CONTACT MECHANICS OF ULTRAHIGH-MOLECULAR-WEIGHT POLYETHYLENE FOR ARTIFICIAL KNEE-JOINT

To investigate the wear mechanism of an ultrahigh-molecular-weight polyethylene (UHMWPE) for an artificial knee joint, the pin-on-disk-type wear test and the numerical analysis of contact mechanics of the UHMWPE were performed. In this analysis, to calculate the cyclic deformation of the UHMWPE, a constitutive equation for cyclic plasticity was used. In the initial stage of deformation, the UHMWPE was deformed only plastically; beyond this stage, however, wear of the UWMWPE progressed rapidly with weight loss. In this initial stage, shear stress and equivalent plastic strain were accumulated by cyclic loading on the contact surface of the UHMWPE and it was expected that the microcracks that create wear particles would be generated on the surface.