The coated surface hardness: a kinematic model

A study of the mechanical behaviour of a composite ®lm-substrate material during the hardness test is undertaken. An analytical calculation is proposed applying the kinematic model to the case of the coated spherical cavity problem. The aim of this paper is to discuss the parameters that in ̄uence the mechanical behaviour, in order to understand the observed experimental results. The parameters studied are the size of the plastic deformed region, the ratio between the yield stresses of the ®lm and the substrate and the relative work-hardening ratios of both materials. The results show that an important parameter that in ̄uences the composite behaviour is the size of the plastic deformed region. The other parameters play an important role in the de®nition of the size of this region and in ̄uence the hardness behaviour as well in a direct way. q 1998 Elsevier Science S.A. All rights reserved.