Thermodynamics and kinetics of boundary friction

A deterministic theory describing the behavior of an ultrathin lubricant film between two atomically smooth solid surfaces is proposed. For the description of lubricant state the parameter of excess volume arising due to chaotization of solid medium structure in the course of melting is introduced. Thermodynamic and shear melting are described. Dependences of friction force on temperature of lubricant, shear velocity of rubbing surfaces, and pressure upon surfaces are analyzed. Within the framework of a simple tribological model the stick–slip mode of friction, when the lubricant periodically melts and solidifies, is described. The obtained results are qualitatively compared with the experimental data.

Research highlights
► This paper presents a new approach in finding a solution to the ultrathin lubricant film problem.
► The proposed procedure is based on the concept of phase transition.
► Our theory is deterministic. Thermodynamic and shear melting are described consistently.
► The basic aim of this work is to calculate dependences of friction force on temperature of lubricant, shear velocity of rubbing surfaces, and pressure upon surfaces.