Liquid Foams Rheology

 

Coworkers: J. Scheibert, G. Debregeas

The evolution of a bidimensional foam submitted to oscillating and continuous quasistatic shearing is investigated experimentally and numerically. We extract, from the images of the sheared foam, the plastic flow profiles as well as the local statistical properties of the stress field. When the imposed strain becomes larger than the yield strain, the plastic events develop large spatial and temporal correlations, and the plastic flow gets confined to a narrow shear-band. This transition and the steady-state regime of flow are investigated by first focusing on the elastic deformation produced by an elementary plastic event. This allows us to understand (1) the appearance of long-lived spatial heterogeneities of the stress field, which we believe are at the origin of the shear-banding transition, (2) the statistics of the dynamic fluctuations of the stress field induced by plastic rearrangements in steady-state regime.

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Numerical simulation of a 2D sheared foam.

Presentation of the numerical model (french)

 

Continuous shear

 

Quastatic shear experiment on a confined 2D foam.