An Irreversible Thermodynamic Theory of Friction and Wear

Friction and wear are typical irreversible processes. Friction irreversibly degrades and dissipates high quality energy and wear irreversibly removes materials from the load-carrying surface. The two irreversible processes can be presented by entropy production, which is a non-negative quantity based on irreversible thermodynamics and thus serves as a basis for the systematic description of irreversible processes occurring in tribological system. In this paper, a thermodynamic framework has been presented for the mechanisms of friction and wear of continuum materials, where entropy production is used as the sole measure of energy dissipation and material damage evolution in the system. As a result, there is no need for physically meaningless empirical parameters to define the phenomenological frictional and wear parameters to trace tribological evolution in a friction and wear system. To validate the model, predictions are compared with experimental results, which indicate that entropy production can be used as a friction and wear evolution metric. The theory is founded on the basic premise that a solid continuum obeys the first and second laws of thermodynamics.