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Apr 27, 2020: CEE C.C. Mei Distinguished Speaker Series- Prof. Jean-Louis Barrat at 1-190
April 27, 2020 @ 5:00 pm
I will present our current understanding, based on microscopic simulations and experiments, of the elementary mechanisms that govern the deformation and flow of amorphous materials. I will show how these mechanisms can be incorporated into simple lattice models governed by long-range elastic interactions. These elastoplastic models describe the deformation of amorphous solids through a simple lattice-based implementation of the scenario identified in numerous experiments and simulations: irreversible, “shear transformations”, take place in localized regions in the stressed material, and the corresponding stress release is transferred elastically to the surrounding medium. As a result of this supplementary load, new transformations may occur in cascade, resulting in a so-called “avalanche” behavior, with critical features (diverging size and power-law distributions) in the limit of large systems and low strain rates. This critical behavior has interesting similarities, but also deep differences, with other systems exhibiting avalanche behavior, such as elastic lines pinned by disorder. Elastoplastic models, with less severe size and time limitations than molecular dynamics simulations, are particularly useful to study these critical features. I will discuss the mean-field analysis of these models as well as fluctuation related issues such as the statistics of avalanche-like events.
My research interests are in the application of (essentially classical) statistical physics to various problems of condensed matter physics, engineering and materials sciences. My work generally involves a strong numerical component, from molecular dynamics and Monte Carlo methods to coarse-grained, mesoscale quasicontinuum approach. I view such
numerical approaches as an essential part of modern statistical physics when combined with theoretical analysis and experiments. Although I have been working on both equilibrium and nonequilibrium problems, my main interest lies in the understanding of transport phenomena and systems out of equilibrium. In recent years, my research concentrated on the physics of glassy systems and that of interfacial transport phenomena. Glassy systems are the paradigm of nonequilibrium statistical physics, and I was able to introduce
a number of new tools to analyze their behavior in numerical simulations. In particular, the study of controlled deformations provides a novel and interesting angle of attack on the physics of these systems, in terms of statistical as well as mechanical properties. Interfacial transport phenomena are essential in the physics of nanostructured materials or devices. The approach to heat transport and ow boundary conditions I proposed allows one to describe
in a consistent manner the complexity of nanostructured interfaces in terms of simple boundary conditions. My work is usually of a fundamental, rather than applied, nature. However, I often deal with subjects that touch upon elds close to actual applications and laboratory experiments. I have been able to stimulate the development
of a number of experiments by introducing new theoretical concepts and to establish connections with engineering
sciences. Examples of such connections include the rheology of complex systems, micro uidics, nanoscale heat transport or nanoporous materials. I also had the opportunity to collaborate with colleagues from earth sciences, astrophysics or computer sciences on subjects of common interest. On several occasions, such interactions involved co-supervision
of graduate students. I have also worked in close collaboration with some industrial research centers, in particular Michelin and L’Oreal. Since 2012, I divide my time between the Laboratory for Interdisciplinary Physics (as a director since 2014), a research
institute of about 160 members with a very broad range of experimental and theoretical activities, in which I have created the statistical physics and modeling team, and the Institut Laue Langevin theory group, in which I am in charge of the soft matter activities.