Problems of Friction and Wear

IMPROVEMENT OF THE CHARACTERISTICS OF A SINGLE-SUPPORT AEROSTATIC BEARING SYSTEM WITH LABYRINTH SEALS

2026-04-08T12:34:19+03:00

This study focuses on the characteristics and optimization of a mechanical system with a single support element that utilizes an angular contact aerostatic bearing, which is used in high-speed machining. To solve the problem of increasing load-carrying capacity and stiffness, a new approach is proposed: adjusting the flow of gaseous lubricant at the outlet of the gap using external labyrinth seals. Mathematical modeling shows that increasing the outlet pressure prevents the occurrence of critical supersonic flow while significantly improving operating parameters. The results show that the use of external labyrinth seals increases the bearing load capacity by 10% while reducing air consumption by 30%. A comparative analysis shows that at an optimal average clearance of 15 μm, a single-support system demonstrates a load-carrying capacity 2.1 times greater than that of an equivalent double-support system. Single-support aerostatic systems are highly effective for non-contact drives subjected to relatively low bending moments.

ENERGY LOAD CONTROL OF BRAKES' FRICTION PAIRS

2026-04-08T07:56:19+03:00

Theoretical research and a computational experiment dedicated to optimal control of thermal processes in friction pairs during frictional interaction in braking devices have allowed us to establish and propose the following. Thermal process control is accomplished mathematically using the heat equation with initial and boundary conditions, employing a control function, as well as the method of thermoelastic potentials and moving local heat sources in brake friction pairs. Material selection based on the mechanical properties of drill drawworks brake pulleys was conducted using a computational experiment. Based on the research conducted, a discovery formula was formulated: "Unknown patterns of microcrack occurrence and development on the working surfaces of metal friction brake elements have been established."

PARAMETRIC EFFECT OF STEADY AND UNSTEADY FRICTION ON THE ORIGIN AND INITIAL PROPAGATION OF THE SHOCK PULSE

2026-04-08T07:49:57+03:00

The phenomenon of unsteady flow is widespread in engineering. It is known to generate a shock pulse (water hammer). The nature of this phenomenon is nonlinear and depends on several factors: steady friction, unsteady friction, convection of velocity and pressure fields, bulk viscosity, and the conditions under which the shock pulse occurs. Using models in modern software requires an accurate understanding of the physics of the generation and primary propagation of a shock pulse—a nonlinear process that, under certain conditions, allows for the existence of more than one fluid flow mode. Therefore, a parametric study of previously obtained analytical solutions is of practical interest. The results presented in this paper highlight the importance of parameters corresponding to steady and unsteady friction. While steady friction affects the size of the shock pulse region (the size decreases with increasing friction), unsteady friction has a completely different effect. As the parameter responsible for unsteady friction increases, the possibility of the existence of two shock pulses—one weaker and one stronger—emerges. In this case, hydraulic concepts based on the Bernoulli equation prove inapplicable: higher pressure values correspond to higher shock pulse propagation velocities. This is entirely logical: the greater the non-stationarity (and the shock pulse propagation velocity), the greater the pressure surges.

EVALUATION OF THE STRESS-STRAIN STATE OF INTERACTING SURFACE LAYERS USING ELASTICITY THEORY METHODS UNDER FRICTION AND WEAR CONDITIONS

2026-04-07T16:05:08+03:00

In the course of research in the field of friction and wear theory, one of the working hypotheses is that under the influence of tangential loads, the outer layers of interacting parts change their flat shape to a wave-like one. That is, the flat cross-sections of the outer layer are distorted and lose their longitudinal stability [1]. Therefore, this problem becomes an anisotropic problem of elasticity theory, taking into account the properties of the outer contact layer. Otherwise, the problem has a peculiarity within the boundary (contact) condition, which complicates its solution in this formulation. However, in a number of calculation cases, it can be assumed that at the moment of interaction of parts on distorted planes, the deformed micro-irregularities on both parts were mutually destroyed due to shear deformation or crushing to such values of micro-irregularity heights at which the outer layers can be considered as layers that have restored their original flat shape (without taking into account worn microportions of material).

As a result of cutting off deformation micro-irregularities under the die and in front of the die, the outer layers of interacting parts restore their original flat (pre-deformation) shape as a result of brittle and plastic wear.

Therefore, when assessing the stress-strain state of interacting parts, it can be assumed that two elastic half-spaces are operating under the influence of a system of vertical and tangential forces.

Thus, the problem under consideration can be reduced to a plane problem of elasticity theory under the influence of a vertical weight load P and a tangential load fP caused by shear resistance or deformation (wave) micro-irregularities. In other words, in this problem, we neglect the influence of deformation waves formed as a result of loss of longitudinal stability on the stress-strain state of the outer layer of the part.

