If you push a pile of sand very lightly, it will respond elastically, but if you push beyond an extremely low threshold, it will begin to flow. But the system that it flows into will be qualitatively similar to the state it was just in. We are studying that marginal transition in low dimensional systems (2D and 3D) using multiple approaches.
Granular materials, glasses, and other disordered materials fail in ways that are hard to predict. By examining the vibrational properties in simulations of jammed packings of particles, we are able to determine both where and how these materials are likely to deform.