ENERGY ABSORPTION IN A LOAD–UNLOAD CYCLE OF KNEE IMPLANT USING FRACTAL MODEL OF ROUGH SURFACES

Abstract

Roughness measurement of knee implant surfaces is investigated. The study of roughness measurement show that the topography of knee implant surface is multi-scale and surface spectra follows a power law behavior. A magnification of rough surface topography implies that there is no difference between original and magnified profile of implant surface. For implant surface, statistical parameters such as variance of height, curvature, and slope are found to be scale-dependent. Fractal representation of implant surface shows that the size-distribution of the multi-scale contacts spots follows a power law and is characterized by the fractal dimension of implant surface. Fractal surface description of the rough surfaces of knee implant is used to obtain force–displacement relationship of the contact force. Using an approximate function through the fusion of two piecewise functions, energy absorption of a knee implant in a single cycle of load–unload is obtained.