Precursors of fluidisation in the creep response of a soft glass

TL;DR

This study uses numerical simulations to identify precursors to fluidisation in dense amorphous materials under shear stress, highlighting finite size effects and providing a protocol to analyze bulk dynamics prior to yielding.

Contribution

Introduces a novel geometry-constrained simulation protocol to study fluidisation, enabling clear identification of precursors and finite size effects in bulk material behavior.

Findings

Peak in strain-rate fluctuations signals fluidisation precursors

Fluidisation time can be robustly defined from strain-rate fluctuations

Finite size effects influence the onset of fluidisation but not the creep exponents

Abstract

Using extensive numerical simulations, we study the fluidisation process of dense amorphous materials subjected to an external shear stress, using a three-dimensional colloidal glass model. In order to disentangle possible boundary effects from finite size effects in the process of fluidisation, we implement a novel geometry-constrained protocol with periodic boundary conditions. We show that this protocol is well controlled and that the longtime fluidisation dynamics is, to a great extent, independent of the details of the protocol parameters. Our protocol, therefore, provides an ideal tool to investigate the bulk dynamics prior to yielding and to study finite size effects regarding the fluidisation process. Our study reveals the existence of precursors to fluidisation observed as a peak in the strain-rate fluctuations, that allows for a robust definition of a fluidisation time. Although the exponents in the power-law creep dynamics seem not to depend significantly on the system size, we reveal strong finite size effects for the onset of fluidisation.