Shear bands in a continuum model of foams: how a 3D homogeneous material may seem inhomogeneous in 2D
Résumé
We describe possible conditions for stationnary inhomogeneous flow behaviour (sheared and blocked bands) in a continuous mechanical model of a soft visco-elasto-plastic material such as a foam or a concentrated emulsion under controled shear rate conditions. Usually, the occurence of shear bands in a complex fluid is understood as resulting from a structural evolution of the material under shear, which leads from a theoretical perspective to a non-monotonic stationnary flow curve. Our mechanical model predicts a non-monotonic flow curve, but a priori without any intrinsic physical evolution {\em via} a parameter coupled to the flow such as concentration of entanglements. Nevertheless, we predict the appearence of shear bands. In our case, the non-monotonic flow curve and the appearence of shear bands result specifically from the tensorial character of the underlying model (2D or 3D). For a Couette flow, a 3D tensorial formalism allows us to introduce an additional relaxtion freedom for the system in the third direction, which affects the material fluidity.
Domaines
Matière Molle [cond-mat.soft]Origine | Fichiers produits par l'(les) auteur(s) |
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