FINITE-ELEMENT ANALYSIS OF THE CONTACT STRESSES IN AN ELASTIC COATING ON AN ELASTIC SUBSTRATE

A finite element method has been used to investigate the contact stresses due to elastic indentation of coating/substrate systems consisting of a high modulus surface coating on a relatively low modulus substrate. Calculations have been made for two imposed pressure distributions identical to those arising during hertzian indentation of a homogeneous elastic half-space by spherical and cylindrical indenters respectively. For each distribution the stresses have been investigated in terms of the ratio of the Young moduli of the coating and substrate and the ratio of the coating thickness to the contact halfwidth. It has been shown that the stresses of both the outer surface of the coating and the coating substrate interface are complicated functions of the two variables and that the stresses which could be responsible for coating failure cannot simultaneously be minimized by appropriate choice of variables.