Strain localisation above the yielding point in cyclically deformed glasses

TL;DR

This study computationally investigates the yielding behavior of glasses under cyclic deformation, revealing shear band formation, energy changes, and the reversible nature of shear bands upon reducing deformation amplitude.

Contribution

It demonstrates the discontinuous formation of shear bands during cyclic deformation and their reversible healing, providing new insights into the microscopic mechanisms of yielding in glasses.

Findings

Shear bands appear discontinuously at yielding with a width of about ten particles.

Energy and density changes are localized within shear bands.

Shear bands can heal when cyclic deformation amplitude is reduced.

Abstract

We study the yielding behaviour of a model glass under cyclic athermal quastistatic deformation computationally, and show that yielding is characterised by the discontinuous appearance of shear bands, whose width is about ten particle diameters at their initiation, in which the strain gets localised. Strain localisation is accompanied by a corresponding change in the energies, and a decrease in the density in the shear band. We show that the glass remains well annealed outside the shear band whereas the energies correspond to the highest possible energy minima at the given density within the shear band. Diffusive motion of particles characterising the yielded state are confined to the shear bands, whose mean positions display movement over repeated cycles. Outside the shear band, particle motions are sub-diffusive but remain finite. Despite the discontinuous nature of their appearance, shear bands are reversible in the sense that a reduction in the amplitude of cyclic deformation to values below yielding leads to the healing and disappearance of the shear bands.