Revisiting mean-field elasto-plastic models at the mesoscopic scale
Elisabeth Agoritsas (Université Grenoble-Alpes)
Encompassing very dissimilar systems (such as foams, emulsions, or granular materials), amorphous materials are composed of constituents of different shapes and sizes, such as bubbles in a soap foam or sand grains in a sandpile, so that they exhibit a structural disorder that plays a determinant role in their mechanical properties, while challenging their very description. Several elasto-plastic models have been developed at the mesoscopic scale, in order to account for the plasticity in sheared amorphous materials, such as the Hébraud- Lequeux (HL) model [P. Hébraud & F. Lequeux, Phys.Rev.Lett. 81, 2934 (1998)]. They have proven to be rather successful in reproducing certain features observed in amorphous systems, but not all at once. Moreover, a consistent picture connecting them is still missing. Here we discuss the physical ingredients that are put in such mean-field models, distinguishing between thermal and mechanical noises in the mean-field dynamics of amorphous materials. We focus in particular on the role of structural disorder, implemented by means of a distribution of energy barriers for the system to overcome locally when an external constant shear rate is applied to the material, and discuss specifically its implications for a generalization of the HL model [E. Agoritsas et al., Eur.Phys.J.E 38, 71 (2015)].