Giant fluctuations in the flow of fluidised soft glassy materials: an elasto-plastic modelling approach

TL;DR

This paper investigates how mechanical noise influences the flow behavior of yield stress materials, revealing a transition from localized to homogeneous flow and giant fluctuations, interpreted as an out-of-equilibrium phase transition.

Contribution

It introduces a mesoscale elasto-plastic model demonstrating noise-induced fluidization and flow transition phenomena in soft glassy materials.

Findings

Noise can induce fluidization in yield stress materials.

A transition from non-monotonic to monotonic rheology occurs with increasing noise.

The flow transition exhibits characteristics of an out-of-equilibrium phase transition.

Abstract

In this work we study the rheological features of yield stress materials that exhibit non-homogeneous steady flows and that are subjected to an additional mechanical noise. Using a mesoscale elasto-plastic model accounting for a viscosity bifurcation in the flow response to an external shear stress, we find that additional sources of noise can lead to a fluidisation effect. As we increase the noise intensity we evidence a transition from a non-monotonic to a monotonic rheology, associated with giant fluctuations of the macroscopic shear rate and long-time correlated dynamics. Although distinct noise models can lead to different rheological behaviours in the low stress regime, we show that the noise-induced transition from shear-localised to homogeneous flow at higher stresses appears very generic. The observed features in the dynamics can be interpreted as a result of an out-of-equilibrium phase transition, for which we estimate the critical exponents that appear to be independent of the specific choice of the noise implementation for the microscopic dynamics.