In this case, the influence of deformation waves of one part on the loaded half-space of the second part is replaced by a system of impulse (periodic) forces.

CHARACTERISTICS OF THROTTLE CAVITATION GENERATORS FOR EROSION TESTING OF STRUCTURAL MATERIALS

2026-04-07T15:30:58+03:00

Practical interest for researchers and engineers in hydraulic machinery engineering lies in the development of effective methods for accelerated erosion testing of structural materials under conditions that are as close as possible to real hydrodynamic cavitation regimes. This paper investigates the characteristics of throttle-type hydrodynamic generators of cavitation-induced pressure fluctuations and evaluates their suitability for erosion testing of structural materials.

The aim of the study is to determine effective operating regimes of throttle cavitation generators and to assess the influence of generator operating conditions on the intensity and localization of cavitation erosion.

Experimental investigations were carried out on a hydraulic test bench at pressures of up to 25 MPa using throttle devices of various types (cylindrical nozzle, converging–diverging nozzle, Borda nozzle, rectangular channel, and orifice plate). Aluminum alloys D16ATV and AMtsM, which are characterized by increased sensitivity to cavitation damage, were used as model materials. Measurements of rapidly varying cavitation-induced pressure fluctuations were performed over a wide frequency range, accompanied by simultaneous evaluation of specimen mass loss.

It was established that throttle cavitation generators produce stochastic cavitation pressure fluctuations with a wide frequency band ranging from several hundred hertz to several tens of kilohertz, with amplitudes comparable to the supply pressure. It is shown that with an increase in dimensionless back pressure, the amplitude of cavitation pressure fluctuations decreases, while the spectral energy maxima shift toward the high-frequency range, which is associated with the dominance of small-cavity collapse. Optimal distances from the throttle generator to the specimen surface and operating regimes providing maximum cavitation erosion intensity were determined. It is demonstrated that cylindrical and converging–diverging nozzles ensure the most efficient conversion of flow energy into the energy of cavitation pressure fluctuations.

The obtained results confirm the feasibility of using throttle-type hydrodynamic cavitation generators for erosion testing of structural materials and make it possible to bring laboratory cavitation erosion studies closer to the real operating conditions of hydraulic system components.

LOCAL EQUIVALENT STRESSES IN METAL FRICTION ELEMENTS OF BRAKING DEVICES

2026-04-07T06:59:33+03:00

Theoretical research and a computational experiment applied to local equivalent stresses in metal friction elements of braking devices allowed us to establish and propose a flowchart for assessing the energy load of friction pairs, in which the assessment of equivalent stresses is presented last. A mathematical description of the relationship between local temperature zones and equivalent stresses in friction pairs. A computational and experimental study to determine equivalent stresses on the working surface of metal friction elements. A patent claim for "Method for the occurrence and prediction of a microcrack network on the working surface of metal elements at different rates" was submitted. Method: finite element modeling using the Ansys Workbench program for the stress state of metal friction elements.

CLASSIFICATION AND MATERIALS OF HIGH-PRESSURE COMPOSITE CYLINDERS FOR AVIATION APPLICATIONS

2026-04-07T06:48:22+03:00

This paper presents an extensive systematic analysis of high-pressure composite overwrapped pressure vessels (COPVs) and the materials used in their fabrication for aviation and aerospace systems. The classification of cylinders of types 1–5 is considered based on the ratio of metallic to composite components, and their structural features, functional purpose, and operational limitations are analyzed. Liner materials are examined with regard to their density, mechanical properties, corrosion resistance, and role in ensuring the hermeticity of the vessel. Special attention is given to reinforcing composite materials—carbon fiber, E-glass fiber, aramid fibers—as well as alternative materials (basalt, flax, and recycled carbon fibers). A comparative analysis of their physical and mechanical properties (density, tensile strength, elastic modulus, elongation at break) is conducted, and their influence on mass efficiency, high-pressure performance, and vessel durability is evaluated. It is shown that the use of carbon fiber provides maximum specific strength and allows the structure’s mass to be reduced by 45–70% compared to fully metallic cylinders, whereas glass fiber is economically advantageous for medium-pressure levels. Based on the synthesis of research results, it is determined that for stationary aviation systems, types II and III cylinders are the most rational. Type 2 (metal liner with glass-fiber overwrap) reduces mass by 30–40% while maintaining acceptable cost, whereas type 3 (aluminum liner with full carbon-fiber overwrap) exhibits higher specific strength and the ability to operate at high pressures, making it optimal for critical aviation applications. The potential development of linerless type V constructions is also highlighted as a promising direction for future high-performance solutions. The results of this study can be applied in the design and modernization of gas storage systems in modern aviation technology.

