Problems of Friction and Wear

CLASSIFICATION, CALCULATION METHODS, AND DIRECTIONS FOR TECHNICAL IMPROVEMENT OF GAS-LUBRICATED BEARINGS

2025-11-05T07:53:30+02:00

The article classifies and discusses methods for calculating and improving gas-lubricated bearings. The classification takes into account the nature of the loads, the design, the method of generating lifting force, and the characteristics of the bearings. It is shown that the methods for calculating and designing gas-lubricated bearings in a drive are based on the joint iterative solution of a series of problems, the classical theory of motion stability by A.M. Lyapunov, and the solution of the generalized unsteady Reynolds equation. It has been determined that the main directions for improving (modernizing) contactless drives are the use of aerostatic bearings with conical bearings surfaces of various geometries (length, cone angle), ensuring the adjustability of stiffness and load-bearing capacity, natural frequencies of conical aerostatic bearings by changing the value of their average clearance with gas lubricant, comprehensive provision of dynamic stability of the contactless drive by adjusting the stiffness of conical aerostatic bearings in conjunction with adjusting the parameters of supercharging and throttling of lubricant, design changes in the distribution of masses and external loads, etc.

ASSESSMENT OF TRIBOLOGICAL PROPERTIES OF TRANSMISSION OIL WITH COMPLEXES OF MICRO- AND NANOADDITIVES

2025-10-13T15:52:23+03:00

This paper presents an in-depth experimental study of how micro- and nanoadditives influence the tribological performance of transmission oils under boundary lubrication in non-stationary friction regimes. The motivation stems from the fact that up to 30% of total energy losses in mechanical systems are caused by friction, and the optimization of lubricant formulations is one of the most effective ways to improve energy efficiency and extend the durability of friction units. Particular attention was paid to the comparative behavior of base mineral oil TAD-17i and its modified compositions.

The experimental program involved rolling with sliding and pure sliding tests, measuring friction coefficients, linear wear, and surface microhardness. The results revealed that the base oil TAD-17i alone provides only partial friction reduction (about 33%), while the addition of nanodispersed components significantly enhances lubricant efficiency. Specifically, MoS₂ and XENUM MG GEAR demonstrated the highest effectiveness: they reduced the steady-state friction coefficient by 52–56% and decreased wear by a factor of 2–3 compared to the unmodified base oil. These additives formed stable, thermally resistant boundary films capable of withstanding variable loads, start–stop conditions, and elevated temperatures.

By contrast, graphite S-1 showed limited effectiveness due to the large particle size, which contributed to abrasive wear, while XADO 1 Stage Transmission initially increased wear because of coarse active particles, although a partial improvement in surface protection was observed after a running-in period. The study further established that the dominant wear mechanisms shifted from adhesive at the early stage to oxidative, abrasive, and corrosion-mechanical types depending on the applied additive and operating conditions.

Overall, the findings highlight that the efficiency of transmission oils in dynamic operating modes is largely determined by the rheological stability of boundary layers and the ability of additives to form protective adsorption films. Nanodispersed additives, especially MoS₂ and composite formulations like XENUM MG GEAR, proved to be the most promising for extending the service life of friction pairs, ensuring smoother transmission operation, and reducing energy losses. The practical implementation of such additives in the production of automotive and aviation transmission oils opens prospects for developing advanced lubricant formulations with enhanced reliability, wear resistance, and long-term stability under non-stationary conditions.

VOID CONTENT IN POLYMER COMPOSITE MATERIALS, THEIR NATURE OF AND WAYS TO MINIMIZE THEIR PRESENCE

2025-10-13T15:44:00+03:00

This article is an insight on the topic void content and associated hygroscopicity of polymer composite materials (PCM), made of carbon and glass fibers, their influence on mechanical strength and provides ways to minimize such influence of those phenomena on final characteristics of parts, made out of these materials. The issue of porosity and hygroscopicity of PCM materials becoming more relevant with more searches of engineering solutions for the introduction of such materials into fluid systems of the vehicles. A disclosure is given about the influence of above-mentioned phenomena on characteristics of carbon and glass fiber PCMs, as those are main fibers used in aviation industry. A number of technologies of manufacturing parts from such fibers is provided and their void content percentage is described.

DYNAMICS OF FRICTION COUPLES OF A BAND-SHOE BRAKE

2025-10-13T12:59:13+03:00

Based on a computational experiment concerning the dynamics of frictional interaction of the pulley rim with a system of linings arranged according to different layout schemes on the belt branches in the belt-pad brake of a drilling winch, the following research results were obtained. The condition of dynamic equilibrium of a flexible brake band with linings in contact with the pulley rim was established with different schemes of their arrangement on the belt. It was proved that with a uniform arrangement of linings, the impulse specific loads in the direction of the approaching belt branch increase by 1.5–3.0 times than in the direction of the converging belt branch. In order to ensure a uniform distribution of impulse specific loads along the arc of contact of the microprotrusions of friction pairs, a method was proposed for determining the values of the lining arrangement angles and their working areas on the belt branches. Recurrent dependencies were obtained for calculating the lining arrangement angles and their area, and therefore, the quantity. This allowed the pulse specific loads in the friction pairs to be quasi-equalized on the belt branches, and as a result, the wear of the working surfaces of the linings.

WEAR RESISTANCE OF CONTACT OF TITANIUM ALLOYS WITH COMPOSITE MATERIALS DEPENDING ON THE TECHNOLOGY OF THEIR MANUFACTURING UNDER CONDITIONS OF NOMINALLY FIXED CONTACT

2025-10-13T10:26:59+03:00

Titanium alloys as well as composite materials (carbon fiber and fiberglass) have recently been widely used in modern aircraft. Contact of titanium materials with polymer power composite materials under vibration loading conditions is accompanied by damage to both titanium and composite materials. The paper presents the effect on the wear resistance of contacting materials depending on the method of their manufacture and the composition of the composite material. It was determined that the wear resistance of fiberglass is 1.7-1.8 times lower than that of carbon fiber. It was determined that the total wear resistance of the Ti-CFRP contact increased by 10 % when forming the fabric in different directions compared to unidirectional forming. It was also determined that the wear resistance of the Ti5Al5V5Мо1Cr1Fe alloy increased by up to 20 % compared to the Ti6Al4V alloy when tested with composite materials.

CORROSION PROCESSES IN BRAKE FRICTION PAIRS

2025-10-13T09:12:15+03:00

The article discusses theoretical studies of corrosion processes in brake friction pairs in closed and open states used in lifting and transport equipment. Electrochemical corrosion is a heterogeneous and multistage process caused by the thermodynamic instability of the working surfaces of friction pairs in a given corrosive environment. The main calculation parameters of corrosion processes in friction pairs of brake devices are: local area of action; maximum permissible speed; permissible depth of influence; wear of micro-protrusion contact spots per unit of time; loss of micro-protrusion mass. It has been established that the sources of contact corrosion are: energy levels of materials (triboelectric effect), air and water, and the formation of electrolyte on the working surface of the lining during the destruction of its materials. The metal-polymer friction pair is a cathode (-) and an anode (+). The process of electrochemical corrosion is a combination of two related reactions: anodic (oxidation) and cathodic (reduction) , where Ox is a depolarizer (oxidizer) that attaches n electrons released as a result of the anodic reaction (metal ionization), Red is the reduced form of the oxidizer. A schematic diagram of the electrochemical destruction of the working surface of the overlay is presented. At the anodic sites (+), atoms lose and the ions formed pass into the solution , while the released electrons move from the anodic sites to the cathodic sites (-). Oxidizing agent (depolarizer) molecules Ox approach the cathode areas from the solution and attach themselves, forming the reduced form of the oxidizing agent - Red. It turns out that electrochemical corrosion on a heterogeneous surface of the overlay is similar to the operation of a short-circuited galvanic cell. The following features of the electrochemical corrosion process have been identified, which can be represented as two simultaneously occurring but largely independent electrode processes: anodic (ionization of the overlay) and cathodic. The kinetics of the anodic and cathodic processes, and therefore the corrosion rate, depend on the electrode potential of the metal; the electrode processes are localized in different areas of the working surface of the lining, where their flow is facilitated; material losses can be established mainly in the anodic areas of the lining surface.

