nowshir Fatima1*, Ichiro Minami1, Allan Holmgren2, Pär Marklund1, Roland Larsson
1
Affiliation 1: Division of Machine Elements, Department of Engineering Sciences and Mathematics, Luleå
University of Technology, Luleå SE-97187, Sweden.
2
Affiliation 2: Division of Sustainable Process Engineering, Department of Civil, Environmental and
Natural Engineering, Luleå University of Technology, Luleå SE-97187, Sweden.
Stable friction and positive slope of friction-speed is the typical criterion for a good clutch
performance. Lubricated friction interfaces used for wet clutches produces different friction
behavior depending on the lubricant conditions. Usually the lubricant conditions vary for
different automatic transmission fluid (ATF) formulations implying e.g. water contamination
and these conditions might influence the deterioration of the clutch plates. The aim of this
paper is to verify additive adsorption on friction interfaces and ageing of the friction material
in wet clutch system for a water contaminated commercial ATF (DEXRON® VI). Standard
clutch plates are employed in an automated wet clutch test rig to evaluate the friction
characteristics of the tested lubricant. For controlled test conditions (speed, contact pressure,
oil temperature) and specific number of test cycles, the mean friction coefficient and the
friction vs. speed relations are monitored during sliding test. The resultant tribofilms on the
tested friction interface surfaces are characterized by means of Scanning Electron
Microscopy-Energy Dispersive X-ray spectroscopy (SEM- EDS), Attenuated Total
Reflectance -Fourier Transform Infrared Spectroscopy (ATR-FTIR) and X-ray Photoelectron
Spectroscopy (XPS analysis). The spectroscopic techniques were used to analyse adsorbed
additives on friction interfaces and made it possible to correlate measured data to the specific
friction behavior obtained after water contamination of the ATF.
Keywords: Wet clutch, water contamination, ATF, additive, surface analysis.
*Corresponding author: Nowshir Fatima1*, ([email protected]).
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119
The viscosity of Dimethyl Ether (DME) determined by Quartz Crystal Micro-balance
(QCM)
Hansen A., Rechter C., *Sivebaek I.M., Jacobsen J.
Technical University of Denmark, Mechanical Engineering. DK-2800 Lyngby, Denmark
*Presenting and corresponding author: [email protected]
Dimethyl Ether is known as a green fuel capable of giving high efficiency to diesel engines
without forming particulate matter in the exhaust [1]. While the combustion qualities of this fuel
are excellent, its low lubricity [2] and viscosity [3] cause the fuel injection equipment to break
down prematurely due to wear. A minor drawback is the low boiling point of the fuel which
implies pressurisation to obtain a liquid.
The viscosity of DME at the vapour pressure has been determined [3] but in the diesel engine the
fuel is pressurised to 40-50 bar before the high-pressure pump brings it to 300 bars. These
pressure levels are though interesting for the lubrication of the injection equipment.
Pressurising DME with different gases seems to alter the viscosity of the fuel. This has been
visually observed at the Shell Eco Marathon in France in 2004 but no direct measurement of this
phenomenon has been conducted.
The present work uses a Quartz Crystal Micro-balance (QCM) to measure the viscosity of DME
at different pressures. The QCM is a small crystal used for weighing e.g. molecules as its
frequency is dependent on the mass adsorbed to the surfaces. The viscosity of a surrounding
liquid also affects the frequency so the QCM can be used to characterise this property.
A series of viscosity measurements are performed both to establish the pressure-viscosity
coefficient of DME and to characterise the effect of gases on the viscosity of DME as a function
of the pressure. It appears that there is a significant difference in the viscosity of DME when
helium and nitrogen are used. The experimental results are analysed and a tentative model is
derived. The results have a significant impact on the use of DME in diesel engines as
pressurisation with an optimised gas composition could reduce the lubricity challenge of this
green fuel.
1.
Sorenson S.C., Mikkelsen S-E. “Performance and emission of a 0.273 liter direct
injection diesel engine fuelled with neat dimethyl ether.” Society of Automotive Engineers, SAE Paper 950064, 1995.
2.
Sivebaek, I.M., Sorenson S.C. “Dimethyl Ether (DME) – Assessment of Lubricity Using the Medium Frequency
Pressurised Reciprocating Rig Version 2 (MFPRR2).” SAE* Paper 2000-01-2970. 2000.
Sivebaek, I.M., Sorenson S.C., Jakobsen J. “Dimethyl Ether (DME) – Assessment of Viscosity Using the New Volatile
Fuel Viscometer (VFVM)” SAE* Paper 2001-01-2013. 2001.
3.
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16th Nordic Symposium on Tribology, Aarhus, Denmark
45
Characterization of start-stop motions – a novel approach
Frederik Wolf, Kartik Pondicherry
Anton Paar Germany GmbH, Ostfildern, Germany
1. Introduction
Critical aspects of tribological system like start-stop motions or stick-slip properties are
characterized by mechanisms that take place in the regime between static and dynamic friction.
Measurements at extremely low speeds are necessary to look at these phenomena in detail, to
investigate the nature of the phenomena.
2. Approach
Rheometers are optimized for controlling precise movements (min. deflection angles 0.1 µrad,
resolution 10 nrad) and torques (min. torque: 10 nNm, resolution: 0.1 nNm) and for measuring the
reaction movement or the reaction torque. This precision allows for the characterization of the
transition from static to dynamic friction.
In Rheology, the transition from static to dynamics, the determination of yield and flow point, is
characterized by the so called amplitude sweep. At a constant frequency, deflection is induced in
the sample through sinusoidal motion. The reaction of the sample is measured and from the phase
shift and changes in amplitude, the storage (G’) and loss (G’’) moduli can be calculated. These
hold information about the stored (elastic) and dissipated (viscous) properties of the characterized
system. This approach is transferred to tribo-systems.
3. Results
Depending on the lubricant, different
transition
patterns
can
be
differentiated, including information
pertaining to the ratio between elastic
and dissipated energy. Lubricant 2
shows a smooth transition from static
to dynamic friction. Lubricant 1 breaks
free abruptly. Break away torque and
deflection angle can be determined
from the measurements. Details of the
method, its scope and limitations, will
be discussed here.
Figure 1: Storage and Loss modulus, and Torque as a function of deflection angle of a lubricated tribo-contact between steel and steel
Keywords: tribology of materials, friction, lubrication, tribological testing
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16th Nordic Symposium on Tribology, Aarhus, Denmark
88
Feedback-Controlled Lubrication for Reducing the Lateral Vibration of Flexible Rotors
supported by Tilting-Pad Journal Bearings
J.G. Salazar1*, I.F. Santos2
1
Technical University of Denmark, 2800 Kgs. Lyngby, Denmark. ([email protected]).
2
Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
Fluid film journal bearings are well known machine elements with a long history of development and
improvement. Such a history turned them into a standardized element which can be easily specified within
the designing process of new machines. Nevertheless, due to the continuous requirements of higher
efficiency performance for rotating machines, there is still space for further improvements. In such a
framework, Tilting-Pad Journal Bearings (TPJBs) – well known type of fluid film bearing – have naturally
evolved to mechatronic machine elements by means of the addition of electromechanical components which
enable them to adjust their behaviour to new conditions and requirements. TPJBs with electronic radial oil
injection or actively-lubricated TPJBs or simply active TPJB are provided with hydraulic actuators such as
servovalves, which connected to a high pressure supply unit can inject pressurized lubricant into the bearing
clearance through orifices commonly machined in the middle of the pad surface. For these mechatronic
machine elements, digital control systems govern the servovalves, regulating the lubricant injection flow
and hence the pressure distribution composed of hydrodynamic and hydrostatic effects. As a result, the
bearing stiffness and damping properties are modified depending on control signals. Different lubrication
regimes can be featured depending on whether the control laws are used or not and also depending on the
type of controllers used. For surely enhance the system dynamic performance of rotating machines, a
feedback-controlled regime must be implemented, referred here as an active lubrication regime.
In this work, the feedback-controlled lubrication regime is studied and experimentally tested, based on a
proportional-integral-derivative (PID) controller. A model-free approach was used to design and built the
controller. For synthesizing the controller gains, special focus is given to the problem of reducing the system
lateral vibration around its equilibrium position in a wide excitation frequency range. With such a lubrication
regime, the resulting pressure distribution over the pads is dynamically modified by using the servovalves
as actuators and the lateral movements of the flexible rotor as feedback control signals. The lateral dynamics
of a large overhung centrifugal compressor is resembled by a test rig designed with such a goal. The flexible
rotor is supported by an active TPJB provided with two high-frequency response servovalves. The rotorbearing system is capable to operate under three different lubrication regimes, namely a) the conventional
or passive lubrication regime, dominated by the hydrodynamic effect, b) the hybrid or adjustable lubrication
regime, built up on the hydrodynamic and hydrostatic effects, and c) the feedback-controlled or active
lubrication regime for which the hydrostatic contribution to the pressure field is controlled by well-tuned
control gains.
The main contribution of this work is to demonstrate the enhancement of the dynamic properties of a flexible
rotor-bearing system supported by active TPJB by means of the feedback-controlled lubrication regime via
PID-controller, whose gains are synthesized from a model-free control design approach. Good experimental
results are obtained, and a significant improvement of the rotor-bearing system dynamic performance can
be experimentally demonstrated in a wide frequency range, when feedback-controlled lubrication regime is
used.
Keywords: Tilting-pad Journal Bearing, Mechatronic machine element, Feedback-controlled lubrication.
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16th Nordic Symposium on Tribology, Aarhus, Denmark
89
Tribofilms of MoS 2 nanotubes on steel and DLC-coated surfaces
Janez Kogovšek1, Janez Kovač2, Maja Remškar2, Mitjan Kalin1*
1
Laboratory for Tribology and Interface Nanotechnology, University of Ljubljana, 1000
Ljubljana, Slovenia. ([email protected]).
2
Jožef Stefan Institute, 1000 Ljubljana, Slovenia.
MoS2 and WS2 solid-lubricant nanoparticles as additives in oil provide good tribological properties
based on the physical lubrication mechanisms in the contact. Therefore, they are strong candidates
for use in the lubrication of DLC coatings, which only poorly interact with the traditional,
chemically based additives. But until recently, attempts of lubrication of the DLC coatings with
oils containing nanoparticles have been very scarce and thus the understanding of the interactions
of the nanoparticles with the diamond-like carbon (DLC) coatings remained limited. We showed
that the use of MoS2 nanotubes in oil can provide very effective lubrication for the steel and also
for the DLC coatings, in spite of their lower chemical reactivity. Furthermore, formation of a
tribofilm from the solid nanoparticles is decisive for their beneficial performance with both types
of surfaces. We studied how a tribofilm formed from the MoS2 nanotubes is related to the
tribological properties of these nanotubes and we analysed such a tribofilm on steel and DLCcoated surfaces using SEM, EDS, XPS and AES to observe any differences in the structure and
interactions of the tribofilm with steel and DLC coating. The major difference between the steel
and the DLC contacts is that the MoS2-based tribofilm surface coverage is greater in the case of
the steel/steel contacts compared to the DLC/DLC contacts. Nevertheless, no direct evidence of
any chemical reactions between the MoS2 and the steel or DLC coating was observed and we found
that the chemical and functional properties of the MoS2-based tribofilm are very similar, or even
the same, for both the steel and DLC-coated surfaces.
Keywords: MoS2 nanotubes; Tribofilm; DLC; steel; XPS
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16th Nordic Symposium on Tribology, Aarhus, Denmark
Coatings 2
Chair: Albano Cavaleiro
Thursday 12 June 2014 – 12.00-13.00
Room: Suecia
105
16th Nordic Symposium on Tribology, Aarhus, Denmark
139
Integration of HiPIMS Equipment into an Industrial Coating Production
for Cutting Tools
Toni Leyendecker1, Oliver Lemmer1, Werner Kölker1, Christoph Schiffers1*
1
CemeCon AG, Adenauerstrasse 20A4, 52146 Würselen, Germany
*Corresponding author: Christoph Schiffers ([email protected]).
HiPIMS coatings are rapidly gaining ground for cutting tool applications due to advantages such
as smooth, droplet free coatings with superb adhesion and perfect homogeneity all around the tool
geometry. Hence, more and more cutting tool producers are in the process of integrating HiPIMS
coating machines into their production.
This paper will discuss the full process chain of an industrial coating production – starting with
jigging, surface and cutting edge preparing, cleaning, coating and finishing operation – dedicated
to the HiPIMS coating process. Advances of the HiPIMS deposition equipment will be presented
as well as specific modifications of the auxiliary processes prior and after coating.
A novel AlTiSiN film deposited with HiPIMS will be presented as a model system for all the steps
of a commercial coating production. The evaluation will include film characterisation and recent
cutting test results.
Keywords: HiPIMS, sputtering, cutting tools
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16th Nordic Symposium on Tribology, Aarhus, Denmark
144
Characterisation of Nanocomposite Ti-C-N Coatings Deposited by Industrial-Scale DC
Magnetron Sputtering for Tribological Applications
Sascha Louring, Bjarke Holl Christensen, Klaus Pagh Almtoft and Lars Pleth Nielsen
Danish Technological Institute, Tribology Centre, Teknologiparken,
Kongsvang Allé 29, DK-8000 Aarhus C, Denmark
Corresponding author: [email protected]
Amorphous carbon is well-known for its low friction due to its self-lubricating behaviour. By
combining amorphous carbon with hard nanocrystallites, nanocomposite coatings with low
friction, high hardness and improved fracture toughness may be obtained. In this work,
nanocomposite coatings consisting of Ti(C,N) nanocrystallites embedded in an amorphous carbonbased matrix were studied. The coatings were deposited at an elevated temperature of ~370 °C by
reactive DC magnetron sputtering using an industrial-scale CemeCon deposition system. A mixture
of Ar and N2 was used in combination with a graphite and a titanium target. Keeping the working
pressure constant, the N2-fraction in the sputter gas was varied in order to study its impact on the
microstructure and the mechanical and tribological properties of the coatings. The microstructure
of the nanocomposite coatings was evaluated using XRD, XPS, TEM and Raman spectroscopy. It
was found that the highest amount of crystalline material was obtained at the lowest N2-fractions,
where the highest concentration of titanium was likewise observed by RBS. Depending on the N2fraction in the sputter gas, nanoindentation revealed hardness values exceeding 20 GPa, whereas
compressive stresses of 0.8 GPa to 2.8 GPa were determined from substrate bending. Finally, the
tribological performance of the coatings was evaluated in a pin-on-disc test. It was found that the
wear rate was sensitive to the relative content of amorphous and nanocrystalline material, whereas
the friction coefficient against alumina was essentially unchanged.
Keywords: nanocomposite; microstructure; mechanical properties; pin-on-disc; amorphous
carbon
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137
The effect of V additions on the tribological behaviour of sputtered TiSi(V)N coatings at
room temperature
Filipe Fernandes1*, Tomas Polcar2,3, Albano Cavaleiro1
1
SEG-CEMUC - Department of Mechanical Engineering, University of Coimbra, Rua Luís Reis Santos, 3030-788
Coimbra, Portugal; 2n-CATS University of Southampton Highfield Campus SO17 1BJ Southampton, UK;
3
Department of Control Engineering Czech Technical University in Prague Technicka 2, Prague 6, 166 27 Czech
Republic.
*Presenting author - Email address: [email protected], tel. + (351) 239 790 745, fax. + (351) 239 790 701
TiSiN hard coatings are well established in commercial tribological applications such as
high speed cutting and dry machining processes due to their excellent oxidation, and extremely
high hardness. However, their friction coefficient revealed to be fairly high. Therefore, a lot of
efforts has been carried out in the last years to develop self-lubricant coatings, that retains the good
properties of the common ternary (TiX)N films (X = B, Cr, Al, Si, Cr, C, etc) and offers lubricity
through the formation of low-friction oxides. Magnéli phase oxides have attracted the scientific
community attention, particularly those formed in vanadium containing coatings. The beneficial
influence of Magnéli oxides formed by oxidation of vanadium has already been reported by several
researchers; however, in ternary systems they only have considered the effect of V dopping on
CrAlN and TiAlN coatings in single layer or multilayered configurations. Thus, the aim of this
investigation was to study the effect of V content on the tribological behaviour of Ti-Si-V-N
coatings deposited by DC reactive magnetron sputtering. Comparison of these results with those
achieved for TiN, and TiSiN coatings prepared as references is also provided. The tribological
properties of coatings were evaluated at room temperature in pin-on-disc wear equipment, using as
counterparts Al2O3 and HSS balls. After wear tests, the wear tracks and wear debris were
characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEMEDS) and Raman spectroscopy. V additions successfully decreased the wear rate and the friction
coefficient of TiSiN coatings, due to V2O5 oxide formation. When Al2O3 balls were used as
counterparts the wear rate and friction coefficient of coatings are much lower than when sliding
against HSS steel balls. TiSiN displayed the lowest wear resistance among all the tested coatings.
