Shock Propagation in Soft Granular Materials
Abstract
Shock propagation in particulate materials is governed by the nonlinear interactions between particles. Spherical elastic particles have Hertzian contacts, meaning that they effectively interact via nonlinear springs. Hertzian interactions give rise to nonlinear wave behavior, which has been studied extensively for 1D chains of spheres (e.g., Newtons cradle), where energy is transmitted perfectly from one particle to the next and the internal sound speed of a particle is assumed to be quasi-infinite. In more realistic situations, forces do not propagate along a single network, but along force chains, which are spatially anisotropic structures that transmit stress. Additionally, shocks can propagate at speeds similar to the internal sound speed. Through shock experiments on 2D assemblies of frictional, photoelastic disks, we show three key results: (1) Two distinct wave speeds emerge after impact, one of which represents the primary force propagation wave; (2) this force propagation speed scales (as a power law) with the intruder velocity can indeed approach the characteristic sound speed inside a grain; and (3) in the shock regime, these propagation speeds are independent of confining pressure and fall along a single branch.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 2019
- Accession Number
- AD1080400
Entities
People
- Anthony D. Severson
Organizations
- Naval Postgraduate School