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Granular Flows in the Elastic Limit

Published online by Cambridge University Press:  01 February 2011

Charles S. Campbell*
Affiliation:
Department of Mechanical Engineering, University of Southern California, Los Angeles, CA 90089–1453
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Abstract

This paper describes recent computer simulation studies into the rheological behavior of granular materials in the regime that lies between the quasistatic and rapid-flow regime. This investigation was prompted by studies of landslides, hopper flows and the “phase change” (i.e. the change between solidlike and fluid-like behavior) all of which indicated that the shear-to-normal stress ratio (the effective friction coefficient for the material) increased with shear rate. The results presented herein do demonstrate that the stress ratio varies with a dimensionless parameter created by scaling the shear rate with the stiffness of the interparticle contacts. In dense regimes, the stresses themselves scale with the stiffness indicating that they are generated by the elastic response of particle networks. Such speculation is supported by studies that show that the normal stresses are strongly dependent on the interparticle friction coefficient which affects the ability of internal elastic particle structures to support load and by the time variation of stress, which shows a spiky behavior as the structures form and break. However, analyses also indicate that these observations cannot explain the hopper, landslide and phase-change as these systems operate in regimes different from those in which the effect was observed. Finally, the effects of non-linear contacts are investigated and an appropriate scaling that takes the non-linearity into account is proposed.

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Type
Research Article
Copyright
Copyright © Materials Research Society 2000

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