Influence of pre-existing plasticity on nanoindentation: an atomistic analysis of the dislocation fields produced

Abstract

In atomistic simulations, nanoindentation is usually studied for ideal substrates. Here we explore the effects induced by pre-existing dislocations in the substrate on the indentation process. We find that the averaged response on the indenter (force, contact pressure) is close to that of an ideal crystal. Also the build-up of stress in the target, the creation of new dislocation lines and of junctions, and the size of the plastic zone show no significant differences. In detail, the evolution of stress with dislocation density follows the well-known Taylor hardening relationship, while the frequency distribution of dislocation segments approaches an exponential distribution, as postulated for work-hardened materials. We conclude that the present work justifies the use of ideal crystals in simulations of nanoindentation processes.