Effect of Surface Steps on Dislocation Structure During Nanoindentation

Abstract

ABSTRACTNucleation of dislocations during nanoindentation is a prime example of how nanoscopic details play an important role in the evolution of macroscopic mechanical behavior. Experimental studies of nanoindentation show that surface irregularities, such as steps, alter the mechanical response during indentation. Atomistic simulations using the embedded atom method are used to examine the indentation of a Au(111) crystal with a surface step. The amount of force needed to nucleate dislocations decreases significantly for indentation close to the step. A recently formulated atomistic deformation metric, the slip vector, is used to quantify dislocation content. This metric is used with the local atomic stress to determine the critical resolved shear stress necessary for dislocation nucleation. Atomic stress fields are also compared with continuum calculations performed using non-linear elasticity with a constitutive relation based on the same interatomic potential. This constitutive model shows good agreement of indentation forces and stresses with the atomistic simulations.