Problems of Friction and Wear

A REVIEW OF MACHINES FOR WIRE ROPES FATIGUE TEST

2024-06-25T06:58:05+03:00

Review of the test machines designed to assess characteristics of steel wire ropes covers analysis of the equipment for fatigue tension-tension tests, torsion tests, sheave bending tests. Variety of the test machines concepts is determined by the diversity of the operational factors influencing the wire ropes loading. The importance of the single wire tests for the understanding of steel wire ropes fatigue behavior in terms of the step-by-step study of the wire ropes damage mechanism study is shown. Necessity to account for effects caused by contact interactions between the wires, as well as between ropes and environment is shown.

INCREASING THE WEAR RESISTANCE OF AGRICULTURAL MACHINERY PARTS WITH COATINGS OF A DISCRETE STRUCTURE. TECHNOLOGICAL SUPPORT OF DISCRETE STRUCTURE COATINGS BY ELECTROSPARK ALLOYING

2024-06-25T00:22:19+03:00

Primed to improve wear resistance, renovation and improvement of parts of the working bodies of agricultural machines by applying coatings of discrete structures using the method of electric spark coating. The advantages of the electric spark alloying process are significant. The results of the stress-strain study of the “stressed surface - coating” composition are presented. To simplify the divisions, a model was developed using an ordered scheme for the distribution of discretes. The dimensions and configuration of the adjacent sections of the coating are established based on minimizing the level of the stress-deformation mill (SDS) with force and temperature influxes on the coating. It is shown that it is necessary to minimize stress-strain The formation of the composition “size surface - coating” is possible by changing the strength and size of discrete pieces on a special surface, as well as the selection of materials for coatings. The proponation method allows, at the design stage, to determine the size of a discrete plot covering the level of excess stress and analyze the influx of their magnitude and sign on the process of cohesive cracking.

Discrete coating has much less microstress than when applied with a ball. Coating with tungsten carbide increased the service life of parts by 2.5 times. The hardness of the coating reaches HRC 55...60. When the electrical spark shields of the discrete structure are removed, there is a decrease in the voltage in the same way as the electrical spark shields. The coating of the discrete structure includes a balled coating, which dramatically increases its wear resistance, and the discrete structure of the coating prevents local overstressing, which is the cause of wear of traditional coatings.

The design of a discrete coating with optimal matching of geometric parameters makes it possible to ensure the durability of the knives of the harvester's trimming drum, which work in high-contact grinding and grinding basins. The research results can be used in the development of technological processes for the formation of electric spark coatings of a discrete structure in the production, development and updating of working bodies and parts of agricultural machines and equipment in general, by improving wear resistance and service life.

THERMODYNAMIC ANALYSIS AND PREDICTION OF HIGH-TEMPERATURE OXIDATION OF COMPOSITE ALLOYS

2024-06-24T08:33:44+03:00

The thermodynamic analysis of the interaction of composite powder alloys of the Co-TiC system with air is carried out. The main regularities of their oxidation are established. The mutual influence of the content of chromium and titanium carbide on the quantitative composition of oxidation products is shown.Based on the analytical studies, the dependence of the quantitative and qualitative composition of the products of interaction with air of powdered alloys of the Co-TiC system on the ratio of their components was determined. The formation of protective layers can be predicted, and their formation can be controlled by selecting appropriate alloying elements and strengthening phases by thermodynamic analysis.The general laws of oxidation of powdered composite alloys of the Co-TiC system have been established. The influence of chromium content in the material on the composition and properties of oxide layers is shown. It was found that at a high chromium content in the matrix (more than 25% by volume), the brittleness of the oxide layer increases, which will lead to its intensive wear.

ANALYSIS OF THE MAIN FUNCTIONAL PARAMETERS OF POLYMER SURFACE MICRORELIEF ROUGHNESS

2024-06-24T08:24:38+03:00

The results of the functional parameters of the surface roughness profile after a series of experiments for a single material at different sliding speeds have been analyzed. The study of surface characteristics of materials is of great importance for understanding their behavior and properties under various operating conditions. It is especially important to analyze the roughness parameters after experiments in different modes, as this allows for an understanding of how the surface condition and its interaction with other elements change under different load conditions. Using an optical profilometer for this study provides detailed information about the microstructure of the surface and allows for an objective assessment of changes in its parameters after changes in modes. Given the widespread application of polymeric materials in various industries and engineering fields, it is crucial to investigate their properties and changes during operation. One of the key aspects is studying the wear resistance of polymers under different conditions, particularly at various sliding speeds. In this context, research has been conducted on the impact of sliding speed on the microrelief and wear resistance of polymer materials. Adsorption on surfaces with greater roughness occurs more easily. Thus, a rough surface (counterbody) can adsorb a polymer, whereas a smooth surface of the same material does not. Consequently, roughness can significantly alter the effective interaction between the polymer and the surface.

