Title
Jamming and Dynamics of Granular Materials
Speaker
Robert P. Behringer (Duke University)
Abstract
This talk will consider the near-jamming behavior of granular systems
consisting of frictional particles. We have recently shown that there
exists a range of packing fractions for which it is possible to start
from zero stress states, and by applying shear strain, traverse a
regime of fragile states, ultimately arriving at a jammed state.
These results have been obtained by using photoelastic particles,
which allow detailed force and contact information, and from several
different kinds of experiments. The largest density, phi_J, for which
this behavior applies is comparable to the jamming density of
frictionless disks, and the lowest density for which this occurs,
phi_S, may be tied to the random loose packing density. Shear-jammed
states are characterized by anisotropy in various quantities such as
the stress stress, the fabric, and in general, the force networks.
Shear jamming is of particular interest for granular dynamics, since
many slow granular shear flows occur near this regime, and the arrest
of flow occurs due to shear jamming, not to isotropic jamming. For
example, Couette flow, flows in shear bands, and flows in hoppers may
all be influenced by shear jamming.
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