Three-dimensional contact analysis of layered elastic/plastic solids with rough surfaces

A three-dimensional numerical model is presented to investigate the contact behavior of layered elastic/plastic solids with rough surfaces. The surface deformation and pressure distributions are obtained based on a variational principle with a fast Fourier transform (FFT)-based scheme. The surface and subsurface stresses in the layer and the substrate are determined and a von Mises yield criterion is used to determine onset of yield. The model is applicable for both single-asperity contact and multiple-asperity contact. Three-dimensional layered elastic/plastic solids with rough surfaces are generated on the computer with specified standard deviation of surface heights, correlation length, layer thickness, stiffness and hardness ratio of the layer to the substrate. The contact statistics of layered solids under a designated normal load are predicted, namely, the fractional contact area, contact pressures, surface and subsurface stress, and relative meniscus force. These contact statistics are used to investigate friction, stiction, and wear problems such as debris generation, brittle failure, and delamination. The results yield insight into the effects of the layer, surface roughness, and normal load on the tribological performance of layered elastic/plastic solids. It allows the specification of layer properties to realize elastic contact and to reduce wear of materials. Optimum layer parameters are identified to provide low friction, stiction and wear.