Law of Friction: from Tribology to Tribo-Fatigue. Report 1. Classical Law of (Dry) Friction and Need for its Adjustment

• Main Author: Leonid A. Sosnovskiy
• Format: Article
• Language: English
• Published: National Academy of Sciences of Belarus, State Scientific Institution “The Joint Institute of Mechanical Engineering" 2019-03-01
• Series: Механика машин, механизмов и материалов
• Subjects: friction law; tribology; friction pair; tribo-fatigue; tribo-fatigue system; friction force and coefficient; sliding; rolling; slipping; contact load; pressure; non-contact (volume) load; stress; strain
• Online Access: http://mmmm.by/en/readers-en/archive-room-en?layout=edit&id=1449

To date, many laws of Nature have been discovered. The knowledge of each of them led to the accelerated development of the relevant sections of Science and further, as a rule, to progress in any practical area of the community of people. The empirical law of dry friction [1, 2], first formulated by Leonardo da Vinci 500 years ago, went down in history of technology as one of the most applicable laws in engineering calculations [3]. Moreover, our worldview is unthinkable without an understanding of the general processes of movement with friction (as well as movement without friction). All this gives grounds to say: “Friction is an amazing phenomenon of nature” (D. Garkunov). Two hundred years later (after da Vinci) Amonton G., Coulomb C.A., and Euler L. [4–7] made a decisive contribution to the substantiation and understanding of the law of dry friction, and it became classical: the force of sliding friction is proportional to the contact load. Studies show 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, there is a problem of adjusting the classical law of friction. A set of theoretical and experimental studies was carried out, the results of which make it possible 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 proposed generalized law of friction in the engineering is considered as a very urgent task. In conclusion of the article, some directions for further research (theoretical and experimental) are formulated. The article is published in three reports.