Discrete dislocation simulation of nanoindentation: Indentation size effect and the influence of slip band orientation

Nanoindentation is modelled on the computer by means of a simple two-dimensional discrete dislocation model in order to study the influence of the orientation of predefined slip bands on certain phenomena, which often occur during real indentation experiments, systematically. By assuming single slip, different simulations were performed, which show that the increase of the hardness with decreasing indentation depth, known as the indentation size effect, is significantly influenced by the slip band orientation in such a model. Compared to a case where the slip bands are oriented parallel to the surface, a less pronounced decrease of the hardness with increasing indentation depth is observed for the non-parallel slip band orientation. The value at which the hardness remains constant independent of the indentation depth is also significantly affected by these assumptions. Possible reasons for the origin of the different effects, which can partly be attributed to the discrete nature of plasticity, apparent in the nanometer regime, and Hall–Petch type mechanism, will be discussed.