The contact problem of free rolling on a rigid foundation of a cylindrical body consisting of a non-deformable central part and an elastic rim is considered. A technique for an analytical solution is developed on the basis of a second-order asymptotic approximation. The contact interaction of the composite body with a non-deformable foundation under the action of a vertical force is investigated as a calculation example assuming a small rolling resistance moment. The calculated distributions of normal and tangential contact stresses, the distribution of the stress tensor intensity in the rim near the contact area, and the “force—displacement” dependence are obtained. These data are compared with the estimates obtained by the authors on the basis of finite element modeling and the results of using an alternative version of the asymptotic approximation. A conclusion is made about the advantages of the developed technique in comparison with the known asymptotic approach in terms of the accuracy of calculating the contact parameters and the simplicity of the applied mathematical apparatus. It is shown that the maximum of the stress tensor intensity is localized on the line of action of the vertical force (axis of symmetry) for a deformable rim material with Poisson's ratio n less than 0.4 and on the inner surface of the rim near the boundary of the adhesion and slip zones for n > 0.4. The data derived are used to analyze the loading of roller interfaces of mining equipment.

The paper presents one of the options for solving the scientific and applied problem of the predicted formation of tribotechnical characteristics of an ion-plasma coating. The problem is solved by creating and subsequently analyzing a database of carbon coatings, including technological parameters of coating application, their elemental compositions, structural and morphological characteristics of coatings, their physical, mechanical and tribological properties, as well as characteristics of the substrate and indicators of the quality of its surface. The object of research in this work is DLC ion plasma coatings deposited on a steel substrate. The work shows that the use of nitrogen to stabilize carbon coatings instead of hydrogen ensures not only obtaining stable thicknesses of DLC coatings at the level of 1.0—1.5 mm, but also serves as an important and convenient technological parameter for regulating the tribological characteristics of the coating during its application. Based on the predicted and experimental values of the friction coefficient m and data on the sample run length L, the intervals of optimal values of the technological parameters %N and l were determined. The studied carbon ion-plasma DLC coatings, obtained according to the established optimal application modes, can be recommended for applied use under friction conditions equivalent to the tribotechnical tests carried out at a friction load of F » 10 N.

The article is devoted to an experimental study of the influence of wear-resistant coatings ZrN, TiN+ZrN, (Ti-Zr)N, ZrN-(Ti-Zr)N-TiN, TiN, deposited on T15K6 hard alloy inserts, on the tribological and deformation characteristics of the process of turning steel workpieces 45 and 12Х18Н10Т, and subsequent comparison of the calculated values of the maximum temperatures of the rake face of the lathe cutter. When processing steel 45, a significant reduction in contact and average temperature in the cutting zone is ensured by a combination of tribological and deformation indicators when using TiN+ZrN and ZrN+(Ti,Zr)N+TiN compositions. When turning stainless steel 12Х18Н10Т, the presence of coatings on carbide inserts had a lesser effect on the course of deformation processes. The main effect of modifying the working surfaces of the tool is to change the thickness of the zone of secondary plastic deformations and reduce the length of contact of the chips with the rake surface. In this case, the greatest effect in reducing surface temperatures due to the influence on the complex of tribostrain indicators and enhancing the thermodissipative capabilities of the contact zone is demonstrated by ZrN and ZrN+(Ti,Zr)N+TiN coatings. Based on the results of full-scale experiments and digital modeling using the obtained experimental data, it was established that the temperature distributions in the area of tribocoupling of chips with the surface of a hard alloy in the presence of a multilayer coating on it are associated with the wear of a metal-cutting tool, which makes it possible to evaluate the impact of wear-resistant coatings through changes in the temperature regime in contact zone. This influence of surface modification on a set of tribostrain indicators, which also determine the nature of the distribution of contact temperatures, should be taken into account when developing new compositions and structures of wear-resistant coatings along with their physical and mechanical properties at the microlevel.

Friction and wear of polyoxymethylene upon friction against polyoxymethylene and polyetheretherketone have been analyzed. It is shown that wear exponentially increases upon growth of contact pressure and sliding velocity in the homogeneous friction pair polyoxymethylene-polyoxymethylene. In the heterogeneous pair polyetheretherketone-polyoxymethylene the wear of POM is small and exhibits no registered dependence on sliding velocity and contact pressure. Mass-spectrometric analysis shows that the macromolecular decomposition products are not detected for polyetheretherketone-polyoxymethylene pair. However, for thermodynamically compatible polyoxymethylene-polyoxymethylene pair their formation, accompanied by the growth of friction force, is detected at the levels of friction power as low as 10^–2 MPa·m/s. These differences have been interpreted to result from interpenetration of polyoxymethylene macromolecules and their rupture in the shear field at the homogeneous polyoxymethylene-polyoxymethylene friction interface, absent in polyetheretherketone-polyoxymethylene pair. Thermally activated interpenetration of macromolecules for polyoxymethylene-polyoxymethylene pair and its absence in polyetheretherketone-polyoxy­methylene pair has been visualized by means of molecular dynamics calculations. The experimental approach and the results of its application will be useful in detailed studies of molecular level friction mechanisms of friction and wear of industrially used polymers and their composites.

