An analytical method of calculation of contact parameters at rolling of cylindrical body, having a thin viscoelastic surface layer, over rigid sideway was developed. The technique is based on elastic-viscoelastic analogy and asymptotic approximation of the exact solution of the elasticity theory problem for a thin strip. The mode of steady rolling at given normal force and speed of motion of the center of the rolling body is considered. In the example of calculation the initial parameters were corresponded to rolling support of a mine skip with rolling elements in form of steel rollers with polyurethane rim. The dependences of rolling resistance force (which is parallel to the supporting surface) on speed, friction coefficient at sliding and Poisson's ratio of the rim material were obtained. The dependence of rolling resistance force on speed has a maximum, which corresponds to a speed of 8 m/s in the example considered. The rolling resistance decreases as the Poisson's ratio of the rim material increases. The calculated values are compared with assessments of contact parameters obtained within the framework of a simplified Winkler foundation model. It is shown that the discrepancy of results does not exceed 5 %. The developed technique can be used for design and prediction the durability of metal-polymer rolling bearings.

A study was carried out of the influence of the cooling rate of gas-thermal coatings made of high-chromium steel 95Cr18 on their phase composition and tribotechnical properties. It has been established that preheating the steel substrate to 400 °C before spraying the coating leads to a 2.7 fold decrease in its cooling rate in the region of bainite transformation and an increase in the content of retained austenite in the coating to 83.5 vol. %. It is shown that the stabilization of austenite is due to the redistribution of carbon between the α and γ phases and the enrichment of austenite with carbon. It has been established that a coating made of steel 95Cr18, sprayed onto a substrate heated to 400 °C, is characterized by higher wear resistance under various friction conditions (by 12—24 %) compared to a coating formed on a cold substrate. High wear resistance of coatings with a high content of the γ-phase is achieved due to the deformation-activated γ→α transformation, leading to a significant increase in microhardness and wear resistance of the surface layers of coatings.

Based on the mechanics of discrete contact of rough surfaces of machine parts, quantitative criteria are proposed that determine the boundaries of fretting wear regimes. The physical foundation of these criteria is the ratio of the amplitude of tangential oscillatory displacements of contacting bodies and characteristic linear quantities associated with the dimensions of the real contact areas of the contacting surfaces. It is convenient to characterize fretting wear regimes using maps on which the boundaries of the areas of the corresponding regimes are shown in the coordinates: oscillation amplitude/normal contact load (or nominal contact pressure). The influence of the wear regime on the life of one of the common types of connections subject to fretting wear, namely electrical contacts, has been shown experimentally. Using a map of fretting wear regimes, the influence of the amplitude of tangential oscillations and normal load on the dependence of the contact electrical resistance on the number of oscillation cycles under different regimes was analyzed. The fundamental difference between this dependence in the fretting wear regime and in the normal reciprocating sliding of contacting surfaces is shown. The proposed criteria of fretting wear modes and their visual representation in the form of wear mode maps allow predicting the wear mechanism of a given contact joint. Understanding the wear mechanism allows for a reasonable choice of materials for contacting parts and con-tact joint parameters (contact pressure, contact rigidity) to ensure the reliability of friction joints, including electrical contacts, under fretting wear conditions.

Compositions of ashless thiophosphoric and thiocarbamine compounds were studied as a tribologically active additive. Studies of the anti-wear properties of compositions in both fresh and oxidized oil samples in comparison with the effectiveness of a similar functional effect of a traditional additive — zinc dialkyldithiophosphate were carried out on a tribometer that implements the wear process of conjugated pairs under sliding friction conditions simulating the boundary lubrication mode. The results of tribotests of mixtures of these compositions with metal-containing detergents of various chemical nature in a solution of synthetic lubricating oil as model variants of the composition of motor oils are presented. The synergism of the action of the ammonium salt composition of dialkyldithiophosphoric acid and methylene bis-dibutyldithio-carbamate, which provides a reduced content of sulfate ash and phosphorus, factors of environmental safety of the use of oils, is noted.

