ABSTRACT
Friction is the most widespread phenomenon in daily life. Studies of friction date back to the times of Aristotle and Leonardo. Friction accompanies not only any motion, but also tendency for displacement. Although the term “friction” is well-known, few people realize what it really means because of the highly intricate nature of this phenomenon. Apparently, there is a force that impedes the break of relative state at rest and incipient motion. The force is always nonzero and possesses a finite value. This principal fact should be treated as the fundamental law of friction that can be formulated as follows: a static friction exists when two solids form a contact. When two surfaces approach each other, their opposing asperities with maximum height come into contact. As the load is increased, new pairs of asperities with smaller heights come into contact, forming individual spots.
