Session H13: Focus Session: Jamming Theory and Experiment I

8:00 AM–11:00 AM, Tuesday, March 22, 2011
Room: D225/226

Sponsoring Unit: GSNP
Chair: Mark Shattuck, City College of New York

Abstract ID: BAPS.2011.MAR.H13.9

Abstract: H13.00009 : Shear-jammed states in granular materials

10:00 AM–10:12 AM

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  Dapeng Bi
    (Brandeis University)

  Jie Zhang
    (Indiana University - Purdue University Fort Wayne)

  R.P. Behringer
    (Duke University)

  Bulbul Chakraborty
    (Brandeis University)

For frictionless particles with purely repulsive interactions, there is a critical packing fraction $\phi_J$ below which no jammed states exist. Experiments by Zhang \& Behringer on physical granular systems show jammed states in the regime of $\phi < \phi_J$ can be created by the application of shear stress. Compared to the states above $\phi_J$, the shear-jammed states are mechanically more fragile, but they resist shear. These shear-jammed states cannot exist under isotropic stress. Rather, their formation require the anisotropic contact network as a backbone which is created by an applied shear stress. The anisotropic components of the stress tensor and contact network fabric tensor form a classic hysteresis loop suggesting an analogy to ferromagnetic behavior and critical phenomena. These new states must be incorporated into a more general jamming picture. We also carry out extensive analysis on shear-jammed states and find local stress fluctuations are controlled by their respective global pressures. To explain the scaling of local stress fluctuations, we construct a mean-field model based on the entropy of stress configurations.

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