Uniaxial cyclic deformation and internal heat production of ultra-high molecular weight polyethylene

Abstract

The cyclic deformation and corresponding internal heat production of ultra-high molecular weight polyethylene (UHMWPE) polymer were investigated under the uniaxial strain-controlled and stress-controlled cyclic loading conditions. It is seen that the UHMWPE behaves basically a cyclic stabilizing feature since the responding stress amplitude does not remarkably change during the cyclic loading, except for that at high strain rate (where an obvious cyclic softening is caused partially by the thermal softening); an apparent mean stress relaxation occurs in the asymmetrical strain-controlled cyclic tests, and the degree of mean stress relaxation increases with the increasing mean strain; an obvious ratchetting takes place in the asymmetrical stress-controlled cyclic tests, and the ratchetting strain depends greatly upon the applied mean stress and stress amplitude, as well as the prescribed stress rate. Moreover, it is found that the temperature on the surface of specimen increases apparently in the uniaxial strain-controlled cyclic tests and the temperature variation becomes more remarkable when the prescribed strain rate is higher. However, the temperature variation is not so apparent in the uniaxial stress-controlled cyclic tests due to much smaller responding strain amplitude.