Tribological pairs between polymers and 30KhGSA steel combine the high mechanical properties and wear resistance of steel with the low friction coefficient and self-lubricating properties of polymers, making them effective for use under significant mechanical loads. Polymers also provide corrosion resistance, reducing the need for additional lubrication and ensuring a longer service life. This combination of materials is widely used in the automotive, aerospace, medical, and other industries where high reliability and cost-effectiveness are essential.

COMBINED TREATMENT AND WEAR MECHANISM OF NITRIDED COATINGS ON TITANIUM ALLOY VT-6

2024-06-24T07:51:45+03:00

The wear process in the tribological system: nitrided titanium alloy - hydraulic fluid - steel is studied. It is shown that the level of wear is determined by tribological structures of the dissipative type, which are self-formed at the evolutionary stage of running-in. Using a linear approximation of the Boltzmann transfer equation, the exponential nature of the running-in stage was established, at which the wear intensity decreases from the initial to the steady-state level and then fluctuates around a constant mean with a constant variance. AMG-10 liquid selectively interacts with the elements. Electronegative elements dissolve in the lubricant, while electropositive elements are transferred to the counterbody, interact with the products of the mechanical destruction of lubricant molecules, and take an active part in the formation of the tribostructure, which reduces the level of direct interaction of the solids in contact. Preliminary laser treatment of titanium alloy activates the process of subsequent nitriding, which makes it possible to reduce the nitriding time while increasing the thickness of the wear-resistant nitrided layer. The use of laser pretreatment on real parts makes it possible to increase the service life of friction units and reduce production costs during their manufacture.

STUDY OF THE DYNAMICS OF A PNEUMATIC SPINDLE ON CONICAL GAS-STATIC SUPPORTS WITH THE HELP OF COMPUTATIONAL EXPERIMENTS USING CAD/CAE TOOLS

2024-06-17T17:39:11+03:00

The results of a study of the dynamic stability of a pneumatic spindle on tapered gas-static bearings are presented based on determining the critical shaft rotation speeds, the amplitudes of forced vibrations and reactions in the supports, and the level of its permissible imbalance. Three-dimensional solid-state, dynamic and finite element models in CAD were developed, natural vibration frequencies and critical rotation frequencies of the pneumatic spindle were determined, the possibility of shifting the rotor natural frequencies caused by the action of centrifugal forces and the gyroscopic effect were explained. Calculations and analysis of the magnitudes of the amplitudes of forced vibrations, reactions in the pneumatic spindle supports in steady-state and transient rotation modes were carried out; it is shown that in the subcritical and postcritical regions, the trajectories of the center of masses remain symmetrical, in the critical region of the rotation speed, the amplitudes of oscillations of the spindle shaft center of masses increase, maintaining its dynamic stability and efficiency, and the increase in amplitudes at resonance does not lead to a violation of the support serviceability. The conditions under which a high-speed pneumatic spindle will retain its dynamic stability and performance in the case of simultaneous loading of the supports by both external forces and forces occurring at resonance have been determined.

STRUCTURAL ANALYSIS AND DESIGN APPROACHES FOR A NON-CONTACT ROTATIONAL DRIVE ON GAS-LUBRICATED SUPPORTS AS A SINGLE AND ADJUSTABLE DYNAMIC SYSTEM

2024-06-17T16:09:16+03:00

The paper presents a comparative analysis of the designs of non-contact rotational drives on gas-lubricated bearings used in machines and mechanisms for various purposes, such as microturbine generators, two-axis displacement tables, pneumatic spindles, and single-crystal cutting machines. The technical and technological advantages of non-contact direct rotational drives with gas-lubricated bearings are shown; the use of a non-contact drive with an aerostatic bearing in precision positioning mechanisms results in a uniform (smooth) movement with maximum positioning accuracy of the actuator. The approaches to designing the drive as a single and adjustable dynamic system, the characteristics of which are established and adjusted by changing the design, technological parameters, and adjusting the aerostatic supports, are considered. Based on the research, the directions of technical improvement of drives on gas-static supports which allow to maximize the existing advantages and features of gas-lubricated supports are outlined.

