Finite element analysis of interface cracking in sliding contacts

Abstract

The sliding failures of the Au/Ni/Cu multilayer structure used in electrical contacts have been found to be related to interfacial delamination. In this paper a plane strain finite element model for the growth of an interface crack in an elastic-plastic two-layer half-space is presented for a sliding contact. The elastic theories of interface cracking are briefly reviewed and the limitations of elastic solutions to the present problem are discussed on the basis of the finite element calculations. The elastic-plastic analysis has shown that the size of the plastic zone around the crack tips is comparable to the crack length and the coating thickness. Plastic deformation at crack tips expands primarily in two directions as predicted by a slip line field for a closed interface crack. The crack tip sliding displacement (CTSD), a measure of the growth rate of a closed interface crack, is calculated. Both the surface sliding friction and the crack face friction are found to have significant effects on the plastic zone size and the CTSD. The surface sliding friction tends to increase the plastic zone size and enhance the relative displacement of the crack faces in the direction of the friction force. The crack face friction, by contrast, considerably reduces the plastic zone size and the CTSD. The implications of these findings are also discussed.