Role of surface roughness in superlubricity

TL;DR

This paper investigates how surface roughness and elastic modulus influence superlubricity in elastic solids, revealing that roughness can eliminate superlubricity and that softer materials exhibit higher friction.

Contribution

It demonstrates the critical role of surface roughness and elastic modulus in superlubricity, highlighting conditions that preserve or destroy ultra-low friction states.

Findings

Superlubricity occurs in hard, incommensurate surface contacts.

Surface roughness can eliminate superlubricity.

Lower elastic modulus increases sliding friction.

Abstract

We study the sliding of elastic solids in adhesive contact with flat and rough interfaces. We consider the dependence of the sliding friction on the elastic modulus of the solids. For elastically hard solids with planar surfaces with incommensurate surface structures we observe extremely low friction (superlubricity), which very abruptly increases as the elastic modulus decreases. We show that even a relatively small surface roughness may completely kill the superlubricity state.