INFLUENCE OF MICROADDITIVES ON MECHANICAL PROPERTIES OF POLYMER COMPOSITES FOR WATER TRANSPORT VEHICLES

2025-10-13T08:59:33+03:00

The study investigates the influence of microdispersed titanium-aluminum charge synthesized by high-voltage electrospark method on the adhesive and mechanical properties of epoxy composites. Optimal filler concentrations were determined that ensure significant improvement in the operational characteristics of the materials.

It was established that the introduction of 0.04 wt.% microdispersed charge provides maximum improvement in composite properties: adhesive strength under tension increases by 53%, adhesive strength under shear improves by 27%, and residual stress level rises by 33%. These indicators demonstrate the formation of strong interfacial bonds between the filler and matrix, significantly enhancing the composite's adhesion to metal substrates.

Additionally, improvements in mechanical properties of the epoxy composite were observed when introducing the filler at 0.2…0.5 wt.%. The study revealed a 40…56% increase in ultimate strength, 33…40% improvement in impact toughness, and stable elastic modulus (without significant changes). This indicates that this concentration range allows achieving an optimal balance of strength, impact resistance, and elastic characteristics of the obtained materials.

The obtained results confirm the effectiveness of using microdispersed charge for modifying epoxy composites. Precise dosage of the filler enables control over material properties, ensuring high operational performance.

These findings hold significant importance for industrial applications of modified epoxy composites. Particular attention should be paid to the following aspects. The process of introducing microdispersed charge doesn't require complex equipment, and the forming method allows precise control of filler concentration. From an economic perspective, using optimal concentrations (0.04…0.5 wt.%) minimizes filler costs, suggesting reduced operational and maintenance expenses for transport equipment.

The research proved the high effectiveness of microdispersed titanium-aluminum charge for modifying epoxy composites. The established optimal filler concentrations allow substantial improvement of mechanical and adhesive properties without significant changes to the technological process. The results open new possibilities for creating high-performance composite materials with tailored characteristics.

DAMAGE OF CARBON PLASTICS FROM LOW-VELOCITY IMPACT AND THEIR RELAXATION

2025-06-16T09:34:56+03:00

The damage assessment of carbon plastics with different filler structures based on the same epoxy matrix HexPly M 21 from low-velocity impact was carried out. The purpose of the research was to determine the difference between the depths of dents and the diameters of damage of carbon plastics that had two different fillers, namely bidirectional fabric and unidirectional carbon tape. Low-velocity impact tests were carried out with the same energy of 6.7 J per 1 mm of sample thickness. Immediately after the impact, damage parameters such as the depth of the dent and the maximum size (diameter) were measured, with the latter being determined from both the front and back sides. The depth of the dent was measured immediately after impact and after 7 days to determine the degree of damage relaxation, which reached 17%. The results of the studies are presented in the form of histograms of dent depths and damage diameters on both sides of the samples. It was found that the damage diameters for carbon plastics of both performances on the back side are significantly larger than on the front side.

INFLUENCE OF THERMAL REGIME ON THE STRUCTURAL-PHASE STATE OF COATINGS BASED ON 11Р3АМФ2 STEEL

2025-06-16T09:16:24+03:00

This study investigates the dependence of reinforcing particle distribution on thermal regimes within the carbide subsystem of coatings based on 11P3AMФ2 steel, obtained through surfacing. The variations in the volume fraction of secondary carbides and residual austenite in the matrix of the deposited coating were analyzed as functions of the thermal cycle during weld surfacing. The composition of secondary carbides was compared to that of eutectic carbides. It was determined that an increase in residual austenite content enhances the wear resistance of the coatings due to the γ→α'-martensitic transformation and the presence of dispersed secondary carbides within the matrix grains. The highest concentration of dispersed secondary carbides was observed in the reinforced layer heated to temperatures in the range of 600-700 °C. The wear resistance of the obtained coatings was evaluated using quartz sand and electrocorundum abrasives.

ANALYSIS OF FIBER-REINFORCED ELEMENTS FROM COMPOSITE MATERIALS

2025-06-16T09:01:27+03:00

The limit state of two polymer layered composite elements was studied using a numerical-analytical method, employing the finite element method during their deformation, damage, and failure. Stress intensity factors for normal separation were determined for developed complex-shaped models with initial imperfections in the form of cracks, simulating defects in the composite structure. A comparative analysis of the obtained calculated values of critical load with the experimental studies and adaptation of the developed methodology were conducted.

PREREQUISITES FOR THE DESTRUCTION OF THE SURFACE LAYERS OF DETAILS DURING THEIR FRICTION AND WEAR

2025-06-16T07:02:32+03:00

In the process of calculating friction and wear of surface layers, significant emphasis is placed on calculations for local stretching in the contact zone and the longitudinal stability of the material layers. Calculations are usually performed based on the classical laws of Hooke and Euler. For example, Hooke's laws are used for tensile calculations, where the stress is proportional to the strain , with . Additionally, the Euler formula is used for the stability calculations of the outer layers of the material. If , the outer layer material, associated with the base material of the part, loses its original shape, and elements of such a layer, supported by deeper plastic layers, can become brittle and lose longitudinal stability. In most loading cases, normal stresses in the zone under the stamp follow Hooke's law, and rupture stresses generally do not occur. In the zone ahead of the stamp, local stability of the layer is often lost under the same loads, leading to the formation of a corrugated surface. The change in the layer's shape indicates the presence of residual inelastic deformations.

Scattered literary sources containing data on different types of surface layers, mainly working under tension and compression, indicate that the material in the compression zone in front of the stamp behaves as an elastoplastic material. Consequently, deflection (initially flat cross-sections before deformation) and wave formation (corrugations) appear similar to initial geometrical micro-roughness after mutual shearing due to mechanical interaction. Such ambiguous material behavior during deformation suggests that instead of Hooke's and Euler's laws, their inelastic analogs manifest. Additionally, a thin surface layer due to strain hardening and re-hardening supported by the elastic base behaves like a rod with a low flexibility coefficient . In this case, local loss of stability of the surface layer may not occur, and brittle fatigue failure of the layer may occur. This process can end with the formation of local cracks.

Data from sources on different types of surface layer parameters, plastic, elastic, and elastoplastic, indicate that the conclusions obtained were confirmed by creating a mathematical model of the problem, reflecting the manifestations of the nonlinear properties of material parts after considering the geometric and physical nonlinearity of the deformed layer. In the mathematical model of the problem, the influence of brittle fracture of the outer layer, its cracking, and chipping on the deformation ridges can be established.

The results of the work can be refined by introducing a term describing the brittle fracture of the outer layers into the differential equation of the problem.

OPTIMIZATION OF DESIGN AND OPERATING PARAMETERS DURING THE OPERATION OF BRAKE FRICTION PAIRS

2025-06-10T21:25:23+03:00

Theoretical and experimental studies of optimization of design and operating parameters during operation of friction pairs of band-shoe brakes have allowed to establish the following. A comprehensive assessment of design and operating parameters of brake friction pairs at the stage of optimization design is proposed. In the unsteady process of electrothermomechanical friction, which is usually the frictional interaction of the conjugated sections of the surfaces of the friction pairs "metal - polymer" in time with changes in parameters while observing the sequence are interconnected and mutually conditioned. Experimental studies of the energy load of friction pairs under load were conducted and the uneven linear wear of friction linings along the branches of the brake band was determined. Based on the uneven linear wear of the running surfaces of the band linings, the dynamic coefficient of mutual overlap of the brake friction pairs was determined, which was 0.42.

INVESTIGATION OF THE IMPACT OF HAIL STRIKES ON THE STRENGTH OF CARBON COMPOSITES IN AIRCRAFT STRUCTURES

2025-06-10T20:40:28+03:00

This paper presents the results of an experimental study on the impact of hail strikes on the residual strength of carbon-fiber composite materials used in aircraft structures, particularly fuselage skins. A special method was developed to form ice pellets and apply damage simulating hail impact when an aircraft is stationary. Samples with various reinforcement schemes were tested under two different molding pressure regimes. The findings show that, in most cases, hail impact does not cause significant reduction in material strength. In some cases, a slight increase in strength was observed, likely due to experimental variability. The study provides valuable insights into the potential damage risks from hail to aircraft structures and highlights the relevance of further research in this field to enhance the reliability and durability of aerospace components.

RESEARCH OF THE VACUUM THERMOCYCLIC NITROGEN PROCESS IN A PLASMA PULSING GLOW DISCHARGE

2025-06-10T18:09:13+03:00

Analysis of literary sources and recent research, as well as patent information search showed that the use of vacuum thermocyclic nitriding technology in pulsating glow discharge plasma is limited by the lack of research on the relationship between the factors that determine the course of the process and general conclusions and recommendations for choosing the optimal parameters of this technology. These circumstances confirm the relevance of the research.

