Jamming for a 2D granular material
Abstract
This paper focuses on the nature of jamming, as seen in two-dimensional frictional
granular systems consisting of photoelastic particles. The photoelastic technique
is unique at this time, in its capability to provide detailed particle-scale information
on forces and kinematic quantities such as particle displacements and rotations. These
experiments first explore isotropic stress states near point J through measurements
of the mean contact number per particle, Z, and the pressure, P as functions of the
packing fraction, . In this case, the experiments show some but not all aspects of
jamming, as expected on the basis of simulations and models that typically assume
conservative, hence frictionless, forces between particles. Specifically, there is
a rapid growth in Z, at a reasonable which we identify with as c. It is possible to
fit Z and P, to power law expressions in - c above c, and to obtain exponents that
are in agreement with simulations and models. However, the experiments differ from
theory on several points, as typified by the rounding that is observed in Z and P
near c. The application of shear to these same 2D granular systems leads to phenomena
that are qualitatively different from the standard picture of jamming. In particular,
there is a range of packing fractions below c, where the application of shear strain
at constant leads to jammed stress-anisotropic states, i.e. they have a non-zero shear
stress, τ. The application of shear strain to an initially isotropically compressed
(hence jammed) state, does not lead to an unjammed state per se. Rather, shear strain
at constant first leads to an increase of both τ and P. Additional strain leads to
a succession of jammed states interspersed with relatively localized failures of the
force network leading to other stress-anisotropic states that are jammed at typically
somewhat lower stress. The locus of jammed states requires a state space that involves
not only and τ, but also P. P, τ, and Z are all hysteretic functions of shear strain
for fixed . However, we find that both P and τ are roughly linear functions of Z for
strains large enough to jam the system. This implies that these shear-jammed states
satisfy a Coulomb like-relation, τ = μP. © 2010 The Royal Society of Chemistry.
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https://hdl.handle.net/10161/4125Published Version (Please cite this version)
10.1039/c000147cPublication Info
Zhang, J; Majmudar, TS; Sperl, M; & Behringer, RP (2010). Jamming for a 2D granular material. Soft Matter, 6(13). pp. 2982-2991. 10.1039/c000147c. Retrieved from https://hdl.handle.net/10161/4125.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
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Show full item recordScholars@Duke
Robert P. Behringer
James B. Duke Professor of Physics
Dr. Behringer's research interests include granular materials: friction, earthquakes,
jamming; nonlinear dynamics; and fluids: Rayleigh-Benard convection, the flow of thin
liquid films, porous media flow, and quantum fluids. His studies focus particularly
on experiments (with some theory/simulation) that yield new insights into the dynamics
and complex behavior of these systems. His experiments involve a number of highly
novel approaches, including the use of photoelasticity for probing granular
This author no longer has a Scholars@Duke profile, so the information shown here reflects
their Duke status at the time this item was deposited.

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