SOME PECULIARITIES OF TRIBOMECHANICS ELEMENTS USE IN DESIGN AND OPERATION OF DRILLING MACHINES FOR DRILLING OF UPRISING WORKINGS AND WELLS

2024-06-17T01:37:45+03:00

Modern mining enterprises widely use rotary drilling rigs equipped with ball drill heads, which are used to drill holes ∅250 - ∅320 mm in hard rocks for blasting operations. Drilling of such wells is associated with the use of significant axial forces and torques , which cause longitudinal deformation (compression) and torsional deformation of the rods and the drillstock as a whole. Therefore, the intensification of rotary drilling processes to increase the diameter of the drilled well is associated with significant technical difficulties and economic costs. In a number of practical cases, it is possible to drill large diameter wells in two stages. The first stage involves drilling a small-diameter (∅250 - ∅320 mm) advance well from the outer horizons of a mining enterprise (e.g., a mine) to a lower horizon or a network of horizontal workings connected to a pit. After drilling the advance borehole (∅250 - ∅320 mm), a drill bit is lowered to the horizon below, which is put on a drill bit instead of a small diameter crown. After replacing the working tool with a diameter of ∅250 - ∅320 mm with a drill bit with a diameter of ∅1500 - ∅3000 mm, drilling is carried out vertically upwards (sometimes at an angle). When drilling, the drill stand is subjected to torque and tensile axial force. In this mode of operation, the loads on the drillstring increase significantly, but the longitudinal axis of the drillstring remains straight, as the influence of longitudinal bending is eliminated, and the influence of drillstring unbalance due to initial misalignment and centrifugal forces is reduced. However, the moment of friction forces during drilling increases significantly, the influence of the drillstring stiffness increases, and there is a possibility of longer stops during the driller's operation in the bottom hole, while the value of the elastic forces of the drillstring decreases with an increase in its length, and therefore the twist angle increases. In the case of an increase in the angle of rotation of the drill string, the dynamic torque and tangential stresses increase due to significant differences in the angular speed of rotation of the string (from to 0). In this case, there are significant changes in the kinetic energy of the pile with a decrease in the angular velocity of its rotation. In fact, a decrease in the rigidity of the mill leads to an increase in the increase in the kinetic energy of the system on the drill. That is, the dynamic angle of shaft torsion increases and leads to the manifestation of a torsional impact with a large coefficient of dynamism ( ).

As follows from the industrial tests of the 2KV 3000 machine, the possibility of a torsional impact in the driller-drillstock-rotator system under the influence of a variable torque of friction forces between the rock and the tool was not taken into account. Therefore, at the maximum length of the drillstring, the increase in the kinetic energy of the impact causes the largest dynamic angle of twisting of the drillstring, which is perceived by the first rods from the driller, and they experience the ultimate induced normal stresses that lead to rod breakage.

For these reasons, for the efficient operation of drilling rigs in the drilling mode, it is necessary to create and apply an engineering methodology for calculating the dynamic parameters of the drill string and the rig as a whole under the influence of the frictional interaction between the tool and the rock.

EVALUATION OF THE RESIDUAL STRENGTH OF STRUCTURAL CARBON PLASTICS IN THE PROCESS OF THEIR MOISTURE SATURATION CHARACTERISTIC FOR OPERATING CONDITIONS

2024-06-16T19:44:11+03:00

The nature of the moisture saturation of constructive skin carbon plastics is examined, as well as the effect of the previous static load and the process pressure of formation on the moisture content of the material. The change in the residual strength of carbon plastics in the process of their moisture saturation characteristic for the operating conditions is shown.

EVALUATION OF THE RHEOLOGICAL CHARACTERISTICS OF GEAR OILS UNDER UNSTEADY FRICTION CONDITIONS

2024-06-16T17:04:55+03:00

The aim of the study was to evaluate the rheological characteristics of the lubricant during the formation of hydrodynamic and nonhydrodynamic components of the lubricating layer in tribotechnical contact. Two gear oils for hypoid gears were chosen as lubricants for the study. The studies were carried out on a hardware and software complex using a roller analogy that modeled the operation of gears under rolling and slipping conditions. The ‘Bora B’ T-Shyp gear oil (sample 1) is characterized by more effective rheological characteristics under unsteady friction conditions in the rolling sliding mode (30%), compared to the T-Shyp gear oil for hypoid gears (sample 2) due to the greater resistance of the boundary layers to the deformation rate of the lubricant under conditions of increasing the shear rate gradient. The non-Newtonian properties of oils according to the Ostwald-de Weyl power law are considered and the manifestation of pseudoplastic properties by lubricants is substantiated - the model of the behavior of gear oils corresponds to pseudoplastic fluids with a degree index n of 0.45...0.85. The expediency of using the Barus dependence to estimate the viscosity of a lubricant at a contact pressure of 200 MPa is analyzed. It is substantiated that when using the Barus dependence to calculate the viscosity of a lubricant, it is necessary to take into account the change in the piezoelectric viscosity coefficient, taking into account the manifestation of non-Newtonian properties in the formation of boundary layers of the lubricant. The regularities of changes in the elastic and viscous components of stress in the lubricant under conditions of increasing the gradient of the shear rate at friction are established. With an increase in the shear rate gradient from 2.5∙10² to 7.4∙10⁵ s^-1, the deformation rate increases by a factor of 2.9∙10³, and the destruction of boundary layers occurs. At the same time, the lubricant loses its pseudoplastic properties and becomes a Newtonian fluid, the elastic component of the stresses under such conditions being zero.