Most of the reasons for the destruction of structural elements of parts of machines and mechanisms are related to their cyclic strength, namely thermomechanical fatigue, which is expressed in the gradual accumulation of damage in the material under conditions of simultaneous exposure to variable loads, aggressive environment and temperature. This leads to the appearance of a fatigue crack, its development and the final destruction of the material. One of the important and promising directions in solving problems related to increasing the resistance to thermomechanical fatigue of structural elements is the use of vacuum thermocyclic nitriding in the plasma of a pulsating glow discharge. To analyze the mechanism of phenomena and control the process of vacuum thermocyclic nitriding in the plasma of a pulsating glow discharge, it is necessary to identify the interrelationship of factors that determine the course of the process.

The purpose of the article is to provide an analysis of the phenomena in the process of vacuum thermocyclic nitriding in the plasma of a pulsating glow discharge, to establish the interrelationship of factors that determine the course of the VTAPPTR process and to determine its optimal parameters.

As a result of the conducted research, the regularities of the influence of the parameters of the process of vacuum thermocyclic nitriding in the plasma of a pulsating glow discharge on the microhardness, the depth of diffusion saturation, the magnitude and distribution of residual stresses in the strengthened layers of steel surfaces were established. Based on the results of the experiments, the endurance limit and corrosion resistance of strengthened ion nitrided surface layers were determined. As a result of conducting research on the properties of the surface layers of samples strengthened by nitriding, it was established that thanks to the use of vacuum thermocyclic nitriding in the plasma of a pulsating glow discharge, the thickness of the diffusion layer is 40...300 μm; the microhardness of the surface layer reaches 7600 MPa; there are residual compressive stresses of the order of 445...950 MPa, corrosion resistance increases by 3.1 times, and. the endurance limit of steel structures at temperatures up to 640 °C increases by 15...20%.

The analysis of the conducted studies showed the absence of studies on the interrelationship of factors that determine the course of the process of vacuum thermocyclic nitriding in the plasma of a pulsating glow discharge and recommendations for the selection of technological parameters of vacuum thermocyclic nitriding in the plasma of a pulsating glow discharge, which would be used for the practical application of this technology. On the basis of the conducted experimental studies, it was established that the main mechanisms of increasing the endurance limit of materials due to the application of the process of diffusion saturation of the surface with nitrogen in a pulsating glow discharge in the thermocyclic mode are: creation of a favorable scheme of residual stresses; change in patterns of deformation of surface layers, their chemical and adhesive properties.

IMPROVING THE WEAR RESISTANCE OF STRUCTURAL STEELS BY ELECTROSPARK DEPOSITION

2025-06-09T11:35:59+03:00

The advantages of the electrospark deposition method in forming wear-resistant coatings on steel parts have been analyzed, and the main requirements for electrode materials for forming coatings with high hardness, wear resistance, and crack resistance have been identified. The aim of this work was to assess the wear resistance of electrospark coatings made from high-carbon steel U10 (DIN: 1.1645) and high-speed steel R18 (DIN: 1.3355) on structural steels in an abrasive environment. It was found that for uncoated structural steels, weight loss due to abrasion decreases with increasing material hardness. This is caused by improved abrasion resistance in steel 45 due to a higher proportion of iron carbides, and in medium-alloy steel 30ХГСА due to deposition carbide-forming elements such as manganese and chromium. The enhancement in wear resistance of structural steels with electrospark coatings is substantiated by the more effective resistance of hardened surface layers under abrasive particle impact, which is due to the formation of coatings with a high content of Fe carbides (U10 and R18 coatings), W, Cr, and V carbides (R18 coatings). The possibility of controlling structural effects and phase composition of modified surface layers of structural steels by applying electrospark coatings with the required level of tribotechnical properties has been demonstrated.

PARAMETERS AND CHARACTERISTICS OF A SINGLE-SUPPORT DRIVE SYSTEM WITH TAPERED AEROSTATIC BEARINGS

2025-06-09T10:19:13+03:00

A theoretical analysis of a single-point drive system with aerostatic bearings is presented in this study, focusing on the selection and modeling of flow control devices, in particular, annular diaphragms. The paper derives a dimensionless operating parameter that relates the pressure drops between the lubricating film and the flow control device, taking into account the properties of the gas and the bearing geometry. A set of standardized formulas is used to determine the stiffness and lift coefficients for subcritical laminar flow conditions. The model takes into account the influence of conical bearing surfaces, which allows calculating radial and axial load capacities, as well as ultimate moment loads. The results demonstrate a significant dependence of performance on the average air gap and discharge pressure. Thus, the simultaneous adjustment of these parameters can increase the bearing load capacity by up to 24 times, while the practical functionality is maintained within a more limited range of approximately three times the variability.

DEVELOPMENT OF A DESIGN SCHEME OF A SINGLE-SUPPORT DRIVE SYSTEM WITH AEROSTATIC BEARINGS

2025-06-09T08:49:32+03:00

This study introduces an enhanced computational model for a single-support spindle system equipped with aerostatic bearings, intended for use in semi-automatic monocrystal cutting machines. The model addresses critical geometric and operational features specifically, a low relative bearing length (λ < 0.5) and conical support surfaces which are not adequately considered in conventional calculation methodologies. To improve modeling accuracy, the original bearing geometry is transformed into an equivalent radial configuration, allowing adaptation of an existing method. The approach includes the assessment of radial displacements and evaluates the influence of gas-lubricant parameters, supply pressure, and stiffness coefficients. The proposed model enables more precise estimation of the bearing’s load-carrying capacity and stiffness, thereby enhancing the operational stability and performance of the spindle unit. The findings emphasize the importance of accounting for specific geometric deviations in bearing analysis.

IMPROVING THE WEAR RESISTANCE OF TITANIUM ALLOYS BY THERMAL SPRAYING METHODS

2025-06-09T08:06:36+03:00

The study aims to enhance the wear resistance of titanium alloys by applying thermal spray coatings using plasma and detonation spraying techniques. The structural features and phase composition of thermal spray coatings were investigated through chemical analysis and X-ray diffraction. The microstructure, particle size, and hardness were evaluated by microhardness testing and micro X-ray spectral analysis. It was established that the coatings formed by plasma and detonation spraying of titanium carbide powders clad with nickel and copper exhibit a heterogeneous microstructure. Carbide particles are dispersed in a metallic matrix containing oxide inclusions. The microhardness of the particles depends on the cladding material and initial powder size. Detonation coatings showed a more uniform distribution and finer particle sizes (10–15 µm) compared to plasma coatings (20–60 µm). The presence of nickel phosphides and various intermetallic compounds was confirmed in both types of coatings. The detonation method led to a higher phosphorus content in the matrix due to reduced losses during spraying. Despite similarities in phase composition, structural uniformity and lower porosity were more prominent in detonation-sprayed coatings. Titanium alloys possess poor antifriction characteristics, which can be significantly improved by applying thermal spray coatings. Plasma and detonation spraying methods effectively enhance wear resistance, with detonation spraying offering better microstructural uniformity and phase distribution.

METHODS FOR STUDYING FATIGUE CRACK NUCLEATION AND PROPAGATION IN ALUMINUM ALLOYS EXPOSED TO SURFACTANTS

2025-06-08T20:17:53+03:00

The issue described in the paper arises from the growing number of substances interacting with aircraft metallic components. This paper examines newly developed and recommended methods for studying the nucleation and propagation of fatigue cracks in aluminum alloys exposed to surfactants, with a particular focus on corrosion preventive compounds. While many of these compounds exhibit excellent functional properties, their potential side effects have been studied insufficiently and remain unclear, thus targeted experimental investigations are required. Given that the fatigue life of metal components comprises two distinct stages, fatigue crack nucleation and crack propagation, separate analyses are essential to assess the applicability of specific surfactants.

The first stage of the fatigue for many metals is associated with formation of so called surface deformation relief, which constituents are extrusions, intrusions, persistent slip bands. The dislocation nature of these substructures presumes the possibility of their sensitivity to the surfactants. Among the metal exhibiting surface deformation relief there are alclad alloys having layer of the pure aluminium, particular alclad alloys 2024T3, 7075T6 widely used in the aircraft manufacturing, for example for the skin of the fuselage. The intensity of the surface relief evolves with the number of loading cycles, thus providing the information regarding the consumption of the duration of the nucleation stage.

