Power fluctuations in sheared amorphous materials: A minimal model

TL;DR

This paper introduces a mean-field elastoplastic model to study power fluctuations in sheared amorphous materials, revealing how fluctuations behave near the liquid-solid transition and connecting predictions with numerical experiments.

Contribution

It presents a novel minimal model capturing stress and strain-rate fluctuations and analyzes their power distribution under steady shear flow.

Findings

Negative power fluctuations are suppressed near the liquid-solid transition.

A fluctuation relation exists in certain regimes, with tails described by stretched-exponential distributions.

Different mechanisms govern negative power fluctuations in liquid and solid phases.

Abstract

The importance of mesoscale fluctuations in flowing amorphous materials is widely accepted, without a clear understanding of their role. We propose a mean-field elastoplastic model that admits both stress and strain-rate fluctuations, and investigate the character of its power distribution under steady shear flow. The model predicts the suppression of negative power fluctuations near the liquid-solid transition; the existence of a fluctuation relation in limiting regimes but its replacement in general by stretched-exponential power-distribution tails; and a crossover between two distinct mechanisms for negative power fluctuations in the liquid and the yielding solid phases. We connect these predictions with recent results from particle-based, numerical micro-rheological experiments.