A Comparative Study on the Fretting Behaviors of Human Femur Compact Bone under Tangential and Radial Fretting Models in vitro

Testes of two fretting modes (i.e. tangential and radial fretting) of human human femur cortical bone against TA2 ball in vitro have been carried out under the varied imposed normal loads. Much severer surface damage occurred at high displacement amplitudes under the testing of tangential fretting than that of radial fretting. Ploughs and detachment of particles were observed in the wear scars of tangential fretting specimens. Combination of abrasive wear and delamination was the mechanism of tangential fretting of cortical bone. The results under radial fretting condition show that circumferential lamella of osteon presented a better resistance than that of interstitial lamella. Micro-cracks and delamination occurred primarily at the edge of contact zone. It was found that Haversian system of cortical bone played an important role under the two fretting modes. Tthe liquid exudant come from the degradation of bone was played an important role as a lubricant.