The influence of the elastic-plastic properties of the coating-substrate system on the mechanical and tribological properties of coatings is investigated in the present work. The mechanical and tribological properties of the coatings were obtained by tribological testing and indentation. A screening experiment for vacuum ion plasma coatings of nitride systems TiAlN, CrAlSiN deposited on steel substrates (38X2MYA, 12X2H4A) was performed. The mechanical properties of the coatings were determined using the NanoTest 600 continuous indentation method. The microstructure of the coatings and their surface topography were studied using a high-resolution ZEISS CrossBeam 340 scanning electron microscope (SEM). Tribological tests of the nitride coatings were performed on a TRB friction machine (Anton Paar Tritec) according to the methods of DIN 50324 and ASTM G99. In addition, the indentation process of nitride coatings was studied based on the solution of the quasi-static contact problem when introducing a rigid indenter into an elastoplastic two-layer half-space. The mechanical characteristics of the considered coatings H/E and H³/E², the conditions of adhesion failure between the layers have been determined. Theoretical studies are complexed with the results of laboratory experiments. It is shown that when setting up laboratory experiments on indentation and tribological tests of coatings it is necessary to control not only the permissible depth of penetration of the indenter, but also the ratios of elastic-plastic properties of the coating and the substrate. It has been found that the service life of tribo-conjugate elements with coatings of a certain thickness can be increased by combining the elastic-plastic properties of the layered medium adapted to the given loading modes. This will prevent the localization of tensile and compressive stresses, delamination and cracking at the interface of two materials.

The aim of the work is to analyze the dynamic response of a layered medium (on the example of road pavement of highways), on dynamic impact for the conditions of “soldered” contact between separate layers, and conditions of full slip. To solve this problem, a mathematical model of the dynamic stress-strain state of a layered half-space is applied, based on the solution of the Lame equation in displacements, using the Hankel integral transformation, construction of the amplitude-frequency response (AFR) of accelerations on the surface of the studied medium, obtained directly from the AFR of displacements. In the course of numerical experiment on this model, it was found that the case of mating contact between the pavement layers corresponds to the presence of one well-defined frequency extremum on the AFC of accelerations. The case of “full slip” corresponds to the presence of a number of frequency extrema on the acceleration frequency response. In this case, when modeling the full slip at the boundary of the bottom layer of the half-space and the underlying half-space and varying the modulus of elasticity of the half-space, the presence of a well-defined frequency extremum in the range of 426—531 Hz is noted, presumably corresponding to the oscillations of the underlying half-space itself. The established regularities can be used at perfection of methods and means of nondestructive control of layered media, in particular for increase of informativeness about their structural condition necessary for decision-making about repair or major repair.

The results of testing a pair of reversible sliding friction “bronze BrA5 — steel 45” in dispersion-lubricating media characterized by varying degrees of surface activity with respect to bronze are presented. Changes in microstructural characteristics during tribo-deformation of metal were analyzed from the standpoint of the Rebinder effect, which determines the possibility of implementing the phenomenon of selective transfer (wear-free mode) during tribopair operation. It is shown that when bronze is rubbed in lubricant-dispersion media characterized by relatively low surface activity, the influence of the medium on the surface structure of the tribo-material is based on the realization of a surface-strengthening effect — the total density of dislocations in the deformed near-surface layer increases. The wear intensity in this case is I_h ≈ 1.5ꞏ10^–7—4.0ꞏ10^–8. When bronze is rubbed in moderately surfactants, both surface-plasticizing and surface-hardening effects are realized with the predominance of the latter. At the same time, the wear intensity decreases slightly, taking values in the range of I_h ≈ 1,2∙0^–7—1,5∙10^–8. During tribo-tests of bronze in environments with increased surface activity, the bronze wear intensity remains at a fairly low level: I_h ≈ 2.2ꞏ10^–8—3.0ꞏ10^–8. However, in this case, two crystallographically isostructured solid solutions are formed in the near-surface layer of the tribomaterial, one of which is enriched with copper. Based on the concepts of the physical-chemical mechanics of contact interaction, the system-structural foundations of the material science approach, underlying the analysis of the tribological efficiency of liquids used as dispersion media for plastic lubricants are described.

The evaluation of the determination of the friction coefficients and the wear intensity of an anti-friction material based on silver with the addition of molybdenum disulfide is given. The results of studies of the friction coefficients in the contacting pair are presented — steel SHX-15 and antifriction material based on silver with the addition of molybdenum disulfide. The average value of the coefficient of friction at a run of 1200 m. in a pair, a ball made of SHX-15 steel and a ring with a cover made of an antifriction material containing 94 % silver and 6 % molybdenum disulfide is 0,128 with a standard deviation of 0.006. At a run of 15000 m, the average coefficient of friction was 0.129 with a standard deviation of 0.01. For a friction pair of an anti-friction material containing 94 % silver and 6 % molybdenum disulfide and steel SHX-15, the coefficient of wear intensity of the antifriction surface at a contact voltage of 330 MPa is I = 0.86×10^–6 mm³/m, and for a counterbody in the form of a steel ball I_sh = 2.85×10^–8 mm³/m. Since the wear rate of the ball is two orders of magnitude lower than the wear rate of the friction material, the wear of the ball can be ignored in resource calculations. The obtained dependence of the coefficient of wear intensity on the maximum contact stresses will allow us to develop a calculation method for wear spherical articulated bearings.