| Summary |
Amorphous packings of spheres have been intensely investigated in order to understand the mechanical and flow behaviour of dense granular matter, and to explore universal aspects of the transition from fluid to structurally arrested or jammed states. Packings of rictionless spheres jam at the random close packing density, of about 64% in volume fraction. However, in the presence of friction, jamming can occur over a broad range of densities, down to the so called random loose packing limit, of 55% in volume fraction. This range also corresponds to interesting phenomena in granular and colloidal suspensions. Recent investigations have focussed on anisotropic packings of frictional grains generated by shear deformation leading to shear jamming, which occurs over a range of densities below the density at which frictionless spheres jam. With the aim of disentangling the role of structures induced by shear deformation and friction in generating shear jamming, we study sheared assemblies of frictionless spheres computationally, over a wide range of densities, extending far below their jamming point. We demonstrate the emergence of a variety of geometric features characteristic of jammed packings with the increase of shear strain. We thus argue that shear deformation alone is able to generate the necessary structures for shear jamming, while friction is instrumental in stabilising packings over a range of densities below the isotropic jamming point. We substantiate this claim by showing that configurations generated by shear deformation of frictionless sphere jam with no structural change upon the introduction of frictional forces, and further that contact forces leading to force balance for such configurations can be deduced from geometric information alone. These results provide a new perspective on random loose packing, and shear thickening behavior that arises above the corresponding density.
Speaker：http://www.jncasr.ac.in/sastry/
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