Creep dynamics of athermal amorphous materials: a mesoscopic approach

TL;DR

This paper presents a mesoscopic modeling approach to understand the complex creep and fluidization dynamics in athermal amorphous materials, reproducing experimental responses and revealing cooperative motion modes.

Contribution

It introduces a mesoscopic elasto-plastic framework that captures transient creep behavior and fluidization in athermal systems, linking microscopic dynamics to macroscopic responses.

Findings

Power-law increase of fluidization time near yield stress

Reproduction of experimental strain rate responses

Identification of cooperative motion modes during creep

Abstract

Yield stress fluids display complex dynamics, in particular when driven into the transient regime between the solid and the flowing state. Inspired by creep experiments on dense amorphous materials, we implement mesocale elasto-plastic descriptions to analyze such transient dynamics in athermal systems. Both our mean-field and space-dependent approaches consistently reproduce the typical experimental strain rate responses to different applied steps in stress. Moreover, they allow us to understand basic processes involved in the strain rate slowing down (creep) and the strain rate acceleration (fluidization) phases. The fluidization time increases in a power-law fashion as the applied external stress approaches a static yield stress. This stress value is related to the stress over-shoot in shear start-up experiments, and it is known to depend on sample preparation and age. By calculating correlations of the accumulated plasticity in the spatially resolved model, we reveal different modes of cooperative motion during the creep dynamics.