Three-dimensional jamming and flows of glassy materials

Guillaume Ovarlez (1) , Quentin Barral (2) , Philippe Coussot (3)

1 Rhéophysique
2 navier umr 8205 - Laboratoire Navier
3 Physique des milieux poreux

Various disordered dense systems (foams, gels, emulsions, colloidal suspensions) exhibit a transition from a liquid state to a solid state when submitted to an insufficient stress. The structure of such systems exhibits some analogy with that of glasses and is now being thoroughly studied with powerful means of 3D characterization. However, despite its huge importance for geophysical and industrial applications, their rheological behavior and its relation with jamming is still poorly known, in particular because of the nonlinear nature of flow equations. Here we show from two original experiments that a simple 3D continuum description of the behaviour of glassy materials can be built. We first show that when a flow is imposed in some direction there is no yield resistance to a secondary flow: these systems are always unjammed simultaneously in all directions of space. The 3D jamming criterion then appears to be the same as the plasticity criterion encountered in most solids. We also find that they behave as simple liquids in the direction orthogonal to that of the main flow; their viscosity is inversely proportional to the shear rate of the main flow, as a signature of shear-induced structural relaxation. Our approach provides a new way for probing the rheological behaviour of such materials, which makes it possible to build the general 3D form of the constitutive equation of glassy systems in a straightforward way from experimental data. These results also provide strong evidence that there are close similarities between temperature, density and shear rate in driving the structural relaxation of different glassy materials.

Domaines: Matière Molle [cond-mat.soft]

Guillaume Ovarlez, Quentin Barral, Philippe Coussot. Three-dimensional jamming and flows of glassy materials. Nature Materials, 2010, 9, pp.115 - 119. ⟨10.1038/nmat2615⟩. ⟨hal-00422092v1⟩