Nonlinear plastic modes in disordered solids
Orateur : Edan Lerner
Institute for Theoretical Physics, University of Amsterdam, The Netherlands
Résumé : Understanding the yielding transition observed upon deforming a glass beyong its elastic limit requires the proper identification of the objects, akin to dislocations in crystals, that carry plastic flow. In my talk I will introduce a theoretical framework within which a robust, micro-mechanical definition of precursors to plastic instabilities in glassy solids, often termed `soft-spots’, naturally emerges. They are shown to be collective displacements pi^, referred to here as `plastic modes’, that lead to transitions over energy barriers in the glass. We demonstrate how plastic modes can be calculated without resorting to conventional harmonic eigen mode analyses, but instead by properly accounting for nonlinearities of the potential energy landscape. Using our theoretical framework, we rigorously derive an equation of motion that describes both the coupling of plastic modes to external deformation, and the resulting mechanical destabilization process, and validate it via numerical simulations of model glasses. We further demonstrate how a heuristic search for nonlinear plastic modes in a-thermally deformed glassy solids can a-priori detect the locus and geometry of imminent plastic instabilities with remarkable accuracy, at strains as large as g-gc 10^-2 away from an instability strain gc.
Date et lieu : le Vendredi 6 Mai 2016 à 11h, salle 250, IUSTI