PROSPECTS OF USE AND ASSESSMENT OF CONDITIONS FOR IMPLEMENTATION OF PROCESSES OF BURNISHING OF TITANIUM ALLOY PARTS

2026-04-07T00:22:07+03:00

Based on the analysis of scientific publications, the prospects of using the process of diamond burnishing of titanium alloy parts are considered. It is shown that an effective finishing treatment for increasing the service life of products is burnishing the surface of parts by creating a surface with low roughness and residual compressive stresses in the surface layer with a thickness of up to 140 - 200 microns. It is practically impossible to achieve such a level of quality parameters for titanium alloys due to the high adhesive properties of titanium. Numerical calculation methods show that in the range of friction coefficient values from 0.05 to 0.25 at the active stage under load, the value of normal stresses in the direction of burnishing practically does not depend on the friction coefficient. At the same time, the maximum value of shear stresses on the surface of the part increases as the friction coefficient increases by more than 3 times. This leads to a decrease in residual normal stresses after burnishing with an increase in the friction coefficient and to a decrease in the endurance limit of the material, and accordingly, the resource of the part. It has been established that to increase the efficiency of burnishing of titanium-based alloys, it is necessary to create conditions for reducing the friction coefficient. The work proposes the most effective directions for reducing the friction coefficient during burnishing of titanium alloys: applying physicochemical coatings to the surface of the part and controlling the technological modes of the burnishing process.

STRENGTHENING OF INTERNAL SURFACES OF HOLES WITH RELATIVELY SMALL DIAMETERS

2026-03-27T13:50:16+02:00

Increasing the wear resistance of the internal surfaces of small holes, which include holes with a ratio of the internal diameter to the length (depth) of the hole exceeding the value of four for through holes and two for blind holes, is of important national economic importance. Almost all kinematic friction pairs with translational motion in machine building (internal surfaces of pneumatic and hydraulic cylinders, surfaces of material cylinders of thermoplastic automatic machines, surfaces of plunger pumps of fuel equipment of engines, barrels of mortars, guns, etc.) belong to this category of holes. One of the effective ways to increase the wear resistance of such holes is hydrogen-free glow discharge nitriding (BAT). However, glow discharge nitriding with constant current supply does not ensure uniform treatment of the internal surface over the entire depth, and with significant length-to-diameter ratios, the internal surface of the hole remote from the ends is practically not nitrided. Therefore, the technology of the hydrogen-free nitriding process in a glow discharge (GBN) with cyclically switched power supply (CSPS) has been developed.

The main regularities and conditions of nitriding in a glow discharge of relatively small diameter holes are established. The possibility of the main processes of nitriding of such holes under different types of gas discharge is analyzed. Recommendations are offered regarding the parameters of the energy discharge in the gas to ensure the efficiency of the process of modifying the internal surfaces of relatively small diameter holes. The main regularities that characterize the technological features of nitriding of the internal surface of holes are given.

WEAR RESISTANCE OF ELECTRIC-SPARK COATINGS CREATED BY TRANSITION METALS WITH IRON INTERMEDIATE LAYER

2026-03-27T13:25:27+02:00

The effect of treatment by Fe-anode in the electric-spark alloying (ESA) process of the iron sample surface by transition metals, which were applied according to the Me-Fe-Me scheme, where Me - Cr, Cu, Ni, Ti, W, Zr, on the wear resistance of the resulting coatings was investigated. Testing of samples with coatings under dry friction-sliding conditions «plane by plane» for 10 hours showed an increase in wear resistance to 4.92–12.64 times compared to the original sample that was not alloyed.

INFLUENCE OF ALUMINIUM AND HIGH-ENTROPIC ALLOY FeNiCoB0,7Si0,3BeNb ON THE ABRASIVE WEAR RATE OF ULTRA-HIGH-MOLECULAR-WEIGHT POLYETHYLENE

2026-03-27T12:31:47+02:00

The article investigates the influence of industrial B95 aluminium alloy and the high-entropy alloy FeNiCoB_0,7Si_0,3BeNb on the abrasive wear rate of ultra-high-molecular-weight polyethylene. It is shown that the introduction of both metal fillers increases the wear resistance of ultra-high-molecular-weight polyethylene to the fixed abrasive particles by approximately 50%. This improvement is attributed to the strengthening of the surface layer of the polymer matrix resulting from the incorporation of solid filler particles. This effect is confirmed by an increase in the hardness of the material on the Rockwell scale (HRR) by approximately 35% and a reduction in surface roughness by 40%. It is found that the high-entropy alloy has a more pronounced effect on reducing the abrasive wear rate of the polymer matrix. In both cases, the optimal complex of an optimal combination of functional properties is observed for composite materials containing 25 wt.% of B95 and FeNiCoB_0,7Si_0,3BeNb alloys. A further increase in the filler concentration in the polyethylene volume results in a reduction in abrasive wear resistance and hardness. This behaviour is explained by an increased number of structural defects in the polymer matrix, which degrade its mechanical integrity and reduce its ability to withstand external loads effectively.

