  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.
