On the velocity-strengthening behavior of dry friction

TL;DR

This paper explores the transition from velocity-weakening to velocity-strengthening friction in dry interfaces, highlighting its implications for frictional phenomena and proposing mechanisms for stronger-than-logarithmic strengthening at higher slip velocities.

Contribution

It introduces the concept of a crossover from velocity-weakening to velocity-strengthening friction and discusses potential physical mechanisms and experimental evidence for this transition.

Findings

Crossover from velocity-weakening to velocity-strengthening is likely a generic feature.

Logarithmic velocity-strengthening can transition to stronger-than-logarithmic behavior.

Experimental data supports the existence of this crossover and related mechanisms.

Abstract

The onset of frictional instabilities, e.g. earthquakes nucleation, is intimately related to velocity-weakening friction, in which the frictional resistance of interfaces decreases with increasing slip velocity. While this frictional response has been studied extensively, less attention has been given to steady-state velocity-strengthening friction, in spite of its potential importance for various aspects of frictional phenomena such as the propagation speed of interfacial rupture fronts and the amount of stored energy released by them. In this note we suggest that a crossover from steady-state velocity-weakening friction at small slip velocities to steady-state velocity-strengthening friction at higher velocities might be a generic feature of dry friction. We further argue that while thermally activated rheology naturally gives rise to logarithmic steady-state velocity-strengthening friction, a crossover to stronger-than-logarithmic strengthening might take place at higher slip velocities, possibly accompanied by a change in the dominant dissipation mechanism. We sketch a few physical mechanisms that may account for the crossover to stronger-than-logarithmic steady-state velocity-strengthening and compile a rather extensive set of experimental data available in the literature, lending support to these ideas.