Biological & Soft Matter Seminar: Stress Localization in Jammed Packings: Insights from networks in real-space and force space

Abstract:

Jammed states necessarily satisfy all the constraints of mechanical equilibrium.   In non-cohesive systems, such as granular materials, these constraints strongly influence the geometrical network of contacts.  Dual to this network of contacts is a network of contact forces, which in 2D, correspond to Maxwell-Cremona tilings (force tilings).    A characteristic of jammed granular systems is stress localization.  Experiments using photoelastic beads provide clear evidence of this phenomenon of force localization, and force chains have emerged as the defining characteristic of granular solids.   In this talk, I will explore stress transmission and the jamming transition in assemblies of frictional grains in two dimensions through the lens of these two networks.   I will analyze the signatures of jamming observed in statistical properties of force tilings, and argue that there is an order parameter that can be defined in this space, and setup a framework, based on force tilings, that relates the disorder in the underlying contact network to spatial localization of forces.

Seminar Organizer: Guy Yaacoby