Scaling Description of Creep Flow in Amorphous Solids

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