Influence of frozen capillary waves on contact mechanics

TL;DR

This paper investigates how thermally excited capillary surface waves create surface roughness in cooled glassy materials, significantly affecting contact mechanics and providing new insights into frictional behavior.

Contribution

It introduces a theory linking capillary wave-induced roughness to contact mechanics and explains previously puzzling experimental results.

Findings

Capillary waves cause significant surface roughness in cooled glassy materials.

Surface roughness influences the frictional shear stress in contact mechanics.

The theory supports and extends existing contact mechanics models.

Abstract

Free surfaces of liquids exhibit thermally excited (capillary) surface waves. We show that the surface roughness which results from capillary waves when a glassy material is cooled below the glass transition temperature can have a large influence on the contact mechanics between the solids. The theory suggest a new explanation for puzzling experimental results [L. Bureau, T. Baumberger and C. Caroli, arXiv:cond-mat/0510232] about the dependence of the frictional shear stress on the load for contact between a glassy polymer lens and flat substrates. It also lend support for a recently developed contact mechanics theory.