Modern methods and equipment for testing and studying chain transmissions including specialized stands for bicycle transmissions are considered. It analyzes their advantages, limitations, and future development trends, such as the use of next-generation sensors and the automation of testing processes. Special attention is given to the standardization of testing and the adaptation of industrial methods to the specific needs of the bicycle industry and in scientific research. It has been established that in most cases, the industry uses standard calculation methods and universal testing machines, which explains the limited use of such testing stands and friction machines. Despite the widespread use of bicycles there is very little literature available on the wear and efficiency of bicycle chains.

Thus, this article can serve as a useful resource for professionals involved in the design, testing, and analysis of the material properties of drive roller chains under friction and wear conditions.

The purpose of the work is to compare the tribotechnical properties of industrial working rollers made of steel SHKH15SG (before and after operation) and cast iron IChX28H2 (before operation) to select the material of the rollers and increase the service life of pendulum mills.

Metallographic studies were performed on IM7000 optical microscopes with a Thixomet image analyzer and a microvizo-MET microimage. Microhardness measurements were carried out automatically using the Vickers method at a load of 50 g over the entire cross-section of industrial rollers. Tribotechnical tests were performed on a SMC-2 friction machine according to the “roller — abrasive roller” scheme (rotation speed 500 rpm, load 45 N, test time 2 hours) with an assessment of the coefficient of friction, wear and surface roughness.

It was found that steel SHX15SG in its initial state had a homogeneous structure of low-pressure marten-site with a carbide heterogeneity of (Cr,Fe)₃C (HV 828) with an average hardness of HV 630. After 3 months of operation, under the influence of softening processes (temperature and plastic deformation), martensite was transformed into tempering troostite in the subsurface layers, and bands with martensitic and martensitictroostite structures were formed with an average hardness of HV 443, which is 1.5 times less than the hardness (HV 630) in the initial state. Internal arc-shaped cracks were found.

The IChX28H2 cast iron had a white pre-eutectic cast iron structure consisting of alloyed austenite (670—750 HV), cementite type carbides (Cr,Fe)₃C (856 HV) and special carbides (Cr,Fe)₇C₃ (1389 HV) and (Cr,Fe)₂₃C₆ (1389 HV). The average hardness of cast iron was HV 781, which is 1.2 times higher than the hardness of steel in its initial state. Tribotechnical tests have shown that cast iron had a lower coefficient of friction (0.58 versus 0.68—0.85 for steel), 1.7 times less wear (214 mg versus 358 mg for steel) and the ability to run in under friction (reducing the roughness of R_a by 3.7 times). Based on the structural characteristics, hardness and tribotechnical properties, wear-resistant cast iron IChX28H2 is recommended as a material for the manufacture of rollers of pendulum mills operating under conditions of intense abrasive wear, which will increase their service life.

The present study evaluates the effectiveness of low-temperature gas nitriding of alloy structural steels 38KhMYuA, 38KhN3MA, and 38KhN3MFA used in heavily loaded gear transmissions, and determines the applicability limits of thin nitrided layers from the standpoint of contact fatigue. The investigations were carried out after nitriding at a temperature of 580 °C for 7 h using microhardness profiling, layer-by-layer chemical analysis by high-temperature gas analysis, X-ray diffraction analysis, and contact fatigue testing of rollers simulating rolling with sliding conditions typical of helical gear engagement. It was found that lowtemperature nitriding produces a hardened surface layer with a thickness of 0.18—0.25 mm and a microhardness of 4.8—5.5 GPa, while maintaining a ductile core with a hardness of 240—260 HB. The results show that under elevated contact stresses, failure of nitrided specimens initiates in the subsurface region and develops according to a deep contact fatigue mechanism, accompanied by deep spalling and the formation of a so-called white etching layer. The obtained data indicate the limited effectiveness of thin nitrided layers in highly loaded gear systems and demonstrate that materials with thicker hardened layers (0.8—1.2 mm), or design and technological solutions aimed at reducing contact stresses, are more appropriate for improving service life under severe cyclic loading conditions.