MATERIAL SCIENCE ASPECTS OF EXTENDING THE SERVICE LIFE OF CYCLICALLY LOADED COMPONENTS IN FRICTION ASSEMBLIES WITH GAS-THERMAL COATINGS

2026-03-25T15:41:33+02:00

The paper considers the technological features of increasing the service life of cyclically loaded parts of friction units with gas-thermal coatings. The results of research and their analysis of the influence of individual technological options for forming wear-resistant coatings obtained by the detonation-gas spraying (DGP) method on the cyclic strength of the base material - titanium alloy VT8 are presented. The use of variants of the chemical Ni-sublayer in the research program provided a smoother change in elastic properties from the base material to the coating. The influence of the structure, phase composition, porosity and adhesion strength of gas-thermal coatings on fatigue resistance, wear resistance and crack resistance of parts under conditions of variable loads and friction is analyzed. The role of residual stresses, mechanisms of nucleation and development of fatigue cracks in the "base - coating" system is shown, as well as the influence of technological parameters of spraying and post-spraying treatment on operational characteristics. The directions for optimizing the composition and structure of coatings in order to increase the durability and reliability of friction units under cyclic loading conditions are substantiated.

EFFECT OF TEMPERATURE ON THE WEAR RESISTANCE TI6AL4V-CFRP/GFRP CONTACT UNDER VIBRATION CONDITIONS

2026-03-20T08:13:14+02:00

A study of the influence of temperatures from minus 50 to plus 50 ºС on the contact of TI6AL4V-СFRP/GFRP materials under the influence of the vibration factor is presented. It was determined that at temperatures of minus 50 ºС the wear resistance of composite materials increased by 20-25%. When the temperature decreases, the epoxy resins that make up the matrix change their mechanical characteristics towards increasing hardness, mechanical strength, creep, etc. It was found that GFRP with glass fibers showed less results in increasing wear resistance at negative temperatures, since glass fibers are more sensitive to low temperatures than carbon fibers in CFRP. Increasing the brittleness of glass reinforcing fibers allowed to increase wear resistance by 20% overall. While materials with carbon fibers demonstrate an increase in wear resistance by 25%.

It was found that the wear resistance of the Ti6Al4V alloy during testing almost does not change. A slight increase in wear up to 3-5% on the one hand may indicate an error in the research during measurement, and on the other hand, the influence of the environment on the friction process.

The studies established the stability of the contact and the balance of wear of the power elements of the structures in the TI6AL4V-CFRP/GFRP contacts under vibration action and changes in the temperature conditions of the tests from minus 50 to 50 ºС. An increase in wear resistance up to 25% of materials based on epoxy resins and carbon and glass fibers is noted due to changes in the physical and mechanical properties of the matrix at negative temperatures up to minus 50 ºС.

STUDY OF THE STRUCTURE AND ADHESIVE PROPERTIES OF EPOXY COMPOSITES FILLED WITH BIOGENIC MICRODISPERSE FILLER

2026-01-22T20:33:38+02:00

The work investigated the effect of organic biogenic lignocellulosic filler obtained from coffee production waste on the adhesive properties and residual stresses of epoxy composites. The relevance of this study stems from the growing interest in utilizing renewable secondary raw materials as functional additives for the development of polymeric materials. The adhesive strength at separation and residual stresses were determined using the ASTM separation method, and the mechanism of interfacial interaction was analyzed based on morphological analysis of the fracture surfaces. The polyfunctional nature of the filler was established by the method of IR spectroscopy, due to the presence of hydroxyl –OH (ν = 3425 cm^–1), carbonyl C=O (ν = 1655 cm⁻¹) and ether (ν = 1057 cm^–1) C–O–C groups, which form a high density of polar centers. It has been established that the introduction of a filler in the amount of 0.50…1.00 wt.% into the epoxy binder ED-20 provides a synergistic effect of the interaction of the ingredients (hydrogen and dipole-dipole interactions), which leads to the transition of the failure mechanism from adhesive to cohesive. At the optimal filler content (0.50…1.00 wt.%), the adhesive strength increases from 24.4 MPa to 34.2 MPa, and the residual stresses decrease by half.

