Abstract:
We have explored isotropically jammed states of semi-2D granular materials
through cyclic compression. In each compression cycle, systems of either
identical ellipses or bi-disperse disks, transition between jammed and unjammed
states. We determine the evolution of the average pressure, P, and structure
through consecutive jammed states. We observe a transition point, {\phi}m,
above which P persists over many cycles; below {\phi}m, P relaxes slowly. The
relaxation time scale associated with P increases with packing fraction, while
the relaxation time scale for collective particle motion remains constant. The
collective motion of the ellipses is hindered compared to disks, due to the
rotational constraints on elliptical particles.
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