WEAR RESISTANCE OF POLYMER COMPOSITE MATERIALS FOR PLANE SPHERICAL BEARINGS

2024-06-16T13:48:27+03:00

The use of polymer composite materials allows significantly reduce the labor intensity of manufacturing friction unit parts due to high-performance and economical resources.

According to the definition, a composite material consists of one or more continuous phases of a homogeneous matrix with one or more dispersive phases. In this regard, the reliable operation of metal-polymer tribosystems primarily depends on the structural and morphological factor influencing the tribomechanical characteristics of materials. The principle of producing composite materials consists of a pre-created combination of two different phases (fillers and matrix) using certain technological techniques. As a result of filling, materials are obtained whose physical and mechanical properties differ from the matrix. The choice of fillers for metal-polymer materials depends on the purpose of the material, the need to change some tribomechanical characteristics and the type of polymer matrix.

Plain spherical bearings with metal-polymer tribosystems are very popular in the aviation industry. They are made from stainless and corrosion-resistant steels and do not require maintenance. Compacts have an extremely high payload-to-weight ratio and are used in primary and secondary flight control systems. They have a hinged type design.

The work identifies modern antifriction composite materials for use in plain spherical bearings. The structures and wear resistance characteristics of polymer materials under special operating conditions - vibration, reverse movements - have been determined.

It has been established that the design of the composite material is of paramount importance under increased loads in low-frequency vibration tests. It has been determined that the Fluroglide material, consisting of carbon fibers with the addition of PTFE material with functional additives, shows high tribological characteristics comparable to classic metal fluoroplastic tape. At extreme loads of metal-polymer composite materials, a key role is played by relaxation processes and the ability of the base of the composite material to restrain polymer materials and fillers from crushing and from the action of reverse movements. Under these critical operating conditions, Fluroglide exhibits superior wear resistance to metal fluoroplastic tape.

STAGES OF HEATING AND COOLING OF FRICTION PAIRS OF BRAKE DEVICES

2024-06-16T12:27:50+03:00

In the process of intense electrical-thermo-mechanical loading of friction pairs of braking devices, which take place on transport, technological equipment, etc., the surface-volume temperatures of their elements can reach significant values, at which the thermophysical properties of the surface and subsurface layers of materials change significantly. Their change is influenced by surface and deep temperature gradients, as well as heating rates and forced air cooling of friction brake elements. Theoretical and experimental studies of the energy load of various types of friction brake units under pulsed and long-term braking modes made it possible to determine the surface and deep temperature gradients, as well as the rate of heating and forced air cooling of the friction elements, and it was established: the most common with local contact of microprotrusions the emerging fields of current lines is the thermodynamic potential, which includes external and internal parameters in their working layers; the thermodynamic potential is determined by the conditions of thermodynamic equilibrium of the tribosystem and the criteria for its stability in a variety of processes accompanied by changes in energy; a local area of actual contact of microprotrusions, formed by the simultaneous action of normal and tangential impulse loads, causing electric and thermal currents that do not completely disappear when the pulsed specific loads are removed, forming frictional connections of microprotrusions; the magnitude of surface and deep temperature gradients and their limitations for metal friction elements, as well as the rates of heating and cooling, knowledge of which allows us to move on to the patterns of changes in the thermophysical parameters of friction pair materials. The regularities of changes in surface and deep temperature gradients and rates of heating and forced air cooling of metal friction brake elements have been established.

