Torsional fretting wear behaviour of nature articular cartilage in vitro

Torsional wear tests of bovine hip joint articular cartilage against Al2O3 femoral heads with a diameter of 28 mm were carried out on a new torsional fretting wear apparatus. The damage characteristics of articular cartilage were discussed in detail based on an analysis of frictional kinetics behaviours, SEM observations and hematoxylin-eosin staining. The results indicated that the behaviours of torsional wear were strongly dependent on angular displacement amplitudes and the number of cycles, which can be characterised by the curves of friction torque/angular displacement (T-theta). Three kinds of T-theta curves (i.e., linear, parallelogram, and elliptical curves) were observed during the process of torsional fretting wear and during the use of articular cartilage while running in partial slip and gross slip conditions. Along the radial direction, the wear scar could be divided into three parts, namely, the central sticking zone, the radial ridges and micro-crazes zone and the detachment zone. With an increase in angular displacement amplitude, the netlike shape ridge can be observed along the radial direction from the contact centre. The wear mechanisms of the cartilage was mainly similar to fatigue wear or similar to the mechanism of delamination in metal materials. Copyright (C) 2011 Inderscience Enterprises Ltd.