Finite element solutions comparing the normal contact of an elastic-plastic layered medium under loading by (a) a rigid and (b) a deformable indenter

The main purpose of this paper is to assess the influence of a deformable indenter by comparing the finite element results for a deformable indenter with those of a rigid indenter. Elastic-plastic solutions for the case of a stiff hard layer rigidly bonded to a softer substrate are given and the effect of the indenters (i.e. rigid; deformable, E = 600 GPa; deformable, E = 1000 GPa) on the contact pressures and stresses and strains are critically examined. The results showed that, when the indenter is assumed to be rigid, the contact pressures in the elastic regime are higher than those given by the deformable indenters. However, as deformation proceeds and plasticity becomes dominant, the differences between the three sets of results reduce. The rigid indenter results were also shown to give the lowest peak radial tensile stress which is responsible for cracking of the film normal to the surface. Finally, comparison of the von Mises stress contours revealed that varying the indenter properties affects the point at which yielding commences. Results showed that the rigid indenter caused the coating and substrate to yield prematurely, i.e. at a lower load than the deformable indenters.