Journal of Friction and Wear

In this paper, we present a model of the effect of the contact interaction velocity and the mechanical properties of contacting materials on contact stresses and deformations in carbon structural steels caused by a solid particle flow. The existence of three critical states of the material exposed to impact deformation is considered. The first state is characterized by the formation of a plastic flow zone in the surface layer (transition from perfectly elastic to constrained elastic–plastic deformation). The second state is characterized by the exit of this zone to the part surface (transition from constrained elastic–plastic deformation to a free plastic flow, i.e., dynamic indentation). The third state is characterized by the destruction of surface layers due to tensile stresses on the contour of the contact spot values equal to the true tensile strength of the deformable material under tension with allowance for strain hardening. The characteristic values of the dynamic microcontact interaction velocities that correspond to the ranges of the existence of each of the critical state forms were determined. The dominant mechanisms of erosive wear of parts for each of the states (multi-cycle fatigue wear for the first state, low-cycle fatigue wear with an incubation period for the second state, and intensive formation of erosion damage with a minimal incubation period for the third state) were indicated.

An algorithm for computer design (calculated determination of the composition) of a multicomponent antifriction material is proposed. First, the minimum initial set of composite characteristics is determined experimentally for a number of controlling parameters from tribological and mechanical tests. The subsequent computer-aided design of the material in the form of constructing the corresponding response surfaces in the space of states makes it possible to identify the range of variation of the controlling parameters to provide the specified operational and technological characteristics. This approach is illustrated by the computer-aided design of the material composition (feedstock) in the form of an extrudable polymer composite based on ultra-high molecular weight polyethylene (UHMWPE) for applications in additive technologies. An optimal formulation is proposed for the UHMWPE + n wt % HDPE-g-SMA + n wt % PP ternary mixture that has tribological and mechanical properties at the level of unfilled UHMWPE and, at the same time, the melt flow index required for 3D printing by the fused deposition modeling method.

The causes of an abrupt decrease in the wear and in the friction coefficient from 0.6 to 0.24 for poly(arylene ether ketone) copolymers containing 10, 15, and 25 mol % of cardo bisphenol moieties in the main chain have been investigated. The presence of cardo groups in the copolymers promotes an increase in the microhardness from 12 to 22 kgf/mm² and maintains a high antifrictionality as a parameter that characterizes the dispersion interaction energy contribution to the total energy of the intermolecular interaction. The XPS examination of the copolymers has shown that only in the case of poly(arylene ether ketone) copolymer containing 10 mol % cardo groups, wear products do not undergo any considerable structural changes in the friction process. The studies demonstrated that a significant improvement of friction-and-wear parameters in the case of a poly(arylene ether ketone) copolymer containing a 10 mol % of cardo groups is caused by an optimal combination of increasing microhardness, formation of a discrete surface, and by maintaining a high antifrictionality. With increasing cardo group content in the copolymers to 15 and 25%, a gradual increase in the friction coefficient to 0.5 and 0.75, respectively, was observed.

In this work the displacement function of the external contour points of a hub and the friction surface microgeometry that correspond to the uniform distribution of the contact pressure over a friction surface are theoretically determined. The model of a rough friction surface is used. A closed system of algebraic equations is constructed that allows solution of the optimal design problem for a friction unit with account for the geometrical and mechanical properties of its elements.

In this article a new universal technique for the mathematical determination of the friction coefficient between a steady elastic wheel and a solid support surface is proposed. The technique is valid when there is a lateral force that occurs before or after the braking on the wheel. It is based on the computation of the relative limiting realized static friction and may be applied when there is a lack in initial data in the form of the primary φ_x–s_x interaction diagram of a specific wheel and a specific support surface. The results of the work improve the accuracy of friction coefficient modeling in the design-stage prediction of the stability, controllability, and braking dynamic properties of wheeled vehicles.

This study focuses on the tribological properties of superhard and functional coatings on the basis of carbide and boron nitride, which were optionally doped with powdered graphite and molybdenum disulfide. Coatings were obtained by highly concentrated short-pulse laser treatment of powder compositions on metal surfaces. The resulting coatings were subjected to wear tests under conditions of dry sliding friction with friction coefficient fixation, depending on the applied load and the composition of the powder composition. The results provide an idea of the degree of change in the coefficient of friction of coatings from the composition of powder compositions, as well as their alloying. The features of the behavior of boron carbide and nitride at high temperatures and their influence on the coefficient of friction are presented.

An experimental study made it possible to identify the stages and mechanism of deterioration of a rubber surface in an aqueous medium for conditions of impact with a single solid particle and impact with a hydroabrasive jet. The deterioration has a fatigue character and is divided into two stages: formation of the primary site of deterioration and subsequent fatigue spalling of rubber microfragments by the water flow. Rubber wear in water and air differ significantly in topography and durability. A reduction in the friction coefficient in the aqueous medium leads to a large increase in rubber durability.