Static and dynamic coefficient of friction in friction pairs of disc-pad brakes

Abstract

Problem This scientific article is devoted to the value of static and dynamic coefficients of friction of disc-pad brakes. The issue of disc-pad brake wear is very acute because the safety of using the machine itself depends on its reliable operation. Therefore, the relevance of the chosen topic cannot be doubted. Goal. The aim is to establish patters of influence of the main operational parameters of friction pairs of a model disc-pad brake on the potential and kinematic coefficient of friction. Methodology. The methods of analytical mechanics and the theory of elasticity were used in the article. Results. Theoretical and experimental studies of the static (former rest) and dynamic coefficients of friction in the frictional interaction of materials FK-24A - steel 35KhNL were carried out on a model disk-shoe brake in a long-term braking mode. At the same time, it was established in the range of real impulse loads implemented during braking in the contact area of the friction lining with the brake disc, the stress-strain state of the contact according to the criterion of micro deformation in the contact corresponds to the elastic-plastic property. The elastic and plastic properties of materials appear when, in each individual case, the total stresses exceed the yield strength or reach its limit. With an increase in the impulse force of the normal pressing of the pad lining to the treadmill of the disc friction, the static coefficient of friction tends to increase, and with an increase in the static coefficient of mutual overlap kvz.s, it tends to decrease with the elastic-plastic property of materials. When choosing materials for friction pairs, the dynamic coefficient of friction must include the value of the static coefficient of friction and be at least 20% greater than the calculated value of the dynamic coefficient of friction. Practical value An increase in the static and dynamic friction coefficient in the friction pairs of a disk-pad brake leads to an increase in the plastic deformation of their microprotrusions. The data obtained can be used in the design of disc-shoe brakes