The wear of V rich coatings was driven by polishing wear when tested against Al2O3 balls, whilst
adhesion wear took place when tested against HSS balls.
Keywords: TiSi(V)N coatings, Tribology, Wear, Magnéli oxides
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16th Nordic Symposium on Tribology, Aarhus, Denmark
Polymer 1
Chair: Ion Marius Sivebæk
Thursday 12 June 2014 – 11.40-13.00
Room: Dania
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122
The impact of the standard turbine oil and the biodegradable synthethic oil on properties of
the polymers used as sliding layers in the hydrodynamic thrust bearings.
Michal Strankowski, Michal Wasilczuk, Justyna Zorn
Gdansk University of Technology, Faculty of Mechanical Engineering
The polymers used as sliding layers in hydrodynamic thrust bearings are exposed to severe
conditions: relatively high temperature, high pressure and sheering of the fluid film.
The results of investigations on the impact of the fluid film conditions on the mechanical and the
tribological properties of thermoplastics used as sliding layers will be presented in the paper.
Standard turbine oil ISO VG 32 and biodegradable synthetic oil were used in the tests. Although
the oils are used for lubrications of the polymers, there are realatively few information about their
impact on the thermoplastics.n The polymers used in the tests were selected due to their industrial
applications in the hydrodynamic bearings. Composite based on PTFE and PEEK as well pure
PTFE, PEEK, UHMWPE and PVDF were tested.
Two factors (temperature of oil and pressure of oil ) have been taken into account. The research
showed that exposure to high temperature (100°C) in the oil, caused the change of the elastic
modulus of the material. The other properties as for example thermal stability also changed after
exposure to both types of oil irrespective of conditions of immersing.
Keywords: polymers, standard turbine oil, biodegradable synthetic oil
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130
Friction and wear studies of some PEEK materials
Jonna Holmgren1*, Per O. Lindholm2, Jian Qin2 and Åsa Kassman Rudolphi1
1
Applied Materials Science, Department of Engineering Sciences, Uppsala University, Box 534,
SE-751 21 Uppsala, Sweden
2
ABB Corporate Research, SE-721 28 Västerås, Sweden
*
Presenting author
Replacing conventional steel by polymer composite materials is one way to achieve lightweight
and lubricant-free machine components. Mechanical strength and thermal properties are two
major criteria for the application and selection of polymer materials in high performance
industrial systems. Depending on actual application a compromise between mechanical and
thermal properties often needs to be considered within the tolerance boundary in order to obtain
optimized results.
In this study the tribological performance of some PEEK (polyether ether ketone) polymers, both
pure and carbon fibre filled materials, are experimentally evaluated. A reciprocating sliding
laboratory test with a steel ball against polymer disc geometry was used. The effects of contact
load, number of cycles, temperature, and surface roughness of the steel counter surface, on
friction and polymer wear are investigated. The thermoplastic PEEK was selected due to its high
strength properties at elevated temperatures.
The long-term aim of the study is to evaluate the possibilities and limitations for using polymer
materials in tribological contacts, e.g. in a polymer/steel spur gear pair. Therefore, modelling of
the gear mesh and analysis of the contact forces and heat generated in the gear tooth is also
included in this study.
This study suggests a guideline of materials selection, while gear design such will not be
discussed. Different tribology test conditions showed very different friction level and wear
behaviour. The implications of these tribology test results on the modelling results and the
function of a possible application are discussed.
Keywords: PEEK, friction, wear, FEM
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35
Tribological behaviour of peek/MoS₂ composites: Influence of MoS₂ particles concentration
and processing temperature
Maša Zalaznik1, Mitjan Kalin1, Saša Novak Krmpotič2
1
Laboratory for tribology and interface nanotechnology, Faculty of Mechanical Engineering,
University of Ljubljana, Slovenia,
2
Institut “Jožef Stefan”, Ljubljana, Slovenia
The use of high-resistant polymers is becoming more and more interesting from tribological,
mechanical, manufacturing and economical point of view. Poly-ether-ether-ketone (PEEK) is a
high-resistant polymer with high melting temperature, good mechanical and promising tribological
properties. The increasing use of PEEK for different applications showed a need for PEEK material
(and its composites) to withstand severe contact conditions, such as non-lubricated contacts.
PEEK’s relatively high coefficient of friction in dry contacts (≈0,4-0,6) intensified a need for
further improvement of its tribological properties, especially lowering coefficient of friction which
can be achieved by incorporating self-lubricated particles such as Molybdenum disulphide (MoS₂).
The use of conventional manufacturing procedures, such as injection molding and extrusion, limit
researches and manufacturers to the material melting properties. By using non-conventional
procedures, processing temperatures can be varied and their affect can be studied.
In this study, coefficient of friction, wear rate and wear mechanisms of PEEK/MoS₂ composites
are presented, in a relationship to MoS₂ particles concentration (0 – 10 wt.%) and processing
temperature (300 – 350 °C). Tribological tests were performed by reciprocating sliding in dry
conditions with steel pin as a counter-material. Results show that processing temperature has a
considerable influence on tribological and mechanical properties while MoS₂ particle
concentration have only minor effect onto the tribological behaviour.
Keywords: polymer composites, friction, wear, processing temperature, PEEK, MoS₂
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75
Low Wear of Carbon Fiber Filled PTFE in Gaseous Hydrogen
Yoshinori Sawae1,2, Kazumi Okada3, Takehiro Morita1,2, Yoshie Kurono3, Joichi Sugimura1,2,3
1. Department of Mechanical Engineering, Faculty of Engineering, Kyushu University, 744 Motooka,
Nishi-ku, Fukuoka 819-0395, JAPAN
2. International Institute for Carbon-Neutral Energy Research, Kyushu University, 744 Motooka, Nishiku, Fukuoka 819-0395, JAPAN
3. Research Center for Hydrogen Industrial Use and Storage, Kyushu University, 744 Motooka, Nishi-ku,
Fukuoka 819-0395, JAPAN
Presenting author: Yoshinori Sawae (E-mail: [email protected])
A fuel cell vehicle (FCV) is expected as an ultimate environment-friendly transportation
system since it can travel without fossil fuel consumption and greenhouse gas emissions by using
hydrogen as a fuel. For the current generation of FCV, which is using 70 MPa high-pressure
hydrogen gas to get a long cruising distance as gasoline engine vehicles, hydrogen gas should be
pressurized up to 100 MPa and stored in hydrogen fuelling stations. Therefore, improvements in
the performance and cost efficiency of high-pressure gas compressors are important tasks for
establishing successful hydrogen infrastructure.
Authors have been examined tribological performance of various kinds of polymer
composites in gaseous hydrogen to find the ideal composition of polymer sealing material for
high-pressure hydrogen gas applications. In this study, we would like to report some friction and
wear measurement results of carbon fiber filled polytetrafluoroethylene (PTFE) in hydrogen gas,
since the PTFE composite filled with 15 wt% pitch-based carbon fiber showed characteristics low
wear behavior in gaseous hydrogen under the sliding speed of 2 m/s and contact pressures from 1
MPa to 3 MPa. To understand the low wear mechanism in hydrogen, detailed analyses for
chemical composition and structure of polymer transfer film formed on the sliding counterface,
440C martensitic stainless steel, were conducted after sliding tests by using XPS, Raman
microscopy and imaging FT-IR. Results of surface analyses indicated that a smooth and
homogeneous polymer transfer film composed of PTFE and carbon was formed on the metal
counterface only in hydrogen, which might be preventing further material adhesion from the
composite surface and reduce the wear amount.
Keywords: carbon fiber filled PTFE, hydrogen, seal, friction, wear
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16th Nordic Symposium on Tribology, Aarhus, Denmark
Lubrication 2
Chair: Mathew Mate
Thursday 12 June 2014 - 11.40-13.00
Room: Nortvegia
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16th Nordic Symposium on Tribology, Aarhus, Denmark
98
Lubricating properties of MR fluid
Shinnosuke Yano1, Shinji Kato2, Ryo Tsuboi3, Shinya Sasaki3*
1
Graduate School, Tokyo University of Science
Niijuku 6-3-1, Katsushika-ku, Tokyo, 125-8585 Japan
2
KYB Corporation
1-12-1 Asamizodai, Minami-ku, Sagamihara-shi, Kanagawa, 252-0328, Japan
3
Tokyo University of Science, Japan
*Corresponding author: [email protected]
Magneto-rheological (MR) fluids are obtained by dispersing ferri-magnetic particles (e.g.,
carbonyl iron particles) in oil. The viscosity of MR fluids is dramatically changed in a magnetic
field and the change is reversible. The response of the change depends on magnitude of a magnetic
field, and the scale of the response speed is in milliseconds. From this characteristic, MR fluids are
expected as new hydraulic oil applied for dampers, actuators and brakes. However, lubrication
properties of the MR fluids were inferior to that of conventional oil because of the component
particles in the MR fluids. Accordingly, if lubricating properties of MR fluids will be improved, it
is possible to extend their application field. For that reason, the objective of this research is to
investigate the lubricity of the MR fluids focusing on the particle size.
The sliding tests were conducted by using a cylinder on disk type reciprocating sliding tester
(SRV1, Optimol) and the test condition is listed in Table 1. Disk and cylinder specimens were made
of AISI 1010 and AISI 52100, respectively. For the lubricants, Base oil and three types of MR
fluids: Fine (Average particle size 2 m), Medium (4 m), and Coarse (8 m) were used.
Surface profile was measured by surface roughness tester (SURFCOM 1500SD3-12,
ACCRETECH).
The friction behavior is shown in Fig. 1. The result shows that all MR fluids show higher
friction coefficients than the base oil at the end of the test. However, during the term from 1000
to 2000 sec, the friction coefficient of Fine is lower compared with than that of Base oil.
Maximum wear depth of disk specimens in sliding surface is shown in Fig. 2. The Fine case
shows the lowest wear depth in all lubricants. Focusing on the influence of particle behavior on
lubricating properties of MR fluids, the particle motion is investigated and discussed by in-situ
observation using a high speed camera.
30 C
Amplitude
1 mm
Frequency
50 Hz
Load
20 N
Time
60 min.
Keywords:
Base oil
Fine+ Medium
0.3
0.2
0.1
0
0
1000
2000
Time [s]
Fig. 2 Maximum wear depth of each lubricant
4
Coarse
Maximum wear depth [ m]
Temperature
Fig. 1 Friction behavior of each lubricant
Friction cofficient
Table 1 Test condition
3000
2
0
MR fluids, friction, wear, particle, in-situ observation
116
Base oil
Fine
Medium Coarse
16th Nordic Symposium on Tribology, Aarhus, Denmark
115
EHL Traction Analysis of Perfluoropolyether Fluids Based on Bulk Modulus
Nobuyoshi Ohno*1, Toshifumi Mawatari 1, Bo Zhang1, Motohiro Kaneta2, Petr Sperka2,
Ivan Krupka2 and Martin Hartl2
1
Department of Mechanical Engineering, Saga University, 1, Honjo, Saga 840-8502, JAPAN
2
Faculty of Mechanical Engineering, Brno University of Technology, Tecknicka 2896/2, 616 69 Brno,
Czech Republic
*Corresponding author, E-mail address: [email protected] (N. Ohno)
Perfluoropolyether (PFPE) fluid are used in magnetic recording media, aerospace industry
and satellite instruments satisfactorily. Recently these oils have been introduced as hydraulic
fluids, high temperature liquid lubricants in turbine engines and base oils of high-temperature
greases. Despite considerable research on PFPE, the rheological characteristics at high pressure
and EHL traction have not been understood yet.
High pressure density measurements of these three kinds of commercial PFPE fluids
(Krytox, Demnum and Fomblin) were done at temperatures from 293K to 333K and pressure up
to 1.2 GPa. The tangent bulk modulus - pressure - temperature relation and secant bulk modulus pressure - temperature relation of PFPE fluids were proposed based on the free volume and the
phase diagram.
The traction coefficient was also measured using a ball on disk machine. It was found that the
maximum traction coefficient and the limiting shear stress are closely related to the tangent bulk
modulus and the secant bulk modulus, respectively. That is, the traction characteristics are mainly
influenced by the bulk modulus of the oil.
Keywords: PFPE fluid, rheology, bulk modulus, traction, EHL
117
26
EHL for lubricated contacts of DLC – role of interfacial and contact properties
M. Polajnar, M. Kalin
University of Ljubljana, Ljubljana, Slovenia
Preference of presentation: Oral
Keywords: DLC, EHD lubrication, solid-liquid interface
Abstract
Tailoring friction properties of lubricated contacts operating under EHD lubrication regime
came in the recent years in the forefront, especially in terms of reducing viscous friction that
govern friction performance of those contacts. Several studies in past several years [1-4]
showed potential perspective effect of reducing coefficient of friction of lubricated contacts in
EHL when using DLC coatings and different models that explain reduction in coefficient of
friction were proposed. In our recent study [2] we introduced “Slip inducing interaction model
based on surface forces” that explain DLC-oil slip on terms of surface forces and connects
this phenomenon with reduced coefficient of friction in EHL.
With this study we upgrade our previous results. Series of test were performed, by using
different types of DLC coatings deposited on surfaces with different roughness, using two
different types of lubricants and tested with variation contact properties (load, slide-to-roll
ratio). Results show that important role in tailoring friction properties of lubricated contacts in
EHL in addition to surface properties, such as roughness, wetting and surface energy, play
also contact conditions and selection of the lubricant. We also show that relative surface speed
is the important parameter that influence on friction properties for steel-mated contacts of
DLC.
References
1.
2.
3.
4.
Kalin, M., I. Velkavrh, and J. Vižintin, The Stribeck curve and lubrication design for
non-fully wetted surfaces. Wear, 2009. 267(5): p. 1232-1240.
Kalin, M. and M. Polajnar, The Effect of Wetting and Surface Energy on the Friction
and Slip in Oil-Lubricated Contacts. Tribology Letters, 2013. 52(2): p. 185-194.
Jahanmir, S., A.Z. Hunsberger, and H. Heshmat, Load capacity and durability of HDLC coated hydrodynamic thrust bearings. Journal of tribology, 2011. 133(3).
Björling, M., et al., The Influence of DLC Coating on EHL Friction Coefficient.
Tribology Letters, 2012. 47(2): p. 285-294.
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16th Nordic Symposium on Tribology, Aarhus, Denmark
2
Overcoming starvation in EHL point contacts by enhanced replenishment
F.Ali1*, I.Křupka1, M.Hartl1
1
Institute of Machine and Industrial design, Faulty of Mechanical engineering, Brno University
of Technology, Technická 2896/2, 61669, Brno, the Czech Republic.
*Corresponding author: Fadi Ali ([email protected]).
An innovative approach for enhancing replenishment in starved EHL contacts is introduced in this
paper. An external restriction (frictionless slider) is used to create a forced hydrodynamic
channelling of lubricant towards the rolled track. The hydrodynamic entrainment induced by the
slider leads to recover the displaced lubricant and enriching the depleted track. Measurements have
been carried out by a Tribometer equipped for measuring friction and film thickness
simultaneously. The results showed a significant reduction of friction after introducing the
mechanism of induced replenishment even with a very little amount of lubricant available on the
track. Measurements of film thickness showed that the severely starved EHL contacts transform
completely to the flooded regime, indeed the film thickness has been doubled many times, after
applying the channelling by the slider even under extreme operating conditions. Otherwise, the
performance of this approach was assessed over time by measuring friction and film thickness
simultaneously and it was found that the mechanism of channelling lubricant was stable and
reliable in generating induced replenishment. Therefore, the mechanism can be easily integrated in
some industrial applications such as rolling bearings to overcome the phenomenon of starvation.
Keywords: starvation, replenishment, EHL, friction, film thickness.
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16th Nordic Symposium on Tribology, Aarhus, Denmark
Coatings 3
Chair: Nuria Espallargas
Thursday 12 June 2014 – 14.00-15.20
Room: Suecia
121
16th Nordic Symposium on Tribology, Aarhus, Denmark
73
On the low friction of W-S-N coatings
Jill Sundberg1, Harald Nyberg2, Erik Särhammar3, Tomas Nyberg3, Staffan Jacobson2, Ulf
Jansson1
1
2
Department of Chemistry - Ångström laboratory, Uppsala University, Sweden
Tribomaterials group, Department of Engineering Sciences, Uppsala University, Sweden
3 Thin Films Group, Department of Engineering Sciences, Uppsala University, Sweden
Tungsten disulphide, WS2, is a material with a highly anisotropic, layered structure. The chemical
bonds between layers are weak, and so the layers are easily sheared, making WS 2 an excellent
intrinsic solid lubricant. It can be used as an additive in liquid lubricants and greases, but also as a
coating, so that the surface itself is modified to have low-friction properties. A convenient method
to deposit WS2 is by magnetron sputtering. Sputtered WS2 coatings exhibit very low friction levels
in dry conditions, but they are often porous, soft and subject to wear. One way to improve the
mechanical properties is the addition of other elements, which favours the formation of denser
coatings with smaller crystallites. During tribological contact a tribofilm of, crystalline WS2, with
the easy shear planes aligned along the sliding direction, is formed on the outermost surface, which
gives low friction. This has been shown for a number of elements, both non-metals such as C and
N, and metals such as Ti and Cr. An important consideration, however, is that the added element(s)
should not disturb the tribofilm formation.
