The Wear Process Between Normally Impacting Elastic Bodies

Abstract

The wear process between two elastic bodies, repeatedly impacting in an axially symmetric configuration is investigated analytically and experimentally. The mechanism initiating wear is that of surface fatigue, and the paper aims to explain the geometric process of wear formation beyond the “zero wear limit.” In doing so, an engineering, predictive model is sought, whereby the depth of a worn crater is related to the stresses arising during impact and to the number of loading cycles on the specimen. Four major accomplishments are embodied in the paper: (1) the quasi-static analysis of impact on a medium of nonuniform (cratered) surface geometry, (2) a heuristic derivation of the optimum wearpath, (3) derivation of the partial differential equation of normal impact wear, and (4) computation of the impact wear process for two discrete impact wear configurations and comparison of experimental work with the analytical results. The resulting conclusion is that impact wear proceeds at continuously varying curvature until the soft body conforms to the shape of the hard indenter. By equating the hysteretic wear energy with a fraction of the peak strain energy, quantitative wear history predictions are made for discrete geometries, such as a hard sphere impacting against a soft plane. Some experimental results are given between steel and aluminum specimens, confirming the analytical predictions.