To study the first stage of the fatigue, i.e. fatigue crack nucleation, computer-aided optical analysis of surface deformation relief is proposed as the primary method. The method was tested and proved by numerous tests of aluminium alloys specimens and aircraft structural components. For examining fatigue crack behavior in contact with surfactants, linear fracture mechanics techniques are considered reliable and indispensable. Details of both procedures are described.

ANALYSIS OF DAMAGE TO AIRCRAFT PARTS MADE OF TITANIUM ALLOYS AND INCREASE OF THEIR WEAR RESISTANCE BY GAS-THERMAL COATINGS

2025-06-04T08:58:25+03:00

The damage analysis of aircraft parts made of titanium alloys is carried out. Damage resulting from cyclic loads in the form of wear is shown. Gas-thermal coatings based on nickel for protection and restoration of parts made of titanium alloys are analyzed. The results on fretting resistance of some coatings that were applied by plasma method are carried out. It is established that the most fretting-resistant are coatings based on ВK, as well as a molybdenum coating. It is theoretically determined that with an increase in temperature in the friction zone, the logarithmic decrement of the molybdenum coating increases more than that of nickel-based coatings. It is established that due to the high hardness of the ВK type coating, it is possible to protect titanium parts of high rigidity, where the main operational factor is friction. In cases where wear of parts is combined with other loads such as bending, torsion, stretching, the optimal choice will be a molybdenum coating on parts made of titanium alloys.

ANALYSIS OF THE CHEMICAL COMPOSITION OF SURFACE TRIBOFILMS FORMED IN LOCAL CONTACT OF GEAR TRANSMISSIONS AFTER RUNNING IN AN OIL ENVIRONMENT WITH CARBONFLUORIDE ADDITIVES

2025-03-26T17:42:43+02:00

The content of chemical elements and their distribution along the depth of organic films of SOP for industrial oils of the ITD series of different viscosities without additives and with chemically active additives were determined by bombardment OGE spectroscopy methods. SOP films are formed more intensively under friction conditions, in an environment with a more viscous oil, and contain a greater amount of carbon and oxygen. By methods of metallophysical analysis of surfaces, after friction in CF-containing environments, CF2/CF3 groups and also metal fluoride compounds of the MeF3 type were detected in the surface layer. Moreover, the former, having a shielding effect, localize shear deformations, as a result of which friction losses of contacting surfaces are significantly reduced, and the latter increase the anti-wear and anti-seize properties of friction pairs, due to the formation of an anti-wear surface layer chemically modified with fluorine to a depth of about 5 microns.

ANALYSIS OF RUNNING-IN PROCESSES IN TRIBOLOGICAL SYSTEMS

2025-03-26T17:25:47+02:00

A brief analysis of the study of the running-in process is presented. The inconsistency of mechanistic representations of the running-in stage is established. An atomic and molecular model of tribological contact is presented. The mechanism of running-in is proposed, in which the main role is played by synthesis, in the process of which molecules, clusters, and nanosized particles are formed. By applying the Boltzmann transfer equation, an analytical expression for the evolutionary process of the exponential type of acclimation is obtained. The main characteristics of running-in are the running-in time and wear from the initial stage.

The level of characteristics can be controlled by external factors (increasing the load in the process) and internal factors (structure of solids and lubricant).

ASSESSMENT OF THE STRESS-STRAIGHTENING STATE OF SURFACES WITH COMPOSITE COATINGS FORMED BY THE ELECTRO-SPIRCULATION DOPING METHOD

2025-03-26T08:57:05+02:00

The results of the assessment of the stress-strain state of surfaces with composite coatings formed by the method of electric spark alloying are presented, which made it possible to choose the optimal variant of the surface design, the coating application process modes and the composition of the composite material. The parameters of electrospark composite coatings were determined by the stressed-deformed state of the composition "reinforcing surface - coating". Modeling of the stressed-deformed state of the composition "reinforcing surface - coating" was carried out by the method of finite element analysis in the licensed software package MSC VisualNastran for Windows 2003. The conducted studies of composite electric spark coatings of variable continuity showed that coatings with a continuity of 70…90% have much lower microstresses than coatings applied in a continuous layer. The conducted studies showed that by changing the continuity and thickness of the coating, as well as by selecting a range of materials according to their physical and mechanical characteristics, it is possible to minimize the stress-strain state of the surfaces to be strengthened and control it. Variable continuity electrospark composite coatings with an optimal thickness of 200 microns allow solving the main issue that arises during the formation of superhard strengthening surface layers - to form a coating that will not be characterized by brittleness. Variable continuity electrospark coatings provide limited stress growth and the process of crack formation, which significantly increases its wear resistance, strength and durability, eliminating cohesive cracking and adhesive delamination of the coating.

METHODOLOGICAL SUPPORT FOR RESEARCH ON THE FEASIBILITY OF USING HIGH-SPEED TOOL STEEL AS COATINGS IN FRICTION UNITS

2025-03-24T12:33:02+02:00

The paper considers methods of research in the field of composite materials used as surfacing materials. In particular, the modern equipment used in the analysis of experimental samples obtained in the study of the use of tool high-speed steels as a coating applied by vacuum electron beam treatment in order to organize micrometallurgical processes with minimal impact on the base metal and the ability to form a hardened layer whose thickness is adjustable within wide limits is considered.

DIFFUSION PHENOMENA IN COOLED BRAKE TRIBOSYSTEMS

2025-03-24T10:43:16+02:00

The materials of the article show that, based on multifactor analysis, nanofluid models have been proposed that take into account in base fluids: collisions between: nanoparticles and molecules; nanoparticles caused by Brownian motion; thermal diffusion of nanoparticles and their interaction with molecules; formation of percolation trajectories with low heat resistance in the fluid; influence of: interfacial and boundary layers during the separation of solid and liquid phases; effect of surface shells; thin nanolayers; particle clustering. The study of nanofluids is reduced to determining their thermal conductivity coefficient. When assessing diffusion in rotating systems with nanofluids, forces, various flows, motion speeds, gradients, specific volumes, sedimentation, emerging coefficients, and porosity of liquid nanoparticles in the chamber were taken into account. The interaction of nanoparticles in liquid cooling systems is considered, and nanofluid flows under heat exchange conditions in the chamber of the pulley rim cooling system are evaluated. The heat transfer coefficient from both metallic and non-metallic friction elements of band-pad brakes can be increased by creating a developed heat exchange surface (using fins or pulley deflectors, making air intakes in the form of ribs, etc.), as well as by placing turbulators in the brake parts, which can be made in the form of a hole in the flange or a system of holes and channels in the pulley. The location of bellows above the brake band, interacting with the pulley flange and connected to the holes in the brake band and in the friction lining, or confusers, diffusers, vortex tubes in pairs "pulley - lining" or "lining - band section" also intensifies the cooling of the friction unit [1]. The listed design solutions are aimed at changing the thermodynamic parameters of the air circulating between the working parts of the brake and, as a result, increasing the efficiency of natural-forced cooling. However, natural-forced cooling of the friction pairs of the belt-pad brake of drilling winches is not able to provide a temperature regime lower than that permissible for the friction lining materials during the lowering of the drill pipe string into the well, and therefore we will proceed to consider forced air-liquid cooling.

REDUCTION OF ENERGY CONSUMPTION OF FRICTION ASSEMBLY OF STRIP-PAD BRAKES OF DRILLING WINCHES

2025-03-24T06:34:12+02:00

The materials of the article consider the issue of forced air-liquid cooling of the composite pulley of the belt-pad brake of a drilling winch. The brake pulley consisted of two parts, between which there is a gap and they are connected by metal thermal bridges with offset holes. The lower part of the pulley rim has a polished surface that interacts with the heat carrier located in the pulley rim chamber. Air and liquid forced cooling of the working surface of the belt-pad brake pulley rim is described separately. An assessment of the efficiency of forced cooling of the brake friction pairs is given. The heat transfer coefficient from both metallic and non-metallic friction elements of band-pad brakes can be increased by creating a developed heat exchange surface (using fins or pulley deflectors, making air intakes in the form of ribs, etc.), as well as by placing turbulators in the brake parts, which can be made in the form of a hole in the flange or a system of holes and channels in the pulley. The location of bellows above the brake band, interacting with the pulley flange and connected to the holes in the brake band and in the friction lining, or confusers, diffusers, vortex tubes in pairs "pulley - lining" or "lining - band section" also intensifies the cooling of the friction unit. The listed design solutions are aimed at changing the thermodynamic parameters of the air circulating between the working parts of the brake and, as a result, increasing the efficiency of natural-forced cooling. In a self-ventilated brake disc, half-discs are connected by cylindrical studs. All elements of the self-ventilated disc are hollow and filled with 2/3 of their volume with liquid. In this way, indirect cooling of the friction belts of the disc-pad brake of the vehicle is carried out.

