Vol 37, No 2 (2016)

A numerical solution of the heat-friction problem for a brake pad–brake disk system during repeated intermittent braking has been obtained using the finite-element method. The obtained temperature field has been used to study the thermal stress state of the disk. A numerical analysis has been carried out for a metal-ceramic pad–cast iron disk friction pair during ten intermittent brakings. The effect of the coefficient of the coefficient of heat transfer on the temperature, the stress tensor components, and the Huber–Mises–Henky stresses on the working surface of the disk has been investigated.

The results of experimental studies of the effect of the merchant-mill raceways geometry on the rolling-friction torque of the thrust ball bearing have been presented. It has been shown that, despite that merchant-mill raceways have much higher compliance than standard raceways, the rolling-friction torque of the bearing does not exceed the rolling-friction torque of the bearing with solid-metal raceways.

The effect of layered silicates on the structure and performance characteristics of polytetrafluoroethylene is studied using IR spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy, as well as tribological and physicomechanical testing. It has been shown that the filling of polytetrafluoroethylene with layered silicates leads to a substantial (up to 2500 times) decrease in its mass wear rate, while its strength characteristics remain similar to those of the original polymer. The use of IR spectroscopy and X-ray photoelectron spectroscopy to study structural transformations that occur during the friction of the polymer composite materials with various compositions of fillers has revealed the formation of intermediate products in the course of the oxidative destruction of polytetrafluoroethylene.

This work is an extension of the study of the use of alumina nanopowder as an additive to oils [1]. Oleic acid, which acts as a strong surfactant, is used to eliminate the coagulation of particles of alumina nanopowder. A suspension with a particle size of 20–80 nm that does not precipitate in oil, has been produced using the ultrasonic dispersion of powder with oleic acid. An optimum proportion of alumina nanopowder, surfactant, and oil has been determined using the results of comparative tribotests. A composition has been developed that reduces friction in bearings.

The tribological properties of metal-containing composite materials have been studied. The effect of filling materials on the composite materials’ thermal diffusivity and physical and mechanical properties has been established. It has been shown that the introduction of fine metal powders into phenylone, a heat-resistant polyamide, considerably enhances the wear resistance of phenylone. It has been established that the wear resistance of the developed metal-containing polymers reaches the maximum value with a content of the filling material of 15 wt %. It has been shown that the wear rate upon oil lubrication is strongly influenced by the temperature properties of the metal-containing polymers.

The development of metal–ceramic copper-based materials that operate under lubrication requires experience in operation under normal conditions, as well as with disruption of operation. The exclusion of a component or substitutions in the material composition is an important issue when taking into account that the component belongs to a group of hazardous substances that contain lead in MK-5 metal–ceramic copper-based friction materials.

The results of studying the impact-abrasive wear of manual arc welded Hadfield steel hardfacings and this steel alloyed with Cr, Ni, Mo, B, Cu, and Si, both without and with coarse-grained tungsten carbide reinforcement, are presented. It has been found that under conditions of impactless wear the presence of the hardening phase in the Hadfield steel increases its wear by 40% on average compared to the wear of the base and alloyed Hadfield steels. With an increase in the impact energy from 2.8 to 5.6 J, the wear of the reinforced Hadfield steels decreases and becomes comparable with the wear of the base and alloyed Hadfield steels. Under the conditions of erosion by coarse particles, layers of the Hadfield steel reinforced by tungsten carbide have slightly lower wear rate than unreinforced ones.

The design of a pin-on-disk friction machine intended for the testing materials under boundary lubrication has been considered. Engineering solutions involved in the development of the machine that are used to provide the precision of the adjustment of friction surfaces of specimens with regard to the counterface and to retain stable thermal conditions in the zone of contact at any duration of the test have been described. The machine is intended for carrying out wear tests of materials and coatings under various conditions, including conditions that correspond to the operation of shut-off valves of oil pipelines.