Roller Shear
The roller shear is used to determine the resistance to compression fatigue. The roller shear fatigues the sample dynamically with constant force both laterally and vertically.
The test is run as listed below:
Adjust the roller to obtain a constant force of 130 ± 2 on the foam specimen. This critical measurement may be made by fashioning a lightweight fabric sling around the roller at its center and measuring the force downward while holding the weighing scale vertically over the roller and maintaining the roller axis in a horizontal plane with the pivot axis.
Set the vertical adjustment of the roller or the mounting base by placing the specimen in position and lowering the roller so it is supported by the specimen. Observe the pivot axis and roller axis relationship and adjust the vertical height so that the axes lie in an essentially horizontal plane at the start of the test.
Mount the test specimen on the base platen with the long dimension parallel to the stroke of the dynamic fatigue machine and secure by means of the tape and metal-retainer strips. When mounting cored pieces, coring is to be against the platen. Set the counter to zero, start the machine, and fatigue test the sample for either 8000 cycles (Procedure A) or 20 000 cycles (Procedure B) or another number of cycles specified by the customer.