INTEGRATED TECHNOLOGIES CREATION OF WEAR-RESISTANT COATINGS

2026-01-21T07:47:52+02:00

The study investigates the behavior of interlayer hybrid polymer composite materials (HPC) based on carbon and glass fabric under static tension, considering the specific features of their deformation. Hybrid composites based on carbon and glass fabric with different layer stacking schemes by vacuum forming are studied. The results show that the deformation of HPC under tension in the longitudinal direction is complex and is accompanied by the occurrence of various processes that dominate at certain stages of elongation of the studied sample under load. Deformation diagrams for HPC samples were obtained, revealing a nonlinear deformation response in the strain range of 0.25–0.8%. This nonlinearity is attributed to increasing stress concentrations in the polymer matrix, intensified plastic deformation, matrix cracking, interfacial delamination, and load transfer to the reinforcing fibers. Two points of rupture of the samples during uniaxial tension were determined: the first rupture is caused by brittle fracture of carbon fibers, the second rupture is associated with the destruction of glass fibers by the pulling mechanism. The formation of an 8-layer HPC with two outer layers based on structural roving glass fabric and two layers of unidirectional carbon fabric parallel to the applied load and four inner layers of satin weave glass fabric provides a maximum tensile strength of 660.7 MPa (first rupture), a tensile strength of 275.5 MPa (second rupture) with a maximum relative elongation of the composite of 1.88%. The results of the research are relevant in the development of interlayer HPCs by combining carbon and glass fibers in order to achieve high strength of the HPC through carbon fiber and improved energy absorption processes due to plastic deformation of glass fibers in the structure of the hybrid composite.

HYDROSTATIC LINEAR GUIDE DESIGN

2026-01-20T17:35:54+02:00

The geometric parameters of the hydrostatic pockets in the structural steel bearing elements have been calculated. A model has been developed for analyzing the distribution of hydrostatic pressure depending on the shape and arrangement of the hydrostatic pockets. The surface roughness values of the granite guideway have been established as a function of abrasive grit size. The straightness and perpendicularity of the load-carrying surface of the granite guideway have been measured. Preliminary values of pressure and film thickness for the linear hydrostatic bearing have been selected. The pressure distribution between the guideway and the moving surface has been investigated in ANSYS Fluent, taking into account the measured surface roughness and the geometric configuration of the granite guideway. Diagrams of the predicted static pressure, stiffness and load-carrying capacity of the hydrostatic linear bearing have been obtained as functions of the operating pump pressure and oil viscosity. The results are relevant for the integration of the design into precision machine tools and instruments due to the accessibility, cost-effectiveness, ease of manufacturing, and advantageous mechanical properties of granite compared to metallic analogues.

SIMULATION MODELING IN HYDRODYNAMIC ANALYSIS SOFTWARE FOR THE FLOW OF PUMPED FLUID IN A CENTRIFUGAL PUMP IMPELLER

2026-01-20T08:33:39+02:00

This paper presents the methodology and results of simulation modeling of the flow of pumped fluid within a centrifugal pump impeller, along with a comparison to analytical calculation results. The functional performance of dynamic pumps, including generated head, capacity, axial and radial forces, and efficiency, is directly governed by internal fluid flow parameters. Classical analytical models often rely on simplifying assumptions that significantly diverge from real physical flow behavior due to the theoretical complexity of analyzing 3D, non-uniform (turbulent) flow. The use of modern Computer-Aided Engineering (CAE) tools allows for high-fidelity 3D simulation, enabling researchers to drastically reduce or entirely eliminate the need for physical prototypes and significantly shorten the overall design cycle. A structured methodology for simulation modeling is developed and applied here to analyze liquid flow in the impeller of a novel shaftless centrifugal pump design. Deviations between the outcomes obtained by the two methods do not exceed 15%, which is acceptable for the design of pumps and other turbomachinery. Based on the conducted research, a general scheme for computer-aided design (CAD) of pumps is proposed

TRIBOLOGICAL TESTING AND STRUCTURAL ADAPTATION OF POLYMER COMPOSITES

2026-01-20T08:06:36+02:00

Polymer composites are increasingly applied in sliding friction units due to their low friction coefficient, chemical resistance, and ability to adapt structurally under mechanical loading. One of the key parameters determining their performance is microhardness, which may change during operation and thus reflect the material’s capacity for structural adaptation. This study presents the results of tribological testing of several polymer composites, including industrial and laboratory-prepared materials, with a focus on microhardness variation and wear resistance under different sliding regimes.

Three types of composites were investigated:

- Zedex zx‑324V2T (PEEK + PTFE): a commercial composite combining high thermal stability and mechanical strength of PEEK with the low friction and antiwear properties of PTFE.

- Polystyrene/graphite composite (PS‑6): prepared by suspension polymerization, where graphite acts as a solid lubricant and reinforcement. Literature reports indicate that graphite addition influences polymerization kinetics, particle size, and molecular weight, while also reducing thermal conductivity and improving foam uniformity.

- Epoxy resin composites (Epikote LR285 + graphite): experimental samples fabricated with varying graphite concentrations (7.9%, 14.6%, 20.5%), cured under controlled thermal conditions to ensure homogeneous filler distribution.

