Structural-Energy Aspect of the Friction Coefficient

Over five centuries, friction science used the friction coefficient as the main quantitative characteristic of the friction process. The concept of the friction coefficient as a characteristic of resistance to the movement of frictional surfaces in a latent form was formulated by Leonardo da Vinci. Two centuries later, already in an explicit form, as a formula, the friction coefficient appeared in the studies of Guillaume Amonton. Modern engineering believes that the friction coefficient has no physical meaning, it is merely a convenient friction parameter that can be easily determined in an experiment. What is the physical meaning of resistance to the movement of frictional surfaces? If we perform a thermodynamic analysis of the friction process, considering each deformable friction contact element as an independent transformer and dissipator of energy of the external relative displacement (motion) of surfaces, then it becomes possible to consider the friction coefficient in a new physical sense. The accumulation of the potential energy of a deformed structure (defects in the crystalline structure) by a friction contact is, in essence, a method of deceleration of frictional surfaces moving relative to each other. The static potential energy of the formed defects in the structure of the contact structure is a measure of the decrease in the kinetic energy of the relative motion of the frictional surfaces. The pragmatism of the energy (thermodynamic) approach of friction is organically embedded in the general problems of energy consumption and saving energy resources of modern tribology.