Discrete rearranging disordered patterns, part II: 2D plasticity, elasticity and flow of a foam.
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.
Marmottant
P
P
Laboratoire de Spectrométrie Physique, UMR5588, CNRS-Université Grenoble I, France. philippe.marmottant@ujf-grenoble.fr
Raufaste
C
C
Graner
F
F
D000465:Algorithms; D001696:Biomechanical Phenomena; D001709:Biotechnology / Q000379:methods*; D004548:Elasticity; D004655:Emulsions; D008422:Materials Testing / Q000379:methods*; D010969:Plastics / Q000737:chemistry*; D012399:Rotation; D014783:Viscosity
D004655:Emulsions; D010969:Plastics