Rotating Shear Tester

Rotating Shear Tester
SOLIDS PROCESSING
November 2002
Prepared by Brian Raber
LAB 2-Rotating Shear Tester
Purpose:
The purpose of this lab is to determine the powder properties that allow us to determine
whether selected powder samples will flow in funnel flow or mass flow in a given hopper design.
You will measure the yield loci on the rotating shear tester for internal friction and wall friction. (What
you do with this information will be given in class lecture). You will predict how your powder will
perform in a small-scale plexiglas hopper (mass or funnel flow). Last, you will load your powder into the
hopper and determine whether your predictions are correct.
Caution:
If available, read the MSDS on the powder or material you are using. When working with
powders on the shear test or the hopper the powder will get on the floor and tables. You must periodically
clean up the powder so that its presence does not become a safety or fire hazard. When you are done with
your experiments the lab area must be thoroughly swept, vacuumed, and/or dusted with the waste properly
disposed in the trash. If any test material is not contaminated, it may be returned to its original container
for future use.
Equipment and materials required:
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Dust masks (if powder disperses easily into the air), goggles, gloves (if required by MSDS), broom,
dustpan, vacuum (with HEPA filter to remove suspended dust).
Plexiglas hopper with adjustable opening.
Rotating shear tester, power supply, computer, Camille ™ data acquisition system.
Selected powder(s), powder scoop, spoon, spatula, rubber tubs.
Notebook, pencil, compass.
Rotating Shear Test start-up procedures:
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Read operating instructions Chapters 7-9 in Operating Instructions book. (You may copy pages out of
this book but make sure the book is returned to the lab.)
Turn on the computer and Camille using busbar switch. Turn on the monitor separately.
Plug-in and turn on the DC power supply. Plug the shear test wires into the DC power supply. The
plugs must follow this arrangement; plug black-to-black, red-to- red. The shear test power supply
must be set at 20 volts (gauge indicated, not by dial).
Power up the shear tester via switch on backside of instrument (do not start rotation). All electrical
equipment should be powered for 30 minutes before running the tests to allow them to reach operating
temperature and to ensure consistent measurement results.
Start Camille software and load the rotating shear test file. To do this, click on
START_PROGRAMS_CAMILETG_CAMILETG4.1.1. This should start the Camille program.
There may be more than one version of Camille on the computer, make sure you start version 4.1.1.
Go to FILE_OPEN and select ROTSHR to start the rotating shear test program. A schematic of the
rotating shear test with instrument tags for the load cell and the height measurement should appear.
We will ignore the height measurement other than to determine when the test material has reached
steady-state.
The shear test signal output cables must be plugged into the correct plug receptacles on the computer
box located on the side of the Camille test stand (position number must be correct and red-to-red,
black-to-black). The cables are labeled as to which ports they should be plugged into.
To check to make sure the Camille set-up is communicating properly with the RST, click on the RUN
button and run the program. You should see the screen change (grid lines disappear) and numerical
values should appear above the instruments on the screen. If you pull on one of the load cells where
the load beam connects you should see the numerical value change. This shows that the Camille is
detecting the output from the load cell. With no force applied the load cell output should be about
zero.
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Check to make sure the connections are working by moving the counter weight arm (should show a
change in height) and by nudging the load cells (should indicate a change in the load).
10. If the load cell needs calibrated, use the procedure described in Chapter 7 of the RST manual to apply a
known force on the load cell. With Camille running, you right-click on the measurement tag icon to
get an options menu, open PROPERTIES, and select CALIBRATION. Follow Camille calibration
procedures as described in the help utility.
11. Measure the diameters of the shear plates used in the experiments below to determine the surface area
of the applied shear. Record these values to use in your data analysis below.
Experimental:
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Place an appropriate amount of material to be tested into the shear plate apparatus. Do not overfill the
container. An appropriate amount of material is slightly less than filling. Take the cover plate and
lightly rotate it on the material to gain a slight packing of the material. Check for its evenness
(levelness of the cover plate) and consistency.
2. The test material must first be consolidated by pre-shearing at a known maximum normal load. After
the powder is pre-sheared and the bulk density of the powder has reached a steady value then proceed
with the yield loci tests.
3. To complete the pre-shearing, follow the instructions given in Chapter 8 of the RST instruction
manual.
4. For a given maximum normal load during pre-shearing, reduce the normal load and operate the shear
tester to determine the yield stress. Do this according to the instructions given in Chapter 8 of the RST
instruction manual.
5. You must repeat the above procedure for at least 5 different initial normal loads. These loads are 24kg,
20kg, 16kg, 12kg, 8kg. Do this by taking the test material and dumping it out and reusing it between
different initial normal loads.
6. If you should encounter a test material that exhibits slip-stop behavior (a noticeable jerking will occur
in the test apparatus and the output signal will fluctuate and not settle down), then use the following
instructions. If you do not have a slip-stop material, disregard the following instructions and go on to
number 7. The output signal you obtain should vary from a high value to a low value. Allow for the
high signal to settle down to a constant value, report this as the shear value for this data point (at a
given normal load). Take notice of the low value to determine the amount of fluctuation present in the
material. If the fluctuation between the high and low values is less than a 1/3 of the maximum reported
shear value, then multiply your flow function (used in the data analysis below) by 1.2. If the
fluctuation of the output signal is 2/3 the magnitude of your maximum value (i.e. high value=max, low
value =1/3 max value), then multiply you flow function by 1.4. If the output signal fluctuates more
than 2/3 from the reported maximum values, then multiply your flow function by 1.6.
7. Measure the wall yield loci. Use either stainless steel or plexiglas wall materials per your instructors
discretion. Samples of each wall material have been prepared for use in this measurement. Be sure
you use the correct shear plate and material holder for this portion of the experiment.
8. Follow the instructions above and in Chapter 8 for pre-shearing the material.
9. Start at a normal load of 24kg and come to a steady readout for the wall shear value. Reduce the
normal load by 2kg and run till steady shear value achieved. Repeat until you are down to 2kg and
then climb back up to 24kg by 2kg increments by re-adding the same weights you previously removed.
Report the steady output values obtained to use in the data analysis below.
10. Data analysis (Chapter 9 and from class notes).
Hopper test procedures:
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Set the desired opening size on the hopper (be careful to not drop the Plexiglas plates because they
may crack or chip).
Use a piece of Plexiglas to plug off the hopper exit (hold in place by hand).
Place capture vessel under the hopper opening.
Fill hopper with powder or test material to within a few inches from the top.
Remove the plug and observe from the side and top whether the hopper flows in funnel or mass flow.
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Clean-up:
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Clean up all powder spills and dispose of spilled powder.
Powder that has remained clean, not contaminated with other powders, may be returned to original
container.
Components of the shear tester and hopper should be emptied, brushed or vacuumed to remove
residual powder so that the equipment is available for the next experiment. Do not use compressed air
to clean components as this will disperse organic particles into the air thereby risking explosion or
flash fire.
If test material is difficult to remove, you may rinse the components with lukewarm water to rinse then
clean. Thoroughly dry the components after cleaning using paper towels and compressed air.
Equipment should be returned to its original storage place.
Turn off power to the RST using switch on backside of the instrument. Unplug the power cables for
the RST from the DC power supply.
Power down the Dc power supply. Turn off the Dc power supply and unplug.
Stop the Camille program run and shut down the program. Turn off the computer and Camille.
Unplug the signal connections.
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