title: Dynamics of yielding observed in a three-dimensional aqueous dry foam.
abstract: We study the onset of yielding in stable three-dimensional dry foams following the start up of steady shear flow. By means of a charge-coupled device camera equipped with a small depth-of-field objective, we visualize the Plateau border network in the bulk of the foam. The onset of yielding is identified with the deformation gamma(c) for which shear induced rearrangements start occurring. We show that gamma(c) is independent of shear rate gamma; in a quasistatic regime whereas at high strain rates, a rapid increase of gamma(c) with gamma; is observed, in qualitative agreement with theoretical models. Moreover, spatiotemporal image analyses are used to determine the velocity profile in the gap. We find that this profile remains linear up to strains far beyond gamma(c). Moreover, we have studied the strain history dependence of gamma(c).
authors.affiliation: Laboratoire de Physique des Matériaux Divisés et des Interfaces, UMR 8108 du CNRS, Université de Marne-la-Vallée, 5 Boulevard Descartes, 77454 Marne-la-Vallée cedex 2, France.
authors.forename: Florence
authors.initials: F
authors.lastname: Rouyer
authors.forename: Sylvie
authors.initials: S
authors.lastname: Cohen-Addad
authors.forename: Michèle
authors.initials: M
authors.lastname: Vignes-Adler
authors.forename: Reinhard
authors.initials: R
authors.lastname: Höhler