Tribological tests were performed under three sliding speeds (1.4, 2.8, and 5.5 m/s) using steel counter bodies. Microhardness was measured before and after testing with a PMT‑3 microhardness tester, while weight loss was recorded to evaluate wear. The results reveal distinct behaviors depending on composite type:

- Epoxy-based composites exhibited a decrease in microhardness after testing, with higher graphite content mitigating but not eliminating softening effects.

- The PS‑6 composite demonstrated an increase in microhardness (ΔH = 64 MPa), indicating structural adaptation through molecular orientation and surface densification, accompanied by relatively low wear.

- Zedex zx‑324V2T showed the most pronounced strengthening effect, with microhardness increasing up to ΔH = 305 MPa at higher sliding speeds, while wear decreased due to the formation of a stable PTFE-based transfer film.

These findings confirm that structural adaptation is a critical mechanism for enhancing the tribological performance of polymer composites. The degree of adaptation depends strongly on the polymer matrix and filler type.

Practical significance: The results provide guidance for optimizing composite formulations intended for sliding bearings and friction units operating under severe conditions. In particular, PEEK/PTFE systems and polystyrene/graphite composites demonstrate promising self-strengthening behavior, opening pathways for the development of advanced self-adaptive polymer materials for automotive, aerospace, and energy applications

ASSESSMENT OF THE ENERGY CONSUMPTION OF FRICTION COUPLES OF DISC-PAD BRAKE DEVICES

2026-01-20T07:43:49+02:00

The materials of the article have conducted studies of energy loading in relation to vehicle disc brakes, which allowed us to establish the following: specific heat losses in the disc friction zone change in time according to the law of simple harmonic oscillation with the same oscillation period as the ambient temperature oscillation period, but with a phase shift; it has been confirmed by calculation that the thin surface layer of the disc friction zone is subjected to cyclic thermal loading of an impulse and long-term nature during vehicle braking modes, after which thermal waves penetrate deep into the thickness of the brake disc; the main parameter of the energy loading of friction pairs is the local temperature gradient in the zone of local frictional interaction of their microprotrusion contact spots, which significantly affects the operational parameters of the brake with its fluctuation properties; the local potential acts as a function of the fluctuating temperature and the established temperature of the brake friction pairs.

EVALUATION OF THE MECHANICAL PROPERTIES OF HYBRID COMPOSITE MATERIALS UNDER TENSION

2026-01-20T07:23:56+02:00

THE INFLUENCE OF CORROSIVE AND AGGRESSIVE ENVIRONMENTS ON THE CONTACT OF ALUMINUM AND TITANIUM ALLOYS WITH CFRP UNDER VIBRATION LOADING CONDITIONS

2026-01-20T07:13:35+02:00

A study of the influence of the corrosive environment of seawater and an aggressive alkaline environment on the contact of the aluminum alloy D16T and the titanium alloy Ti6Al4V in a pair with the composite material CFRP under the action of the vibration factor is presented. Catastrophic destruction of the Al-CFRP contact in the conditions of the alkaline environment KOH with pH 11 was established. It was determined that the alloy D16T is very sensitive to changes in the environment. When tested in a NaCl solution, its wear increased by 1.4 times. The wear of the titanium sample decreased due to the presence of water and a humid environment in the friction zone, which lubricated the friction surfaces in some places. Temperatures of 20 ºС did not allow the processes of hydrogenation of the titanium alloy surface to occur, and as a result of the test, we record a decrease in wear by 1.09 times compared to the study in air. It has been established that the wear of the D16T material in salt water is a complex phenomenon that combines chemical corrosion and mechanical abrasion, which is often called three-component or combined corrosion. Mechanical loads caused by vibration additionally accelerate the destruction process, since the worn surface becomes even more susceptible to the aggressive effects of salts. Titanium alloys are much more resistant to the marine environment. It has been determined that high pH values actively affect the D16T and Ti6Al4V materials, sometimes leading to the destruction of passivating oxide films that naturally form on the materials. Catastrophic destruction of the D16T alloy shows chemical degradation and dissolution in an alkaline environment, which increases the wear of the material by more than 4 times.

CREATION OF FUNCTIONAL COATINGS ON STEEL BY ELECTRIC-SPARK ALLOYING IN COMBINED INTERELECTRODE ENVIRONMENTS

2026-01-20T06:52:52+02:00

The influence of the combined interelectrode environment composition at the process of electric spark alloying (ESA) by titanium and chromium on the structure, microhardness and wear resistance of the St.3 steel surface layers was revealed. The change in the environment composition occurred in 2 stages according to new technological schemes: argon - nitrogen, propane-butane - argon. An increase in the microhardness of titanium coatings to 6–7 GPa, and chromium coatings to 5–5.2 GPa was established due to the presence of nitrides (TiN, CrN) and carbides (TiC, Cr₇C₃) in them. The wear resistance of samples with coatings under friction-sliding conditions without lubrication for 5 hours is 6.14–10.32 times greater than the value of untreated St.3 steel.