In this study, W-S-N coatings were deposited by reactive magnetron sputtering from a WS 2 target
and N2 gas. A series of coatings with increasing N content was obtained, which have been
characterized with respect to their elemental composition and chemical bonding, their structure and
morphology, and their mechanical properties. The coatings were tribologically tested in a ball-ondisc setup with reciprocating geometry, using a steel ball as counter-surface. Tests were performed
in atmospheres of N2, dry air, and humid (ambient) air. In N2, extremely low and stable friction
levels (µ=0.01-0.04) were observed for all coatings. In dehumidified air, containing O2, the friction
levels were higher (µ=0.06-0.3), with the lowest level observed for the coating with the lowest N
content, and then increasing with the N content. In humid air, containing H2O as well as O2, the
friction levels were higher and in some cases lead to failure. The wear of the coatings was
measured, and low friction levels were found to correspond to low wear rates, down to 50 µm3/Nm.
A pure W-S coating, however, displayed similar friction levels but higher wear, due to its porosity
and low hardness. The wear tracks on the coatings and the wear marks on the steel balls were
studied by Raman spectroscopy in mapping mode, which revealed the presence of WS 2, but also
of tungsten oxides and carbon. In this study, the friction and wear of the W-S-N coatings in the
various environments are related to the structure and chemistry of the coatings, and the composition
of the tribofilms and wear debris formed.
Keywords: WS2, coatings, reactive sputtering, unlubricated sliding, tribofilm
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126
Enhanced contact fatigue behavior of coated tool steel by using W-C:H thin film
Giselle Ramírez*1,2, Emilio Jiménez-Piqué2, Alvaro Mestra 2, Montserrat Vilaseca1,
Daniel Casellas 1, Luis Llanes 2
1
2
Fundació CTM Centre Tecnològic, Spain
CIEFMA-Universitat Politècnica de Catalunya, Spain
*[email protected]com.es
Susceptibility of coated tool steels to mechanical degradation associated with repetitive contact
loading has been shown in previous work. The influence of tool steels microstructure was
evidenced by consideration of thin film detachment as critical damage mechanism. In this regard,
delamination process was related with cracks nucleated on primary carbides which propagate
radially through the metal matrix. Thus, finer and tougher, as well as less irregular and more
homogeneously distributed primary carbides were pointed out as key microstructural features for
enhancing contact fatigue response of coated cold-work tool steels. However, properties of TiN
coating were also important on fatigue contact response, where microdroplets were critical defects
to induce decohesion mechanisms. Specifically, when steels processed by conventional casting and
forging route were used as substrates.
Taking into account all these factors, the main objective of present study is to evaluate the contact
fatigue behavior of a metal containing diamond-like carbon coating (W-C:H), with low friction and
enhanced surface roughness, deposited on wrought cold work tool steel (Universal). Chemical
composition, microstructure and mechanical properties of thin film and substrate are described.
Spherical indentation technique is used to evaluate the contact behavior under monotonic and cyclic
loading conditions.
Although W-C:H coating experienced premature fracture under monotonic loads, delamination do
not appear under cyclic loading conditions even when a load of 800 N was applied during 106
cycles. At this cyclic loading condition, TiN coating was detached from Universal steel substrate.
Cross-section analysis exhibited that subsurface cracks nucleated on primary carbides are
connected with thin film cracks. However, buckling damage was not discerned at interface
coating/substrate. Local graphitization and surface free of droplets are pointed out as the main
enhancing factors to contact response.
Keywords: Contact fatigue, spherical indentation, W-C:H coating
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72
Performance of WS2-based coatings under lubricated sliding
Harald Nyberg1, Jill Sundberg2, Erik Särhammar3, Tomas Nyberg3, Ulf Jansson2,
Staffan Jacobson1
1
Tribomaterials group, Department of Engineering Sciences, Uppsala University, Sweden
2
Department of Chemistry - Ångström laboratory, Uppsala University, Sweden
3
Thin Films Group, Department of Engineering Sciences, Uppsala University, Sweden
Transition metal dichalcogenides (TMDs), such as MoS2 and WS2, are well known intrinsic solid
lubricants. Their low-friction properties are due to the layered crystallographic structure of the
materials, where the shear strength along the layers is very low, facilitating sliding with low
resistance. PVD coatings based on tungsten disulphide have been investigated in a number of
studies, where they have shown very promising results in terms of friction and wear, particularly
in unlubricated sliding in low humidity conditions. The best wear properties are observed for
alloyed coatings, where a third element (C, N, Cr, Ti etc.) is added to the WS2 coatings. The benefit
of adding the third element is mainly that it reduces the crystallinity of the deposited films, which
leads to increased hardness, since the number of easily sheared crystallographic planes is reduced.
For such poorly crystalline or amorphous coatings, low friction is still observed, and is still due to
sliding in easily sheared planes of the WS2 crystal. However, here the WS2 crystals are formed
during sliding, within the tribofilms found on the contacting surfaces.
Due to their intrinsic low friction properties, combined with good wear resistance, WS 2-based
coatings are an interesting option for coating of machine elements that sometimes operate under
poor lubrication. The tribological properties of WS2-based coatings have been characterised under
various conditions, but almost exclusively without lubrication. Their performance in lubricated
sliding is therefore mostly unknown, and requires attention before they can be considered for
lubricated applications.
This work deals with the lubricated sliding behaviour of a number of WS 2-based coatings, which
have shown promising properties in unlubricated sliding in previous studies. The coatings include
pure WS2, as well as W-S-C, W-S-N and W-S-C-Ti coatings, all produced by magnetron sputtering
(reactive or non-reactive). The coatings are tested in a reciprocating sliding rig, lubricated with
pure base oil (PAO), and are evaluated in terms of friction and wear. The influence of lubrication
on the formation and composition of the tribofilms on the coatings and counter-surfaces are also
studied, with special emphasis on the oxidation of the tribofilms, since the presence of humidity
and oxygen is known to have a large impact on their tribological performance.
Keywords: TMD, WS2, component coatings, low friction, lubrication
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96
The effects of aging and elevated temperatures on of DLC films
H. Ronkainen, K. Holmberg, A. Laukkanen,
VTT Technical Research Centre of Finland, P.O. Box 1000, FI02044 VTT, Finland
Presenting author: Helena Ronkainen
Diamond-like carbon (DLC) films cover a wide range of different carbon based coatings, starting
from soft hydrogenated films to extremely hard hydrogen-free films. Due to the varying
characteristics of DLC coatings, they have differing tribological properties that influence on their
performance and applicability. Coating properties, such as elasticity and fracture toughness,
greatly influence on the practical performance of the coatings in real applications. An interesting
aspect is also the influence of tempering or aging of the coating on the performance.
In order to study how aging influences the tribological performance of DLC coatings we have
evaluated 20 years old DLC coatings and compared the results to earlier results reported. It seems
that the effect on the wear resistance has not changed greatly. However, variation in the friction
performance for the a-C:H type coatings was observed. When studying the temperature effects on
a-C:H type DLC coatings similar type of effects were observed. These aging and temperature
effects were further elaborated by multi-scale modeling. In multiscale modelling the integrated
approach combining material microstructural features modelled by molecular dynamic simulation
(MDS) on nanoscale with FE modeling was applied. The tribological aspects of aging and
elevated temperatures on DLC films will be reviewed with the validation of the models in
different scaled and the arguments for aging mechanisms are presented.
Keywords: DLC, a-C:H, ta-C, tribo-performance, aging, elevated temperature, modeling.
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16th Nordic Symposium on Tribology, Aarhus, Denmark
Polymer 2
Chair: Yoshinori Sawae
Thursday 12 June 2014 – 14.00-15.20
Room: Dania
127
16th Nordic Symposium on Tribology, Aarhus, Denmark
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An unconventional approach in polymer wear: Online vision system
Jacob Sukumaran1*, Seyfollah Soleimani2, Vanessa Rodriguez1,
Wilfried Philips2, Patrick. De Baets1
1
Department of Mechanical Construction and Production, Laboratory Soete, Ghent University,
Technologiepark 903, Zwijnaarde, B-9052 Gent, Belgium
2
Ghent University iMinds-Telin-IPI, St-Pietersnieuwstraat 41, B-9000 Gent, Belgium
*Corresponding author: Jacob Sukumaran ([email protected]).
Tribology which deals with the fundamental interaction of materials has robust link with
morphological modification of contacting surfaces. Hence, adequate information on surface
modification is essential for an effectual design of tribological system. Amongst different existing
materials, polymer-metal pairs are commonly used in bearings, rollers and gears. Tribological
interaction of this tribo-pair requires ample understanding of its surface responses. Generally, these
surfaces are studied using traditional post-mortem analysis based on macro- and micrographs
(qualitative), and roughness (quantitative) changes. These conventional techniques do not capture
critical information such as “evolution” of morphological features. Nevertheless, with the recent
advancements in electronic imaging, the morphological changes of moving surface are studied in
real-time at a micro scale. In our investigation, a polymer-metal pair is studied for its surface
evolution under Hertzian line contact using a high speed online vision system. The acquired real
time images are segmented and processed in order to segregate the surface scars produced by wear
mechanisms such as abrasion, adhesion and fibre damage. The quantitative estimate of these
surface scars from the segmented images represents an evolution curve of surface morphology.
Furthermore, the online vision monitoring reveals that the conformal contact has been established
through breaking of asperities followed by plastic flow of polymers. Once, after achieving the
conformity in contact surfaces at the steady stage, dynamic mechanisms such as back transfer of
polymers from steel surface and plastic flow are observed for obtaining a clear understanding of
the wear process. Additionally, the blur of the acquired images due to the wear process serves as a
quantitative estimate for wear. The evolution curves together with friction, wear, and temperature
response provides complete understanding of the tribological process. This combined information
can be beneficial for material designers and maintenance engineers for new material design and
condition monitoring respectively.
Keywords: Online vision system, polymer wear, quantitative micrography
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8
Erosion wear of glass fibre reinforced vinylester
Reija Suihkonen1, Juuso Perolainen1, Mari Lindgren2, Kati Valtonen1, Niko Ojala1, Jyrki
Vuorinen1*
1
Tampere University of Technology, Department of Materials Science, P.O. Box 589, FI-33101
Tampere, Finland
2
Outotec Research Center, P.O.Box 69, FI-28101 Pori, Finland
* Presenting author
Glass fibre reinforced vinylester composites are widely used in tanks, piping, ducts, and fans in
demanding applications, such as waste water treatment plants, chemical processing, and pulp and
paper manufacturing due to their excellent chemical resistance and mechanical performance. In
addition to corrosive environments, materials are exposed to erosion wear and high temperatures
(close to 100°C) in many hydrometallurgical processes. However, there is limited understanding
on the erosion wear of vinylester based composites and therefore knowledge should be gained on
this field in order to evaluate their long-term behaviour and optimize the maintenance intervals of
different structures in various wear conditions.
This study evaluates the erosion wear of glass fibre reinforced vinylester composites (FRP) using
a high speed slurry-pot type wear tester. The wear rates of FRP were also compared using different
abrasives, namely quartz, copper ore, chromite, zinc concentrate, and tailings. Furthermore, the
effect of particle size and the abrasive concentration on the FRP wear was studied. The erosion
wear results of FRP were compared to different rubbers, such as natural rubber (NR) and
bromobutyl rubber (BIIR) as well as few common thermoplastics, such as polypropylene (PP) and
polyvinyl chloride (PVC), which are potential sensor, gauge, lining, and other wear resistant part
materials in hydrometallurgical reactors.
The results show that coarse quartz produces the largest wear rates on FRP samples, while zinc
concentrate shows the lowest wear. Minor changes in the abrasive particle size have no effect on
the wear results: similar wear rates were obtained with fine quartz grades with the particle size
varying between 75-100, 100-125, or 125-185 µm. Only when the particle size was increased to
300-600 µm, wear rates were markedly increased. When comparing the wear rates of different
materials, it can be concluded that with all abrasive types, tested rubbers and thermoplastics have
lower wear rates than FRP.
Keywords: erosion wear, FRP, glass fibre, vinylester composite
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The Wear and Thermal Mechanical contact Behaviour of Polymer Gears
Dr. Ken Mao and Dr. Wei Li
School of Engineering, The University of Warwick, Coventry, CV4 7AL, UK
email: [email protected]
Presenting author: Dr. Ken Mao
The present paper will concentrate on the extensive investigation of polymer composite gear wear
and thermal mechanical contact behaviour. A test method for polymer composite gear wear has
been proposed in the current paper and extensive investigations on polymer composite gear wear
have been carried out.
It has been found from the tests that the polymer gear wear rate will be increased dramatically
when the load reaches a critical value for a specific geometry. The gear surface will wear slowly
with a low specific wear rate if the gear is loaded below the critical one. The possible reason of
the sudden increase in wear rate is due to the gear operating temperature reaching the material
melting point under the critical load condition. Gear surface temperature has been then
investigated in detail through three components: ambient, bulk and flash temperatures. Through
extensive experimental investigations and modelling on gear surface temperature variations, a
general relation has been built up between gear surface temperature and gear load capacity. The
method has been related to test results under different operating ambient temperature and gear
geometries. Good agreement has been achieved between the proposed method predictions and
experimental test results.
Keywords: wear, polymer gear, specific wear rate.
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Wear resistance of polymeric materials based on PBT
M. Botan, C. Pirvu, C. Georgescu, L. Deleanu
“Dunarea de Jos” University of Galati, 47 Domneasca, 800008 Galati, Romania.
Corresponding author: Lorena Deleanu ([email protected]).
Abstract
This paper presents the tribological behavior of four polymeric materials, polybutylene terephthalate (PBT),
PBT +10% micro glass beads, PBT + 10% polytetrafluoroethylene (PTFE) and PBT + 10% aramidic fibers,
in order to rank them in dry regime. Tests were done using a block-on-ring module (tribometer CETR®).
The test parameters were: sliding speed (0.25 m/s, 0.50 m/s and 0.75 m/s), the load and the sliding distance
being kept constant (5 N and 10 N and 5000 m, respectively). There were analyzed the dependence of
friction coefficient and linear wear rate on the adding material. Particular wear mechanisms were identified
with the help of SEM images.
Polyamide with 10% aramid fiber, F=10 N, v=0.75 m/s
Aramid fibers before adding into PBT
Fig. 1. SEM images of the tested materials
6
v = 0.25 m/s
5
Wl [μm/N km]
The tested materials they were obtained by
molding at ICEFS Savinesti Romania, in order
to obtain bone samples type 1A, as
recommended by SR EN ISO 527-2:2000. These
have a matrix of PBT, the commercial name
being Crastin 6130 NC010 (as supplied by
DuPont). After the samples' molding, they were
heat treated, being maintained for 2 hours at a
constant temperature of 175-180ºC.
Wear behavior of the obtained materials was
pointed out with the help of a block-on-ring
tester and the ranking was in the favor of PBT +
10% aramid fibers as the wear parameter was
the lowest and the friction couple has a very
poor sensitivity to the variation of sliding speed
(0.25-0.75 m/s).
v = 0.5 m/s
v = 0.75 m/s
4
3
2
1
0
PBT
GB10
PF10
Fig. 2. Linear wear rate of the tested materials for
F = 5 N and L = 5000 m
Keywords: polybutylene terephthalate (PBT), aramid fibers, wear, glass beads, PTFE.
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AF10
Material
16 Nordic Symposium on Tribology, Aarhus, Denmark
Brakes
Chair: Ilmar Santos
Thursday 12 June 2014 – 14.20-15.20
Room: Nortvegia
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Influence of pin contact geometry and friction material behavior on disc brake squeal noise
M. Duboc , J.F. Brunel , V. Magnier, P. Dufrénoy
Univ Lille Nord de France, F-59000 Lille, France
USTL, LML, F-59650 Villeneuve d'Ascq, France
CNRS, UMR 8107, F-59650 Villeneuve d'Ascq, France
Brake squeal noise is defined as a noise at frequencies higher than 1000 Hz and occurring
when the system has very high mechanical vibration amplitude, with sound pressure level above
80 dB. Brake squeal remains a very complex phenomenon to investigate because of a wide variety
of dynamic aspects at different scales. It is well accepted that squeal noise is associated to mode
lock-in of the system modes initiated by the friction forces and leading to self-excitation vibrations.
Even if the physical couplings leading to squeal are relatively well understood and identified at the
system scale, friction conditions at the interface scale leading to squeal are not well known. This is
mainly due to the complexity of the physics between the two surfaces in contact.