TESTING OF CONSTRUCTION MATERIALS FOR CAVITATION RESISTANCE

2024-06-16T11:37:21+03:00

The article presents the results of experimental studies of the cavitation erosion of structural materials widely used in aviation hydraulic drives. The effect of the air saturation of the working fluid on the intensity of the cavitation erosion of structural materials was determined. It is proposed to use as a cavitation generator a throttle device functioning in the mode of developed cavitation when investigating the cavitation resistance of structural materials. The effectiveness of throttle cavitation generators was evaluated based on their flow-difference characteristics. The design of the cavitation chamber for testing structural materials for cavitation resistance is presented. A mechanism of cavitation erosion is proposed, in which the mechanical influence of shock waves and microjets on the surface of the test sample dominates. The incubation period of structural materials that are widely used in hydraulic engineering and their cavitation resistance are determined. The rate of cavitation erosion caused by the supply pressure on the cavitation generator was studied. It was determined that the cavitation erosion of plastic materials occurs almost linearly, while for solid materials the nonlinear dependence is observed. It is proposed to increase the fatigue life of structural materials, which are widely used in aircraft construction, by cavitation treatment of their surface within the incubation period of the cavitation.

ANALYSIS OF SIGNALS OF ACOUSTIC EMISSION OF TRIBOSYSTEM IN CONDITIONS OF STEPPED LOAD INCREASE

2024-03-30T03:20:20+02:00

An evaluation of the performance of electric spark coating in conditions of stepped load increase was carried out based on the analysis of acoustic emission (AE) signals. The purpose of the research was to determine the changes in the frictional contact during the transition of the tribosystem from the normal to the catastrophic stage of wear. The research was carried out for tribosystem steel 30ХГСА - unmodified or modified Д16 duralumin alloy. Modification was carried out by applying a combined discrete coating of hard alloy ВК8 and copper with a density of 55-65% by the method of electrospark alloying. Modification of Д16 duralumin provides efficient operation of friction pairs up to 1200 N, the average power of AE signals and their dispersion values are reduced by 2...4 times. An 80% reduction in wear intensity of tribosystems with combined electric spark coating was established, the depth of propagation of plastic deformations is reduced by 2 times. Empirical dependences of wear intensity on loading parameters and AE signals were obtained.

INCREASING THE EFFICIENCY OF TECHNOLOGICAL PROCESSES OF DRAWING AND ROLLING IN CONDITIONS OF RATIONAL USE OF DRY AND SEMI-LIQUID FRICTION FORCES UNDER THE INFLUENCE OF EXTERNAL VIBRATIONS

2024-03-30T02:50:58+02:00

In modern technological processes of metal forming, such as cold rolling, rolling and drawing, a significant proportion of energy supplied to the rolling device is irretrievably lost to friction and wear, as well as giving the workpiece a given shape (or dimensions) as a result of plastic deformation.

To assess the nature of friction in such machines, the types of frictional interaction between the material of the processed workpiece and the tool were determined, taking into account the influence of lubricants. As it was established, during metal pressure treatment, there is both "dry" and "semi-liquid" friction. Even in the presence of lubricant in the kinematic pair: fiber-wire billet dry friction prevails. As practice shows - the occurrence of significant friction forces and forces of tension of the workpiece is caused by the presence of multiple deformation microroughnesses in the receiving part of the fiber, at its interaction with the moving workpiece. These microroughnesses (on the workpiece) are sheared and plastically deformed by the interaction of the contacting pair. Moreover, this deformation process is accompanied by a continuous wave background in the sound range.

For intensification of rolling and drawing processes it is recommended to use, by analogy with vibration metal cutting treatment, vibration rolling and drawing, by installing additional vibrators acting in the direction of rolling or drawing on the applied fibers. The proposed vibrators operate, as a rule, in the ultrasonic range. Optimization of the rolling (drawing) unit operation is carried out by selection of amplitude and frequency of additional vibration, providing the required mode of machine operation, which realizes the transition from "dry" friction between wire and die to "semi-liquid" friction.

Implementation of measures on creation of additional devices for ultrasonic drawing and rolling allows to reduce energy costs of the rolling and drawing operation, as well as to increase the wear resistance of the tool.

STUDY OF THE DYNAMICS OF SPINDLE SHAFT ON GAS-STATIC BEARINGS

2024-03-30T02:23:06+02:00

This study delves into the complex dynamics of spindle shafts mounted on gas-static bearings, employing computational experiments and analysis to reveal crucial insights for optimizing high-precision machining processes. We identify natural frequencies and resonant tendencies of spindle vibrations through advanced Finite Element Method (FEM) simulations, highlighting their impact on operational stability and machining quality. Deliberately introduced imbalances further illuminate the dynamic behavior, displaying the detrimental effects of resonance on spindle performance. To mitigate these effects, we explore various technical solutions, including reducing rotor imbalances and intensifying acceleration through critical regions. Ultimately, this investigation provides a comprehensive understanding of spindle dynamics on gas-static bearings, guiding the development of robust and high-precision spindles for a range of industrial applications beyond just machining, such as precision robotics and microfabrication.

