An Examination on Atomic-level Stress Calculations by Nanoindentation Simulation via the Quasicontinuum Method

Abstract

Nanoindentation simulations on single crystals Al and Cu via the quasicontinuum method have been performed. Two kinds of atomic-level local stress calculation methods, i.e. the coarse-grained local stress and the virial local stress, are employed to calculate the stress state of the contact area. Various comparisons between the coarse-grained local stress and the virial local stress have been made. Firstly, the averaged normal stress beneath the contact surface calculated by coarse-grained method agrees well with continuum mechanical pressure measurement, while the virial method gives unphysical results sometimes. Secondly, the coarsegrained results reflect the indenter size effect on the critical shear stress quite accurately, while the virial calculations fail. Thirdly, the distribution of maximum shear stress of the coarse-grained method predicts the defects nucleation locations reliably, while the distribution of virial local stress gives an incorrect prediction sometimes. Thus it is concluded that the coarse-grained method can offer a more reliable description of the local stress states of atoms in spatially inhomogeneous solids.