In this paper, experimental investigations are performed to study the influence of pad
geometry and friction material on squeal occurrences. A simplified set up has been developed : it
is based on a pin on disc tribometer with a friction pad attached on a flexible plate fixed on a rigid
stand. The pad is made of a specific friction material with only six components. Four contact
geometries have been studied with contact length from 10 to 40 mm. In addition, an analytical
model of the simplified set-up has been developed. It is a three degrees of freedom including a
disc-pad surface contact model with frictional contact surface and friction material behavior.
Figure 1 : Experimental setup
Figure 2 : Pad configurations and static contact
localizations
Figure 3 : Analytical model
Results show clearly the influence of the contact conditions on squeal occurrence specially by
varying the contact length size. The numerical results are compared to experiments and show the
keyrole of the nonlinear behavior of the material. This aspect has been taken into account in the
analytical model and results present good agreement with experiments.
This study gives informations on the comprehension of the squeal mechanisms and on the minimal
model allowing to simulate the phenomenon.
Keywords: braking, friction, squeal, vibrations, analytical model, nonlinear material behavior
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Influence of snow on train block braking performance – a pin on disc simulation in a
climate chamber
Ulf Olofsson1, Jon Sundh1, Ulf Bik2 and Rickard Nilsson2
1
Department of Machine Design KTH Sweden,
2
Stockholm Public Transport Sweden
The coefficient of friction between two sliding surfaces is a surface and environmental parameter
influenced by environmental conditions such as: humidity, temperature and snow. In trains with
block brakes the coefficient of friction between the block and the railway wheel determines the
braking performance and thus the stopping distance. Traditionally has the blocks been
manufactured by cast iron materials. Although, they provide good braking capability during snow
and winter condition, their use is more and more restricted due to the squealing noise they
produce. Test with alternative block materials has worked well during summer conditions but for
regions and countries with snowy winters their use has been limited due to problem with their
braking capability during snowy conditions.
This research aims to develop a test methodology in laboratory scale to evaluate the braking
capacity of block brake materials. A pin-on disc machine placed in a climate chamber was
utilized. In addition to control of temperature and humidity was also snow introduced to the
contact. The coefficient of friction and the sound pressure near the contact were measured and the
surface topography of the contacting specimens was also measured before and after test. Discs
were manufactured from railway wheel material and pins from the block materials. Cast iron
block material was in this study compared with blocks manufactured from alternative materials.
The results show that the alternative block materials generate a much smoother counter wheel
surface. These smoother surfaces are more easily separated by a water film introduced in to the
contact by melting snow resulting in a lower sliding coefficient of friction. In a second test series
alternative block materials were evaluated and a candidate material with low noise and high
enough sliding coefficient of friction were selected for further studies in full scale.
Keywords: friction, snow, block brakes
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Brass in brake lining: elements of understanding for its replacement
M. Baklouti1,2,3,4, A.L. Cristol2,3,4*, R. Elleuch1, Y. Desplanques2,3,4
1
Université de Sfax, Ecole Nationale d’Ingénieurs de Sfax, LASEM, 3038 Sfax, Tunisie.
2
Univ Lille Nord de France, F-59000 Lille, France.
3
ECLille, LML, F-59650 Villeneuve d’Ascq, France.
3
CNRS, UMR 8107, F-59650 Villeneuve d’Ascq, France.
*([email protected])
In the field of friction braking, the regulation objectives in terms of reduction of the
environmental impact (noise, pollutant emission) and augmentation of the energy dissipation
performances require the understanding of friction phenomena and of friction material choice,
especially for brake lining materials. Since the interdiction of asbestos use, new formulations with
organic matrix are developed. Their performances have been significantly improved by
formulations ever more complex, including several classes of constituents but without a real
understanding of each single function. The development of these friction materials is based on an
industrial know-how essentially inspired by feedback and trial-error tests leading to the recipe of
formulations but without a structure scientific approach of understanding of the role of each
constituent. In this paper, we propose a new methodology based on a simplified formulation
derivate from an industrial one and a specific friction test in temperature to identify the contribution
of one constituent in the friction behavior of the brake lining material. As copper will be prohibited
in few years, we choose to work on brass fibers which contain copper with the aim of providing
understanding keys for its replacement. Two materials are manufactured, one without brass and
one with 6wt% of brass fibers.
In the first step, the friction materials are characterized. Observation of the microstructure
shows that the brass fibers are mainly oriented in the transverse direction. This is due to the fiber
shape: they lay down during the hot molding processing. It erases the initial anisotropy of the
material and creates anisotropy in terms of thermal expansion. The presence of brass also increases
the thermal properties of the material leading to higher temperature reached in the bulk.
In the second step, the two materials are submitted to friction tests at 3 various ranges of
temperature: 100-150°C, 200-250°C and 300-350°C. Results in terms of wear show an increase of
wear with the presence of brass which can be correlated to higher temperature reached in the bulk
leading to higher degradation. In terms of friction coefficient, material with brass shows good
performances at medium and high temperatures.
At least, surface observations after friction tests permit to identify the role of brass at the
interface. The high thermal properties leads to a high degradation of the material and a high debit
flow of 3d body which is identify by a low presence of secondary plateaus. But brass fibers create
also primary plateaus helping to bear the load and to promote the expansion of the secondary
plateaus with a very homogeneous in composition. This permits to maintain a good friction level
at high temperatures.
Keywords: brake lining, brass, thermal and mechanical characterization, friction tests, 3d body
behaviour.
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Test Methods 3
Chair: Markus Varga
Thursday 12 June 2014 – 15.40-16.20
Room: Suecia
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109
Improvements to Tribological Testing for industry, Practical solutions
D. Drees1*, E. Georgiou2
1
2
Falex Tribology NV, Wingepark 23B, B3110 Rotselaar, Belgium.
Katholieke Universiteit Leuven, Department of Materials Engineering, Kasteelpark 44, B3001
Leuven, Belgium
*Corresponding author: Drees Dirk ([email protected]).
Today’s industrial challenges in the ever faster global world include the need to respond and
develop ever faster. This means, that tribological issues need to be solved faster and faster. This
puts some challenges to the tribology testing community : faster, more efficient testing with
correlation to the real applications is needed. On the other hand, the main industrial tribological
issue is still wear resistance, and to test wear in realistic conditions usually results in long term
testing.
The contradictory requirements of realistic wear testing and fast/efficient testing need to be met,
and require some different approaches to the tribological lab testing. These approaches are
presented in this paper.
On the one hand, the number of tests can be reduced if precision is improved; precision in friction
measurements by a new generation of test equipment, and precision in wear measurements by
incorporation of a TLA (thin layer activation) technique on the lab scale. On the other hand, by an
approach of parallel testing, the number of test results can be multiplied; this allows comparison of
materials and statistical data development while at the same time keeping the cost and time
requirement realistic.
Keywords: wear testing, high precision, repeatability, multistation, TLA
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Scratch & Failure Detection Method for Shaft and Rod Surfaces
F. Bauer*, M. Baumann, W. Haas
University of Stuttgart, Institute of Machine Components (IMA)
*Presenting author: Dr. Bauer, Frank ([email protected])
The sealing element, the shaft surface, the lubricant and the surrounding comprise the tribological system
“seal”. The dynamic sealing mechanism (e.g. for a radial lip seal) is based on the reverse pumping
capability of the lip seal. This in turn strongly depends on the quality of the shaft counter surface. Surface
structures that create superimposed pumping disturb the sealing mechanism and cause failure via either
leakage or dryrun. These oriented structures are also known as lead. One method for measuring shafts and
analysing microlead has recently been developed and proofed at the University of Stuttgart [0].
Another influence on the surface of shafts and rods are manufacturing and handling failures like scratches
and dents [1]. Those do not only pump fluid in an axial direction and cause failure via either leakage or
dryrun but also can wear the soft elastomer because of their raised sharp walls. Additionally this effect
changes the friction and the complete tribology of the machine element “seal”.
A comprehensive quality control is not possible on the present state of technology and therefore not
satisfying. For this reason, new approaches are being pursued at the University of Stuttgart to solve these
problems. A measurement strategy, based on optical metrology (Fig. 1) and proofed methods of digital
image processing provides promising results. With the microlead analysis method like in [0] the
orientation of each single grinding structure is analysed and displayed (Fig. 2). In this revision the failures
like scratches and dents can be found visually in the disturbed structures of the grinding surface.
Disturbed grinding structures
 Oriented scratches
 Leakage and heavy wear
Figure 1: WLI-Surface Topography
of a grinded surface with deep
scratches due to handling failures
Figure 2: Microlead analysis software revision V1:
Lead orientation of the single grinding structures
(red: <-0,1°; white: -0,1°… +0,1°; blue > +0,1°)
In the actual work the method will be upgraded to separate and analyse the scratches and dents in detail.
Information like depth, length, volume and the angular orientation can be calculated and compared to the
structures of the original surface. Therefore the failures can not only be found automated but also
characterised and compared.
Combining IMA’s new analysis methods with a white light interferometer with a rotational unit provides
the accuracy, speed and large field of view necessary to properly characterize the shafts at different
circumferential positions. This will provide a rapid, reliable production-worthy method to evaluate the
quality of shaft counter surfaces and determine if leakage and heavy wear is likely.
Keywords: Surface Topography, Failure Analysis, Scratches, Shaft & Rod, Seal
1.
2.
Baumann, M.; Bauer, F.; Haas, W.: Comprehensive Lead Analysis of Shaft Counterfaces for the Tribological System Radial
Lip Seal, 22nd International Conference on Fluid Sealing, BHR Group, Düsseldorf, 3./4. Dezember 2013 ISBN: 978 1 85598
139 3
ISO 8785 (1998): Geometrical Product Specifications (GPS) – Surface Imperfections
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16 Nordic Symposium on Tribology, Aarhus, Denmark
Polymer 3
Chair: Jacob Sukumaran
Thursday 12 June 2014 – 15.40-16.20
Room: Dania
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64
On the existence of a friction-modified surface layer of BR/SSBR elastomers reinforced
with different silica or carbon black contents
Milad Mokhtari1*, Dirk J. Schipper1 and Tetyana V. Tolpekina2
1
: University of Twente, Faculty of Engineering Technology, Surface Technology and Tribology,
P.O. Box 217, 7500 AE Enschede, The Netherlands.
2
: Apollo Tyres Global R&D B.V., Colosseum 2, 7521 PT, Enschede, The Netherlands.
*Corresponding author: Milad Mokhtari ([email protected]).
Pin on disk friction tests are performed on different rubber samples in contact with a granite sphere.
The rubber samples are prepared from a combination of butadiene rubber (BR) and solution
styrene-butadiene rubber (S-SBR) reinforced with different amounts of carbon black or silica. The
friction tests are performed at different velocities and loads. Mechanical changes inside and outside
the wear track are determined by Atomic force microscopy (AFM) nano-indentation. AFM is used
to determine the nanoscale mechanical properties which are compared with the macroscale
mechanical properties measured by Dynamical Mechanical Analysis (DMA). The existence of a
friction-modified layer as a function of the operational conditions and its effect on friction and
friction modeling of a rubber in contact with a rough surface as a function of reinforcement filler
and its content is discussed.
Keywords: friction-modified surface layer, BR/S-SBR, AFM nanoindentation, mechanical
properties, rubber friction.
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The role of frictional work in tribological behavior of
polyamide 66 composites containing hard particles
Kei Shibata1, Takeshi Yamaguchi1, Moeko Kishi1 and Kazuo Hokkirigawa1
Graduate School of Engineering, Tohoku University, 6-6-01 Aramaki Aza-Aoba, Aoba-ku, Sendai, Japan,
[email protected]
[1] K. Shibata, et al., Final Papers of NordTrib, (2012), 1–6.
Keywords: resin composite, particulate filler, frictional work, sliding wear.
PA66
Compounding
Filler
Rice bran
ceramics
particles
PA66/RBC,
PA66/GB
composites
Pellet
20 mm
Test surface
Glass beads
Injection molding
Fig. 1 Manufacturing process of PA66/RBC
and PA66/GB composites
Friction coefficient 
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Sliding velocity v: 0.2–2.0 m/s Normal load W: 9.8–19.6 N
Sliding distance L: 2103 m
Lubrication condition: Dry
PA66/RBC_8vol%
PA66/RBC_26vol%
PA66/GB_8vol%
PA66/GB_26vol%
Pure PA66
0
1
2
3
4
5
Pv, MPa・m/s
6
7
Fig.2 Friction coefficients vs. Pv
Surface temperature of pin
Ts, oC
Particulate fillers are used to improve the mechanical
and tribological properties of resin materials. In previous
study, polyamide 66/rice bran ceramics particles
(PA66/RBC) and PA66/glass bead (PA66/GB) composites
were developed as tribomaterials [1]. However, the role of
frictional work in the tribological behavior of these
composites has not been reported.
Friction tests were conducted using a rotation-motiontype friction apparatus under dry conditions. PA66/RBC,
PA66/GB composites, and pure PA66 were used as pin
specimens (Fig. 1). Austenate stainless steel was used as a
disk specimen. The sliding velocity was 0.2–2.0 m/s, and
the normal load was 9.8–19.6 N.
The friction coefficients for pure PA66 increased with
incresing Pv value (Fig. 2). Conversely, PA66/RBC
composites showed approximately same friciton
coefficients, and PA66/GB composites showed a decrease
in friction.
The suraface temperatures of pin specimen increased
with increasing frictional work, irrespective of pin
material (Fig. 3). The maximum temperature was
approximately 90 °C, which exceeded the glass transition
temperature of PA66 resin.
The specific wear rates of pure PA66 decreased with
increasing frictional work, but those were high, particularly
at low frictional work (Fig. 4). At high frictional work,
softening of PA66 resin occurred because of frictional heat.
Then the counterpart material was easily covered with
softened PA66. In contrast, except PA66/RBC_26vol%
composite, the PA66 composites showed low specific wear
rate values, irrespective of frictional work. Unavoidable
softening can occur on the composites at high frictional
work. However, plastic flows of PA66 were still prevented
because of an anchor effect of particulate fillers.
120
Sliding velocity v: 0.2–2.0 m/s Normal load W: 9.8–19.6 N
Sliding distance L: 2103 m
Lubrication condition: Dry
100
80
60
40
PA66/RBC_8vol%
PA66/RBC_26vol%
PA66/GB_8vol%
PA66/GB_26vol%
Pure PA66
20
0
0
1
2
3
4
5
Frictional work Wfriction, ×106 J/(m2s)
Fig.3 Surface temperature vs. frictional work
Specific wear rate of pin
ws, ×10−8 mm2/N
1
1.5
1.0
0.5
PA66/RBC_8vol%
PA66/RBC_26vol%
PA66/GB_8vol%
PA66/GB_26vol%
Pure PA66
Sliding velocity v: 0.2–2.0 m/s
Normal load W: 9.8–19.6 N
Sliding distance L: 2103 m
Lubrication condition: Dry
0
0
1
2
3
4
5
Frictional work Wfriction, ×106 J/(m2s)
Fig.4 Specific wear rates vs. frictional work
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16 Nordic Symposium on Tribology, Aarhus, Denmark
Lubrication 3
Chair: Thomas Norrby
Thursday 12 June 2014 – 15.40-16.20
Room: Nortvegia
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47
Grease free surface flow on a rotating plate
J. X. LI1, Lars G. Westerberg2, E. Höglund 1, T. S. Lundström2,
1
2
Division of Machine Elements, Luleå University of Technology, SE-971 87 Luleå, Sweden
Division of Fluid and Experimental Mechanics, Luleå University of Technology, SE-971 87
Luleå, Sweden
Presenting author: Jinxia Li
In order to improve the understanding of grease flow in various applications such as gears, seals
and rolling element bearings, free surface flow of different greases under different running
conditions has been investigated. A rotating disc has been used to study grease flow as the grease
is subjected to a centrifugal force. The adhesion and mass loss was detected for greases with
different rheology on different surfaces and surface textures. It is shown that the speed at which
grease starts to move is mostly determined by grease type, yield stress and bleeding properties
rather than surface material. Also, the surface adhesion is shown to be influenced both by the
rheology of the grease and the surface material.
Keywords: grease flow; axial seal; rheology
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12
Grease + Water = fatal attraction?
Johan Leckner
Axel Christiernsson Int. AB Nol, Sweden
[email protected]
In the real world, it is often difficult, if not impossible, to avoid the ingress of water into bearings
and other types of machine elements. The ability of a lubricating grease to withstand, reject or
absorb water can therefore be vital to optimal performance in many areas. Using generally available
laboratory standards, lubricating greases with different thickener systems have been tested to
compare their ability to perform even when contaminated with water. The results are then matched
with experiences from real life applications and conclusions drawn on how to select greases for use
under wet conditions.