FEATURES OF THE BEHAVIOR OF LUBRICANT MATERIAL IN TEXTURED REGIONS UNDER BOUNDARY FRICTION

2026-01-20T00:57:06+02:00

Prospects for the formation of a textured surface on tribological elements (tribo-pairs) were analyzed. The goal of this work is to construct a mathematical model for the location of a lubricant droplet both within the depressions (dimples) of the textured surface and outside of them, depending on kinematic factors, structural characteristics of the surface, and properties of the lubricant. The mathematical model for the movement of an oil droplet in a single dimple of the textured surface is based on the influence of centrifugal force, the force of gravity, and the surface tension force of the oil on the droplet during friction. A limit condition has been established at a sample rotation frequency greater than $27 \text{ rpm}$, under which the oil droplet "leaves" the dimple at the upper position of the sample and remains in the space between the sample and the counter-body surface, ensuring the regeneration of the boundary lubricating film on the tribocontact surface when it breaks down. When the sample rotation frequency is reduced to $26.8 \text{ rpm}$, the oil droplet remains in the dimple and does not affect the processes of lubricating film regeneration. The modeling results will make it possible to predict the oil-holding capacity (oil retention) of the textured surface dimples, which will contribute to increasing the wear resistance of the contact surfaces during the regeneration of the boundary lubricating layer.

OILINESS OF INDIVIDUAL HYDROCARBONS AND ITS INFLUENCE ON THE FORMATION OF SURFACE TRIBOFILMS UNDER FRICTION IN LOCALLY CONTACTING SURFACES

2026-01-20T00:01:42+02:00

The effect of bulk temperature of individual hydrocarbons (paraffinic, naphthenic, and aromatic) on the formation of self-generating organic films (SOP) was studied over the range from each fluid’s melting point to its boiling point. The results reveal a consistent pattern: for each hydrocarbon there exists a characteristic temperature, dependent on molecular weight and lying between its melting and boiling points, at which the intensity of SOP formation increases while the friction torque decreases. Tests with naphthenic hydrocarbons showed that, similar to paraffinic ones, they form SOP on the friction surfaces within a certain temperature interval. With increasing molecular weight, both the temperature of maximum SOP-formation intensity and the final film thickness increase. For aromatic hydrocarbons, the temperature dependence follows the same trend as for paraffinic and naphthenic hydrocarbons but with considerably lower formation intensity and smaller final thickness.

ROTATING BENDING FATIGUE TEST MACHINE

2026-01-19T06:32:21+02:00

Steel wire ropes are widely employed across numerous industries, particularly in aviation, where they are used in onboard cranes, winches, hoists, mechanical control systems, and cargo-securing tie-down assemblies. The mechanical performance of steel wire ropes is governed by the properties of their individual components. Steel wire is a primary structural element of these ropes. In service, wire ropes are exposed to cyclic operational loading during cargo lifting, movement, and handling, as well as additional dynamic loads caused by acceleration. In many cases, they also operate in unfavorable and aggressive environments. Together, these factors lead to fatigue, wear, and corrosion, critically influencing the service life and reliability of wire ropes. This study presents the development of a compact rotating-bending fatigue testing machine specifically designed to evaluate the fatigue behavior of steel wires. The base configuration is intended for laboratory testing at dry air; however, further upgrades will enable testing in aggressive corrosive media, various surfactants, greases, and corrosion-preventive compounds to investigate adsorption-induced weakening phenomena, including the Rebinder effect. Analytical stress calculations based on Reuleaux’s classical approach were validated by finite element modeling, demonstrating close agreement between the methods. The developed machine provides an efficient and reliable tool for studying fatigue mechanisms in steel wire materials under realistic operating conditions.

DETERMINATION OF OPTIMAL OPERATING MODES TO INCREASE THE SERVICE LIFE OF GRAPHITE PLASTIC

2026-01-19T05:05:35+02:00

The article presents the results of scientific research on the processes of operation of graphite plastic in a tribological unit. The effect of sliding speed and load on the intensity of wear and coefficient of friction of graphite plastic was determined, and mathematical models describing the tribotechnical behavior of graphite plastic depending on the load and sliding speed of the friction unit were developed. The research carried out in the paper made it possible to reveal the influence of the technological parameters of the operation process on the intensity of linear wear and the coefficient of friction of graphite plastic. The obtained mathematical dependencies make it possible to reliably predict the duration of the developed graphite plastic in tribological units of modern technology, which is important for ensuring the efficiency and reliability of machines and mechanisms.

