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Title: Patterned non-affine motion in granular media
Authors: Military Engineering Basic Research Program (U.S.)
Peters, John F.
Walizer, Laura E.
Keywords: Affine motion
Multiscale modeling
Non-local continuum
Discrete Element Method (DEM)
Granular media
Publisher: Geotechnical and Structures Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: ERDC/GSL TR ; 12-28.
Description: Technical Report
Abstract: Vortex-like flow patterns often are observed in experiments on granular media for which uniform strain is expected based on the loading boundary conditions. These deformations become apparent when the motion associated with uniform strain is subtracted from the total particle motion. Besides presenting an interesting phenomenon that begs explanation, these vortex patterns suggest multi-scale structure to non-affine motion as suggested by modern continuum theories. Further, the rotational velocity field added to a uniform strain field produces a planar slip field. Thus, these structures are associated with the slip-band fields that eventually form and generally are associated with bifurcations in the solution path of the governing partial differential equations. A procedure is presented to extract these motion fields from discrete element simulations, along with conjugate forces associated with these motions. A key finding from the simulations is that the motions that eventually lead to shear band formation develop throughout the loading history rather than arising as a distinct bifurcation. Further, the pattern of rotational fields and, hence, the shear banding pattern are controlled by the boundary conditions. A question, only partly resolved here, is the origin of forces driving the rotational fields, considering no force exists at the boundaries in the case of frictionless platens.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Technical Report

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