INFLUENCE OF FLUOROCARBON COMPOUNDS ON ANTI-FRICTION AND OPPOSITE PROPERTIES OF TRICOMPOUNDS

2024-03-30T02:08:13+02:00

The results of the study of the influence of fluorocarbon compounds of the type (СХ)n on the antifriction and antiwear properties of tribocompounds are presented. It is shown that in conditions of extreme lubrication of gears and bearings, these compounds have good prospects for use as additives and additives to oils. Mechanisms of lubricating action and some examples of practical application are considered. The developed methods of using carbonofluorides include running-in of friction nodes in environments that contain carbonofluorides, introduction of carbonofluoride additives in oils, plastic lubricants, lubricating-cooling and hydraulic fluids. Approbation of these methods in friction nodes of gas turbine engines (GTD) showed the prospect of their wide use in aviation technology. The most important results of the test are that in the presence of carbonofluorides, the service life and maximum allowable contact stresses of rolling bearings and gears can be significantly increased, and after the introduction of carbonofluorides, the friction nodes become less sensitive to the quality of lubricants.

DEVELOPMENT AND MODERNIZATION OF A COMPLEX OF INSTALLATIONS FOR WEAR TESTING OF METAL-POLYMER COMPOSITE MATERIALS FOR SPHERI-CAL SLIDING BEARINGS

2024-03-30T01:46:09+02:00

The fretting corrosion machine has been modernized for testing spherical bearings under vibration conditions. The method of research of anti-friction composite materials and coatings for low-frequency reversible movements has been developed. A method for laboratory resource tests of aviation spherical sliding bearings with metal-polymer composite materials in conditions close to real has been developed.

OF THE SERVICE LEVEL IN AN AIRCRAFT MAINTENANCE ORGANIZATION BY GROUP QUALITY INDICATORS

2024-03-30T01:00:45+02:00

The article presents the results of a comparative analysis of the assessment of the efficiency of three aviation enterprises: AVIATECH LLC, SPC MS AVIA-GRADE LLC and AIR SERVICE LLC by quality indicators. These organizations provide aircraft maintenance services. The average quality assessment in an aircraft maintenance organization is calculated as the arithmetic mean of group quality indicators for each maintenance organization. It is proposed to assess the level of service quality by an integral quality indicator. The integral indicator is the final indicator of the service quality, calculated on the basis of a set of quality assessments of various components of the processes of activity of aircraft maintenance organizations obtained in the process of monitoring.

REGULAR WEAR DETONATION COATINGS ON TITANIUM ALLOY VT-22

2024-03-21T03:30:47+02:00

The paper presents the results of experimental studies of the wear process of detonation coatings and counterbodies and compares them with other types of coatings, obtaining wear characteristics. The characteristics of wear of coatings are described in an analytical form, as well as the results of the study of tribological structures. The tribotechnical characteristics of detonation coatings are determined, taking into account the properties of dissipative structures that are self-formed in contact with friction. The effectiveness of the method of researching the process of wear of detonation coatings has been determined. It has been established that when coatings are rubbed against chrome, the total wear of the friction pair is significantly less than when rubbed against bronze. This is due to the best tribotechnical properties of chromium in the experimental field. The coefficient of friction of electrochemical chromium coatings is of the same order as when rubbing on bronze. The total intensity of wear of the coating and the counterbody when rubbing against chrome is somewhat lower than when rubbing against bronze. Since tribological structures are formed from complex oxides, asphaltenes, cokes, etc. during friction of coatings on chrome alloy VT-22, therefore the tribotechnical characteristics of such systems are somewhat lower than in systems that include bronze.

BEARINGLESS ROTOR SYSTEM MAIN COMPONENTS DESIGNING

2024-03-21T02:27:29+02:00

Bearingless rotor system design optimizes mechanical simplicity, eliminates frictional losses typical of conventional bearing systems, and improves the overall efficiency of the rotor system. Based on the findings of the research, it is possible to determine that composite materials can be applied in order to improve the performance of the rotorcraft rotor system.A theoretical analysis of the influence of input parameters on the aerodynamic quality of the main rotor of a rotorcraft was carried out. The strength and aerodynamic quality of the designed parts were calculated using the finite element analysis method. The energy efficiency of the use of composite materials is substantiated, which will ensure better efficiency and competitiveness of the aircraft.

