Simulated defect growth avalanches during deformation of nanocrystalline copper

Abstract

In this work we introduce a method to capture the proliferation of material defects that carry inelastic deformation, in microstructures simulated through isobaric–isothermal molecular dynamics. Based on the premise that inelastic dissipation is accompanied by a local temperature rise, our method involves analyzing the response of a chain of Nosé–Hoover thermostats that are coupled to the atomic velocities, while the microstructure deforms under the influence of a ramped external stress. We report results obtained from the uniaxial deformation of two nanocrystalline copper microstructures and show that our analysis allows the dissipative signal of a variety of inelastic events to be effectively unified via an ‘avalanche’ of dissipation. Based on this avalanche, we quantitatively compare dissipation for inelastic deformation under tension vs. compression, observing a significant tension–compression asymmetry in this regard. It is concluded that the present method is useful for discerning critical points that correspond to collective yield and inelastic flow.