Friction and wear behaviour of UHMWPE against titanium alloy ball and alumina femoral head due to torsional fretting

The torsional wear behaviours of ultra high molecular weight polyethylene (UHMWPE) were investigated in ball-on-plate torsional wear device. Alumina femoral head and Ti6Al4V alloy ball, were selected as the counterballs in this study. It was found that the torsional fretting running regimes transferred from partial slip regime (PSR) to slip regime (SR) were analysed, however the mixed fretting regime (MFR) was never appeared in this tests. In PSR (lower angular displacement amplitudes), slight damage occurred at small angular displacement and several wear appeared at large value. Adhesion appeared at the centre zone of all fretting scars in SR. Detachment of particles, ripples and ploughs were observed under higher angular displacement amplitudes. The UHWMPE/Ti6Al4V pair showed higher contact stiffness, friction torque, wear damage and material transfer than that of the presentation of UHWMPE/Al2O3 pairs. The wear mechanisms of UHWMPE/Ti6Al4V were combined with abrasive wear and delamination. The generation of radial ripples and micro-cracking were the main damage modes for UHMWPE/Al2O3.