Speaker: Roux, J-N (Paris)

Title: Geometry and mechanics of frictionless or frictional disk and sphere packings

Abstract:  Packings of rigid (or slighly deformable) particles exhibit collective
mechanical properties that are not easily predicted, as they are often
determined by their geometry as much as by local constitutive laws.
Thanks to various numerical simulation techniques, it is possible to
discuss the existence and the form of macroscopic quasistatic stress-strain laws
for assemblies of disks or spheres, with contrasting conclusions, in the
following cases:

- no friction, rigid particles, geometric approximation for displacements
(appropriate for lattices with some contact disorder)
- no friction, rigid particles, no geometric approximation
- frictional and/or elastic particles.

Existing results on those models enable to investigate the influence of the
microscopic parameters on the macroscopic behavior, the physical origins of
strain, the relevance of some possible state variables and the nature of
"random close packing".