Transition from Static to Dynamic Friction in an Array of Frictional Disks

TL;DR

This paper investigates the transition from static to dynamic friction in an array of frictional disks, revealing an oscillatory instability as the underlying mechanism through a Newtonian dynamics model.

Contribution

It demonstrates that an oscillatory instability causes the static-to-dynamic friction transition, providing a clear, physics-based understanding of the phenomenon.

Findings

Identified oscillatory instability as the transition mechanism

Analyzed wave speeds in the frictional disk array

Explained spontaneous sliding at Coulomb limit

Abstract

The nature of an instability that controls the transition from static to dynamical friction is studied in the the context of an array of frictional disks that are pressed from above on a substrate. In this case the forces are all explicit and Newtonian dynamics can be employed without any phenomenological assumptions. We show that an oscillatory instability that had been discovered recently is responsible for the transition, allowing individual disks to spontaneously reach the Coulomb limit and slide with dynamic friction. The transparency of the model allows a full understanding of the phenomenon, including the speeds of the waves that travel from the trailing to the leading edge and vice versa.