INVESTIGATING THE TRIBOLOGICAL PROPERTIES OF FRICTIONAL LININGS OF THE SUBWAY CAR BRAKE PADS

Abstract

The performance characteristics, working conditions and tribological properties of the brake pads of the Republic Armenia subway cars have been studied. A comparative analysis of the tribological properties of frictional materials of rubber enterprises of St. Petersburg (JSC "ATI"), Yaroslavl (JSC "Friteks", JSC "TIIR") Barnaul (LLC "Barnaul plant of autoformed heat-resistant products"), the Ukraine (JSC "TRIBO") and the composite material Bastenit-8 at the FM-9 laboratory unit in accordance with GOST R ISO 7881-94, is carried out.  It is shown that the average friction coefficient of materials, with increasing the temperature initially, increases and has a maximum value at temperatures 230...270°C. Further, with an increase in the surface temperature, the friction coefficient decreases to a minimum value of 300...360°C.  Above 360°C, a repeated increase in the friction coefficient is observed. The dependence of the friction coefficient of selected materials on the surface temperature is expressed by a curve with a reduction zone in the range of 220...360°C. It is established that there are two main aspects of the influence of the thermal regime on the tribological characteristics of frictional materials: 1) the change in physical and mechanical properties at low heat loading of the frictional contact (zone of an increased friction coefficient); 2) the changes caused by mechanochemical processes and structural transformations of the surface layers at high thermal loading of the frictional contact (zones of decrease and re-increase in the friction coefficient at temperatures above 250°C. It is established that the composite material Bastenit-8 has better and more stable tribological properties and meets the requirements of the GOST 33724.1-2016 standard.  It is recommended to carry out further road performance tests and apply it to the manufacture of brake friction linings for subway car brakes.