Universal, additive effect of temperature on the rheology of amorphous solids

TL;DR

This paper demonstrates that temperature has a universal additive effect on the rheology of amorphous solids, primarily lowering the stress at which plastic events occur without altering the underlying avalanche dynamics.

Contribution

It introduces a universal additive correction to the athermal stress in amorphous solids due to temperature, extending previous models and supported by numerical data.

Findings

Temperature decreases flowing stress significantly below the glass transition.

The athermal avalanche dynamics remain largely unaffected by temperature.

The universal additive correction accurately predicts stress behavior up to near the glass transition.

Abstract

Extensive measurements of macroscopic stress in a 2D LJ glass, over a broad range of temperatures ($T$) and strain rates ($\dot\gamma$), demonstrate a very significant decrease of the flowing stress with $T$, even much below the glass transition. A detailed analysis of the interplay between loading, thermal activation, and mechanical noise leads us to propose that over a broad ($\dot\gamma,T$) region, the effect of temperature amounts to a mere lowering of the strains at which plastic events occur, while the athermal avalanche dynamics remains essentially unperturbed. Temperature is then shown to correct the athermal stress by a (negative) additive contribution which presents a universal form, thus bringing support to and extending an expression proposed by Johnson and Samwer [1]. Our prediction is shown to match strikingly well numerical data up to the vicinity of $T_g$.