Influence of crystal anisotropy on elastic deformation and onset of plasticity in nanoindentation -- a simulational study

TL;DR

This study uses molecular dynamics and finite-element modeling to explore how crystal anisotropy affects elastic and plastic deformation during nanoindentation of copper and aluminum surfaces, revealing orientation-dependent elastic behavior and orientation-independent plastic hardness.

Contribution

It provides new insights into the influence of crystal surface orientation on elastic and plastic responses during nanoindentation, combining simulation methods for detailed analysis.

Findings

Elastic regime matches linear elastic theory for anisotropic materials.

Pressure hardening effects become evident with increased indentation depth.

Surface orientation influences force-displacement curves until plasticity occurs, after which it does not.

Abstract

Using molecular-dynamics simulation and finite-element modelling, we simulate nanoindentation into the three principal surfaces -- the (100), (110) and (111) surface -- of Cu and Al. In the elastic regime, the simulation data agree fairly well with the linear elastic theory of indentation into an elastically anisotropic substrate. With increasing indentation, the effect of pressure hardening becomes visible. When the critical stress for dislocation nucleation is reached, even the elastically isotropic Al shows a strong dependence of the surface orientation on the force-displacement curves. After the load drop, when plasticity ahs set in, the influence of the surface orientation is lost, and the contact pressure (hardness) becomes independent of the surface orientation.