title: Emergence of cooperativity in plasticity of soft glassy materials.
abstract: The elastic coupling between plastic events is generally invoked to interpret plastic properties and the failure of amorphous soft glassy materials. We report an experiment where the emergence of a self-organized plastic flow is observed well before the failure. For this we impose an homogeneous stress on a granular material, and measure local deformations for very small strain increments using a light scattering setup. We observe a nonhomogeneous strain that appears as transient bands of mesoscopic size and a well-defined orientation, which is different from the angle of the macroscopic frictional shear band that appears at the failure. The presence and the orientation of those microbands may be understood by considering how localized plastic reorganizations redistribute stresses in a surrounding continuous elastic medium. We characterize the length scale and persistence of the structure. The presence of plastic events and the mesostructure of the plastic flow are compared to numerical simulations.
authors.affiliation: Université de Rennes 1, Institut de Physique de Rennes (UMR UR1-CNRS 6251), Bât. 11A, Campus de Beaulieu, F-35042 Rennes, France.
authors.forename: Antoine
authors.initials: A
authors.lastname: Le Bouil
authors.affiliation: Université de Rennes 1, Institut de Physique de Rennes (UMR UR1-CNRS 6251), Bât. 11A, Campus de Beaulieu, F-35042 Rennes, France.
authors.forename: Axelle
authors.initials: A
authors.lastname: Amon
authors.affiliation: Université de Rennes 1, Institut de Physique de Rennes (UMR UR1-CNRS 6251), Bât. 11A, Campus de Beaulieu, F-35042 Rennes, France.
authors.forename: Sean
authors.initials: S
authors.lastname: McNamara
authors.affiliation: Université de Rennes 1, Institut de Physique de Rennes (UMR UR1-CNRS 6251), Bât. 11A, Campus de Beaulieu, F-35042 Rennes, France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Crassous