The paper presents a comparative analysis of the tribological behavior of copper-based composite materials with different contents (30 and 50 vol. %) of the MAX phases Ti₃SiC₂ and Ti₃AlC₂, obtained by extrusion additive manufacturing.

The samples were manufactured using a multi-stage technology: powder mixing, extrusion, additive formation, decomposition of the polymer binder, and heat treatment. Tribological tests were conducted under dry sliding friction conditions using the pin-on-disk scheme with a counterface made of AISI 52100 steel. The wear surfaces were examined using laser confocal and scanning electron microscopy with elemental mapping.

Composites with 30 vol. % MAX-phase (Cu–30%Ti₃SiC₂, coefficient of friction (COF) = 0.46; Cu–30%Ti₃AlC₂, COF = 0.51) demonstrate significantly higher values of the average friction coefficient in composite — AISI 52100 steel tribosystem compared to the samples containing 50 vol. % MAX-phase (Cu–50%Ti₃SiC₂, COF = 0.28; Cu–50%Ti₃AlC₂, COF = 0.27). An oxide layer formed by oxides of the com-posite components was detected on the wear surfaces of all samples. The wear mechanism is defined as combined oxidative and adhesive, with similar wear particle morphology for all compositions. The tribological properties of composites are determined by both the volume fraction of the MAX phase and its chemical composition. The increased susceptibility of Ti₃SiC₂ to oxidation significantly influences the formation of the tribofilm and, consequently, the friction coefficient and wear resistance of the material.

Polytetrafluoroethylene (PTFE) has a low friction coefficient and high chemical inertness, which makes it popular for the manufacture of tribological materials. However, its main disadvantage is low wear resistance. To improve the characteristics of PTFE, fillers are used, among which natural silicates, including palygorskite, are promising due to their availability, mechanical strength and ability to improve tribological properties. Thus, the aim of the work is to develop polymer composite materials based on PTFE and natural palygorskite silicate with improved tribological characteristics.

The starting materials were PTFE powder grade PN-90 and natural palygorskite of Ural origin. Structural analysis of the samples was performed using IR spectroscopy and scanning electron microscopy with energydispersive analysis, hardness was measured using the Shore A method. The results showed a significant improvement in the tribological characteristics of composites with palygorskite compared to the original PTFE. With the addition of 5 wt. % of mechanically activated palygorskite, the wear rate decreased from 120 mg/h to 0.36 mg/h, and wear resistance increased 330 times. The friction coefficient slightly increases, but remains at a fairly low level, which is due to changes in the microstructure of the friction surface. The results of the conducted studies of the friction surface of composite samples confirm the formation of a strong wear-resistant surface layer (secondary structure). The resulting composites are promising for use in friction units in engineering and industrial equipment, where high wear resistance is required at a low friction coefficient.

The paper explains the need to combine synergetics and fractal analysis to study the contacting elements in friction and wear, as part of self-organizing into open systems dissipative structures known as a fractal behavior. The concept of multifractal analysis introduces the new quantitative parameters for the structures, characterized by a spectrum of generalized fractal dimensions and reflected by the degree of randomness. In accordance with the diversity of types of tribological process, various scenarios of system evolution seem possible. The most adequate description of these scenarios is achieved not in real physical space, but in a hypothetical space with ultrametric topology. Different levels of structures (micro, mesa and macro scale) are described in the framework of multifractal analysis. It has been established that the frictional contact under study is a non-uniform fractal, that is, a multifractal. The procedure for calculating the multifractal dimension of this structure and the results of numerical calculations are presented, which confirm that the analyzed friction unit is a non-uniform fractal, i.e. a multifractal.

The article presents the results of a study examining the effectiveness of copper ion implantation in the steel surface for a similar friction pair without lubricant. It is shown that under steady-state friction conditions with implanted ions at irradiation doses of 10¹⁷ ion/cm² and 5×10¹⁷ ion/cm², the steel wear resistance increases by 2 and 1.5 times, respectively. The effect of preliminary implantation of iron ions at a dose of 10¹⁶ ion/cm² is examined. It is found that the use of preliminary implantation leads to a 2.5-fold increase in wear resistance. The friction surface of samples pre-implanted with iron ions exhibits minimal damage and the highest wear resistance.