With this study we don’t aim at resolving the issue of how bad, or good for that matter, water
contamination is in general. What we hope to achieve is to give a balanced picture of how five
different greases with a track record from real applications, perform in laboratory tests when
contaminated with water. By combining field test data with laboratory data we then hope to be able
to give some general advice concerning which greases that are preferred when there is risk of water
ingress. A secondary topic that we also will get into is how water is taken up by greases and which
components facilitate the incorporation of water into the grease matrix.
Keywords: lubrication, lubricating grease, water contamination, water ingress, laboratory tests, field
data
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146
Novel energy efficient biodegradable turbine oils
1
Prof. Thomas Norrby, 2Åke Byheden, 3Prof. Sergei Glavatskih
1
Statoil Lubricants, Stockholm, Sweden, [email protected], [email protected]
2
Statoil Lubricants, Nynäshamn, Sweden
3
KTH Royal Institute of Technology, Stockholm, Sweden, [email protected]
We have called our concept for environmentally
adapted lubricants “Environmentally Considerate
Choice” (ECC). This concept comprises a broader
scope, including not only Bio-lubricants, but also
energy efficient/ energy saving products and biocompatible products with reduced impact on human
health in the use phase.
inside of the fluid tank and on other surfaces like
hydraulic valves. This interferes with the operation,
and lead to costly down-time of power generating
equipment.
This is an increasing problem, as the Group II and
Group III based turbine fluids, designed for
prolonged oxidative lifetime (and thus intended
longer service life times), are becoming more widely
used.
One important area of development has been turbine
fluids with high energy efficiency. We have shown
that bio lubricant turbine fluids based on advanced
synthetic esters (SE) give extra benefits in improved
energy efficiency of the turbine systems, in addition
to the traditional ones e.g. biodegradability and the
use of renewable raw materials.
Finding the right combination of antioxidants also
helps preserve the fluid, and at the same time
minimise sludge formation. This is related to, but not
identical to, varnish formation and may cause filter
blockage and is in itself an undesirable ageing of the
fluid.
In a field trial at a commercial power plant in
Nyköping, Sweden, we have demonstrated that a
novel ester based turbine fluid yields 20% lower oil
and bearing system power losses, which amounts to
savings of 0,6% overall, corresponding to € 75 000,
in an ABB Stahl VAX 35 MW turbine.
Keywords: Turbine fluids, Bio Lubricants, Varnish,
Sludge, Energy Efficiency, power loss
Another benefit of using synthetic esters is that the
well-known problem with sludge and varnish
formation is alleviated or prevented. Varnish is
formed due to hot spots or static electricity in the
system and at the same time poor conductivity and
poor solvency properties of the turbine fluid itself.
The varnish sticks to the surface of the bearing or
148
16th Nordic Symposium on Tribology, Aarhus, Denmark
PLENARY SESSION 4
Friday 13 June 2014 – 08.40-09.20
Professor Martin Müser
Chair: Ion Marius Sivebæk
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16th Nordic Symposium on Tribology, Aarhus, Denmark
Friction mechanisms at small and large scales: New insights from computer simulations
Martin Müser
Forschungszentrum Jülich, Germany
Abstract:
Surfaces of solids tend to be rather complex. They have roughness on a multitude of length
scales, the chemical composition is undefined and may even change with time. Yet, the laws
describing the friction between two solids are surprisingly simple: To a good approximation,
friction between solids is linear in the force squeezing the solids together and independent of the
apparent contact area. Moreover, kinetic friction barely depends on the sliding velocity, at least at
small velocities.
Many propositions have been made within the last 100 years for the microscopic origin of solid
friction and the laws describing it. In recent years, computer simulations have been very
successful in testing the competing theories. Some simulations lead to new theories. I will review
some of these developments. This includes examples where simulations have triggered new
developments for practical applications.
Keywords: Kinetic friction, computer simulations, relations to practical applications.
Biography:
Diploma in Physics from Saarland University in 1992 and PhD in Theoretical Physics from
Johannes Gutenberg University Mainz in 1995. He spent his postdoctoral time in the Department
of Chemistry at Columbia University and in the Physics & Astronomy Department at The Johns
Hopkins University. In 2002, he became professor of Applied Mathematics at Western University
in London, Ontario. After a Sabbatical year at IBM, T.J. Watson, New York, he moved to
Saarland University in 2009, where he holds the chair of Material Simulations in the Department
of Materials Science and Technology. Since 2011, he also heads the Computational Materials
Research Group at the supercomputing Centre of Forschungszentrum Jülich. Prof. Müser's
research interests focus on the simulation of materials, in particular in non‐equilibrium. His best‐
known contributions elucidate the atomistic origin of friction and the contact mechanics between
solids with rough surfaces. A large fraction of his work is concerned with model and algorithm
development, such as the design of the first polarizable force field for the description of redox
reactions. In 2003, he received the Young Innovator Award from Petro Canada and in 2004 the
Premier's Research Excellence Award by the Ministry of Economic Development and Trade,
Ontario. He was named Faculty Scholar by Western University in 2008 and Outstanding Referee
by the American Physical Society in 2013.
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16th Nordic Symposium on Tribology, Aarhus, Denmark
Industrial Tribology 2
Chair: Arto Lehtovaara
Friday 13 June 2014 – 09.40-11.20
Room: Suecia
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101
Influence of switching speed of connectors in conditions of engaging and separating with
electrical load
Alexander Hornung1, Frank Berger1, 2George Freudiger, 2Tom Ledermann
1
Electrical Apparatus and Switchgear Group, Technische Universität Ilmenau, Ilmenau,
Germany
2
Research & Development, Multi-Contact AG, Allschwil, Switzerland
Corresponding and presenting Author: Alexander Hornung, [email protected]
Plug-in connectors (pins and sockets) are devices used to establish a mechanical and electrical
connection between electrical circuits. Often, these connectors are used under extreme conditions
(hot plugging), far beyond the manufacturer's qualified conditions. In some cases a failure of the
connection is the result. The aim of this research is to gain knowledge about the long-term
behaviour of connectors under standardized test conditions and to research threshold ranges in
hot-plugged applications. A central point of interest is the influence of mechanical, electrical and
other parameters on their operational capability.
In previous times research has been either performed on tribological issues without putting an eye
on the breaking capacity or just on the effects occurring when switching under load. However
both – tribology and electrical - aspects need to be considered in a combined way at applications
of engaging and separating with electrical load when high cycle values has to be reached.
The authors stressed the connectors in numerous tests where they have been switched under
different current loads at low direct voltage. During break operation arcing could be observed as
expected with both a high speed camera as well as in measured voltages and currents.
The experimental setup also allows a variation of the switching speed according to standard and
real-application values. Experiments showed significant differences in connector resistances
which depend strongly on the velocity – a slower speed leads to an increased arc energy
compared to higher ones. This results in a significant reduction of product lifetime as the
connector resistance reaches the crucial limits after fewer cycle times. This paper presents
selected experiments and explains the effects of different arc energies on the contact surface.
Keywords: hot-plugging, tribology, arcing, electrical contacts
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48
Formation and degradation of protective tribofilms on diesel engine valve surfaces
Robin Elo, Staffan Jacobson
The Ångström Tribomaterials group, Department of Engineering Sciences, Uppsala University,
Sweden.
The valve system has a critical role in diesel engines. The intake valves open to let air flow in to
the combustion chamber, the combustion takes place and then the exhaust valves open to let the
combustion products flow out. This is repeated as the engine drives the vehicle forward. At all
other times, the valves must be closed to avoid any leakage, which would reduce the power
output.
The tribological conditions for the valves are tough and include high temperature, repeated
impact and micro sliding in a combustion residue atmosphere. The specified life time of the
valves is very long—they should function during the entire life time of the engines—which
demands an extremely low wear rate. On top of this, legislation on low emissions of particulate
matter and other exhausts is in place. This results in high demands on clean fuels and engine
lubricants, which will change the operation conditions for the valves.
We have recently shown that with current technology, protective tribofilms are formed on the
sealing surfaces of the valves, which lower the wear rate and thus gives the valves the specified
long life time. However, little is known about the mechanisms of how these tribofilms are formed
and how they reduce the wear rate. When analyzing field worn valves, it appears as if additive
elements from the oil have been trapped between the valve and valve seat insert surfaces as they
close. Then—due to micro sliding in the interface—the trapped particles are smeared out into a
smooth layer, protecting the metal surfaces. Since a change to cleaner fuels and engine lubricants
would lead to less of these tribofilm forming particles it is important to understand this formation
process and whether the tribofilm can function without continuous addition of new tribofilm
forming elements.
In the present work, the formation and degradation phases of these tribofilms have been studied
by running real valves and valve seat inserts in an in-house rig. The rig allows the addition of oil
into a hot air stream, which passes the operating valve to simulate the case in real engines. This
rig has been used in earlier studies where it has been shown that it can reproduce the type of oil
residue tribofilm that is commonly found on field worn valves. The rig allows stopping a test at
any point, taking the valve and valve seat insert out to analyze the surfaces and then re-starting
the test. To study the build-up phase of the tribofilm, tests have been run for 10; 100; 1000 and
10000 cycles with the addition of engine oil. Also, tests have been continued after 1000 and
10000 cycles for another 1000 cycles—without the addition of engine oil—to investigate if the
tribofilm can continue to protect the valves.
The results will be discussed regarding their implications for the development of future valve
systems, which will see less and less tribofilm forming elements due to harder legislation on
exhaust limits.
Keywords: combustion valve; tribofilm formation and degradation; experimental
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40
Comprehensive study of wear phenomena during hot rolling of steel
H. Torres1)*, M. Varga1), U. Cihak-Bayr1), K. Adam2), E. Badisch1)
1)
AC²T research GmbH, Viktor-Kaplan-Straße 2D, 2700 Wr. Neustadt, Austria
2)
voestalpine Stahl GmbH, voestalpine-Straße 3, 4020 Linz, Austria
*
Corresponding author. Tel.: +43 2622 81600 190. E-mail address: [email protected]
Wear plates are used for metal sheet alignment prior to coiling during steelmaking. Due to the
extreme operating conditions found after hot rolling, like high temperatures, high metal sheet
sliding speeds and the use of cooling water, alignment plates suffer severe wear and need frequent
repair, thus being a source of increased maintenance efforts and facility downtime.
As a first step towards process optimisation, a damage analysis of wear plates after operation was
carried out, using optical microscopy, micro-hardness measurements and SEM imaging in order to
investigate their microstructure and wear mechanisms. In addition, comprehensive analysis of the
highly stressed near-surface region was done using SEM+FIB and electron back scattering
diffraction (EBSD) mapping for investigation of early damaging phenomena.
In particular, two main damage mechanisms were identified: the initial onset of the wear tracks
was attributed to (i) 2-body abrasion by the high temperature sheet metal, while at a later stage (ii)
significant plastic deformation of the substrate and mixing with transferred material from the
counterbody as well as oxides was found (Fig. 1), eventually leading to plate material loss due to
the delamination of the mixed layer. Microstructural changes were observed in the plates’ base
material, including the formation of a hard surface layer possibly due to the joint thermal and
mechanical effects of the contact with the high temperature metal sheet. It is expected that the
microstructural evolution of the base material will influence the tribological behaviour of the wear
plates.
Experimental simulation of the predominant wear phenomena observed during the failure analysis
was carried out on a two-body abrasion test rig in lab-scale. Testing parameters were best-adapted
to real field conditions (e.g. temperature, sliding speed, contact load). Wear evolution was observed
from the very beginning to advanced stages of the process. Results showed that the predominant
wear mechanisms change with increasing testing time from sliding contact phenomena to
intermixing and adhesion at later stages.
Fig. 1: Cross section of a damaged region at an advanced stage
of the wear process
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16th Nordic Symposium on Tribology, Aarhus, Denmark
Keywords: High Temperature, Sliding, Abrasion, Tribology
29
Friction behaviour of phosphate-free lubricants for steel wire drawing
M. Vilasecaa,*, J. Vidalb, J. Pujantea, G. Ramíreza, N. Cuadradoa, D. Casellasa
a
Department of Materials Technology, Fundació CTM Centre Tecnològic, Plaça de la Ciència, 2,
08243 Manresa, Spain
b
Technical Department SEBIR, S.A., C/ Comunicacions, 14, 08755 Castellbisbal, Spain
*Corresponding author: [email protected]
In cold forming processes, finished parts are produced from semi-finished products where
lubricants are applied to reduce direct contact between tool and workpiece. The large surface
expansion and high normal pressure combined with elevated contact temperature between
workpiece and tool, which prevail in cold forming of metals, cause the necessity of high
performance lubrication systems. Nowadays, phosphate coatings as conversion layers represent the
industrial standard. However, phosphatising produces hazardous wastes and is a major bottleneck
directly affecting productivity. In this way, alternative lubrication systems are continuously
demanded.
In the present work, several alternative phosphate free lubricant systems are applied on wires in
industrial drawing conditions. The coefficient of friction of as-applied lubricants is characterized
by means of a modified scratch test. Measurements are made directly on lubricated wires,
representative of industrial conditions. Additionally, multi-pass effect has also been studied to
determine lubricant run dry stability, surface enlargement and roughness flattening.
Keywords: lubrication, friction, steel wire, drawing
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33
Development of new tapping tool covered with nickel/abrasive particles composite film
Yasuyoshi Saito1*, Takeshi Yamaguchi1, Kei Shibata1, Yuki Kadota1, Takeshi Kubo2,
Wataru Watanabe2, Teruo Sawabe2, and Kazuo Hokkirigawa1
1
Graduate School of Engineering, Tohoku University, 6-6-01 Aramaki Aza-Aoba, Aoba-ku,
Sendai, Miyagi 980-8579, Japan, [email protected]
2
MIYAGITANOI MFG. CO., LTD, 15-1 Shichikashuku-machi Aza-Hagisaki, Katta-gun, Miyagi
989-0537, Japan
Recently several types of tapping tools covered with hard coating film have developed in
order to elongate its tool service life. However, detachment of the film from the tool surface or
chip snarling on the tool is problem for further increase of tool service life and tapping speed. In
this study, a tapping tool covered with nickel/abrasive particles composite film was newly
developed and its superior machining performances were investigated.
Fig. 1 shows an overview and SEM images of newly developed spiral tap covered with
nickel/cubic boron nitride (cBN) particles composite (Ni/cBN) film. The composite film was
formed on the tool surface by electrodeposition method. The mean diameter of cBN particles was
about 10 m.
Tapping tests were carried out with a machining center using high-speed tool steel (HSS)
tap with homotreatment, and HSS tap covered with TiCN, Ni, or Ni/cBN film. The workpiece
material was carbon steel (JIS S45C). The cutting velocity was 10 or 50 m/min. The number of
25 holes was processed.
As shown in Fig. 2, as compared to the HSS tap covered with TiCN film, there found no
chip snarling on the newly developed tap covered with Ni/cBN film at cutting velocity of 50
m/min. The tap covered with Ni/cBN film was able to prevent chip snarling even at high cutting
velocity condition whereas the other taps had chip snarling (Table 1). This result indicated that
the newly developed tap enables continuous tapping process at high cutting velocity (50 m/min)
than the conventional condition. On the basis of the observation and analysis of chips after test,
the tap with Ni/cBN film reduces the length and the curl radius of the chip possibly due to
abrading action of cBN particles on chip surface.
cBN
particles
20μm
cBN
particles
(a) Without chip
(b) With chip
(tap snarling
covered with
(tap covered with
TiCN film)
Ni/cBN film)
Fig. 2 Snap shot of tapping tool)after
cutting
test
Covered
film
20μm
Crest
Root
Fig. 1 SEM images of spiral tap covered with
Ni/cBN film
Keywords: chip snarling, cubic boron nitride,
electrodeposition, friction, tap
on tapping tool
Vr = 10 m/min
Vr = 50 m/min
Homotreatment
No chip
snarling
Chip snarling
Ni plating
No chip
snarling
Chip snarling
TiCN film
Chip snarling
Chip snarling
Ni/cBN particles
Composite film
No chip
snarling
No chip
snarling
Table1 Occurrence of chip snarling
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16th Nordic Symposium on Tribology, Aarhus, Denmark
Bearings
Chair: Martin Müser
Friday 13 June 2014 – 09.40-11.20
Room: Dania
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141
Crack propagation in silicon nitride bearing elements
W. Karaszewski
Technical University of Gdansk, Mechanical Engineering Department, ul. Narutowicza 11/12, 80-233
Gdansk, Poland
Catastrophic fracture failure of engineering structures is caused by cracks that extend beyond a
safe size. Cracks, either as a result of manufacturing fabrication defects or damaged in service,
may grow by mechanisms as fatigue, stress corrosion or creep. The crack growth leads to a
decrease in the structural strength. Fracture, the catastrophic damage that takes place very rapidly,
is preceded by slow crack growth during normal service conditions, mainly by fatigue due to
cyclic loading.
Silicon nitride is one of the most important materials for rolling element bearings applications.
However, the difficulties of sintering and machining the material may result in surface defects.