GENERALIZED METHOD OF DETERMINING THE SURFACE-VOLUME TEMPERATURE OF ELEMENTS OF FRICTION UNITS

2024-03-21T00:42:09+02:00

The materials of the article contain questions: thermophysical parameters of friction pairs of braking devices; project calculation and analysis of results; discussion of the results. A generalized method of determining the surface-volume temperature of the friction pairs of braking devices with given design parameters and constant values of the thermophysical properties of their materials is proposed, provided that the friction power corresponds to linear or parabolic laws of change and corresponds to the laws of generating heat flows in friction couplings, which made it possible to establish such. The connection between graphical dependencies for linear and parabolic laws of heat release was carried out through the dimensionless value K as a function of the Fourier criterion (F₀), and the dependence of the form K=μ(F₀) made it possible to estimate the intensity of cooling of the metal friction element using the Bio criterion (Bi), criterion F₀ varied from zero to 1.2, and criterion Bi from zero to 1.0. When determining the surface-volume temperature of the "metal-polymer" pair, it was carried out through the coefficient of distribution of heat flows; while the latter acted on the entire thickness of the metal, and in the polymer overlay only on its surface and subsurface layers. When selecting the material for the metal friction element, the coefficient of thermal saturation was used, which includes the coefficient of thermal conductivity, heat capacity and density of the material, which has a larger value. The generalized method is confirmed by bench data on friction pairs of a belt-pad brake and operational tests of friction pairs of a drum-pad brake, in which the material was steel 35ХНЛ-retinax ФК-16Л.

COMBINED METHODS OF ENGINEERING OF CONTACT SURFACES OF TRIBOLOGY SYSTEMS

2024-03-21T00:20:41+02:00

The issues of ensuring the durability and reliability of equipment, increasing wear resistance and expanding the range of operation of friction pairs in extreme operating conditions require solutions related to innovative technologies for the formation of wear-resistant surfaces that can significantly increase the efficiency of using hardening methods, creating new ones and improving existing ones.

A brief review of the combined methods of engineering contact surfaces of tribological systems is carried out. The perspective of using this direction to expand the range of use of discrete protective structures, namely in the conditions of fretting, fretting fatigue, and limit friction, is shown.

INFLUENCE OF HIGH-TEMPERATURE LOADING CONDITIONS ON CHANGES IN THE PHYSICAL STATE OF YTTRIUM-CONTAINING COATINGS

2024-03-13T10:07:35+02:00

yttrium content varies linearly and significantly differs from the nature of the mass gain under the conditions of modelling dynamic loading in a burning iso-octane-propane-butane gas mixture at a temperature of 950-1020 ℃. It is determined that the maximum mass increase for gas-flame coatings under static loading is 30-35% at the yttrium concentration of 0.3-0.5%. However, for ionoplasma coatings with the same yttrium concentration, the mass gain is almost 2 times less than that of gas flame coatings. Comparing the peculiarities of changes in the rate of increase in the mass of coatings under dynamic conditions of high-temperature loading, a graphical model of changes in the physical state of coatings was obtained, according to which the minimum amount of secondary compounds will occur at the gas-flame method of formation with a yttrium concentration of 0.1% to 0.47%, at the ion-plasma method of formation with a concentration of 0.25% to 0.35% (under conditions of a slight increase in oxygen in the interaction medium). It was determined that, without taking into account the time of structural-phase transformations and chemical reactions, the weight gain of coating materials under static loading is much greater than under dynamic loading.

SUBSTANTIATION OF EXPEDIENCY OF USE OF TOOL HIGH-SPEED CUTTING STEELS AS COATINGS IN FRICTION UNITS

2024-03-12T23:57:48+02:00

The analysis of modern researches in the field of composite materials on the basis of tungsten carbide used as surfacing materials is carried out. In particular, the influence of morphology of carbide phase on wear resistance of materials is analyzed. Particular attention is paid to the analysis of conducted studies of ultrafine and nanograined composite materials, their comparative analysis with conventional micrograin coatings. The expediency of research of application of tool high-speed steels as coatings, applied by vacuum electron-beam processing method, which allows to organize micro-metallurgical process with minimal impact on the base metal and possibility to form hardened layer, the thickness of which is adjustable within wide limits, is substantiated.

WAYS TO SOLVE THE PROBLEM OF GAS-FLAME SPRAYING OF GLASS-ENAMEL COATINGS

2023-12-12T01:20:51+02:00

Based on the analysis of the gas-dynamic model of two-phase flow in thermospray plants, the temperature of gas and particles was estimated, as well as the analysis of the heat exchange process in the system "extended flare-powder particles with low thermal conductivity", the possibility of spraying enamels by gas-flame method An analytical assessment of the thermal state of enamel particles in the torch and at the time of contact with the substrate is given. The values of glass enamel particle and gas phase temperatures along the torch axis are theoretically determined. It is established that glass enamel particles cannot be softened in the flame of known thermal sprays due to the short length of the high-temperature zone of the torch. Theoretical analysis of the heat transfer process in the system "flare-particles of powder with low thermal conductivity" (for example, powders of glass enamels) showed that to soften them it is necessary to increase the duration of the powder in the flare. A method of gas-flame spraying with an elongated torch based on the formation of a secondary torch due to the use of the effect of combustion with separation is developed. Analytical evaluation of the thermal state of enamel particles in the torch torch and at the time of contact with the base showed the possibility of spraying powders of materials with low thermal conductivity by the gas-flame method by increasing the length of the torch / To increase the length of the torch, it is proposed to form a secondary torch at a distance from the nozzle of the thermospray and theoretically determined the distance of formation of the secondary torch.