The article describes structural changes in the surface plastic deformation zone during sliding friction of steel with a copper-based coating. It is shown that the increase in wear resistance is associated with the presence of a “long-range effect”, which contributes to an increase in the wear resistance of surface layers. The mechanism of the “long-range effect” in ion-alloyed metallic materials under contact deformation conditions is discussed.

Using the finite element method, the effect of load on the stress-strain state of reinforced metal-fluoroplastic plain bearings under static and dynamic loading conditions is investigated. Metal-fluoroplastic bearings are considered as three-layer composites, and the stresses and deformations of the main layers, the antifriction and adhesive layers, responsible for the bearing capacity under load, are studied. The difference in the stress-strain state under static and dynamic loading of bearings is shown. It has been established that the load capacity of bearings under dynamic loading depends on the ratio of the applied stresses and deformations to the strength characteristics of the adhesive layer material. The obtained calculation results are compared with experimental data. The satisfactory correlation between the calculated and experimental data allows us to use this method to determine the dynamic load capacity of plain bearings.

This article examines the problem of increasing the wear resistance of materials. The primary objective of the study was to experimentally validate the effectiveness of 3D-printed porous polymer structures impregnated with lubricant to improve tribological performance by retaining the lubricant within the pores without chemical interaction with the base material. Experimental samples were fabricated from two types of polymers — polylactide (PLA) and acrylonitrile butadiene styrene (ABS) — with a fill density of 90 %. The samples were then impregnated with I-20 industrial oil and tested on an SMT-1 friction rig according to standard procedures. The macroscopic structure of the samples was simultaneously examined using an optical microscope. It was found that impregnation of the samples with industrial oil resulted in improved tribological performance compared to friction without lubrication. However, the PLA plastic samples exhibited a decrease in the friction coefficient of approximately 12 %, while the ABS samples demonstrated a decrease of approximately 60 %. This is due to the specific distribution of lubricant within the porous structure of polymers. Although the PLA sample contained 38 % more oil than the ABS sample, it was bound, preventing its release in the friction zone. For the PLA sample, the friction coefficient was comparable to that of a bath-lubricated sample.

These results demonstrate that the incorporation of porous structures created by 3D printing, followed by impregnation with lubricant, is an effective way to reduce wear and improve the performance of polymeric materials.

A multi-criteria approach to the comprehensive analysis of the tribotechnical characteristics and physical-mechanical properties of vegetable oils is proposed for their comparison and selection as a base for lubricants. The study investigated refined rapeseed oil (RR) and technical rapeseed oil (RT), technical castor oil (CT), unrefined linseed oil (LO), and refined sunflower oil (SO). An assessment was conducted of their fatty acid composition, viscosity index, flash and pour points, oxidative stability, friction coefficient, wear scar diameter, critical load, and welding load. The analyzed objects were represented as points in a multidimensional space of their normalized physical and mechanical properties and tribotechnical characteristics. An integral criterion for comparing oils is proposed as a measure of distance from a hypothetically worst sample, which allowed for the ranking of oils by their suitability as a lubricant base (from best to worst): RT, LO, CT, RR, SO. The position of the oils in the space of principal components was determined, and the directions and magnitudes of the loading vectors for the oil characteristics were established. A correlation between physical and mechanical properties and tribotechnical characteristics was revealed, allowing these indicators to be linked to the features of the oils fatty acid composition. Based on the analysis of the sample arrangement in the principal component space, a conclusion was drawn about the promise of creating a composition from RT, CT, and LO oils, with a potential synergistic effect for improving load-bearing capacity, oxidative stability, and viscosity-temperature properties.

The results obtained can be used for the development of effective biodegradable lubricants from vegetable raw materials.