SCHEDULED MAINTENANCE
Dilatancy, shear jamming, and a generalized jamming phase diagram of frictionless sphere packings†
d
and
Srikanth
Sastry
a
Abstract
Granular packings display the remarkable phenomenon of dilatancy, wherein their volume increases upon shear deformation. Conventional wisdom and previous results suggest that dilatancy, also being the related phenomenon of shear-induced jamming, requires frictional interactions. Here, we show that the occurrence of isotropic jamming densities ϕj above the minimal density (or the J-point density) ϕJ leads both to the emergence of shear-induced jamming and dilatancy in frictionless packings. Under constant pressure shear, the system evolves into a steady-state at sufficiently large strains, whose density only depends on the pressure and is insensitive to the initial jamming density ϕj. In the limit of vanishing pressure, the steady-state exhibits critical behavior at ϕJ. While packings with different ϕj values display equivalent scaling properties under compression, they exhibit striking differences in rheological behaviour under shear. The yield stress under constant volume shear increases discontinuously with density when ϕj > ϕJ, contrary to the continuous behaviour in generic packings that jam at ϕJ. Our results thus lead to a more coherent, generalised picture of jamming in frictionless packings, which also have important implications on how dilatancy is understood in the context of frictional granular matter.
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