Why Do Granular Materials Stiffen with Shear Rate? A Test of Novel Stress-Based Statistics

Abstract

Recent experiments exhibit a rate-dependence for granular shear such that the stress grows linearly in the logarithm of the shear rate, \dotγ. Assuming a generalized activated process mechanism, we show that these observations are consistent with a recent proposal for a stress-based statistical ensemble. By contrast, predictions for rate-dependence using conventional energy-based statistical mechanics to describe activated processes, predicts a rate dependence that of (\ln (\dotγ))^{1/2}.

4 pages, 4 figures