Why do granular materials stiffen with shear rate? Test of novel stress-based statistics.
Recent experiments exhibit a rate dependence for granular shear such that the stress grows linearly in the logarithm of the shear rate, gamma. 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 of (ln(gamma))(1/2).
Department of Physics, Duke University, Box 90305, Durham, North Carolina 27708, USA.
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Behringer
Dapeng
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Chakraborty
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Henkes
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Hartley