Non-monotonic dynamics in the onset of frictional slip

TL;DR

This paper reveals that the onset of frictional slip involves continuous non-monotonic dynamics driven by contact aging and rejuvenation, unifying complex slow slip behavior with rate-and-state models.

Contribution

It introduces a unified evolution equation capturing both non-monotonic slip dynamics and traditional rate-and-state transients.

Findings

Non-monotonic dynamics observed during slow slip experiments.

A single model explains both complex and simple frictional transients.

Contact aging and rejuvenation compete to govern slip onset.

Abstract

The transition from static to dynamic friction is often described as a fracture-like instantaneous slip. However, studies on slow sliding processes aimed at understanding frictional instabilities and earthquakes report slow friction transients that are usually explained by empirical rate-and-state formulations. We perform very slow ($\sim nm/s$) macroscopic-scale sliding experiments and show that the onset of frictional slip is governed by continuous non-monotonic dynamics originating from a competition between contact aging and shear-induced rejuvenation. This allows to describe both our non-monotonic dynamics and the simpler rate-and-state transients with a single evolution equation.