Journal of Friction and Wear最新文献

The questions of frictional interaction during the contact of a vehicle’s elastic wheel and a flat solid support surface under different loading conditions by force and moment are considered. The parameters of this interaction are investigated: the adhesion coefficient; its components by areas with static and sliding friction; static friction use coefficient; static friction proportionality coefficient; and relative coefficient of limiting realized static friction. Mathematical dependences in the form of smooth continuous functions are proposed for physically correct calculation of the specified parameters. Two options for loading an elastic wheel with a force and a moment are considered. It is shown that the adhesion coefficient for a given longitudinal wheel slip depends on the loading conditions: the lateral force along the wheel rotation axis and the moment in the rotation plane, as well as their sequence of occurrence. With the same values of force and moment, the adhesion coefficient can change at different sequences of their occurrence: up to 70% for high lateral forces (near to weight) and up to 12% for small lateral forces (up to 20% of weight). Three methods for calculating the adhesion coefficient in the contact of an elastic wheel with a flat solid support surface are proposed. When calculating the proposed characteristics of the methods, averaged zero diagrams were used in the absence of lateral wheel force for different elastic wheels and different types and conditions of road surfaces. To obtain them, the procedure of approximation of numerous experimental data of different researchers was carried out. The developed methods are valid for all elastic wheels and all types and conditions of solid supporting surfaces. The results of the work can be used with sufficient accuracy for practical calculations in the design modeling of the properties of stability, controllability, and braking dynamics of wheeled vehicles.

An experimental and theoretical method of triboanalysis is proposed to characterize the antifriction properties of polyamides and composites based on them, used in self-lubricated metal-polymer sliding bearings. The indicators of wear resistance of the materials are determined experimentally. The generalized parameters of the mathematical model of wear used in the design of metal-polymer bearings are calculated. The dependences (diagrams) of wear resistance of unfilled polyamides PA6, PA66, and polyamide composites PA6 + 30GF, PA6 + 30CF, PA6 + MoS₂, and PA6 + oil paired with steel 45 on specific friction force are obtained and a comparative assessment of the wear resistance is given. The influence of contact pressure on the friction coefficient is studied and a significant decrease in the latter with increasing contact pressure is shown. A decrease in the Vickers hardness and elastic modulus of the surface layer of the studied materials during wear is also established. It is more significant for unfilled polyamide PA66 (by 1.66 times), PA6 + 30CF (by 1.5 times), PA6 + MoS₂ (by 1.41 times), and less noticeable for polymer composites PA6 + 30GF and PA6 + oil by 1.21 and 1.09 times, respectively. The fact should be taken into account in tribological calculations of metal-polymer sliding bearings. The research results are presented in the form of diagrams, which allow one to compare the wear resistance of the investigative materials in a wide range of specific friction forces. Thus, the practical significance of the results lies in the possibility of their use in tribological engineering to predict the service life of metal-polymer plain bearings and validate the choice of antifriction materials for their manufacturing.

This work is dedicated to assessing the effect of TiN, ZrN, TiN + ZrN, (Ti–Zr)N, ZrN–(Ti–Zr)N–TiN nanostructured coatings, deposited on plates of hard alloy T15K6 by the PVD method, on tool wear and thermoelectric parameters of the process of turning work pieces from steels 45, 38HS, and 12H18N10T. The greatest decrease in temperature in the cutting zone was recorded during the processing of steels 45 and 38HS, characterized by high thermal conductivity coefficients, while the maximum effect was achieved due to TiN + ZrN and ZrN coatings, for low thermal conductivity steel 12H18N10T, the lowest temperature was provided by the ZrN, (Ti–Zr)N and ZrN + (Ti–Zr)N + TiN compositions. Analysis of the variable component of the thermo-EMF signal during cutting shows a decrease in the amplitude of oscillations for coatings that provide the greatest wear resistance of the tool. According to the results of the experiments, such an effect when turning steels 45 and 38HS at optimal speeds was demonstrated by ZrN + (Ti–Zr)N + TiN and TiN + ZrN coatings, and for stainless steel 12H18N10T, ZrN, ZrN + (Ti–Zr)N + TiN and TiN. The established relationship between the wear resistance of carbide inserts and the amplitude of fluctuations of the variable thermos-EMF component makes it possible to use it as an indirect criterion for selecting the optimal composition of the wear-resistant coating from the point of view of thermophysical compatibility with tool and machined materials.

The research of deformation of samples made from high-speed steel R6M5 and treated by volumetric pulsed laser hardening (VPLH) under various laser exposure modes and measurement topology (laser radiation energy, distance from the irradiation site) were carried out using strain measurement. It was found that after VPLH treatment of the samples there are deformations in the longitudinal and transverse sections. This fact indicates the volumetric nature of the deformation changes in the material, and at the same time, it shows the pronounced extremum of relative deformations, which depends on the previously listed conditions of exposure and measurement. The results of abrasive wear tests showed the greatest effect of VPLH for the laser irradiation energy of 300 J and the distance from the irradiation site of 24 mm, which corresponds to the results obtained by the strain measurement for the determination of the samples’ relative deformations. The received extremum corresponds to the optimal hardening modes when changing the relative deformation by 1.06 times and increasing of the hardened resistance samples by 2.3 times. The possibility of joint use (convergence) of the tests results for abrasive wear was determined using the method of retrospective (a posteriori) randomization. This allows recommending the strain measurement method for the optimal modes of VPLH determination and can help to significantly reduce the cost of material consumption and labor intensity of laboratory tests, especially in the process of determining the modes for the samples with variable inputs (structure and chemical composition of materials, geometric parameters of products, operating modes, etc.)