Discrete rearranging disordered patterns, part II: 2D plasticity, elasticity and flow of a foam
Laboratoire de Spectrométrie Physique, UMR5588, CNRS-Université Grenoble I, B.P. 87, F-38402, St Martin d'Hères Cedex, France
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Accepted: 15 February 2008
Published online: 30 April 2008
The plastic flow of a foam results from bubble rearrangements. We study their occurrence in experiments where a foam is forced to flow in 2D: around an obstacle; through a narrow hole; or sheared between rotating disks. We describe their orientation and frequency using a topological matrix defined in the companion paper (F. Graner, B. Dollet, C. Raufaste, and P. Marmottant, this issue, 25 (2008) DOI 10.1140/epje/i2007-10298-8), which links them with continuous plasticity at large scale. We then suggest a phenomenological equation to predict the plastic strain rate: its orientation is determined from the foam's local elastic strain; and its rate is determined from the foam's local elongation rate. We obtain a good agreement with statistical measurements. This enables us to describe the foam as a continuous medium with fluid, elastic and plastic properties. We derive its constitutive equation, then test several of its terms and predictions.
PACS: 83.80.Iz Emulsions and foams – / 83.10.Bb Kinematics of deformation and flow – / 62.20.F- Deformation and plasticity –
© EDP Sciences, Società Italiana di Fisica and Springer-Verlag, 2008