Multiaxial ratcheting behavior of PTFE at room temperature

A series of multiaxial ratcheting experiments have been performed on polyteterafluoroethylene (PTFE) solid cylindrical specimens. All the tests were conducted under cyclic shear strain with a constant axial stress at room temperature. The effects of axial stress, shear strain range, shear strain rate and their histories on the ratcheting behavior of PTFE were studied. It is shown that the ratcheting strain depends on the constant axial stress, cyclic shear strain range and shear strain rate. The ratcheting strain increases more rapidly as the constant axial stress or shear strain range become larger, or the shear strain rate is reduced. Furthermore, the loading histories also play an important role in the progress of ratcheting. The prior cycling with higher axial stress, larger strain range or lower strain rate greatly restrains ratcheting strain of subsequent cycling at lower strains. Such phenomenon is due to the enhancement of the material deformation resistance caused by the prior loadings.