EVENT DETAILS AND ABSTRACT

Title: Compaction and Compression of Granular Matter
Speaker: Professor H. Jaeger
Speaker Info: U. Chicago
Brief Description:
Special Note:
Abstract:

In macroscopic granular materials ordinary thermal energies are irrelevant compared to gravitaty. Granular assemblies therefore become easily trapped in metastable configurations far from the most stable states. In this talk I will discuss two issues connected with this phenomenon. The first issue concerns the manner in which such assemblies relax towards a steady state in the presence of external mechanical forcing. I will review recent experimental results which show that this relaxation proceeds logarithmically in time, a characteristic granular materials share with many other, often more microscopic systems, in which relaxation is hindered by volume exclusion or frustration. I will also discuss a simple one-dimensional model (the "parking lot model") that captures most of the features observed in the experiments. A second, closely connected paradigm of granular materials is the inherently inhomogeneous manner in which external, compressive forces are transmitted through a packing: rather than spreading uniformaly, large stresses follow discrete paths which constitute a ramified network of "force chains", screening large portions of the material from external forces. I will discuss recent experiments that measure the shape of the resulting distribution of forces along the walls of a container filled with granular material and compressed uniaxially.