Hidden Dynamics of Static Friction

Abstract

Static friction, a force fundamental to nearly every mechanical system from micro-machines to basketball shoes to tectonic plates, is in fact anything but static. In contrast to the simplified version taught in high-school, static friction is actually extremely dynamic, complex, and still poorly understood. In this thesis I investigate several types of dynamics hidden within static interfaces. In the first two chapters, I discuss the slow evolution of contacting solids, demonstrating that frictional systems store and evolve according to a memory of their loading history. I build a model that captures these dynamics, linking frictional systems to a broad class of disordered, amorphous, `glassy' systems such as crumpled paper, memory foam, granular materials, and polymer glasses. In the next two chapters I investigate geometry of interfacial contact both locally and globally, and show that the former influences slow evolution in time, while the latter dictates a significant portion of the frictional strength. In the fifth chapter, I detail an experimental system capable of observing the fastest dynamics of static friction, the nucleation of slip, in a table-top model system. In the final chapter, I describe an optical technique capable of taking ultra-fast video on any camera.