About the Law of Friction

The empirical law of dry friction, first formulated by Leonardo da Vinci 500 years ago, entered the history of technology as one of the most applicable laws in engineering calculations. Two hundred years later (after da Vinci) Amonton M., Coulomb C. A. and Euler L. made a decisive contribution to the substantiation and understanding of the law of dry friction, and it became classical: the friction force during sliding is proportional to the contact load. Studies have shown that the classical friction law for the tribo-fatigue system is inaccurate and, therefore, inapplicable. It was established experimentally that the error in estimating the coefficient of friction in a tribo-fatigue system (for example, a wheel / rail type, etc.) reaches 60...70 % or more, if we use the classical law of friction for its analysis. Therefore, the problem arises of adjusting the classical law of friction. A set of theoretical and experimental studies was carried out, the results of which allowed to formulate a generalized law of friction: the friction force is proportional to both contact and non-contact volume loads, if the latter excites a cyclic stress (strain) field in the friction zone. This law describes all the experimental results (more than 100 values ​​of the friction coefficient) with an error of no more than ± 6%. The widespread use of the generalized law of friction in the technique proposed by us is considered a very urgent task.