ADVANTAGES AND DISADVANTAGES OF STATIC AIR BEARING LINEAR GUIDEWAYS IN PRECISION ENGINEERING

2025-03-24T06:20:53+02:00

The aim of this study was to analyze the structural features of gasostatic linear guides and evaluate the influence of their geometry, supply pressure, and surface characteristics on dynamic stiffness and motion accuracy. It was found that uniform air pressure distribution in the load-bearing film minimizes deformations and movement deviations, ensuring high precision and smooth motion. The analysis of pressure distribution in the air film showed that the stiffness of the guides and the characteristics of porous elements significantly affect the stability and accuracy of movement. The absence of mechanical contact eliminates wear and friction, enhancing the durability of the system. The study confirmed that gasostatic supports provide excellent damping properties, as the air layer absorbs vibrations, positively affecting machining quality and positioning accuracy. However, challenges such as sensitivity to contamination, complexity of adjustment, and the need for high-precision surface manufacturing were identified. The necessity for a stable compressed air source and potential air leakage were also noted as limitations. The obtained results will be used for designing precision lathe-grinding machines, optimizing gasostatic systems to achieve minimal friction, high kinematic accuracy, and stable operation under varying loads.

WEAR RESISTANCE AND FAILURE OF ALLOYS STRENGTHENED BY DISPERSED PHASES UNDER ABRASIVE WEAR

2025-03-24T06:03:30+02:00

The article presents the results of the study of the fracture patterns and their effect on the wear resistance of dispersion-hardened alloys: steel 80X20R3T, white cast iron 350X10B8T2, composite KS1 with a reinforcing base of fragmentary relite grains, composite KS2 with a reinforcing base of spherical relite grains. A series of wear resistance of dispersion-hardened alloys corresponding to their location by the value of the rheological parameter was obtained, which indicates the rheological nature of their wear resistance during wear against a monolith and hydroabrasive wear. The controlling role of fracture toughness in the formation of the rheological parameter and wear resistance was established. It is shown that depending on the level of deformation properties, the rheological parameter controls different stages of destruction of dispersion-hardened alloys. Thus, for white cast iron and steel, the stage of crack growth is controlled, at which the level of their plastic deformation is sufficient to slow down the growth of cracks due to the relaxation of stresses at their tips, and for composites - the stage of crack nucleation, when plastic deformation occurs on the scale of monoatomic layers and effectively dissipates the friction work. The rheological and rheological-fatigue parameters are determined as wear resistance criteria that have a direct quantitative relationship with the wear of dispersion-hardened alloys during wear against a monolith and hydroabrasive wear. At the same time, the qualitative nature of wear patterns during wear against a monolith is more adequately reflected by the rheological parameter, and during hydroabrasive wear - by the rheological-fatigue parameter. It has been established that, in addition to increasing the fracture toughness, the reinforcing base of spherical relite grains also promotes the growth of true deformation and localization of its plastic component in a thinner layer of the composite. This entails an increase in the rheological parameter, and, consequently, the wear resistance of the composite with a spherical relite grain shape compared to a fragmentary one.

ANALYSIS OF THE STRESS-STRAIN STATE OF THE GEARING OF A GEAR PUMP IN THE ANSYS SOFTWARE PACKAGE

2025-03-24T04:50:26+02:00

The aim of the work was to evaluate the stress-strain state in the zone of tooth engagement under friction when modeling the gear engagement of a gear pump in ANSYS Workbench. It was found that with an increase in the contact Hertzian stress from 180 to 555 MPa, the depth of the zone of distribution of equivalent Mises stresses and the depth of localization of the maximum equivalent Mises stresses increased by 20% and 23%, respectively. The analysis of the tangential stress diagrams (τ_xy) in the cross-section of the teeth shows that in the contact zone, the tangential stresses vary in magnitude and sign. The diagrams have two extremes, and the value of the maximum stresses on the leading surface (the initial gear tooth head) is approximately 10-15% lower than the stresses on the trailing surface (the initial wheel tooth leg). High discrepancies in determining the maximum tangential stresses in the simulation model of gearing under rolling conditions with slippage according to the Belyaev formula and in modeling have been established. The calculation formulas for determining the magnitude and sign of the maximum tangential stresses in the zone of engagement of teeth with the greatest slippage are proposed, which are consistent with the results of finite element modeling.

ASSESSMENT OF THE STRESS-STRAIGHTENING STATE OF COMPOSITE MATERIALS FOR SPHERICAL PLAIN BEARINGS

2025-03-24T00:00:07+02:00

A model of a spherical plain bearing made of composite materials for the expansion of a stress-strain state has been developed. The model allows to estimate the stress and safety margin of the spherical plain bearing elements. The structure of the bearing model is determined from the storage of high-engineering composite materials. The strength and reserve capacity of the stress-strain state machine in elements of composite materials from various combinations of bearing races at pressures of 3, 100 and 200 kN have been identified. The use of polymer composite materials Zedex ZX-324VMT and Iglidur TX1 on steel 95Х18Ш ensures a reduction in normal Mizer stress by 1.45 and by 1.27 times, equal to the same. with metal-polymer stitching. Depending on the internal and external frame of the spherical plain bearings of titanium alloy ВT-22, the normal stress according to Mizer in models with polymer composite materials Zedex and Iglidur change by 2.08 and 1.55 times, when aligned with metal-polymer stitching on steel. Modeling of the stress-strain state of the spherical plane bearings made of composite antifriction materials resulted in a change in the pressure stress on the surface balls of the bearing materials when replacing titanium alloys BT22 instead of bearing steel 95Х18Ш up to 20%, depending on the material and loading conditions

The results of stress-strain modeling indicate the effectiveness of using Zedex ZX-324VMT and Iglidur TX1 carbon fiber-reinforced polymer composite materials as wear-resistant antifriction composite materials for the outer race of spherical plain bearings. Replacing the steel race with a race made of surface-hardened titanium alloy provides more effective stress relaxation and an increase in the safety factor during modeling.

QUALITY ASSESSMENT OF BIOFUEL USED IN AVIATION

2025-01-12T10:15:40+02:00

The paper analyzes the state of the biofuel energy industry in Ukraine, examines the ways of producing biodiesel, bioethanol, and biogas, describes the physicochemical indicators and quality indicators of biofuels, including those used in aviation. It is shown that one of the priority ways to minimize the impact of aviation on the environment is the introduction of alternative fuels. Prospective types of renewable plant raw materials, which are the most appropriate for the production of aviation biofuels in Ukraine, are considered and substantiated. Thus, the use of aviation biofuels with the content of bio-additives based on vegetable oils makes it possible to achieve a number of positive effects: to reduce the use of non-renewable petroleum raw materials necessary for the production of aviation fuels; o reduce the amount of emissions of exhaust gases, to improve some operational characteristics of aviation biofuels, to reduce Ukraine's energy dependence thanks to the use of its own renewable raw materials for the production of aviation biofuels; to promote the development of agriculture, branches of chemical technology, aviation fuel supply and oil refining; contribute to raising the status of our state at the international level by supporting the policy of international organizations in aviation regarding the greening of aviation through the introduction of alternative aviation fuels

SYSTEMATIZATION OF DESIGN AND OPERATIONAL PARAMETERS OF DISC-PAD BRAKES

2025-01-12T04:18:25+02:00

Conducted research on the construction of multi- and single-disc braking devices with their friction elements, as well as the determination of the main design and operational parameters in the case of local frictional interaction of friction pairs, made it possible to obtain the following: systematization, presenting it in the form of a graphic drawing with types of cooling; clarify the terminology related to the impulse normal force and specific load acting on the microprotrusions of the friction pairs; to recommend using the terminology average braking torque of friction pairs, since its definition is dependent on the average radius of the disc friction belt; the definition of the actual contact area should be represented as the sum of local contacts of microprotrusions of friction pairs; the role of influence of surface-bulk temperature gradients on deformations equivalent to stress is highlighted, taking into account methods of their effective reduction.

