Mechanical Properties and Plasticity of a Model Glass Loaded Under Stress Control

TL;DR

This paper introduces a Monte-Carlo based method for studying the plasticity and failure of amorphous solids under stress control at various temperatures, revealing similarities with strain-control instabilities and higher yield stresses in glasses.

Contribution

A novel Monte-Carlo simulation approach enabling stress control loading in amorphous solids at any temperature, bridging a gap in understanding stress-controlled plasticity.

Findings

Crystals have the highest yield stress, glasses the lowest.

Glass exhibits higher yield stress than defective crystals despite more disorder.

Stress instabilities are saddle-node bifurcations similar to strain-control cases.

Abstract

Much of the progress achieved in understanding plasticity and failure in amorphous solids had been achieved using experiments and simulations in which the materials were loaded using strain control. There is paucity of results under stress control. Here we present a new method that was carefully geared to allow loading under stress control either at $T=0$ or at any other temperature, using Monte-Carlo techniques. The method is applied to a model perfect crystalline solid, to a crystalline solid contaminated with topological defects, and to a generic glass. The highest yield stress belongs to the crystal, the lowest to the crystal with a few defects, with the glass in between. Although the glass is more disordered than the crystal with a few defects, it yields stress is much higher than that of the latter. We explain this fact by considering the actual microscopic interactions that are typical to glass forming materials, pointing out the reasons for the higher cohesive nature of the glass. The main conclusion of this paper is that the instabilities encountered in stress-control condition are the identical saddle-node bifurcation seen in strain-control. Accordingly one can use the latter condition to infer about the former. Finally we discuss temperature effects and comment on the time needed to see a stress controlled material failure.