Multiphysics model of chemical aging in frictional contacts

An increase of static friction during stationary contacts of two solids due\nto interfacial chemical bonding has been reported in multiple experiments.\nHowever, the physics underlying such frictional aging is still not fully\nunderstood because it involves multiple physical and chemical effects coupled\nwith each other, making direct interpretation of experimental results\ndifficult. Here, we develop a multiphysics chemical aging model that combines\ncontact mechanics, mechanochemistry, and interfacial chemical reaction\nkinetics. Our model predicts that aging is proportional to normal loads in a\nlow-load regime and becomes nonlinear at higher loads. We also discovered a\nnonmonotonic temperature dependence of aging with a peak near room temperature.\nIn addition, our simulations provide insights into contributions from specific\nphysical/chemical effects on the overall aging. Our model shows quantitative\nagreement with available single-asperity experiments on silica-silica\ninterfaces, and it provides a framework for building a chemical aging model for\nother material systems with arbitrary types of physical and chemical effects\ninvolved.\n