THERMAL DYNAMICS OF BRAKE DEVICES

2025-01-12T03:33:45+02:00

Theoretical and experimental studies of brake friction pairs under bench conditions under load in different fields of frictional interaction, accompanied by variable operating parameters, made it possible to obtain the following. Show that the main parameter in thermal dynamics is the dynamic coefficient of friction, which is a complex operational parameter of most calculated dependencies with its fluctuating properties. Set the factors that can be set, and a number of factors are classified as difficult to control, and therefore for calculations it is necessary to operate with the values of the intervals of their change, from which to use the average values. To illustrate the dimensionless regularities of changes in sliding speed, braking torque and friction power for different types of brake friction pairs, and for the latter dimensional parameters from the braking time for a disc-pad brake for a vehicle in laboratory conditions. To evaluate the regularity of changes in the dynamic coefficient of the assembly "FK-24 - steel 35KHNL" during frictional interaction under the influence of mechanical, electrical, thermal and chemical fields.

EVALUATION OF FRICTION SURFACE MICRORELIEF PARAMETERS WHEN LUBRICATED WITH TRANSMISSION OILS

2025-01-12T03:19:49+02:00

The article, presents an analysis of the microrelief characteristics of friction surfaces when lubricated with transmission oils containing anti-seizure additives. It explores existing methods for assessing surface quality and evaluates the application of the Abbott curve to analyze the structural adaptation of contact surfaces during friction. The study identifies patterns in the changes to microrelief and wear resistance based on the type of lubricant used.

The research highlights that friction between surfaces during gear transmission operation significantly affects the durability of gearboxes, emphasizing the importance of friction force measurement for predicting seizure resistance and longevity. Traditional assessments of surface roughness, such as average profile deviation (Ra) and maximum profile height (Rmax), are examined in conjunction with the physical and mechanical properties of the surface layer.

The paper discusses the limitations of conventional surface formation technologies, which may not always achieve the optimal combination of microgeometric characteristics and surface properties post-abrasive treatment. The findings underscore that achieving an ideal microgeometry and surface layer properties during the formation stage can lead to a more stable operational state and reduced initial wear period.

The objective of the study is to evaluate the impact of lubricants on the microgeometric parameters of a 30KhGSA steel sample under sliding conditions using a laser scanning differential-phase microscope-profiler.

The findings underscore that achieving an ideal microgeometry and surface layer properties during the formation stage can lead to a more stable operational state and reduced initial wear period.

PROBLEMS AND PROSPECT OF THE IMPLEMENTATION OF COMPOSITE MATERIALS INTO THE FUEL SYSTEMS OF AIRCRAFTS

2025-01-12T03:10:30+02:00

An overview of the current state of the implementation of composite materials into the structure of aircraft is provided, and the problems of using such materials in fuel systems, related to their requirements, as well as factors and phenomena occurring in such systems are given. Main requirements, according to the 25th chapter of aviation regulations are described, as well as factors that affect the performance of fuel systems, such as atmospheric pressure, temperature, humidity, etc. Presented multiple researches that highlights the issue of wear resistance of fuel systems, methods of researching friction and wear processes in metal and fuel pairs are described. A separate paragraph examines the interaction of composite polymer materials with aviation fuel from the point of view of strength, the phenomena provided by such interaction are described. The problems and prospects of future research on the tribopair of polymer composite material and aviation fuel are outlined.

ASSESSMENT OF THE INFLUENCE OF EXTERNAL FACTORS ON THE CORROSION RESISTANCE AND WEAR RESISTANCE OF ZINC COATINGS ON STEEL

2025-01-12T02:34:50+02:00

The aim of the study was to investigate the intensity of corrosion processes in zinc coatings in aggressive and non-aggressive environments and to determine the resistance of zinc coatings to free abrasive attack. The protective properties of zinc coating on metal surfaces, its service life depending on the coating thickness and operating conditions are analyzed. The features of the technological process of anticorrosive protection of metal structures by hot-dip galvanizing are presented. The intensity of corrosion processes in zinc coatings in aggressive and non-aggressive environments is investigated. Intensive destruction of the coating in citric acid solution and gradual oxidation of the coating with the formation of white rust in water and NaCl solution were found. The results of zinc coating wear in an abrasive environment are presented and the influence of external factors and abrasive on the microhardness of the coating is analyzed. The results of the abrasive wear studies in a free, non-rigidly fixed abrasive revealed an increase in weight wear by 1.16, 1.25, 1.3 and 1.62 times for samples after 30-day exposure in soil, distilled water, NaCl and citric acid solutions, respectively, compared to the wear indicators for the sample that was indoors. An increase in microhardness on the friction track was found for all samples, except for the sample exposed to soil. An increase in microhardness on the friction track was found for all samples except the sample kept in soil. It is assumed that the kinetics of changes in the microhardness of the surface layers of the friction raceway depends on the wear rate of individual intermetallic phases of the zinc coating.

PARAMETRIC AND AUTO-STEWED PROCESSES IN THE SURFACE LAYERS OF PARTS AS EXTERNAL SOURCES OF THEIR DESTRUCTION DURING FRICTION AND WEAR

2025-01-12T01:55:54+02:00

During the execution of various technological processes and the operation of general-purpose actuators, oscillatory movements may occur that are excited without a source of oscillatory motion. These oscillations usually occur either in the area where the two parts come into contact or in the area ahead of the leading edge of the moving part. The oscillatory nature of the movements in the contact area of the parts and the area ahead of the leading edge of the moving part have different physical nature. Thus, in the area of interaction of parts (on the contact pad), oscillatory movements occur due to the unsteady characteristic of friction, which depends on the sliding speed of the parts. At certain ratios of sliding speeds, self-oscillatory motions can appear or disappear, as well as be strengthened or weakened. These oscillations are one of the causes of unregulated roughness, (deformation) cracking and peeling of interacting parts, as well as significant dynamic components during loading of actuators, drives and power mechanisms. Self-oscillations in the surface layers of parts with deformation wave formation, which leads to further destruction in these layers, ahead of the front edge of the die due to the formation of residual plastic waves and subsequent destruction of their crests. Due to the dynamic nature of the interaction between the parts during friction, the force acting on the contact line between the die and the extended part exceeds the critical Euler force and is actually a parametric load, accompanied by the phenomenon of parametric resonance, which usually has a more dangerous effect than the usual resonance during forced vibrations. Therefore, the destruction of the surface layer of parts under parametric resonance is more significant. The main vibration frequency at which parametric resonance occurs is equal to twice the frequency of bending vibrations of the beam-strip. The frequency region near the parametric resonance frequency is the main area of dynamic instability ahead of the moving die.

In this problem, we consider frictional self-oscillations in the area under the die, which are a source of loss of dynamic stability in the area in front of the die, development of parametric vibrations of the surface layers of parts and a number of cases of parametric vibrations and parametric resonance of the outer layers of parts that are destroyed during interaction.

The connection between frictional and parametric vibrations is established through two adjacent sections of the beam-strip in its stretched and compressed parts.

THE FORMATION OF NANOCOATINGS BY TRIBOCHEMICAL TECHNOLOGIES IN AN ELECTROLYTE WITH HIGH ELECTRICAL RESISTANCE

2024-10-07T10:26:10+03:00

The basis for limiting the durability of the internal combustion engine is the wear of parts of the cylinder-piston group and the crankshaft, which are characterized by the presence of small gaps between the plunger and the sleeve. High pressure is provided by the presence of small gaps between the plunger and the sleeve (at the level of 1-3 microns). The recovery method proposed by us is based on electrochemical technologies in polyethylene glycol-400 (PEG-400) electrolyte, which dissolves in water, has lubricating properties and fire-fighting ability, belongs to nonionic surfactants. It is necessary to establish the conditions for the formation of protective films on the friction surface of steel 20 according to LS59-1 using the lubricating properties of polyethylene glycol oils in conditions of unidirectional sliding friction. The presented mechanism of electrolytic transfer of constituent elements of alloys allows indicating the surface saturation of the cathode with one of its alloying elements, in this case from a copper alloy, without taking into account the limited difference in the electrode potential between the friction surfaces, taking into account the deformation component.

The main advantage of PEG-400 is its environmental friendliness, which is guaranteed by its chemical composition and solvent - water.

