Numerical Investigations of Mechanical Responses, Friction and the Formation of Debris of UHMWPE in Total Joint Replacements

Finite element models are developed using ABAQUS and LS-DYNA to investigate the mechanical responses, friction and formation of debris in the contact of Ultra High Molecular Weight Polyethylene (UHMWPE) asperities with metal. The objective is to gain an understanding of wear particle generation mechanism in total joint replacements. Several types of materials including UHMWPE, High Density Polyethylene (HDPE) and Carbon Nanotube-reinforced High Density Polyethylene (CNT-HDPE) with different volume fractions of CNTs are selected to investigate the effect of material properties on friction coefficient. The plastic strain contour and stress contour are obtained in micrometer scale. To assess the influence of the material properties to friction coefficient, an energy-based model is adopted to calculate the plastic dissipation. Time averages of the friction coefficient are taken for comparison purposes. The finite element analysis and the energy-based model are capable of predicting the trend of the average friction coefficient changing with the material properties. A plastic strain damage model is used to investigate the formation of debris during the contact of an UHMWPE cup and a CoCr alloy femoral head in total hip joint replacement. The debris size predicted by the finite element model is consistent with some experimental results in the literature.