Modelling surface roughening during plastic deformation of metal crystals under contact shear loading

During plastic deformation, metal surfaces roughen and this has a deleterious impact on their tribological performance. It is therefore desirable to be able to predict and control the amount of roughening caused by subsurface plasticity. As a first step, we focus on modelling plastic deformation during contact shearing of an FCC metallic single crystal, employing a finite strain Discrete Dislocation Plasticity (DDP) formulation. This formulation allows us to capture the finite lattice rotations induced in the material by shearing and the corresponding local rotation of the crystallographic slip planes. The simulations predict a pronounced material pile-up in front of the contact and a sink-in at its rear, which are strongly crystal-orientation dependent. By comparing finite and small strain DDP, we can assess the effect of slip plane rotation on surface roughening and on metal plasticity in general. Results of the simulations are also compared with crystal plasticity, which is also capable of predicting a pile-up and sink-in, but not the crystal-orientation dependency of roughening.