Fatigue experiments with Lumikki

IMPORTANT!
Operator safety
• Do not place your hand in between the crosshead and the compression
plate unless the measurement device is on MODE 0! To operate the clamps,
use manual switches located in the clamp body (operator panel does not
work in 0 mode).
• In case the machine must be stopped immediately, press the red button
on the control panel. To release the button, rotate it clockwise.
• Upper safetylimit is 10 mm for force controlled pulling experiment (e.g.
paper creep). It takes more than 10 mm for clamps to stop moving.
General user rules
• Log out after your experiments for all machines.
• If somebody is logged in, you are not allowed kick him out. For example, if
you are trying to contact the computer remotely, click ”No”, when remote
desktop asks: ”User XYZ is logged in and his session will be closed. Do
you want to proceed?”
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Foreword
This is a list of instructions to bring the Instron measurement device and necessary camera gear on-line and to perform wood fatigue tests. Please read the
manual through before attempting to use the equipment. The Instron measurement device contain safety mechanisms to stop the user from harming it.
Nonetheless, care should be taken not to drive the crosshead into the sample
plate. This can cause damage to the force gauge (rather expensive) in the device.
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Before you start doing set of experiments
• Reboot windows (clear memory).
• Reboot instron (clear memory).
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Before starting each experiment
• Be sure that the Instron machine is calibrated. For example, in constant
strain compression experiments, the force indicator on Instron Computer
(second computer from left) should give 0.000 kN in the start.
• If needed, calibrate the machine (adviced later in Troubleshooting section).
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Checking that the camera takes good images
• Go to the Camera Computer (first computer from right) and open program
called Measurement & Automation Explorer.
• Choose from side bar menu: My System → Devices and Interfaces →
NI-IMAQdx Devices → cam0: DALSA Genie HM1024.
• Then, click button ”Grab”. Now, you should see a real-time video image
of the clamps/compression plates of the machine.
• With the ”video”, you can check if the camera takes proper images, the
sample piece is set straight, etc.
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Putting the sample to the machine
• Set the machine on MODE I, and move the clamps enough for setting the
sample piece right.
• Then, set the machine on MODE 0, to be sure that the clamps/compression
plates are not moving (onto your fingers) when you operate with the sample.
• Put the sample to the clamps/on the compression plate and check that
the camera image looks clear. Adjust lights, camera lenses, position of the
sample etc. if needed.
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• After all looks clear, switch the machine again on MODE II.
In some wood compression experiments, you can also put around the sample
black cardboard pieces (next to the machine or in the shelf in the neighboring
room) to avoid the pieces of explosively shattered samples from flying all over
the laboratory. The samples rarely break down in that way, but it is easier to
collect the pieces if it happens. Samples with vertical annual ring position are
in greatest risk to do this.
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Initial straightening/pinching of the sample
• Go to the Instron Computer and check that the Specimen Protect button
is on. The button can be recognized by shield image that turns green
when Specimen Protect is on.
• Then, go to the machine and move the clamps/plates in the way that either
the sample paper gets straightened or the sample wood piece gets pinched
between the compression plates. Specimen Protect makes sure that the
sample doesn’t get ripped or compressed too much, but the sample is just
adjusted to stay in place.
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Just before starting the experiment itself
• Turn off the Specimen Protect from the Instron Computer AND the Measurement & Automation Explorer from the Camera Computer. If the latter
one asks about saving, click ”No”.
• Then, go to Lumikki Computer (first computer from left) and open its
control tab from web browser. Name your experiment to the text field of
the front page.
• Then, click button ”Force status”, to make sure that all parts of the experiment machine are ready to measure.
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Starting the experiment
• Once the ”Force status” button tells that the whole experiment machine
is ready for measurement, click ”Run”.
• Now the experiment starts, and you can follow the stress-strain curve from
the Instron Computer, in LabVIEW window called startLogging.poller.
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After experiments
• Make sure that the machine isn’t gathering data anymore. In other words,
click button ”Stop” after each experiment, especially the last one. Otherwise, the experiment setting continues gathering data after you have left,
with may eventually fulfill the data storage of the computers.
• Put the machine to (analog) position control.
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Instron initialization
First, before anything else is done with the measurement device, it must be
initialized properly. In the case of compression tests, the measurement device
must be configured so that the crosshead does not reach the sample plate when
fully extended. Also setting proper safety limits and calibration are necessary.
To begin turn on the measurement device. The power switch is on the back
side of the gray box next to the concrete table. The device boots up for a while
and remains in MODE 0, untill at some point it can be switched to MODE I.
The device itself does not give any signal about this. but if you watch the log
on the TTM machine, you will notice activity when the measurement device is
ready to be switched to MODE I.
While the machine is booting up, check logs from the Instron control program
to see when the machine was used last. If you are confident that the machine
was last used for the same measurement and has been initialized already, you
can skip the rest of this section and set the machine on MODE I.
1. Set machine to MODE I.
• Clear all safety limits.
• Loosen the two black screw bolts. When open, the handles are to
be set downwards (as if they were valves). When closed, the handles
point inwards or toward each other.
• Lift the machine using the black rocker switch enough so that you
can fully extend the crosshead.
• Using the arrow buttons on the remote, extend the driver head fully
taking caution not to allow the driver head to touch the sample
pedestal.
• Using the black rocking switch, bring down the machine slowly until
there is only a small gap (about 0.5 mm) between the driver head and
the compression plate. Take care not to ram the driver head
into the compression plate!
• Secure the machine by tightening the screw bolts. Leave the handles
pointing towards each other.
2. Switch the machine to MODE II.
• Calibrate the force sensor by opening the force tab, clicking “Calibration” and then “Balance”.
• Set force safety limits to ±1000 N.
• Set digital position to zero by opening digital position tab, clicking
“Calibration” and then “Balance”.
• Set position safety limits to ±30 mm. To do this, you must set Instron to MODE 1 and moove the crosshead up a bit, as the crosshead
is bellow the −30 mm safety limit at this point.
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11.1
FAQ
How can I calibrate the force and position meters?
• Open the Instron panel and choose either Position or Load tab, depending
on which you want to calibrate.
• Here, open Primary Limits section from side menu, and take the ticks
away from parts ”Limit enabled” and ”Limit tripped”.
• Turn Specimen Protect off.
• Open Calibration section and click ”Balance”.
• Go back to Primary Limits section and put ticks back to ”Limit enabled”
and ”Limit tripped”. If needed, turn Specimen Protect on.
11.2
I have a problem with the Instron Computer, how
can I restart it?
• Close all programs.
• Restart the computer normally.
• Open the Instron Console and wait that its panel stops flashing or turns
green.
• Open LabVIEW from Start menu and choose there lumikkiInterface. Open
and activate all windows that end with ”.poller”.
• Go the the Instron Console panel, then its tabs Position and Load. Go
to Primary Limits section and put ticks to ”Limit enabled” and ”Limit
tripped” in both tabs.
11.3
I accidentally forgot to click ”Stop” after my last
experiment, and the computers continued data unnecessary gathering all the night. What should I do?
• Delete the experimental stress/strain data of the over-long experiment
from the Instron Computer and corresponding pictures from the Camera
Computer to free memory.
• Restart the Instron Computer and open necessary LabVIEW programs
(see the previous question).
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