Microscopic destruction of ultra-high molecular weight polyethylene (UHMWPE) under uniaxial tension

To examine the effects of a networked substructure of granular agglomerate on a style of destruction in prosthetic ultra-high molecular weight polyethylene (UHMWPE), uniaxial tensile simulations were carried out using the numerical model based on the discrete element method (DEM). The numerical simulations were performed taking the difference of mechanical characteristics between inter-granular and intra-granular portions of UHMWPE into consideration. A significant increase in stress and strain was observed along grain boundaries where micro cracks were initiated. This finding suggests that the large difference of mechanical properties between intra-granular and inter-granular portions causes significantly increased local stresses and strains in the vicinity of grain boundaries. The tensile simulation resulted in intra-granular destruction, which had good agreement with a result of previous experimental observation. This is presumably because the directions of principal shear stresses do not coincide with those at stress-concentrated grain boundaries. The dependence of the style of material destruction on forms of loading application could be explained by the relationship between directions of principal shear stress and reorientations of stress-concentrated grain boundaries.