The study of structure and tribotechnical characteristics of composite material based on carbon PAN fabric and matrix obtained by vapor deposition method has been carried out. One of the samples of the investigated material was subjected to laser treatment, with local laser heating of the surface layer to
2800—3000 °C. The other composite sample was heat treated at a temperature T > 2000 °C. Tribotechnical tests were carried out and values of friction and wear coefficients were obtained in the pair with steel and ceramic counterbodies. In order to determine the peculiarities of friction and wear mechanisms of modified materials, the surface of composites after friction was investigated by scanning electron microscopy with X-ray spectral analysis. It was found that laser treatment significantly improves antifriction properties of carbon composite in pair with steel counterbody (friction coefficient reduction by two times, wear reduction by three times). It is revealed that such treatment significantly changes the nature of the film of secondary structures (SS) formed on the friction surface of composites paired with steel. In the composition of the film elements of the counterbody material are not found, which indicates its minimal wear in the process of friction. The BC film itself becomes thicker and denser, completely covering the composite surface. This allows it to a greater extent to show solid-lubricating and anti-wear properties, improving tribotechnical characteristics of the composite.

The study compared properties of carbon-carbon composites for aircraft brakes manufacturing. Composites based on various graphitized and carbonized fibers, coal, tar pitch and pyrocarbon matrices were considered. Friction tests were carried out on full-size brake discs (3-disk stand) and on model samples (testing machine UTM-2168). A significant wear increase of composites based on pyrocarbon matrix was found during taxi braking in the temperature range of 50—250 °C. Wear of composites based on coal tar pitch matrix did not depend on the temperature of friction surface. It was found, that the “third body” of composites based on pyrocarbon has a coarse, rough structure with distinct individual abrasive particles; its hardness is more than twice as high as hardness of “third body” of composites based on pitch matrix. The size distribution of pores for composites based on different matrices is given, the difference in the quantity and size of structural defects is illustrated. The variation in wear of materials during taxi braking is explained. The increase of anisotropy degree of the pitch matrix, provided the decrease of wear of the material. The wear was measured during taxi braking of specimens with a hybrid matrix having a different ratio of coal tar pitch and pyrocarbon components. Carbon-carbon composites containing 45 percent or more of the pitch component in matrix have stable reduced wear during taxi braking, regardless of the reinforcement scheme. The possibility of reducing wear during taxi braking of composites on pyrocompacted matrices by modifying the matrix with pitch is shown.

The results of studies on the wear resistance of machine parts made of aluminum alloys with insulated layers obtained by activating surface layers (SL) are considered. It is shown that, in relation to aluminum alloys, traditional ion nitriding technologies are ineffective due to the low rate of nitrogen diffusion and the heterogeneous structure of the nitrided layer (NL). The results of a fourfold increase in the intensity of diffusion processes of ion nitriding during activation of the surface layer of an aluminum alloy by methods of surface plastic deformation and high-energy ion implantation compared with traditional ion nitriding are presented. It is shown that when preparing the surface of an aluminum alloy by the method of high-energy ion implantation, the wear resistance of the nitrided layer is provided, exceeding by more than three times the wear resistance of the nitrided layer obtained during surface preparation by the method of surface plastic deformation. A new ion nitriding technology has been proposed, which makes it possible to increase the productivity of the nitriding process and the wear resistance of the AC by eliminating the oxide film by ion etching in vacuum. It is shown that the use of the method of high-energy ion implantation at an ion energy of about 25 keV ensures, due to the occurrence of a long-range effect, the formation of aluminum alloy parts in the surface layer at a depth commensurate with the thickness of the nitrided layer of radiation defects of the crystal structure, which significantly intensify nitrogen diffusion, as well as block grain boundaries inhibiting diffusion processes in them.

The wear-free friction of steel balls SHX-15 (ShKh) on the surface of quartz glass (QG) and borosilicate glass (BG) ampoules in organic liquids and water is considered. It is shown that it is impossible to accurately predict which material will wear faster: hard or soft, ball or substrate. The highest correlation of wear of mating friction surfaces was found for balls and total wear of working bodies (r » 1). In the group of glass balls, the balls wear out more often (in 19 experiments out of 21) than in the group of steel balls (in 5 experiments out of 9). Wear-free friction is more often observed in conjugated pairs of BG/ShKh (in 5 cases) than in pairs of QG/ShKh (in 1 case). Mating surfaces containing only one SiOH end group do not provide wear-free boundary friction. The usefulness of the work lies in the fact that the results of studies of wear-free friction obtained for the conjugated pair SH/H₂O can find practical application for the creation of bearings and large human joints.