The finite element analysis of a strain hardening layered medium under normal loading by (a) a rigid and (b) a deformable indenter

Abstract

The finite element method (FEM) is used to investigate the normal indentation problem of a deformable indenter in contact with a strain hardening substrate coated with an elastic—perfectly plastic layer. In order to assess the influence of the deformable indenter, the solution is compared with results of a rigid sphere indenting the same system. The comparison shows that, when the indenter is assumed to be rigid, the contact pressures are significantly higher than those for the deformable indenter during elastic deformation. When plasticity is more pronounced, the peak pressures at just inside the contact edge are also higher for the rigid indenter. Similarly, the results assuming a rigid indenter give a lower value of maximum radial tensile stress along the coating surface when compared with those using a deformable indenter, which is responsible for the cracking of the film. In order to examine the effects of strain hardening, the above solutions are compared with a system having an elastic—perfectly plastic substrate. Comparison between the two sets of results shows that the strain hardening medium develops a smaller contact area and higher central and peak contact pressures inside the contact edge during plastic deformation. It also shows that the use of a strain hardening substrate alleviates the maximum radial tensile stress just outside the contact edge.