Brittle yielding of amorphous solids at finite shear rates

TL;DR

This study investigates how finite shear rates affect the transition from ductile to brittle behavior in amorphous solids, revealing rate-dependent stress overshoot and shear band formation through numerical simulations.

Contribution

It introduces a detailed analysis of the influence of shear rate on yielding and shear band patterns in amorphous solids, extending understanding beyond quasi-static conditions.

Findings

Finite shear rates increase stress overshoot in poorly-annealed systems.

Finite shear rates smear out discontinuous yielding in well-annealed systems.

Shear band size and spacing grow algebraically with inverse shear rate.

Abstract

Amorphous solids display a ductile to brittle transition as the kinetic stability of the quiescent glass is increased, which leads to a material failure controlled by the sudden emergence of a macroscopic shear band in quasi-static protocols. We numerically study how finite deformation rates influence ductile and brittle yielding behaviors using model glasses in two and three spatial dimensions. We find that a finite shear rate systematically enhances the stress overshoot of poorly-annealed systems, without necessarily producing shear bands. For well-annealed systems, the non-equilibrium discontinuous yielding transition is smeared out by finite shear rates and it is accompanied by the emergence of multiple shear bands that have been also reported in metallic glass experiments. We show that the typical size of the bands and the distance between them increases algebraically with the inverse shear rate. We provide a dynamic scaling argument for the corresponding lengthscale, based on the competition between the deformation rate and the propagation time of the shear bands.