Force Mobilization and Generalized Isostaticity in Jammed Packings of Frictional Grains
arXiv:cond-mat/0610205 · doi:10.1103/PhysRevE.75.010301
Abstract
We show that in slowly generated 2d packings of frictional spheres, a significant fraction of the friction forces lies at the Coulomb threshold - for small pressure p and friction coefficient mu, about half of the contacts. Interpreting these contacts as constrained leads to a generalized concept of isostaticity, which relates the maximal fraction of fully mobilized contacts and contact number. For p->0, our frictional packings approximately satisfy this relation over the full range of mu. This is in agreement with a previous conjecture that gently built packings should be marginal solids at jamming. In addition, the contact numbers and packing densities scale with both p and mu.
4 pages, 4 figures, submitted