Problems of Tribology

Tribochemistry of damage to metal joints during fretting corrosion

2026-01-27T21:12:40+02:00

The patterns of fretting wear of a number of structural materials and galvanic coatings were researched, taking into account their mechanical and physicochemical properties. The influence of the composition of the gas environment (air, oxygen) on the intensity of fretting wear was assessed, as well as the contact load with the corresponding temperature recording in the friction zone. Data were obtained indicating the possibility of low-amplitude fretting of metals in an air environment along with the oxidative processes of electrochemical corrosion. The physicochemical prerequisites for the initiation of electrochemical processes in the zone of vibrational contact during the formation of an ultradisperse oxide layer, which becomes a catalyst for the accelerated chemisorption of oxygen and air moisture in radical and ion-radical forms, are considered. As a result, according to the electronic theory of adsorption and catalysis on semiconductors (oxides), contact phenomena begin to develop through the mechanism of autocatalytic corrosion. After a latent period of oxide accumulation, conditions are created for electrochemical processes that contribute to corrosion-fatigue failure of mating surfaces. The results of the study expand existing ideas about the nature of corrosion processes during partial and mixed sliding, focusing on the possibility of using traditional methods of electrochemical protection to increase the fretting resistance of friction units operating under vibration conditions

Lifetime Improvement of Contact Brush Units of Automotive Power Machines. Part 2

2026-01-30T19:44:04+02:00

Lifetime testing of contact brush units of automotive power machines is held. Friction contact of copper and graphite under working voltage and current within ordinary atmosphere environment was simulated on the friction test bench. Wear resistance and friction losses have been detected. Wear mechanisms and friction surfaces were investigated using the scanning electronic microscopy. This study allows recommendation the optimal surface treatment of copper elements of contact brush unit of alternators or commutator unit of power starters.

Lubricating effect of oils by controlling the concentration of chemical components of the additives

2026-01-30T23:28:12+02:00

A proposed and substantiated multifactorial approach to assessing the lubricating effect of oils, considering the influence of physicochemical factors and rheological characteristics on the evolution of the creation and adaptation of chemically modified boundary layers (CMBLs) to real operating conditions in conditions of the partial EHD lubrication mode. Comparing the results of the anti-wear and anti-friction properties of the studied oil samples, while complying with the additive manufacturer's conditions for the mass fraction of sulfur, which is 1.488–1.9662%, a necessary condition for the best results in terms of the combined action of the anti-wear and anti-friction properties of the oils is to establish a total additive concentration of 3.9–4.9% with a phosphorus mass fraction of 0.046–0.057%. In the series of samples studied, sample 4 with a concentration of 4.9% additive shows the best universal properties, especially for the operation of units with combined engine and transmission systems (universal STOU oils for agricultural machinery).

Justification of the microcutting scheme in the friction-mechanical method of applying anti-friction coatings

2026-01-31T17:13:57+02:00

A review of modern approaches to substantiating the patterns of anti-friction coating formation during friction-mechanical application has made it possible to establish the importance of ensuring favourable conditions for microcutting of anti-friction material. Creating these conditions requires studying the interaction scheme of microirregularities in the contact zone between the tool and the part. From the point of view of cutting mechanics, a scheme of interaction of a single micro-irregularity, which is a model – a cutter made of 200 gray cast iron, with a contact surface made of anti-friction material – brass L63, was constructed, which made it possible to establish physical changes in the tool and machined surface system. The value of the front cutting angle has been theoretically established to ensure maximum efficiency of the microcutting process and filling of microcavities between microirregularities. The use of a model experiment, the method of similarity and dimensions made it possible to confirm the main theoretical regularities obtained using characteristic microcutting diagrams. It has been shown that the process of changing the geometry of the micro-irregularity vertex occurs in accordance with the principle of adaptability of the entire ‘tool-part’ system, according to which the minimum micro-cutting energy is realised. The results obtained are an important reserve for improving the quality of anti-friction coating application by the friction-mechanical method

