title: Jamming of three-dimensional prolate granular materials.
abstract: We have found that the ability of long thin rods to jam into a solidlike state in response to a local perturbation depends upon both the particle aspect ratio and the container size. The dynamic phase diagram in this parameter space reveals a broad transition region separating granular stick-slip and solidlike behavior. In this transition region the pile displays both solid and stick-slip behavior. We measure the force on a small object pulled through the pile, and find the fluctuation spectra to have power law tails with an exponent characteristic of the region. The exponent varies from beta=-2 in the stick-slip region to beta=-1 in the solid region. These values reflect the different origins--granular rearrangements vs dry friction--of the fluctuations. Finally, the packing fraction shows only a slight dependence on container size, but depends on aspect ratio in a manner predicted by mean-field theory and implies an aspect-ratio-independent contact number of <c>=5.25 +/- 0.03.
authors.affiliation: Department of Physics, Rochester Institute of Technology, Rochester, New York 14623, USA.
authors.forename: K
authors.initials: K
authors.lastname: Desmond
authors.forename: Scott V
authors.initials: SV
authors.lastname: Franklin