Monday, 11 October 2004 - 1:25 PM

This presentation is part of : Rajagopal Symposium

Entropy estimates and virtual thermomechanics for granular assemblies

Joe D. Goddard, University of California, San Diego, University of California, San Diego, Dept. MAE 0411, 9500 Gilman Drive, La Jolla, CA 92093-0411

This work provides an extension of previous works, dating back some thirty years on more, on maximum-entropy estimates for the micromechanics of granular assemblies. The focus here is on the statistical distribution of contact forces or particle displacements in quasi-static deformations.

The precise form obtained for probability density is shown to depend on the statistical weight assigned to elements in the state space of contact forces or particle displacements, a point overlooked in previous treatments. Comparisons are given with experiment and computer simulations for various assumed weightings.

A synthesis is given of previous descriptions of granular microstructure and micromechanics in terms of Delaunay-Voronoi tesselations. Based on this unified description, the formal methods of statistical thermodynamics are employed to establish a virtual thermomechanics, with no formal requirement of a granular temperature. This leads to an elastoplastic work function, of the type appearing in various phenomenological models of complex solids and fluids. The possibility of non-convexity leading to continuum- and meso-scale material instability is briefly discussed.

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