Correlation between sliding bearing wear rate and material characteristics of friction surfaces in heavily loaded construction and road machinery

2026-01-31T17:53:11+02:00

Based on an investigation of how entropy generation depends on material and tribological characteristics, it was found that the wear rate of a sliding bearing operating under elastic and elastoplastic contact conditions exhibits a nonmonotonic relationship with the surface dislocation density. Specifically, at relatively low dislocation densities, wear intensifies as this parameter increases, whereas in the high-density regime, further growth leads to a reduction in wear. A mathematical model describing entropy generation arising from the interaction between lubricant molecular dipoles and dipoles induced by fluctuations in surface dislocation density has been derived. The results demonstrate that the component of wear associated with this mechanism of entropy production decreases as the dipole moment of the lubricant molecules increases.

An additional analysis focusing on the influence of material parameters on entropy generation shows that bearing wear intensity rises with increasing surface dislocation density. An analytical expression for entropy production due to fluctuations in surface dislocation density has been obtained.

It is also established that, for the crankshaft sliding bearing of the DZk-250 motor grader operating under elastoplastic contact conditions, the wear intensity follows a similar trend: it increases with growing surface dislocation density in the low-value range and decreases when this parameter reaches higher values. Furthermore, an equation describing entropy generation during the interaction between lubricant molecular dipoles and dipoles associated with dislocation density fluctuations has been formulated.

Experimental and Analytical Study of Acid Number Variation in Engine Oils Under Operational Contamination

2026-02-01T10:36:04+02:00

This paper presents an experimental and analytical study of the variation of the total acid number (TAN) in engine oils under operational contamination. The research is aimed at assessing the correlation between the acidity growth of lubricants and their wear behavior in the four-ball test configuration. Theoretical modeling and experimental testing were performed to identify the parameters of a wear law that incorporates contact pressure, oil viscosity, hardness, and TAN as key variables. The obtained results confirm that the acid number increases significantly during oil operation: from 0.9 to 2.9 mg KOH/g—which leads to an intensified wear rate of the contact surfaces. The proposed model quantitatively describes the relationship between the acidity level and wear intensity and enables prediction of oil performance based on its physicochemical degradation. The developed approach allows for improved evaluation of the residual life of lubricants and optimization of maintenance intervals for internal combustion engines.

Investigation of the effect of tribological loading parameters on the linear wear rate of a polytetrafluoroethylene-based composite reinforced with polyimide fiber

2026-03-06T21:19:07+02:00

The article presents the results of a comprehensive experimental and theoretical study of the tribotechnical characteristics of a composite material based on polytetrafluoroethylene reinforced with polyimide fiber. The main objective of the study was to determine the quantitative regularities governing changes in the intensity of linear wear as a function of external tribological loading parameters, as well as to establish optimal operating modes for the material. A mathematical modeling approach based on a full factorial design was employed to plan and conduct the experiments. The experimental results enabled the derivation of a first-order regression equation describing the dependence of wear on the variable parameters. Statistical analysis of the model included an assessment of its adequacy and the significance of the regression coefficients. By constructing response surfaces, zones of minimum wear intensity were identified, and optimal operating conditions for the material under dry friction were determined. The study confirms the significant influence of both individual factors and their interaction on the wear resistance of the composite material. It was established that deviations of tribological loading parameters from their optimal values lead to a substantial increase in linear wear intensity. The proposed approach can be effectively applied to optimize the operating modes of composite materials based on polytetrafluoroethylene and polyimide fiber in friction units of machines and mechanisms operating under high loads and requiring enhanced wear resistance.

