Material BehaviourUniaxial ratcheting behavior of polytetrafluoroethylene at elevated temperature

A series of uniaxial ratcheting experiments has been carried out on cold compaction polytetrafluoroethylene (PTFE) specimens. All the tests were performed under stress control at elevated temperature. The effects of mean stress, stress amplitude, applied temperature and their histories on the ratcheting behavior of PTFE were studied. It is shown that, as the applied temperature was raised, the elastic modulus of PTFE declined rapidly. The ratcheting strain increased as the mean stress, stress amplitude and temperature increased. Especially, when the temperature was over 100 °C, the ratcheting strain accumulated rapidly. Furthermore, the loading histories also play an important role in the progress of ratcheting. Previous cycling with higher mean stress and stress amplitude greatly restrains ratcheting strain of subsequent cycling at lower ones. Such a phenomenon is due to the enhancement of the material deformation resistance caused by the previous loadings. As the applied temperature changes, the ratcheting strain still accumulates along the direction of mean stress.