Surface defects as ring cracks are difficult to detect during high volume production process.
Another surface cracks caused by blunt impact load have also ring shape and are the most
common type found on ceramic ball surface. These defects decrease the rolling contact fatigue
performance considerably so it is important to understand the failure mechanisms caused by such
cracks.
The stress intensity factors along crack front were analyzed using a three-dimensional boundary
element model. The boundary element method (BEM) is a numerical computational method of
solving linear partial differential equations which have been formulated as integral equations. It
can be applied in many areas of engineering and science including fluid mechanics, acoustics,
electromagnetic. The dual boundary element method is also used in fracture mechanics in
incremental analysis of crack extension problems.
The numerical analysis was verified by experimental studies. A four-ball apparatus was used to
test ceramic balls. The upper ball is the silicon nitride test specimen with a pre-existing ring
crack. The ring cracks were created by blunt impact loads. This method was chosen to create
similar cracks which can be created during falls of the balls or exploitation as an effect of impact
load.
Based on the experimental research and numerical analysis the following conclusions may be
drawn:
•
•
•
The process of fatigue failure of silicon nitride with surface ring cracks is influenced not
only by the pre-test crack propagation. Generated subsurface cracks play an important
role in rolling contact fatigue performance and failure modes.
The main problem in numerical analysis is comparison of calculated stress intensity
factors in rolling contact of silicon nitride with existing information in the literature
because of contradictory information.
The structural quality of materials, working environments and external load magnitudes
have a significant impact on the life of rolling elements in bearings.
Keywords: crack propagation, silicon nitride, rolling bearing, numerical analysis
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129
Application of multilobe journal bearings in grinding machines spindle systems
Zdzislaw SOCHA, Stanislaw STRZELECKI
Research Development Centre of Textile Machinery POLAMATEX-CENARO
Wolczanska Str. 55/59, 90-604 Lodz, Poland
Corresponding author: [email protected]
Multilobe journal bearings are applied mainly in high speed rotating machinery, e.g. turbo
compressors, turbines or in grinding machines. Hydrodynamic journal bearings can properly
operate in the strictly determined range of rotational speeds which upper boundary is determined
by the permissible temperature of operation and the possibilities of heat conduction, but the lower
determines the occurrence of fluid friction. It is convenient to apply such bearings in the grinding
machines. However, to operate the grinding machine spindle bearing system at proper temperature
it is important to apply the bearings assuring comparatively low temperatures of oil film. Using
multilobe journal bearings with 3, 4 or 6 lobes of continuous can fulfill such condition of operation
or non-continuous bore profile. The ground for the safe operation of multilobe journal bearings at
proper oil film temperature is the knowledge of bearing thermal characteristics particularly the oil
film maximum temperature. An excessive oil temperature leads to the degradation of lubricant,
bearing material and it generates deformations of bearing structure.
An example of application of multilobe bearings with discontinuous bore profile gives the journal
bearing system of grinder for peripheral grinding; this grinding machine spindle operates in 3-lobe
bearing with pericycloid (continuous, “wave”) bore profile. Another example of bearing applied in
grinding machine is the 4-lobe bearing with discontinuous bore profile.
Classic 3-lobe journal bearing is composed of single circular sections whose centres of curvature
are not in the geometric centre of the bearing. The geometric configuration of the bearing as a
whole is discontinuous and not circular. The 3-lobe pericycloid journal bearing “wave” bearing) is
characterised by continuous profile and three hydrodynamic oil films on the journal perimeter.
Continuous curvature of the operating surface is an important feature of the pericycloid bearing.
Such a configuration allows simultaneous machining of the whole surface by simple workshop
techniques and hence precise shape as well as the dimensional accuracy.
The paper presents the results of the calculations and experimental investigation of oil film
pressures and temperatures of multilobe journal bearings that were applied in the real mechanical
system of grinding spindle. The oil film pressure, temperature and viscosity fields were obtained
by iterative solution of the Reynolds', energy and viscosity equations. Laminar adiabatic and
diathermal oil film, static equilibrium position of journal and parallel axis of journal and bearing
were assumed. The calculated temperatures were compared to the temperatures obtained
experimentally on the test rig designed on the basis of real grinding machine spindle system.
Keywords: hydrodynamic lubrication, multilobe journal bearings,
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16th Nordic Symposium on Tribology, Aarhus, Denmark
127
Experimental Investigation of Fatigue Lifetime for Bearing Materials in Large Two-stroke
Marine Diesel Engines
Peder Klit a, Sebastian Persson b and Anders Vølund b
a
DTU, Department of Mechanical Engineering, Nils Koppels Alle 404, 2800 Lyngby.denmark
b
MAN Diesel & Turbo SE, Teglholmsgade 41, 2450 SV Copenhagen, Denmark
In large two-stroke marine diesel engines bearings are designed with the intention that these need
not be replaced during the life of the engine. The design parameters of the main bearings are,
among others, based on the average maximum specific load which the bearing should operate
under. The frictional loss is less than 1% of the nominal power of the engine, but is still a target
for optimization. Fatigue mechanisms of bearing lining material are not fully understood and the
design limits with regards to minimum oil film thickness, max oil film pressure and oil film
pressure gradient is not established. Large two-stroke journal bearings are not suitable for fatigue
test due to the size, the low rotational speed and the complexity of such test-rig. The Disc Fatigue
Test Rig (DFTR) was designed with the purpose to test white metal coatings under realistic
bearing conditions, in a confined time-frame. The test-rig simulates a scale model of a thrust
bearing, in contrary to standard design the bearing lining material is applied to the rotating collar.
On each side of the disc three stationary tilting-pads applies a load to the test disc, with a
rotational speed of 2000 rpm. Parameters, such as bearing load, rotational speed, oil temperature,
oil contamination is controlled/monitored in order to ensure a systematic approach to the
experiments and to achieve a high degree of repeatability. Test performed on the test-rig shows
good correlation on the fatigue cracks with those experienced on large two-stroke journal
bearings. Observations from the experiments are shown alongside with results from service
experiences. Measured parameters are used for monitoring the condition of the white metal lining
during the experiment.
Keywords: Babbitt, fatigue, combustion engine, experiment
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121
Pressurized oil supply in cylindrical 2-grooves journal bearing
Standziak G. 1) , Strzelecki S. 2)
1)
2)
Katowice Coal Holding Company, A. KWK „Mysłowice-Wesoła”, Katowice, Poland,
[email protected]
Research Development Centre of Textile Machinery “POLMATEX-CENARO”, Lodz Poland
The main shafts of hoisting machines applied in coalmines can operate in rolling or journal
bearings. Journal bearings are characterized by very low friction coefficient, very good reliability
and durability. They allow easy assembling as well as smooth operation without vibrations.
Lubricating system of journal bearings is very simple and it provides continuous pressurized oil
supply to the bearing operating surfaces. In case of hoisting machines the low speed of operation
does not generate high oil film temperatures. Design of such journal bearings should base on good
knowledge of their performance characteristics. Main design elements of hoisting machine
including main shaft, journal bearings and electric motors are designed to assure the reliable
operation through 50 years exploitation.
Determination of bearing characteristics requires the knowledge of load applied to the bearing. This
load can be obtained from the solution of the equations of motion of hoisting machine.
Static characteristics of journal bearings include: oil film pressure, temperature and viscosity
distributions, load capacity that is usually determined by Sommerfeld number, static equilibrium
position angle, minimum oil film thickness, maximum value of oil film pressure and temperature,
friction loss and oil flow. Basic equations of hydrodynamic theory of lubrication, i.e., Reynolds’s,
energy and viscosity equations including geometry of oil gap are the ground of bearing static
characteristics. The supplied oil pressure and temperature affects the operation of journal bearings.
These parameters of lubrication are of great deal in case of very responsible journal bearings
systems such as the bearings of hoisting machine.
An example of hoisting machine operating with 2-axial groove cylindrical journal bearings is the
machine allowing the transportation of coal from the depth, about 700 meters. This hoisting
machine operates with very stiff shaft with fixed winding drum rotating at 70 rpm. The shaft is
designed to connect two direct current electric motors of 3400 kW power each and it runs in two
in two large overall dimensions of 650 mm nominal diameter journal bearings. Lubricating grooves
are placed in the horizontal plane of bearing. Such design classifies these bearings as two-axial
groove cylindrical journal bearings.
This paper presents the effect of pressurized oil supply on the static characteristics of low speed,
heavily loaded, large overall dimensions two-axial groove cylindrical journal bearings of hoisting
machine. Different pressures and temperatures of supplied oil were assumed. Reynolds, energy
and viscosity equations were solved by the method of finite differences. Diathermal model of oil
film, laminar oil flow in the bearing lubricating gap and parallel orientation of bearing and shaft
axis were assumed. All calculations were carried-out at the static equilibrium position of journal.
Some of the results of calculations were compared to the values of temperatures measured by
hoisting machine monitoring system.
Keywords: cylindrical 2-grooves journal bearings, pressurized oil supply
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66
Solution for deposition on bearing pads by insoluble particulates in turbine oils
Fumihiko Yokoyama1), Yuka Iwama2), Yuka, Otsuka1), Masahiro Maruyama3), Mitsuo Sano3)
1)
2)
Machine Elements Dept., Research Laboratory, IHI Corporation, Japan
Fundamental Research & Engineering Dept., R&D Technology Center, IHI Corporation, Japan
3)
Rotating Machinery Engineering Dept., IHI Corporation, Japan
Even slight oxidation degradation could significantly impair
device functionality. In recent years, deposits have been
recognized as problem reaching epidemic proportions in some
applications (1) (2) (3). This is thought to be related to the change
in base oil from Group Ⅰto Groups Ⅱ or Ⅲ.
So far, we have confirmed that particulate insoluble products
increase, even with unchanged viscosity and total acid number;
depending on the base oil type Groups. Moreover, it was also
confirmed that very few insoluble products were
Fig. 1. Presumed deposition mechanism
responsible
for
deposition
though
the
demonstration tests that was simulated the thin gap
in the film thickness as shown in Fig2.
The potential solution for this problem is to
choose good oils and remove contaminants. In this
paper, the dependence of oil type on deposit
formation and the filtration effect using
Electrostatic Oil Cleaners (EOC), which makes use
of principles that the contaminants in oil are
electrically charged and trapped by electrodes, are
reported. The test results are illustrated in Fig3.
Even small particles below 10μm can be removed.
Fig. 2. Demonstration tests as a function of
contamination content
List of References
[1] M. Johnson, et al.: TLT, April (2011) pp. 22-27
[2] M. J. Neale: Tribology Int., August (1982) pp. 184186
[3] G. J. Livingstone, et al.: J. ASTM Int., Vol. 4, No. 1,
paper ID JAI100465
Keywords: Deposit, Lubricant,
Turbine oil, Bearing
Fig. 3. the filtration effect using Electrostatic Oil Cleaners (EOC)
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16th Nordic Symposium on Tribology, Aarhus, Denmark
Tribology of Materials
Chair: Staffan Jacobson
Friday 13 June 2014 – 09.40-11.20
Room: Nortvegia
163
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15
Friction and wear characteristics of different Pb-free bearing materials in mixed and
boundary lubrication regimes
Daniel W. Gebretsadik*, Jens Hardell, Braham Prakash
* [email protected]
Division of Machine Elements, Luleå University of Technology, Luleå SE-971 87 Sweden
Traditional bearing materials contain different amounts of lead (Pb) due to its friction reducing
properties. However, in view of the negative health and environmental impact of Pb, there are new
directives that limit the usage of Pb in engine bearings. Owing to this, new bearing materials that
provide at least comparable tribological performance to that of Pb containing alloys are emerging
and manufacturers have already started manufacturing Pb-free bearing materials. It is, however;
still unclear how these new engine bearing materials would perform in mixed and boundary
lubricated conditions. In this study, a block-on-ring test setup was employed to investigate the
tribological performance of several bimetal and multi-layer Pb-free bearings with different
compositions of lining and overlay materials. Pb-containing bearing material was also studied as a
reference material. Friction and wear properties of these bearing materials were investigated and
their wear mechanisms under lubricated conditions have been analysed.
Keywords: lead-free; bearing materials; friction and wear
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25
The effect of sliding distance and temperature on the initiation and formation of the
aluminium alloy transfer to the uncoated and coated tool steel
J. Jerina, M. Kalin
Laboratory for tribology and interface nanotechnology, Faculty of Mechanical Engineering,
University of Ljubljana, Slovenia
In processes of forming aluminium alloys, there are several difficulties in controlling process
parameters and product quality due to the unfavourable contact conditions and tribological
properties of the contact surfaces. Because of the lower required forming forces and higher material
formability, most of the aluminium bulk-metal forming (i.e. forging, extrusion) is performed at
elevated temperatures, which causes substantial thermal and mechanical stresses and die surface
wear due to the abrasion and adhesion. Adhesion and in particular formation of the aluminium
alloys transfer on the surface of die bearing surface is one of the predominant reasons for tool
failure and inadequate surface quality of products.
The present work was focused on the aluminium alloy (EN AW6060) transfer initiation and
evolution onto the coated (CrN and TiAlN) and uncoated nitrided hot work tool steel (AISI H13)
in a temperature range from 20 °C to 500 °C. All tests were performed on the new Load scanner
tribo test rig in a dry sliding contact conditions. The contact has been investigated in terms of the
surface area and volume of the transferred aluminium alloy to the uncoated and coated tool steel
surface, the topography of the wear trace and corresponding change in the coefficient of friction.
The results show a strong dependence between temperature and the tribological properties of the
uncoated as well as coated tool steel and aluminium alloy sliding contact. In contrast, sliding
distance shows only a limited impact on contact behaviour, especially at higher tested temperatures.
Keywords: elevated temperatures, friction, galling, aluminium alloy, coatings
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133
A pin on disc study of the tribology characteristics of sintered versus standard gear
materials
Xinmin Li, Mario Sosa, Ulf Olofsson
Presenting author: Xinmin Li
Department of Machine Design, Royal Institute of Technology (KTH) SE 100 44 Stockholm
Sweden
Powder metallurgy allows complex component geometries which includes gears. There is however
a lack of knowledge of the tribological performance of powder material gears compared to gears
manufactured from standard gear materials. In this study, a pin on disc machine was used to
simulate the sliding part of gear tooth contact both in boundary and mixed lubricated regions. A
comparative study of the tribology characteristics of two kind of sintered gear materials with a
standard gear material was performed. The comparison comprised of damage mechanisms, wear,
friction and running-in between these materials in different pin on disc configuration (standard vs
standard, sintered versus sintered and sintered versus standard). For the same gear materials
combinations [RS-RS (16MnCr5), AQ-AQ (Distaloy AQ+0.2%C) and Mo-Mo (Astaloy
85Mo+0.2%C)], RS gear material has a lower friction coefficient. When it comes to PM and RS
material combinations, both of the PM materials showed a lower friction coefficient, when the pins
are made of PM materials in contrast if we have RS pin. Also for the wear rate, RS material always
shows the lowest wear rate no matter the disc material. AQ and Mo gear materials have nearly the
same wear rate. A distinct difference between different material combinations, both in friction and
in wear rate, is observed during the running-in phase.
Keywords: Gear material, PM, wear, friction, running-in
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57
Adhesive strength of coated film by aerosol deposition using reactive alumina submicron
powder
Yuji Ohue*, Yuta Haratsuka**, Yukihisa Tamura***
* Prof. Dr., Kagawa University, 2217-20, Hayashi-cho, Takamatsu, 761-0369, Japan
** JTEKT Corporation, 3-5-8 Minami-semba, Chuo-ku, Osaka, 542-8502 Japan
*** Student, Kagawa University, 2217-20, Hayashi-cho, Takamatsu, 761-0369, Japan
Presenting author Yuji Ohue, e-mail: [email protected]
Recent advances in smart surface engineering, coating technologies and cold spray
technologies offer unique possibilities for better controlling friction and wear under lubricated
rolling, sliding or rotating contact conditions. Smart surface technologies such as laser texturing
and/or dimpling, laser glazing, reactive ion etching and shot-peening have also become very
popular. Recently, a novel method for depositing ceramic thick films by aerosol deposition (AD)
has been developed. Submicron ceramics powders are accelerated by fast gas flow and then
impacted on a substrate, to form a dense, uniform and hard ceramic layer at room temperature. In
this study, in order to create the textured surface without the thermal effect, AD method was
employed. The conditions to deposit alumina films on a slide glass and the adhesive strength of
the films were investigated. The thickness of deposited alumina film increased exponentially, as
the reciprocating cycles increased in numbers. The deposited films were scratched using a
diamond indenter. The friction coefficient of contact between the film and the indenter was
almost 0.15 in spite of reciprocating cycles. The reciprocating cycles in depositing exceed 20, the
adhesive strength of the films increased from 75N to 90N.