FORCED COOLING OF BRAKE FRICTION UNITS (part 2)

2024-10-07T09:58:37+03:00

Experimental design developments and theoretical studies of disk (tubular type) - shoe brakes of drilling winches with forced nano-liquid cooling in any state of the unit allowed: to propose a workable design of a tubular-type disk-shoe brake, which is a new direction in brake engineering for drilling equipment, since it has increased energy capacity; to divide the functions between the main and additional disks, the first is a brake, and the second is a heat exchanger; based on the thermal balance of the main brake disk, determine the heat exchange surface area of the additional disk; to connect the volumes of the chambers of the main and additional disks with each other by diffusers and confusers located on semicircles, which are a kind of accelerators and retarders of heat exchange processes; to make the brake disc friction belt thin-walled and thus ensure minimal surface-volume temperature gradients during frictional electrothermomechanical interaction with the linings, and as a consequence, small equivalent stresses.

FORCED COOLING OF BRAKE FRICTION UNITS (part 1)

2024-10-07T08:52:54+03:00

Theoretical and experimental studies on the choice of coolants for forced cooling systems and the requirements for their designs for brake friction pairs allowed to establish the following. The choice of coolants for systems of forced cooling of friction pairs depends on their energy content and is determined by the share of heat by convective heat transfer in complex heat exchange with the environment. The heat carrier must ensure the energy load of the friction pairs at a level lower than that permissible for friction lining materials, based on their regulated wear and friction properties. The most effective are nanofluids, which are metal powders (Li, Na, Al, Cu, Zn, etc.) with a high coefficient of thermal conductivity, diluted in certain proportions with water, acetone, and other refrigerants. The research and development of the system must correspond to the modern level of braking, and the forced circulation of the nano-fluid in a different aggregate state, which increases-decreases and vice versa, convective heat transfer.

EXPERIMENTAL DETERMINATION OF THE INFLUENCE OF THE SIZE AND COMPOSITION OF CONTAMINANT PARTICLES ON THE VIBROACOUSTIC CHARACTERISTICS OF MINIATURE BALL BEARINGS ASSEMBLIES

2024-10-06T16:44:11+03:00

The influence of lubricant and microgeometric characteristics of surfaces on the vibroacoustic characteristics of miniature rolling bearings is analyzed, and the types of defects that occur in bearings during operation are presented. The method of cleaning the working surfaces of aircraft ball bearings is described. A modernized test and measurement complex has been developed to evaluate the effectiveness of ball bearing cleaning by vibroacoustic parameters. The mechanisms of cleaning aircraft ball bearings by pulsed magnetic-turbulent and ultrasonic methods are determined. It has been established that the magnetic-turbulent method allows more efficient removal of contaminant particles whose size is larger than 1-2 microns, while the average value of the total noise level of bearings of series No. 5-1000901T2 - decreased by 4 dB, and of series No. 75-70001016T2 - decreased by 1.2 dB, while the use of the ultrasonic method allowed to reduce the total noise level by 0.67 dB and 0.49 dB, respectively. However, the ultrasonic cleaning method showed the highest efficiency for the smallest contaminants. It has been established that the presence of microparticles whose size is much larger than 1-2 microns leads to an increase in vibration acceleration in the low-frequency measurement range. As shown by the study, cleaning of microbearings on the ОPSH-01 stand is the most effective method of removing bulk contaminants, which reduces the overall noise level by 1.2...4 dB. The presence of a more significant number of microparticles of contaminants with a size of 1-2 microns leads to an increase in vibration acceleration by 2.5...30 % in the high-frequency measurement range. For the removal of this type of particles, the highest efficiency has been achieved by the ultrasonic method, the cleaning of which reduces the overall noise level by 0.49...0.67 dB.

INFLUENCE OF THERMOPHYSICAL PROPERTIES OF THE METAL OF POLYMER COMPOSITE MATERIALS ON WEAR RESISTANCE

2024-09-30T12:11:25+03:00

Metal-polymer composite materials were tested at ambient temperatures of 20 and 60 °C. The most modern composite wear-resistant materials used in mechanisms as sliding bearings were used. The relevance of the tests is determined by the application of worldwide trends to mechanisms without maintenance for the entire life cycle.

The influence of temperature on the wear resistance of metal-polymer composite materials that can be used in aviation spherical plane bearings is determined. It was determined that heat generation caused by both the friction process and dynamic load as a result of reverse motion has the greatest influence on the wear intensity. Increasing the test temperature affects polymer composite materials to a greater extent than metal-polymer tape. At this stage, a significant role in wear resistance is played with the ability of the material to dissipate heat, which occurs in the contact zone from reversible sliding. It has also been established that the carbon fabric of the Fluroglide material can withstand higher temperatures than the babbitt of the metal-polymer tape. A key role in the durability of spherical plane bearings that work in non-standard temperatures will be played by the composite materials design selection and the polymer materials themselves for specific operating conditions.

THE DEPENDENCE OF THE WEAR RESISTANCE OF ELECTRO-SPARK COATINGS IN AN ABRASIVE ENVIRONMENT ON THE STRENGTHENING PHASES

2024-09-30T11:47:52+03:00

The analysis of the defects of parts of the friction units of aviation equipment under the conditions of abrasive wear was carried out. Types of electrode materials for modification of parts by electrospark alloying are considered. The mechanisms of wear under the influence of free abrasive of electrospark coatings of 1.1645 and 1.3355 steels, HG30 alloy and ZLAB-1 ceramics on structural steels 30HGSA and 45 were analyzed. The dependence of the intensity of wear of electrospark coatings on the hardness of carbides and borides and the ratio of the strengthening phase in the matrix was determined. The low wear resistance of the ceramic coating ZLAB-1 is due to the presence of the boride component ZrB2 of increased microhardness in the matrix phase, which leads to the brittleness of the coating. The predominance of brittle fracture of ESC of 1.1645 steel is caused by the presence of iron carbide up to 16% in the structure of secondary cementite and pearlite of the steel. The increase in wear resistance of ESC made of 1.3355steel is due to the presence of a large amount of W, V and Mo carbides. The phase inhomogeneity of ESC made of HG30 alloy, established by X-ray structural and phase analysis of the coating diffractograms and the activation of oxidation processes during friction lead to an increase in the wear resistance of ESC due to the appearance of W2C tungsten semi-carbide and WC_1-x tungsten semi-carbide phases. The obtained results indicate the prospects of ESC made of 1.3355 steel and HG30 alloy with the necessary level of properties to increase the wear resistance of structural steels.

THE INFLUENCE OF THE GEOMETRIC DIMENSIONS OF THE ABRASIVE SOIL PARTICLES ON THE REGULARITY OF DESTRUCTION OF LOW-ALLOY STEEL DURING WEAR

2024-09-30T11:22:36+03:00

The results of the study of patterns of destruction and their influence on the wear resistance of low-alloy steel 65G in the unstrengthened state, as well as after strengthening by thermal and electroerosion treatment during movement in soils of different fractional composition, are presented. It has been confirmed that under such conditions the phenomenon of the presence of a critical size of abrasive particles (CPS) is realized on the wear surface. The role of the geometric size of the particles in the formation of the wear resistance of steel consists in the regulation of active deformation and fatigue phenomena on the wear surface by changing the level of force acting on it. The influence of the fractional composition of the soil on wear resistance is carried out through the rheological-fatigue parameter in the following dependence: the greater the rheological-fatigue parameter, the higher the wear resistance of steel. Therefore, the mechanical component of the contact interaction is decisive in the strength basis of the wear mechanism. Therefore, when choosing a brand of low-alloy steel for the manufacture of machine parts intended for operation in soils of different fractional composition, it is necessary to be guided by its ranking according to the rheological-fatigue parameter. The role of the fractional composition of the soil in the formation of the rheological-fatigue parameter is carried out mainly through the cyclic viscosity of deformation in the sublayer of nonlinear effects in the vicinity of the crack tips of the surface layer in the following dependence: the higher the cyclic viscosity, the lower the rheological-fatigue parameter of steel. The stress that is cyclically repeated during abrasive wear causes in the sublayer of nonlinear effects in the vicinity of the crack tips of the surface layer two opposite phenomena that occur simultaneously: strengthening and weakening. At the same time, the action of the weakening process in soils of different fractional composition is more effective than strengthening. In the region of the subcritical geometric dimensions of the abrasive particles, the intensity of hardening is significantly reduced due to the increase in the effectiveness of the hardening action due to the additional contribution of dispersion hardening. However, this does not entail qualitative changes in the wear process.