Improved algorithm for engineering calculations of the parameters of a container tipping mechanism in a garbage truck taking into account the wear of friction pairs

2026-03-06T21:32:12+02:00

The article is dedicated to the development of the scientifically grounded improved method, based on the analysis of scientific literature sources, for the design calculation of the parameters of a mechanism for tipping a container with municipal solid waste into a garbage truck, taking into account friction wear, in order to determine its main geometric, force, and speed parameters. The drive of the working parts of the mechanism for tipping a container with municipal solid waste into a garbage truck is hydraulic, with a power source from the garbage truck’s pump station. The usage of the proposed improved methodology for the engineering calculation of the parameters of the mechanism for tipping a container with municipal solid waste into a garbage truck, taking into account the wear of friction pairs, allows significant reduction in design time and avoids unnecessary costs for labor-intensive experimental and theoretical research. Using the proposed scientifically based improved method of design calculation of the parameters of the mechanism for tipping a container with municipal solid waste into a garbage truck, taking into account the wear of friction pairs, its main geometric, force, and speed parameters have been determined. It has been established that the development of an improved methodology for the design calculation of the parameters of the mechanism for rotating the manipulator lever during the loading of municipal solid waste into a garbage truck, taking into account the wear of friction pairs, requires further research

Development and Investigation of the Technology of Electro-Induction Surfacing of Parts of Working Bodies of Agricultural Machines

2026-03-06T21:40:18+02:00

This article examines ways to improve the wear resistance of agricultural machinery components operating under intense abrasive wear conditions. The study focused on cultivator shanks made of 50, 50KhGA, and 65G structural steels. The aim of the study is to develop and scientifically validate a technology for electro-induction surfacing of wear-resistant coatings based on Fe–Cr–C and Fe–Cr–C–B alloys, ensuring the formation of an optimal deposited layer structure and improving the performance of the components. A hardening process is proposed, including electro-induction surfacing of a hard-alloy material followed by pulsed high-energy heating, as well as the design of a special inductor that allows for simultaneous surfacing of the shanks' nose and hardening of their wings. The effect of chemical-thermal treatment (boriding) on the formation of a hardened surface layer is also studied. Field tests were conducted under cultivating conditions using pilot and control samples. Working tool wear was assessed based on changes in geometric parameters, overlap area, and mass loss. It was found that the relative wear of surface-hardened wingtip shanks ranged from 8–27%, while for standard parts hardened using traditional methods, it reached 25–40%. This indicates a 30–60% reduction in wear intensity. It was shown that the performance of wingtip shanks during operation is determined primarily by maintaining their overall arrowhead shape. For a more objective wear assessment, it was proposed to use integrated indicators including changes in the overlap area of the working tools and average mass loss.

Study of tribotechnical characteristics of composite coatings formed by the method of electrospark alloying

2026-03-10T20:04:15+02:00

The results of studying the tribotechnical characteristics of composite coatings formed by the electric spark alloying (ESA) method are presented. It has been established that the key factor in controlling the stress-strain state of the “coating-base” system is the optimization of the thickness and continuity of the strengthened layer. Using the finite element method, it was demonstrated that for coatings with a thickness of 100 μm, the minimum stress concentration is achieved when the coating continuity is within 60–80%. Deviations from these values (less than 50% or greater than 80%) lead to an increase in local stresses. Modeling showed that the maximum equivalent stresses are localized at depths up to 30 μm for BK8 coatings and up to 50 μm for KHN25 coatings (with a total layer thickness of 120 μm), which reduces the stress–strain state of the substrate under external loading. Experimental abrasive wear tests in an environment with loosely fixed abrasive particles showed that the minimum weight loss is achieved when the coating continuity is 55–75%, with an optimal value of 70% and a ratio of strengthened to unstrengthened areas of 2:1. Comparative analysis of materials revealed that coatings made of WC-8Co alloy (microhardness 10000 MPa) exhibit 1.8–2 times higher weight wear compared with KHN25 alloy (microhardness 8500 MPa). The obtained results make it possible to scientifically justify the selection of ESA modes and electrode material compositions for the restoration of machine parts operating under conditions of intensive abrasive action