Keywords: aerosol eeposition, alumina, coating, adhesive strength, submicron powder
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POSTER SESSION
Wednesday 11 June 2014 – 15.40-17.00
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4
Modelling of nonlinear dynamic of mechanic systems with the force tribological interaction
Victor Musalimov1, Konstantin Nuzhdin2*, Irina Kalapyshina3
1
National Research University of Information Technologies, Mechanics and Optics,
Saint Petersburg, Kronverkskiy pr., 49, Russian Federation, professor
2
National Research University of Information Technologies, Mechanics and Optics,
Saint Petersburg, Kronverkskiy pr., 49, Russian Federation, PhD-student
3
National Research University of Information Technologies, Mechanics and Optics,
Saint Petersburg, Kronverkskiy pr., 49, Russian Federation, PhD-student
* Presenting author
This paper considers the mechanisms with different structure: tribometric device and a mechanism
for handling of optical glasses. In the first device, the movement of the upper platform is due to a
reciprocating friction interaction. In the second device, the processing of the optical element or group of
elements occurs due to the rotational motion. Modeling of the dynamic of these systems with
Matlab/Simmechanic allowed carrying out the analysis of dynamic of mechanisms considering
nonlinearity tribological interactions for these systems. The article shows that using the computer models
can effectively carry out the selection of the control parameters to create the desired mode of operation, as
well as to investigate the behavior of systems with nonlinear parameters and processes of self-oscillations.
The organization of the managed self-oscillation process is realized to create the relevant highperformance manufacturing, for example, for the processing of optical glasses.
Keywords: handling of optical glasses, tribometric device, friction models, nonlinearity tribological
interaction, simulation in Matlab.
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20
Researches on the Friction between the Guide made of Phosphor Bronze and the Valve
Stem made of Ti6Al4V with and without Protective Layer
Maciej Kuchar1, Krzysztof Jan Siczek 1*
1
Department of Vehicles and Fundamentals of Machine Design, Lodz University of Technology,
Zeromskiego Str. 116, 90-924 Lodz, Poland.
*Corresponding author: Krzysztof Jan Siczek ([email protected]).
Lightweight valves are commonly used in modern combustion engines with cam and camless valve
train. They can be made of TiAl alloys and in particular the inlet valves can be made of Ti6Al4V.
The stems of such valves can be coated by protective layer obtained by nitridation, chroming or
the other one. The stems can mate with guides made of cast iron, of phosphor bronze or berylium
bronze. Mating can take place in conditions of mixed friction with different share of lubricated
friction. The researches have been provided in the tribotester. The analyzed valve has been driven
electromagnetically, for the different valve strokes and frequencies. The guide has been warmed
electrically to the desired temperature. The mating takes place in the condition of oil absence. The
valve has been loaded by additional mass to induce the normal force between valve stem and its
guide. It has been measured the acceleration and the displacement of the valve, the impact force of
the valve into its seat insert, friction force between valve stem and its guide, the temperature of the
guide and the sound level. The aim of the researches is to obtain and compare values and courses
of friction coefficient between the guide made of phosphor bronze and valve stem made of Ti6Al4V
for certain number of the valve strokes, frequencies and temperature of the guide. The researched
stem can be uncoated or coated by Cr layer or by nitridation. The model of valve and guide has
been elaborated using FEM to compute temperature gradient in valve material. Obtained values of
the guide temperature has been used as the boundary conditions in the model. The analytical model
has been elaborated to calculate the contact pressure and the friction force between valve stem and
its guide for the conditions of mixed friction occurring because of selected engine oil and of the
valve motion relative to its guide as obtained from the tribotester. The obtained dry friction
coefficient values have been used in the model. Results of researches have been presented in the
article.
Keywords: friction, tribotester, TiAl alloy, phosphor bronze, protective layer.
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31
Tribological Analysis of the Nano-modified Industrial Polymer
M.Sc.Eng. Olga Konovalovaa), Prof. M.Sc.Eng. Jan Suchanek, CSc. a),
a
Czech Technical University, Faculty of Mechanical Engineering, Department of Manufacturing
Technology, Technicka 4,16607 Prague 6, Czech Republic
Presenting author and corresponding author: M.Sc.Eng.Olga Konovalova,
tel.: +420-775 970 444, [email protected]
The aim of this paper is a research of positive influence of the commercially available nano-additive
on tribological properties of the essential polymer for the industry. The nano-filler amount was
chosen equal to commonly needed for amending of other paramount properties of the polymer. The
tribological behavior of polymer nanocomposite was investigated during the rubbing against low
alloyed steel in oilless contact. The composites consist of Ultramid which was modified by 1, 3
and 5 wt.% of nanoclay Cloisite. Samples were tested on T-05 block-on-ring tribometer and
observed with SEM and Laser Confocal Microscope LEXT OLS 3000. There were observed a
positive and pronounced effect of nano-additive on temperature regulation in contact zone,
investigated and analyzed other aspects of tribological behavior of a polymer/steel contact joints.
Keywords: polymer, nanoparticles, wear, Ultramid, Cloisite, dry friction, oilless contact.
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Wear and Mechanical properties of nodular iron modified with copper
V. Gil; F. Alcalá; F. Correa; N.C. Alba; J. Ramos*
Universidad Autónoma de Occidente. Cali, Colombia
* [email protected] (presenting author)
The nodular iron is a material that has shown great advantages respect to other materials (steel and
gray iron) in the production of machine elements. The engineering industry, especially automobile,
are potential users of this material. As it is known, the alloying elements modify the properties of
steels and castings. Copper has been investigated as a structural modifier of nodular iron, but
studies of its mechanical and tribological implications still need to be addressed for industrial use.
With the aim of improving the mechanical properties of nodular iron, alloying elements (Mn, Si
and Cu) are added in order to increase their pearlite (or ferrite) structure according to the percentage
of the alloying element.
In this research (using induction furnace process) nodular iron with three different percentages of
copper (residual, 0,5% and 1,2%) was obtained. Chemical analysis was performed by optical
emission spectrometry and microstructures were characterized by Optical Microscopy (ASTM E3).
The study of mechanical behavior was carried out in a mechanical test machine (ASTM E8) and a
Pin on disk tribometer (ASTM G99) was used to assess wear resistance. It is observed that copper
increases the pearlite structure improving the wear behavior; tension behavior. This improvement
is observed in higher proportion with 0,5% due to the fact that too much increase of pearlite leads
to ductility loss
Keywords: copper, mechanical properties, nodular iron, pearlite structure, wear.
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43
Observation of Elastic/Plastic Response of Adsorbed Mono-Layer to Friction by Lateral
Force Microscopy
Fumihiro ITOIGAWA, Mina WAKAMATSU, Takashi NAKAMURA
Nagoya Institute of Technology
Presenting Author: Fumihiro ITOIGAWA
Boundary film on a solid surface in practical sliding contacts should be an imperfect film, not an
idealized film with infinite extent such as LB film. In the case of relatively low coverage of
molecular film, the boundary film can be small island shape because of nucleation. In fact, many
observations of the island shape molecular film with atomic force microscopy have been
reported. This fact suggests that one of the origins of friction force in boundary lubrication should
be mechanical response of a mono-molecular island film.
In this study, mechanical response, that is elastic/plastic response to friction, is observed with
lateral force microscopy for various types of island shape molecular film; normally aligned or
oblique aligned cohesive film of octadecyltrichlorosilane(OCT) in decane liquid, and normally
aligned cohesive film of stearic acid(SA) in octadecane liquid and in stearic acid solution with
decane as solvent.
In the case of the normally aligned film of OCT, as to film thickness during friction, elastic
response is observed up to relatively large normal force. On the other hand, height of oblique
aligned film of OCT indicates elastic/plastic response against normal force during friction. In this
case, the plastic strain of film height is quantized by lean by gap of all-trans configuration of alky
chain of OCT.
The normally aligned film of SA is also deformed elastically in lightly loaded friction or
plastically in heavily loaded friction in SA solution although, in decane solvent, it is destroyed
during friction from peripheral area of island as dissolution into decane solvent.
Keywords: mono-layer, boundary film lubrication, friction, elastic/plastic response, LFM
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52
The Resource Estimation of heavy-loaded friction units of internal combustion engine
E. Zadorozhnaya, I. Levanov
Russia, Chelyabinsk, South Ural State University, Department of Motor Transport,
Laboratory of Tribology
The task of boosting energy-efficiency and reliability of diesel engines is associated with the
improvement of the design of friction units, because the thermal loads, gas and inertial forces are
increasing. The integrated approach in the design of new engines is necessary. It takes into account all
important factors affecting the performance of the engine friction units. The most units of friction in the
engine are heavily loaded. In this case, the load changes over time in magnitude and direction. Therefore
approaches, which based on solving the problems of the dynamics and the hydrodynamic lubrication
theory of friction units in the present work, were used. Applied methods take into account the particular
geometry of friction units and crankshaft, non-Newtonian properties of the oils, operating parameters.
On the basis of experimental studies and modern methods of calculation the performance criteria of
hydrodynamic friction units were used: the minimum permissible lubricant film thickness; the maximum
permissible hydrodynamic pressure; the maximum permissible specific bearing load. The minimum
permissible lubricant film thickness is selected from the conditions for ensuring the hydrodynamic regime
of friction in heavy-loaded friction unit. The minimum lubricant film thickness must be more than the
average amount of micro-asperities of interacting friction surfaces.
The main condition for safe operation of friction units is to increase the minimum lubricant film
thickness hmin between the surfaces, for which does not take place the contact of micro-asperities. This
is achieved by the high precision machining of the friction surfaces, by the strict observance of round form
of shaft and bearing (for the case of circular-cylindrical unit of friction), by excluding distortions and
deformations, as well as a thorough cleaning oil.
The assessment of performance of bearings is based on calculating the hydro-mechanical
characteristics (GMC) of friction units. Furthermore zones, where the minimum lubricant film thickness is
less than the minimum permissible lubricant film thickness value h pr , were taken into account. If in
some moments of the engine work hmin  h pr , this means that in this area abnormality liquid
lubrication occurs and bearing operates under mixed lubrication during some part of the work engine
cycle.
Along with a minimum lubricant film thickness the maximum value of the hydrodynamic pressure
must be taken into account. They determine not only the carrying capacity of the bearing, but and the
fatigue life of the inserts of friction units.
The kit of the GMC, which is produced in a parametric studies of heavy-loaded friction units, allows
only indirectly assess their durability. The calculation of GMH is based on decision of three interrelated
problems: the calculation of the dynamics of mobile elements of tribo-units; the definition forces of the
hydrodynamic pressure in lubricating layer; the evaluation of thermal state of friction units.
The task of calculating the dynamics heavy-loaded friction unit reduces to determining the trajectory of
the mass center of each of the movable element under the influence of the external periodic load. The
trajectory is based on the coordinates that are obtained by solving the equations of motion. The field of
hydrodynamic pressures necessary for the calculation of the reaction of the lubricating layer, was
determined by integrating the Reynolds or Elrod equations subject to the availability the lubrication
sources on the friction surfaces (holes, grooves). Simultaneously, the rheological properties of the
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lubricant were involved. To assess the thermal state of friction units the isothermal or non-isothermal
approach was used.
The resource estimation of friction units is made on the basis of molecular-mechanical theory of
friction and wear fatigue theory (Kragelsky), as well as on the basis of the dynamics equations of wear
using the calculated GMH. The possibility of using the developed method was shown by the example of
calculating the dynamics of connecting rod bearings of the crankshaft of the engine.
Keywords: resource, heavy-loaded friction units, hydro-mechanical characteristics, bearing
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63
Tribological properties of friction pair Al2O3/IF-WS2 composite layer with the TG15 plastic
J. Korzekwa1,*, J. Pietraszek2, W. Skoneczny1
1
Faculty of Computer and Materials Science, University of Silesia, Sniezna Str. 2,
41–200 Sosnowiec, Poland
2
Faculty of Mechanical Engineering, Cracow University of Technology,
Jana Pawła II Ave 37, 31-864 Cracow, Poland
*
[email protected]
The aim of this study is to present the result of tribological tests and geometric structure of the
surface measurements. The top layer of anodized (porous) aluminium-oxide film was loaded with
fullerene-like nanoparticles (NP) of WS2 (IF-WS2). The impregnated IF nanoparticles are intended
to improve the wear resistance and reduce the friction of the top-layer [1, 2]. The tribological
properties was investigated by conducting wear tests of Al2O3/IF-WS2 coatings against TG15
plastic counterbody under pin-on-disk reciprocating motion. The friction coefficient was described
by the raw data obtained from the experiment. Such data were a set of stochastic signals probed
with a constant frequency. The data were smoothed by a moving average procedure [3] being a
low-pass digital filter. The smoothed data were modelled by a special kind of a piecewise linear
function being a specific parametric model [4]. The straight-line sections were combined by a
smoothing kernel what guaranteed differentiability class Cω required by a fitting procedure. The
parameters of the model were fitted as maximum likelihood estimates [5] with assumption that the
noise is an additive term of the model. The identified model was the base for further calculations.
Keyword: oxide layer, composite layer, lubricants,wear, friction coefficient
[1] L. Rapoport, N. Fleischer and R. Tenne, Applications of WS2 (MoS2) inorganic nanotubes and fullerene-like
nanoparticles for solid lubrication and for structural nanocomposites. J. Mater. Chem., 15, 1782-1788 (2005)
[2] R. Tenne and M. Redlich, Recent progress in the research of inorganic fullerene-like nanoparticles and inorganic
nanotubes. Chem Soc Rev. 39(5), 1423-1434 (2010)
[3] T.A. Runkler, Data Analytics. Models and Algorithms for Intelligent Data Analysis, Springer Vieweg, Wiesbaden,
2012.
[4] G.E. Gentle, W.K. Härdle, Y. Mori, Handbook of Computational Statistics. Concepts and Methods, Springer,
Berlin-Heidelberg 2012.
[5] S. Heinz, Mathematical Modeling, Springer, Heidelberg, 2011.
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69
Tribological behavior of epoxy and epoxy composites
Iulia GRAUR, Marina BUNEA, Iulian-Gabriel BÎRSAN, Vasile BRIA,
Adrian CÎRCIUMARU
Dunărea de Jos University, Galaţi, Romania
[email protected]
Despite their ecological disadvantages the epoxy resins are still used on a large number of
industrial and domestic applications firstly because of their versatility and secondly because of
their exceptional physical, mechanical and chemical properties. Showing poor electrical properties
the epoxies represent a challenge for the researchers and technological users who are seeking for
various ways to improve, at least, the electrical conductivity of polymers. The organic electronics
had opened a large and extremely promising window toward a trans-disciplinary domain of human
knowledge. It is well known that the best way to improve the electrical properties of a media is to
fill it with a significant amount of conductive elements. CNTs, fullerenes, graphenes, carbon black,
ferrites, various ionic compounds had been used as fillers in order to change the electrical behavior
of thermosetting polymers. Following this, path notable results had been achieved but always they
are associated with poor mechanical properties of materials due to the presence of fillers’ particles.
In other studies the influence of starch over the properties of epoxy resin had been investigated and
it was shown that an amount of starch of 10% volume ratio is not changes the basic properties of
the epoxy matrix excepting the transparency of the material and its chemical tenacity under the
action of high active solvents and acids. On another hand the starch is suitable to obtain chemical
complex substances which might place free radicals in epoxy’s volume. This study is developed to
analyze the effect of ultra-sonication over the properties of epoxy resin and over the properties of
starch filled epoxy compounds. The emphasis is on the tribological behavior of materials during
the pin on disk tests (with steel disk and epoxy pin) and also on wear behavior under abrasive
conditions (the steel disk covered with abrasive paper). The ultra-sonication was made in various
ways and the results of tribological analysis are presented respecting the ultra-sonication path.
Keywords: epoxy, starch, ultrasounds, wear
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Tribological analysis of fabric reinforced epoxy composites
Marina BUNEA, IULIA GRAUR, Adrian CÎRCIUMARU, Vasile BRIA,
Iulian-Gabriel BÎRSAN
Dunărea de Jos University, Galaţi, Romania
[email protected]
Thermosetting resins are extremely used in application in which reinforcements are
required due their sol-gel behavior which is allowing the immersion of the reinforcement elements.
As the epoxy resins are the most versatile polymers they are usually used to obtain reinforced parts
or structures for sport, domestic or transportation purposes. Generally they are used to cover
fiberglass agglomerations (uniformed or ununiformed) which are strengthening the structures and
improving the mechanical behavior of final product. Due to their properties the fabrics are indicated
when the goal is to achieve sinuous surfaces or shapes of final products together with the advantage
that fabrics, due to their structure, are keeping the spatial distribution of the fibers. In this regard it
is interesting to investigate the way to use fabrics (made of various fibers) in order to improve one
property or other of the final material or structure. More than that, it is good to know if there exists
any opportunity to use a fabric reinforced polymer as an electric capacitor. The materials used for
this study had been formed by a modified lay-up method with epoxy resin or filled epoxy resin as
matrix and various fabrics as reinforcements. All the fabrics used to form the materials are woven
simple type fabrics even if there might be necessary to study the effect of various fabric geometry
over the final properties of materials. Four types of fabrics were used namely carbon fiber, Kevlar,
fiberglass and a hybrid fabric made of carbon fiber, Kevlar, fiberglass in which thin wires of cooper
were uniformly placed. The tribological behavior of materials had been developed on the pin-ondisk geometry taking into account the fact that the sliding velocity may by parallel with or
perpendicular on the reinforcement layer. In the first case the main contribution belongs to the
fibers while in the second the main contribution belongs to the matrix-reinforcement interface. The
pin-on-disk geometry (with steel disk and composite pin) was used to analyze abrasive wear with
the disk covered with abrasive paper.
