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Visualization and Penetration by DUKE, YALE and NJIT

The physics of an intruding object impacting and penetrating a granular material is relevant to many situations, including soil penetration, meteor impacts, and ballistics. Related phenomena occur in industrial settings, for instance in mixers or other machinery, where a blade can impact a material.

The figure below shows contrast frames from impacts at low, moderate, and high M′. In evaluating M′, we use the assumption, justified below, that υ_f∝d/t_c. A key observation is that for the lowest M′, the force is carried primarily over a filamentary force network (bright particles in the upper image of the figure below). As M′ increases, the strong force network becomes increasingly dense, so that for the largest M′ case, the propagating force network is spatially dense and not filamentary.

Frames showing force propagation after three impacts with u0%5 m/s. (a) The hardest
particles (M0%0.1) correspond to fast, chain-like force propagation. (b) Forces for intermediate
stiffness particles (M0%0.3) are denser spatially but still relatively chain like. (c) The softest
particles (M0%0.6) show a dense force structure which propagates with a well-defined front

Active Investigators

Lou Kondic [link]

Corey O’Hern [link]

Robert Behringer [link]