Equipment and technology for gas fluorination of polymers to improve their wear resistance under micro-impact loads

2026-03-12T21:33:00+02:00

The article addresses the problem of improving the cavitation–erosion wear resistance of polymer materials operating under micro-impact loads in corrosive environments. It is shown that material degradation under such conditions has a complex mechano-corrosive nature, while corrosion processes can significantly accelerate the degradation of surface layers. In this regard, the use of polymers with high chemical resistance and inertness to aggressive media is relevant. However, the application of such highly resistant polymers is often economically impractical, which necessitates the development of methods for surface modification of available structural polymers to improve their performance properties. he aim of this work is to develop and scientifically substantiate a laboratory installation and technological parameters of the direct gas fluorination process for polymer materials in order to form a modified surface layer without altering the surface microgeometry and to increase their wear resistance. Polypropylene grade 21060, widely used in mechanical engineering, agricultural machinery, and food equipment due to its sufficient strength, chemical resistance, and processability, was selected as the object of the study. A laboratory installation for direct gas fluorination of polymers was designed using a gas mixture of 1% F₂ and 99% Ar followed by treatment with nitric oxide to neutralize active radicals. Experimental studies showed the formation of a modified surface layer about 5 μm thick with increased chemical inertness. It was established that fluorination significantly reduces the intensity of cavitation–erosion wear of polypropylene in various environments, confirming the effectiveness of the method for improving the durability of polymer components.

Surface deformation relief as an indicator of fatigue damage under two-step loading sequences

2026-03-15T11:50:14+02:00

The study investigates the possibility of predicting the residual fatigue life of clad structural aluminum alloys based on the quantitative evaluation of surface deformation relief formed during cyclic loading. Fatigue damage accumulation in metallic structures is accompanied by microstructural transformations caused by dislocation motion along crystallographic planes. These processes lead to the formation of characteristic surface features such as slip bands, extrusions, and intrusions. Although these structures are three-dimensional, their development can be effectively assessed using two-dimensional optical microscopy images, enabling quantitative analysis of the deformation relief evolution during fatigue loading. The research focuses on clad aluminum alloys widely used in aircraft structures, including D16ATV, V95, 2024-T3, and 7075-T6. The obtained data allowed regression models to be developed that relate the damage parameter to the relative residual fatigue life. The proposed approach was extended from regular cyclic loading to simple irregular loading regimes, specifically two-step loading sequences of the “low–high” and “high–low” types. The results were compared with predictions based on Miner’s linear fatigue damage summation rule. Within a certain range of cyclic stresses, the developed regression model provides prediction accuracy comparable to, and in some cases exceeding, that obtained using Miner’s rule. The results confirm that the saturation of surface deformation relief can serve as a structurally sensitive indicator of accumulated fatigue damage. The proposed methodology can be applied both to direct monitoring of clad aluminum structural components and to the fatigue indicators for metal structures of aircraft, bridge, pressure vessels

Electromechanical wear of the contact wire–current collecting insert pair in electric transport systems

2026-03-15T12:00:28+02:00

The article considers the processes of current collection and wear in the sliding electrical contact system "contact wire - current collection insert" of a trolleybus. It is shown that the destruction of contact surfaces has a complex electromechanical nature and is caused by the simultaneous action of mechanical, electrical and thermal factors. The main mechanisms of electrical and mechanical wear of contact elements are analyzed, in particular, electroerosion, abrasive, fatigue and molecular-mechanical wear. The influence of contact pressure, current collector speed, traction current magnitude and properties of contact pair materials on the intensity of destruction of surface layers is considered. It is shown that the uneven distribution of current in the contact zone leads to local overheating of the surface and the formation of electric arcs, which accelerate the electroerosion destruction of contact elements. It is established that the formation of a thin graphite film on the surface of the contact wire can partially reduce the friction coefficient and wear intensity. The results obtained can be used to increase the durability of current-collecting elements of electric transport and optimize their operating modes.