Analytical and experimental study of frictional behavior in through-thickness compression test

The through-thickness compression test is a simple method to measure the work hardening behavior in the biaxial stretching state. However, the friction between the platen and test sample is inevitable. For accurate stress and strain data, the effect of friction has to be corrected, so the accuracy of the test can be established. For the correction of stress and strain data, the frictional behavior of a lubricant, which is preferred to behave invariably under plastic deformation should be determined precisely and the contribution of friction to the flow stress quantitatively defined. In this paper, the frictional behavior of oiled PTFE film has been determined using ring compression and cylindrical compression tests. It is found that oiled PTFE film gives constant friction in compression for a strain interval of approximately 20%; the shear strength of the film is 10.3 MPa. Based on friction-hill analysis, the geometry of stacked specimen has been optimized, and a simple formula has been derived to correct the flow stresses determined in the compression test.