Discrete dislocation plasticity analysis of contact between deformable bodies of simple geometry

A contact mechanical model is presented where both metal bodies can deform by discrete dislocation plasticity. The model intends to improve on previous dislocation dynamics models of contact, where only a plastically deformable body was considered, flattened by a rigid platen. The effect of the rigid platen was mimicked through boundary conditions acting on the deformable body. While the formulation is general, the simulations presented here are only performed for contact between a plastically deforming body with sinusoidal surface and a flat body that is either elastic or rigid. Results show that the contact conditions, i.e. frictionless and full stick, affect the morphology of the contact as well as the contact pressure distribution. This is because dislocations can glide through the frictionless contact and fragment it, but do not penetrate a sticking contact. Average quantities like mean apparent contact pressure and total plastic slip are, instead, independent of contact conditions and of the details of the contact area. A size dependence is observed in relation to the onset of plastic deformation, where surfaces with smaller wavelength and amplitude require a larger contact pressure to yield than self similar surfaces with larger wavelength. The size dependence is very pronounced when the flat body is rigid, but fades when the compliance of the flat body is large.