Influence of surface stress on the mechanical response of nanoporous metals studied by an atomistically informed continuum model

Abstract

The influence of surface stresses on the deformation behavior of nanoporous metals is considered to be the main reason for the tension-compression asymmetry observed in atomistic simulation studies of nanoporous metals. While it is difficult to differentiate between the contributions of linear and non-linear elasticity, dislocation activity, topology and surface stresses from atomistic simulations, continuum mechanics allow to disentangle these effects by systematically varying the applied constitutive relations. In this study, we investigate the elastic response of a nanoporous Au and Ag structure, both by molecular statics simulations and an elastic continuum model, which includes surface stresses and elastic anisotropy. The 3-dimensional periodic atomistic nanoporous structure is triangulated and transferred to the continuum model, where periodicity, elastic anisotropy, and surface stresses are considered. The results show that surface stress acts as a mechanical pre-load and that the elastic response is sensitive to the loading direction. An asymmetric behavior is observed in the elastic regime. Moreover, we show that sites, where dislocation activity is starting, show high von Mises stresses.