A depinning approach of amorphous plasticity and dewetting

Overview & Synopsis

In the present thesis, two disordered systems are investigated from the depinning perspective. In both of them, the dynamics is governed by the competition between elastic interactions and a disordered landscape. In the first part, we use a simplified mesoscopic model to investigate the generic properties of amorphous plasticity. The yielding of amorphous materials shows universal properties similar to the depinning transition. As such, it is often described by mean field approaches. Here we show that the soft modes present in the interaction kernel (based on the Eshelby solution for a plastic inclusion in an elastic matrix) have a dramatic impact on localization and result in diffusively increasing plastic strain fluctuations. This additional phenomenology is absent in standard depinning and, despite its important consequences, is disregarded in mean field descriptions. We show that shear bands are soft modes of the Eshelby interaction kernel and, besides localization, they affect the universal properties as well. At the same time, we found by testing two extreme cases that the form of the disordered landscape has no considerable impact on the universal properties. As an application, we show that the reinforcement of amorphous materials by hard inclusions is related to the percolation of shear bands in between the inclusions. In the second part of the thesis, we study the morphology of a receding dewetting line on inhomogeneous surfaces. Unlike in standard depinning models, here we developed a method suitable to describe the large deformation regime of the contact line and tearing up of the layer. We show the existence of a threshold concentration of inhomogeneities. Above this concentration the line stops within at finite distance, and around the critical concentration it features critical-like properties.