THE EFFECT OF PARTIAL SLIP ON THE SURFACE PRESSURE DISTRIBUTION IN A SLIGHTLY COMPRESIBLE FLOW DEVELOPMENT REGION IN THE BOUNDARY LAYER

2024-09-30T10:48:50+03:00

The study of laminar incompressible fluid flow in the boundary layer revealed, even earlier, that the condition of complete adhesion of fluid particles to the surface (non-slip condition) of the moving body (half-plane) is not met in the flow development (formation) region. The assumption of constancy of the fluid velocity on the surface of a moving body, hence non-slip, leads, in the flow development region, to the complete absence of the normal component of the velocity field. And this contradicts the very concept of the flow development region, where there should be two velocity components - longitudinal (primary) and normal (secondary) ones. In the previous works of the authors, analytical solutions were obtained for the velocity field in the region of development of incompressible fluid flow in the boundary layer. Since the use of the incompressible fluid flow model is restricted by the Mach number, to further expand the speed range, the problem of the of slightly compressible fluid flow development region in the boundary layer was considered. It is analytically proven that all considerations regarding the impossibility of complete non-slip in the flow development region can be applied to a slightly compressible flow. Slight compressibility at the same time means the subsonic nature of the flow and the neglect of temperature effects due to friction. On the basis of a critical analysis of the existing approaches, which consider the flow of a fluid around a immobile plate in the framework of non-gradient flow (which is just impossible due to the lack of a mechanism for creating the motion of the fluid), it is shown that the system of equations is actually non-closed. For the region of flow development, where the longitudinal pressure gradient is not a constant value, one equation is missing. This equation, as in previous works, is obtained from the necessary condition for the extreme of the fluid rate functional. And although the complete solution for the longitudinal component of the velocity contains four constants of integration, to obtain the asymptotics near the solid surface it is sufficient to know only two quantities - the velocity and its first derivative (gradient). These values, as it turns out from the asymptotic solution, coincide with the case of incompressible flow, which allows us to expand the scope of the previously obtained results for a wider domain of Mach numbers, for example . And such values already correspond to the speeds of modern civil aircraft. The dimensionless distribution of pressure in the slightly compressible flow development region is presented and its significant heterogeneity is shown, which, in turn, indicates the importance of the obtained results.

LOCAL CHARACTER OF THE STRESS-STRAIN STATE DURING LASER PROCESSING

2024-09-30T10:01:07+03:00

The nature of the stress state arising under sliding friction loading is investigated on the model of a discretely processed material in which there is an annular transition zone between the inclusions (hardened area) and the matrix according to the known law of change in its mechanical properties. It is shown that local stresses in the material, depending on the type of loading of the elementary volume, can be predicted and calculated, taking into account the mechanical properties, appearance, and structure of the transition zone that occurs as a result of laser processing. The strength of the transition zone has a linear dependence and the stress concentration in the area after laser treatment decreases and smoothly transitions to the matrix, and then it decreases to the stresses in the matrix, which gives the advantage of discrete laser treatment of hardened steel.

PECULIARITIES OF THE Z14XEP ENGINE VIBRATION AT IDLE SPEED UNDER POWER STEERING LOAD

2024-09-30T09:41:20+03:00

The paper presents the results of determining the amplitude-frequency characteristic of the Z14XEP engine vibration of the Opel Astra G (F69) at idle speed depending on the steering wheel position. The opposite of changes in the values of the amplitude and frequency of mechanical vibrations of the engine on its supports was determined: an increase in amplitude and a decrease in frequency under the condition of the beginning of the movement of the hydraulic fluid through the power cylinder of the hydraulic booster. The actuation of the hydraulic boost system with an electric pump drive generally causes an increase in the amplitude of engine oscillations by 24.2% in the longitudinal and vertical planes, which occurred before the fluid was replaced, and by 14.4% after its replacement. It was determined that, regardless of the state of the hydraulic fluid at the beginning of its circulation through the cavities of the amplifier's power cylinder, the frequency of mechanical vibrations of the engine decreases in the longitudinal and vertical planes by 25%. In the transverse plane, the oscillation frequency is reduced by 35%, except when the hydraulic fluid is changed, when the oscillation frequency remains unchanged. It has been established that the quality of the hydraulic fluid of the power steering system significantly affects the change in mechanical vibrations of the engine only when the steering wheel is deviated from the neutral position. It was determined that a decrease in the viscosity of the new hydraulic fluid by 8.3% compared to the fluid that was replaced causes changes only in the amplitude of engine oscillations. In the longitudinal plane, the oscillation amplitude decreases by 13.3%, in the vertical plane - by 15.1%, and in the transverse plane, the oscillation increases by 25.4%. Reducing the viscosity of the hydraulic fluid used reduced the resistance to its movement through the holes, channels and pipelines of the power steering system and reduced the power take-off to drive the power steering pump.

TECHNOLOGIES OF SURFACE STRENGTHENING OF GEARS AND BEARINGS IN OIL WITH AN ADDITIVE OF FLUORINE GRAPHITE

2024-09-29T08:16:14+03:00

The results of research and testing of the technology of strengthening contact surfaces in an oil medium with the addition of fluorinated graphite of the teeth of bevel gears and rolling bearings are presented. The technology provides a significant increase in resource by slowing down the development of fatigue damage to the teeth of bevel gears and rolling bearings of the NK-14ST engine starter drive.

CREATION OF WEAR-RESISTANT COMPOSITES COATED ON THE BASIS OF POWDER-BASED SELF-FLOWING ALLOYS BY ELECTRO-CONTACT SINTERING

2024-09-29T07:57:10+03:00

The paper examines the process of increasing the functional properties of coatings made from powders of self-fluxing alloys by using the method of electric contact sintering. It has been shown that the adhesive strength of the coatings is high. with the base is ensured by the formation of a wide diffusion zone on the side of the base. There is no liquid phase at the coating-part boundary. This indicates that, unlike surfacing, during electrical contact sintering there is no overheating and no mixing zone of the coating material with the metal of the part. X-ray study of the phase composition of coatings shows that under optimal conditions of electric contact sintering, the carbides present in the original powder are mainly retained in the sintered layer, which indicates the preservation of the hereditary properties of the coating material during electric contact sintering. The effect of grinding the carbide phase makes it possible to obtain sintered layers with evenly distributed carbide inclusions, which helps to increase the wear resistance of coatings. Carbide particles have a specific acute-angled shape, which indicates the preservation of the original properties and structure of the coating material during electrical contact sintering. Impulse temperature-force influence in the process of coating formation during electric contact cauterization leads to the dispersion of solid phase particles, which helps to increase the microhardness and wear resistance of the obtained coatings by 2-3 times. The developed technology for obtaining coatings from self-fluxing alloy powders by electric contact sintering leads to a decrease in the cost of manufacturing and restoration of parts due to the replacement of alloy steel with low-carbon steel with coatings from SFP SFS while increasing the resource of parts by 3-5 times.

INCREASING THE WEAR RESISTANCE OF STEEL GAS-THERMAL COATINGS BY ELECTROCONTACT TREATMENT

2024-09-29T06:40:35+03:00

The most promising method of increasing the wear resistance of low-resource parts of machines and mechanisms is the formation of wear-resistant layers on their working surfaces from the most accessible and low-cost materials for coatings in combination with technologies for applying coatings and their subsequent processing. The article proposes a method for creating parts with wear-resistant coatings, combining flame and (or) electric arc spraying of steels of ferritic and martensitic classes and their subsequent electrical contact processing. When creating coatings, it is proposed to use an approach based on the creation and targeted controlled use of deformation-induced structural-phase transformations and metastable states during the application of gas-thermal coatings and their processing, which ensure an increase in microhardness, wear resistance, physical-mechanical and operational properties. A new approach to obtaining gas-thermal steel coatings on low-alloy steels with increased wear resistance is proposed, which is based on the creation and purposeful controlled use of deformation structural-phase γ→α transformations and metastable states by means of temperature-force influence during their electrical contact processing; The relationship between the physico-mechanical properties of steel coatings and structural-phase γ→α transformations in them is established, and it is shown that the level of these properties, controlled by the degree of saturation of the martensitic α-phase with carbon, increases with an increase in the content of carbon and carbide inclusions in steels.