Effect of Residual Stress in Surface Layer on Contact Deformation of Elastic-Plastic Layered Media

The effect of residual stress in the surface layer on the deformation of elastic-plastic layered media due to indentation and sliding contact loading and unloading was analyzed with the finite element method. A three-dimensional finite element model of a rigid sphere interacting with a deformable layered medium was developed, and its accuracy was evaluated by contrasting finite element results with analytical solutions for the surface stresses of an elastic homogeneous half-space subjected to normal and friction surface traction. Deformation of the layered medium is interpreted in terms of the dependence of the von Mises equivalent stress, first principal stress, and equivalent plastic strain on the magnitudes of residual stress and coefficient of friction. The effect of residual stress on the propensity for yielding and cracking in the layered medium is discussed in the context of results for the maximum Mises and tensile stresses and the evolution of plasticity in the subsurface. It is shown that the optimum residual stress in the surface layer depends on the type of contact loading (indentation or sliding), coefficient of friction, and dominant deformation mode in the layer (i.e., plastic deformation or cracking).