Keywords: epoxy, fabric, friction, wear
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82
Flammability of vegetal oils on hot surface
L.C. Solea, C. Georgescu, L. Deleanu
“Dunarea de Jos” University of Galati, 47 Domneasca, 800008 Galati, Romania
*Corresponding author: Lorena Deleanu ([email protected]).
There is a tremendous pressure in the research
world to replace mineral oils as this resource
could be extinguishing sooner as scientists have
been lately be estimated. The vegetal oils could
be solution for this problem but their atypical
behavior and their particular set of properties
constrain the users to do tests for certifying their
quality, especially for particular applications.
This paper presents the results of testing several
vegetal oils for ranking them taking into account
their flammability characteristics on hot surfaces.
Tests were done according to the procedure included
Fig. 1. The ignition temperature of the tested oils on hot surfaces
in SR EN ISO 20823:2004, with the help of test
(tests done according SR ISO 20283:2004, accuracy ±5ºC)
equipment designed by one of the author, in order to
have automation and security during the tests. The
testing method is designed to “imitate” the worst scenario that could happen when fluid leakage could reach
hot surfaces (the causes of having hot surfaces near fluid reservoirs or pipes could be technological ones or
the results of generate abnormally high temperatures, e.g. from friction processes). All oil grades were tested
under the standard conditions (10 ml ± 1ml of tested fluid dropped on the hot manifold in 50 s±10 s, initial
oil temperature: 20…25ºC). The ignition temperature for the vegetal oils is in a narrow range, this being,
with high probability, due to the similar composition in fat acids.
1st second
2nd second
9th second
Fig. 2. Rapeseed oil tested on the manifold having a temperature of 530ºC±5ºC
Keywords: vegetal oil, rapeseed oil, olive oil, corn oil, soybean oil, flammability on hot surface.
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Virtual evaluation of manufactured surfaces
– to use 3D data to predict performance
P-J Lööf4,B.-G. Rosén1 , F. Cabanettes2
1
Halmstad University, SE-301 18 Halmstad, Sweden ;
2
Enise France
*
Corresponding author: [email protected]
The manufacturing and finishing of gears include several processes such as grinding, hobbing,
shaving, honing, shot peening and phosphating. For the automotive industry it is a constant
challenge to improve durability and reduce fuel consumption - still being cost effective using robust
processes for mass manufacturing. A better knowledge of the properties of the manufactured
surfaces in gears, and especially how they interact in different combinations is an important
knowledge when designing gearboxes for the future. The following paper proposes a way to use
simulation software in combination with 3D measurement data to create a performance matrix to
use for choosing between known methods, but also a way to predict the behavior of new
combinations of process parameters in an early stage of the design process. The used simulation
method to predict the ability of a given manufacturing process to resist wear is a rough contact
model including elasto-plastic behavior of materials, computing parameters usable for ranking of
performance. Take off point for the study is a combination of industrial knowledge and sometimes
the feeling for what combinations are better than others. To create this virtual screening procedure
parts from several manufacturers with different processes are measured to gather surface data. In
total up to 20 different surface combinations are evaluated. As a result the simulation strategy used
emphasizes: i) a quick way to evaluate a new process ii) knowledge of the properties of used
processes iii) new light to the beneficial secrets of shot peening and phosphating of surfaces. The
future work for the developed performance matrix using this approach will be validation using a
rig test to compare the virtual performance screening with fatigue testing, looking for pitting
damages as an indicator of performance linked to surface stress and lifetime.
Keywords: gear manufacturing, 3D topography, virtual evaluation
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91
Modern Methods for Estimation of Triboresistance during Nanoscanning of Fiberglass
Surfaces
Victor Musalimov1, Pavel Kovalenko1*, Svetlana Perepelkina1
1
Saint-Petersburg National Research University of Information Technologies, Mechanics and Optics,
197101, Kronverkskiy pr., 49, Saint-Petersburg, Russian Federation.
*Corresponding author: Pavel Kovalenko ([email protected]).
This paper deals with the processes taking place during nanoscanning of surfaces of fiberglass
samples. Nanoscanning has been performed with the use of an atomic force microscope which is a
high-resolution scanning probe microscopy system. Atomic force microscopy (AFM) can be used
for scanning both conductive and non-conductive samples. Analysis of the data obtained from the
AFM system can provide us not only with the topographical image of the scanned surface, but also
with information about the forces of interaction between the sample and the probe, particularly
about the friction forces. Understanding of the processes taking place during nanoscanning,
including friction processes, gives us the opportunity to interpret the obtained results more
correctly. The aim of this research is to develop a method for estimation of friction parameters
during the probe and surface interaction in scanning probe microscopy systems (SPM). Particular
attention is given to estimation of triboresistance [1], which allows us to investigate how the sample
resists to the influence of the tip on it. This resistance depends not only on the forces of interaction
between the tip and the sample, but also on the internal friction in the surface layers of the sample.
Triboresistance helps us to estimate, in some degree, the internal friction in the scanned sample.
To estimate triboresistance, in the previous paper [1, 2], we have introduced action parameters.
According to our method, we have produced cumulative sums of rows and columns of measured
data. After that, we define the maximum value of spectral energy density, the maximum cumulative
value of spectral energy density, and the maximum frequency corresponding to the maximum value
of spectral energy density. Then we define two pairs of action parameters: one pair for data in
columns, and one pair for data in rows. Finally, we define triboresistance using the obtained action
parameters.
In this paper, triboresistance has been estimated for the fiberglass samples scanned with the
atomic force microscope.
Keywords: triboresistance, surface nanoscanning, scanning probe microscopy, action parameters,
internal friction.
References
1. V. Musalimov, P. Kovalenko, S. Perepelkina, Estimation of Triboresistance during Surface Nanoscanning,
Proceedings of WTC2013, Turin, Italy, ISBN 9788890818509.
2. V.M. Musalimov, O.E. Dik, A.E.Turin, Action Parameters of Energy Spectrum of Wavelet Transform, News of
High Education. Instrumentmaking, 52, 5, 2009, 10-15.
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Tribological study of some multilayered ceramic structures in the aeronautical industry
V.Manoliu, Gh.Ionescu, A.Stefan, A.Mihailescu, S.Ivan
Affiliation: National Institute of Aerospatial Research ''Elie Carafoli'',
B-dul Iuliu Maniu no. 220, sect 6, Bucharest, Romania
*Corresponding author: Manoliu Victor ([email protected])
The „hot parts” (combustion chamber, blades and shutters, cover plates, etc.) of the turbo
engines are subject to wear factors with pyrolyzed particles at speeds of up to 5-6 Mach, corrosion,
temperature, thermal shock, adhesive wear that may act simultaneously and harshly at high values.
Increased performance and endurance of the turbo engines can be obtained by using
multilayered micro and nanostructured ceramics.
This paper presents TBC- thermal barrier coating- elaborated structures based on Zirconia
that is doped with Ytrium and Cerium oxides, as well as rare earths, micro and nanostructured.
Tribologycal testing will illustrate the behavior of TBC layers at quick thermal shockheating/cooling speeds of 70°C/s – the most perturbing wear factor for ceramic layers, as well as
its response to adhesive wear, wear that occurs at the adjustable nozzle in turbo engines, through
the relative motion of the shutters and cover plates.
Thermal shock testing will be performed on a unique installation of authors and will
underline micro structural modifications that are dynamic induced by the gradual increasing of the
testing temperature.
The thermal shock behavior of the TBC elaborated structures, crucial to evaluating ceramic
materials for modern turbo engines, will be completed by adhesive wear testing that is associated
with the friction of shutters and cover plates conjugated surfaces.
Keywords: turbo engines, adhesive wear, quick thermal shock, TBC
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111
Study of Torque and Thrust of needle roller bearings
Tetsuzo Hatazawa and Takahisa Kawaguchi
Faculty of Engineering, Utsunomiya University, Japan, 1-2, Yoto 7-chome, Utsunomiya-shi,
Tochig, 321-8585, Japan
Presenting Author [email protected]
Needle roller bearing has a small diameter and large length of roller compared with other roller
bearings. Therefore, this bearing has higher load carrying capacity and stiffness. In addition, this
bearing is suitable for reciprocating motion because of small inertia. Beside, in case of solid type
needle roller bearing, outer ring, inner ring and needle with the retainer of this bearing can be
separated, these parts can set up to an axis or a housing, respectively. On the other hand, there occur
skewing phenomena in the rolling action of needle rollers in a bearing. As a result, thrust will occur
in the needle roller bearing causing from skewing which take place in the direction to the axial.
Therefore it is considered that performances of this bearing under various operating conditions are
not clear sufficiently.
In this study, influences of load, number of revolution and eccentricity of load on the torque and
thrust of needle roller bearing were investigated experimentally. In experiments, single type and
double type of bearing were used.
Keywords: needle roller, torque, thrust
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117
Friction of W-DLC(H) - testing in laboratory and motorcycle engine
P. Mutafov1 * , J. Lanigan2, A. Neville2, A. Cavaleiro3, T. Polcar1,3,4
1
Department of Control Engineering, Faculty of Electrical Engineering, Czech Technical University in
Prague, Technická 2, Prague 6, Czech Republic
2
iETSI, University of Leeds, School of Mechanical Engineering, Leeds LS2 9JT
3
SEG-CEMUC - Department of Mechanical Engineering, University of Coimbra, Rua Luís Reis Santos,
P-3030 788 Coimbra, Portugal
4
nCATS, University of Southampton, Highfield Campus, Southampton, SO17 1BJ, UK
* Corresponding author: Petr Mutafov ([email protected])
Automobiles constitute a significant part of motor vehicles globally. It is believed that the
overall number of cars around the world will exceed 2.9 billion by 2050. Bearing this number in
mind the reduction of friction in internal combustion engines by few per cent could not only bring
more effective powertrains but also save energy and money.
DLC coatings exhibit excellent wear resistance along with high hardness, thereby allowing
their potential application in combustion engines. On the other hand, the chemical interaction with
commercially available oils is very limited, which typically results in higher friction. The aim of
this study is thus to understand tribological behaviour of DLC in lubricated contacts.
Hydrogenated DLCs doped with tungsten were deposited by DC magnetron sputtering in
reactive atmosphere. Four targets in a semi-industrial chamber (Teer) were used: chromium to
deposit adhesion improving interlayer (app. 250 nm thick), two pure graphite targets and one
graphite target with embedded tungsten pellets placed into erosion zone. The tungsten content was
2-20 at.%, hydrogen content was 0-36 at.% resulting in amorphous morphology or nanocrystalline
with tungsten carbide nanograins embedded into amorphous carbon matrix. The hardness of DLC
increased from 10 to 15 GPa with increasing W content.
The coatings were tribologically tested in commercially available oil (Motul 5W-40) using
pin-on-disc tribometer (CSM Instruments). Selected coating was eventually applied on valve lifters
and tested in a Yamaha YZF-R6 motorcycle engine. The wear rate of coated surfaces after
laboratory and engine tests was very low with almost no wear marks, contrary to scratched noncoated steel valve lifters. Raman spectroscopy, HR-TEM and TOF-SIMS was used to identify
coating structure, sp2 /sp3 ratio and tribolayer formed on the coating surface. Despite chemical
inertness W-doped DLC(H) coatings react with oil additives forming a very thin (< 5 nm)
tribolayer.
Keywords: Tribology, DLC coating, motorcycle engine, Raman spectroscopy, Tof-SIMS
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131
Laboratory Investigations about the Mechanisms of Aluminium Transfer on Hot
Forming Tools
Jaume Pujante1, Giselle Ramírez1, Nuria Cuadrado1, Montserrat Vilaseca1, Daniel Casellas1
1
Department of Materials Technology, Fundació CTM Centre Tecnològic, Plaça de la Ciència 2, 08243
Manresa, Spain
The production of complex-shaped components from aluminium alloys offers a combination of light
weight and mechanical properties very attractive for the transport industry. However, the efficiency of
the process is limited by complex tribological interaction between tool and workpiece: galling in
aluminium forming is known to occur at temperatures as low as 100 ºC, and may increase in severity at
higher temperatures, resulting in lower part quality, intensive tool maintenance and increased cost.
In this work, the mechanisms resulting in transfer of aluminium on forming tools have been analised by
means of laboratory tests. The influence of chemical affinity in aluminium adhesion has been studied in a
series of high temperature contact tests, in which a 99% Aluminium ball has been pressed against tool
surface and separated at low velocity, measuring the force used in breaking the interface. On the other
hand, the role of mechanical interaction has been investigated using ball-on-disk sliding tests at high
temperature, using tool steel disks with different surface finish against an aluminium alloy counterpart.
Results show that both chemical affinity and mechanical interaction have relevant contribution in the
phenomenon of material transfer, and any solution designed to minimise adhesion must take into
account the combination of both factors.
Keywords: wear, metal forming, aluminium, high temperature, adhesion
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138
TiO2 and TiO2/Ag nanotubes as coatings for modern dental implants
Ż. Muchewicza, A. Radtkea, P. Piszczeka, T. Jędrzejewskib, W. Kozakb, S. Kącc
a
Faculty of Chemistry, Nicolus Copernicus University, Gagarina 7, 87-100 Toruń, Poland
b
Faculty of Biology and Environment Protection, Nicolaus Copernicus University,
Lwowska 1, 87-100 Toruń, Poland
c
Faculty of Metals Engineering and Industrial Computer Science, Department of Surface Engineering and
Materials Analysis, AGH-University of Science and Technology, al. A Mickiewicza 30, 30-059 Kraków,
Poland
The insertion of dental implants is a routine procedure in dentistry nowadays. Treatment with dental
implants allows outstanding aesthetic reconstruction with optimal masticatory function following
tooth loss. Modern dental implants usually have bioinert titanium surfaces and the healing rates are
over 97 %. Although the modern dentistry has high success rate in the implant technology, many
studies have demonstrated that they do sometimes fail due to peri-implant infection. Epidemiology
and etiology of early infection, which occurs before osseointegration, or late infection which occurs
after prosthetic rehabilitation, indicate on important role of implant materials in these risks. As
implant material differ in the ability of oral bacteria and yeast to form biofilms and colonize them,
they may reflect greater or lesser susceptibility for occurrence of peri-implant infection. It is
believed that bacteria and fungi adhering to the surface of the implant and forming biofilm play a
pivotal role in early peri-implant infection. They usually are difficult to treat, since biofilms show
high resistance to antimicrobial agents, especially when the causative microorganism is multi-drug
resistant.
Because there is still no way to complete elimination of microorganisms from the surface of the
implants after biofilm-associated infections has occurred, it is necessary to develop effective
prevention methods against microbial adhesion and subsequent invasion. Modification of titanium
implants with the compounds possessing antiadhesive or direct biocidal activity, as it is proposed
in the research project, seems to be an important strategy to prevent early peri-implant infection
and their later complications.
Given the fact that the vast majority of dental implants that come into use are made of titanium,
and on their surface there is always present 2-5 nm TiO2 layer (which is often formed in few
seconds after exposing pure titanium or its alloys to air), and that TiO2 exhibits antiseptic properties
(especially when doped by Ag, Au, Cu and Fe), it seems only reasonable and natural to coat
titanium implants with titanium dioxide layers doped with metallic silver nanoclusters. It should
be borne in mind that TiO2 coatings have a positive impact on the process of osseointegration. The
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16th Nordic Symposium on Tribology, Aarhus, Denmark
presence of a TiO2 coating at the implant site will highly likely promote above-average
proliferation of cellular bone matrix and lead to well concrescence between the bone and the
implant. At the same time doping of oxide films with metallic silver will lead to dispersion of Ag
clusters on the entire layer and will positively influence the effectiveness of their antibacterial
activity.
The results of studies on: (a) synthesis of TiO2 and TiO2/Ag nanotubes, (b) surface structure and
morphology, (c) photocatalytic activity and wettability of TiO2 andTiO2/Ag nanotubes, (d)
biological activity of TiO2 and TiO2/Ag nanotubes, and (e) abrasion and friction of TiO2 and
TiO2/Ag nanotubes coatings, will be presented.
Keywords: dental implants, titania nanotubes, silver nanoclusters, biological activity, abrasion,
friction
188
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