Creep and fluidization in thermal amorphous solids

TL;DR

This paper models creep and fluidization in amorphous solids using a mesoscopic viscoplastic approach, revealing how stress redistribution and energy barrier distributions influence deformation behaviors.

Contribution

It introduces a mesoscopic model incorporating thermally activated yielding and barrier distributions, linking creep exponents to microscopic parameters and explaining fluidization dependence on stress.

Findings

Creep exponent relates to barrier distribution width.

Andrade creep involves local strain-hardening.

Fluidization time depends exponentially on applied stress.

Abstract

When submitted to a constant mechanical load, many amorphous solids display power law creep followed by fluidization. A fundamental understanding of these processes is still far from being achieved. Here, we characterize creep and fluidization on the basis of a mesoscopic viscoplastic model that includes thermally activated yielding events and a broad distribution of energy barriers, which may be lowered under the effect of a local deformation. We relate the creep exponent observed before fluidization to the width of barrier distribution and to the specific form of stress redistribution following yielding events. We show that Andrade creep is accompanied by local strain-hardening driven by stress redistribution and find that the fluidization depends exponentially on the applied stress. The simulation results are interpreted in the light of a mean-field analysis, and should help in rationalizing the creep phenomenology of amorphous solids.