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Tinius-Olsen Torsion Testing Machine Procedure

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Last modified 09/24/2008

Tinius-Olsen Torsion Testing Machine Procedure
Only students or TAs who have been shown how to use the machine by ITLL staff may operate the Torsion Test Machine. TA supervision is preferable.
Description of Tinius-Olsen Torsion Tester:
This is a 10,000 in-lb. capacity torsion tester with a reversible electro-mechanical drive system having a 4-channel readout that includes an optical encoder for chuck position. The specimen is held between a loading (twisting) chuck and a weighing (stationary) chuck. Grips accept specimens of 5/16 to 1.5 inch in diameter. Special grip adapters will be required to test non-circular specimen. Controls are manual including rotational speed, direction of rotation, start and stop.
Equipment Setup:

  1. Plug the power cord into a LabStation, front panel outlet. Connect the 9 pin serial connector cable into the Serial A port (front panel) of your computer. If using strain gauges, carefully attach the military connector to plug P1A or P1B corresponding to the side of the LabStation you plan to use.

  1. If you are using strain gauges ensure the SCXI chasis is turned on.

  1. Log into the computer and find the LabVIEW program under the following path: “H:\ITLL Documentation\ITLL Modules\Torsional Testing Machine – Tinius Olsen”. Two LabVIEW VI programs are available, one for use with strain gauges and one without. Double click on the appropriate icon to load the program.

  1. The LabVIEW program will read all data and write to a text file that is readable by Excel or Matlab, for instance. Control of the machine is manual using front panel buttons and speed dial.

Operational procedure:

  1. Lock the rotatable wheels on the cart.

  1. If used, attach specimen to grip adapters by pressing specimen into appropriate adapter slots. Slide outside chuck along machine bed and open jaws of both chucks by turning CCW each of three hex head screws. Insert specimen and slide outside chuck towards inside chuck until it is stopped by the specimen end shaft. Pull the outside chuck back about 1/2 inch and tighten outside-chuck assembly to bed of machine (do not tighten the jaws of the chuck yet).

    1. Note: The clamp mechanism on the bed of the machine should be sufficiently tightened to prevent the outside chuck from lifting, yet loose enough for horizontal movement as the specimen changes length during testing.

  2. Reposition specimen midway between chucks. For each chuck, tighten the three jaws alternately, keeping reference lines on the grips concentric with the reference rings on the chuck faceplates.

    1. Note: Do not over-tighten chuck jaws, as this will prevent the self-tightening feature to operate properly. The gripping inserts in the jaws are designed to pivot in the direction of twist and increase clamping force as the applied force is increased.

  1. Ensure the safety shield is in place and the access door is closed before proceeding.

  1. Torque is displayed on channel 1 (first row). The letter F indicates torque sensor is in a fixed range and torque range must be selected manually. Ranges available are 500, 1000, 5,000 and 10,000 inch-pounds. In SI units the ranges are 50, 100, 500 and 1000 Newton-meters. Change the range by pressing SEL button ‘7’. Selecting an appropriate range is important as it determines data resolution. SEL button ‘1’ indicates the rate of change of torque.

  1. Twist angle is displayed on the second row. A displayed letter “A” indicates the sensor is auto ranging and does not require range selections. Twist angle is displayed in degrees. Speed of rotation is displayed, third row, right side with units of in/m or mm/m (SI). Note: “m” is minutes. Generally this rate indicator is not used even if it is displayed, as the rate is determined from the LabVIEW graph and adjusted using the speed dial setting. (See step 10.)

  1. Press and hold the ZERO button ‘8’ to zero the torque sensor before each test. Likewise, zero the encoder channel by pressing the ZERO button ‘2’. This zeros all initial conditions.

  1. Select direction of twist using front-panel toggle switch (forward or reverse). The drive chuck, which is closest to the controls, is marked to indicate direction of rotation.

Note: The direction of twist can only be changed when the drive motor is stopped.

  1. On the computer, run the LabVIEW program by selecting the right arrow button from the toolbar just under the top menus. Click on the selection bar near the bottom of the program to use either SI or English units. The display on the machine will change to show the selected units.

  1. The speed of rotation is controlled manually from a dial on the machine front panel. Speed dial units are in degrees/minute and are only approximate values. Set the desired speed of rotation and push the green START button. Usually, a setting of 5-15 deg/min is plenty fast. Speed can be adjusted while the drive motor is running, but use caution, as this dial is very sensitive.

  1. From your experimental write-up, or from your own estimate, note final limits of torque allowed. Do not exceed these limits unless you are taking the specimens to failure. Exceeding these limits will destroy the specimen. Monitor the test and note any observations and changes in specimen. Immediately press the red STOP button if any problems are noted or as limits are reached.

  1. Press the red STOP button on the machine when the test is complete. Then select the STOP&SAVE button on the LabVIEW program to stop taking data. When the STOP&SAVE button is selected a dialog box will appear and you will be asked where you want to save your data file. DO NOT select cancel from the dialog box or your data will be LOST. DO NOT save your file in your class directory or anywhere else where you do not have write privileges or the data will be lost. You may save the file in your personal directory (Z:), the Public folder inside your class folder or to a USB flash drive. The program saves all the data from the time the run arrow button is selected until the STOP&SAVE button is selected. The data is saved to a tab delimited text file that can be opened in Excel. DO NOT use the File\Save option from the menu as this saves the LabVIEW program itself and NOT your data.

  1. When testing is complete you must run the machine in the opposite direction until the force display reads ZERO pounds. The testing sample must be unstressed before you try to remove it. Often this does not correspond to a zero angle reading due to slippage!

  1. When you are finished unplug the power and serial cables & log off the computer. Unlock the cart’s wheels and return the Torsional Tester to the module bay (2B60).

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