RESEARCH ON THE INFLUENCE OF TECHNOLOGICAL FORMING PARAMETERS ON THE TRIBOLOGICAL PROPERTIES OF A COMPOSITE BASED ON ULTRA-HIGH-MOLECULAR-WEIGHT POLYETHYLENE

2026-01-19T04:47:47+02:00

The article presents the results of a study on the influence of technological parameters of moulding on the abrasive wear index of a polymer composite based on ultra-high-molecular-weight polyethylene containing 25 wt.% dispersed binary alloy of the Al–10 wt.%Co system as a filler. We applied the method of a full factorial experiment of type 2³ to reduce the volume of experimental tests and establish quantitative relationships between technological parameters of moulding and tribological properties of the material. We obtained an adequate mathematical model that reflects the influence of processing temperature, holding time under load, and load magnitude on the abrasive wear index. We established optimal pressing conditions which allow the wear resistance of the composite to reach its maximum value.

PERFORMANCE OF FRICTION PAIRS OF DISC-SHOE BRAKES (IN A WET ENVIRONMENT)

2026-01-19T00:03:30+02:00

This article examines the effects of water wetting on matte and polished brake disc surfaces when vehicles are moving on wet roads.

Thermokinetic processes occurring in water and humid air surrounding the friction pairs of a disc-and-pad brake, consisting of a disc and a pad, were studied using an SMC-2 friction and wear machine. Patterns of changes in the operating parameters (dynamic friction coefficient, braking torque, and wear) of the pad were established as the disc rotates at 300 min^-1 under specific loads of 1.0 and 1.3 MPa and surface temperatures up to 400°C. An analysis of the intensity of changes in the above operating parameters is provided.

The polished and matte surfaces of brake discs, with hot and cold zones, have different areas. Water in these areas exists in both liquid and gaseous states. All of this facilitates electrochemical and chemical reactions on the surface of the disc friction zone. Moisture condensed on the disc friction zone acts as an electrolyte, reducing the wear and friction properties of friction pairs and forming corrosion pits at the interfaces between polished and matte disc surfaces. A mathematical description was developed for full-scale testing of a MAN TGA 26.430 disc-shoe brake on a vehicle under variable thermodynamic parameters of the friction pair's cleaning medium.

Oxygen and hydrogen, released during the decomposition of water during the reactions, promote oxidative processes on the disc friction zone and intensify hydrogen-induced wear on its surface.

THE EFFECT OF PRESSURE CONVECTION AND UNSTEADY FRICTION ON THE STRUCTURE OF A SHOCK PULSE

2025-12-26T00:35:19+02:00

Unsteady fluid flow refers to those that generate a shock pulse, which is usually called a water hammer. Despite the fact that many works are devoted to this topic, there are still no works that consider such interesting properties of the flow as its self-similarity at the initial moments of time when the shock pulse is formed - taking into account the physical phenomena indicated in the title of the work. This is especially important for the correct physical description phenomena using modern 3-D modeling and calculation tools, since the nonlinearity of the system can become a source of significant deviations of the numerical solution from the exact one. In this work, attention is paid to the influence of unsteady friction of the fluid against the pipe wall (Bruno-Vitkovsky model) and convection of the pressure disturbance field, as well as their combined action. Among the main results of the work, the following should be noted: neither the influence of convection nor the influence of unsteady friction can be neglected; each of the just mentioned physical mechanisms and both together lead to a significant spatial expansion of the region of disturbances from the shock pulse. Another result is that the dimensionless distributions of the shock pulse propagation velocity field and pressure disturbances asymptotically coincide with each other, and without taking into account the convection of the pressure field, these (dimensionless) solutions are equal everywhere.

NON-DESTRUCTIVE TESTING AND QUALITY OF ENGINEERING PRODUCTS QUALITY

2025-12-25T23:38:57+02:00

The article considers the types of non-destructive testing, fatigue failure, quality and effectiveness of non-destructive testing methods. It is indicated that the most complete detection of defects is provided, as a rule, when using several methods. Complex systems of non-destructive testing, consisting of several physical methods, are usually used when the ability to detect defects using individual methods (i.e., type, size, location) is different, unequal. The effectiveness of decisions made when designing various industrial equipment depends on the reliability of knowledge about thermophysical processes during its operation. The methods of modeling and identification of heat transfer processes can be based on solutions of inverse problems of thermal conductivity (TC) and thermoelasticity (TCT). In some cases, determining the thermophysical characteristics (TPC) of a material or heat transfer parameters by the TCT method is practically the only way to obtain the necessary information about the object under study. The main principles of methodological recommendations for determining the economic efficiency of NC are the approach to determining the effect and the formation of a single methodological approach to determining the efficiency of NC both during manufacture and operation. With the help of NC, information can be obtained about individual product properties, that is, about individual unit quality indicators. The development and widespread use of NC methods led to the development of applied qualimetry and the theory of inverse problems.

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.