Torsional friction behavior of the contact interface between the materials of an artificial knee joint replacement.

The torsional friction behavior of the materials (CoCrMo alloy and ultra-high-molecular-weight polyethylene (UHMWPE)) that are used in artificial knee joint replacement (AKJR) were investigated under dynamic loading. The torsional friction torque, wear loss and scars and stress distribution were analyzed and compared. The results show the following: (1) the friction torque declines rapidly at the beginning of the experiments, and meanwhile, the maximum normal load and the torsional angle amplitude show very little effect on the steady value; (2) the wear loss decreases with the increased torsional angle amplitude but increases with the increased maximum normal load; additionally, as the cycle times increase, the wear rate decreases, and the wear is minimal; (3) unloading and secondary loading significantly reduce the friction and wear of the materials, and thus, patients should rest after prolonged exercise to reduce wear; (4) the margins of UHMWPE and CoCrMo are worn, and the wear mechanism is abrasive wear; (5) around the center of the UHMWPE, the surface is peeled off, and the wear mechanism is fatigue wear; and (6) in terms of the compressive stress and shear stress, the calculated results from a finite element model match the experimental results well.