Multiphysics model of chemical aging in frictional contacts

TL;DR

This paper presents a multiphysics model of chemical aging in frictional contacts, integrating contact mechanics, mechanochemistry, and reaction kinetics to explain static friction increase and its dependence on load and temperature.

Contribution

It introduces a comprehensive multiphysics model that predicts chemical aging behavior, including load and temperature effects, and aligns with experimental data.

Findings

Aging proportional to normal load at low loads

Nonmonotonic temperature dependence of aging with a peak near room temperature

Model aligns quantitatively with silica-silica interface experiments

Abstract

An increase of static friction during stationary contacts of two solids due to interfacial chemical bonding has been reported in multiple experiments. However, the physics underlying such frictional aging is still not fully understood because it involves multiple physical and chemical effects coupled with each other, making direct interpretation of experimental results difficult. Here, we develop a multiphysics chemical aging model that combines contact mechanics, mechanochemistry, and interfacial chemical reaction kinetics. Our model predicts that aging is proportional to normal loads in a low-load regime and becomes nonlinear at higher loads. We also discovered a nonmonotonic temperature dependence of aging with a peak near room temperature. In addition, our simulations provide insights into contributions from specific physical/chemical effects on the overall aging. Our model shows quantitative agreement with available single-asperity experiments on silica-silica interfaces, and it provides a framework for building a chemical aging model for other material systems with arbitrary types of physical and chemical effects involved.