The 2-dimensional nano-indentation of a circular Brinell indenter into a monocrystalline metallic thin film, bonded to a rigid substrate, was investigated. The simulation method involved coupled atomistics and discrete dislocations. This linked a continuum region, containing any number of discrete dislocations, to an atomistic region and permitted the accurate automatic detection and passing of dislocations between the atomistic and continuum regions. The model permitted the detailed study of nano-indentation to large penetration depths (up to 60Å), using only a small region of atoms just below the indenter, where dislocation nucleation, cross-slip and annihilation occurred. Indentation of a model hexagonal Al crystal led to the onset of homogeneous dislocation nucleation at points away from the points of maximum resolved shear stress, and to a size-dependence of the material hardness. It also revealed the role of dislocation dissociation in deformation, reverse plasticity (including the nucleation of dislocations upon unloading and annihilation) and permanent deformation (including surface uplift) after full unloading. Finally, the effects of film thickness upon the load–displacement response and differences between displacement and force-controlled loading were modelled. This demonstrated the power of the coupled atomistics and discrete dislocation method in simulating both long-range dislocation plasticity and short-range atomistic phenomena. It permitted the study of the physical and mechanical effects of complex plastic flow and non-continuum atomistic-level processes upon the macroscopic response under indentation loading.

A Coupled Atomistics and Discrete Dislocation Plasticity Simulation of Nanoindentation into Single Crystal Thin Films. R.E.Miller, L.E.Shilkrot, W.A.Curtin: Acta Materialia, 2004, 52[2], 271-84