Scaling Description of Creep Flow in Amorphous Solids

Abstract

Amorphous solids such as coffee foam, toothpaste, or mayonnaise display a transient creep flow when a stress ς is suddenly imposed. The associated strain rate is commonly found to decay in time as γ˙∼t-ν, followed either by arrest or by a sudden fluidization. Various empirical laws have been suggested for the creep exponent ν and fluidization time τf in experimental and numerical studies. Here, we postulate that plastic flow is governed by the difference between ς and the transient yield stress ςt(γ) that characterizes the stability of configurations visited by the system at strain γ. Assuming the analyticity of ςt(γ) allows us to predict ν and asymptotic behaviors of τf in terms of properties of stationary flows. We test successfully our predictions using elastoplastic models and published experimental results.