INTERPRETATION OF ENERGY METHODS IN THE THEORY OF FRICTION AND WEAR FROM THE STANDPOINT OF CONTINUUM MECHANICS AND DISLOCATION THEORY

2023-12-11T06:31:02+02:00

In modern tribotechnical calculations, a significant role is played by theories of friction and wear based on the energy of processes occurring on the outer layers of interacting parts. Thus, the energy approach allowed us to formulate the view that under dynamic loading of two elastic bodies, as a result of friction, part of the energy is reversible and goes to the development of elastic vibrations, another part of the energy of inelastic interaction of parts, at the molecular level, is redistributed to other types of energy and dissipated in the form of thermal energy into the environment, while the remaining energy, in the case of vibrations of surface layers, accumulates as an irreversible part of the potential energy in deeper layers of parts. This energy, when a certain threshold value is reached, contributes to the destruction of the surface and subsurface layers of the friction pair elements. Taking into account the temperature effects of friction has allowed a number of researchers to determine friction coefficients and forces based on the hypothesis of the formation of welding bridges during metal friction and their subsequent destruction. In addition, hypotheses about the diffusion of atoms during the friction of kinematic pair elements, as well as the hypothesis about the possibility of recrystallization of metals (and other materials) at room temperature, have become widespread. As a generalization of the results of the hypotheses considered, the author of [1] proved that the friction process has a dual nature and can be described by the molecular mechanical theory of friction and wear. The existence of a significant number of hypotheses and theories of friction and wear as physical phenomena is due to the convenience of the energy approach and the extreme complexity of the process itself. The proposed work is aimed at clarifying and, in some cases, simplifying tribotechnical and related thermal calculations.

STATISTICAL ANALYSIS OF THE RESULTS OF STUDYING THE TRIBOTECHNICAL CHARACTERISTICS OF LUBRICANTS UNDER FRICTION

2023-12-11T06:06:10+02:00

Effective lubricants play a crucial role in ensuring machinery's smooth operation across diverse industries like aviation, engineering, and automotive sectors. Their significance lies in enhancing operational efficiency, reducing downtime due to equipment breakdowns, and extending machinery lifespan. These lubricants primarily target friction and wear reduction, thereby increasing intervals between maintenance and repair cycles in various equipment. The research aimed to evaluate the specific parameters impacting wear in friction pairs, focusing on the lubricating antifriction and anti-wear properties of Aero Shell Grease 33 and VNIINP-286M. Using an СМЦ -2 installation, real-time monitoring of tribocontact indicators like friction torque, roller speed, and lubricant temperature was conducted. The study considered non-stationary friction conditions, varied contact loads, and different lubricant application methods to prevent boundary lubrication. Statistical processing via Statgraphics Centurion software involved regression analysis and ANOVA. Regression models correlated wear with variables like friction work, lubricant layer thickness, friction coefficient, contact load, and penetration. Stepwise regression eliminated non-significant variables, refining the predictive model's accuracy. ANOVA validated the model's significance. The outcomes highlighted variables like load and friction as significant contributors to wear in friction pairs, leading to a more comprehensive understanding of lubricant performance in various operational conditions. The study emphasized the practical applicability of statistical tools in optimizing lubricant efficiency and machinery reliability, shedding light on key variables driving wear behavior in friction systems.

RESEARCH OF CAVITATION EROSION OF STRUCTURAL MATERIALS

2023-12-11T05:48:06+02:00

The results of experimental studies of the patterns of wearing of structural materials which are used in the hydraulic machine design engineering under the impact of hydrodynamic cavitation are presented. It is proposed to use a throttle device working in the mode of developed cavitation and being the throttle generator of cavitation pressure fluctuations, as a cavitation generator in studies of the cavitation resistance of structural materials. The rational type of throttling device for creating the liquid’s cavitation flow has been established based on the analysis of flow and differential characteristics of throttling devices of various schemes, which work as throttle cavitation generators of pressure fluctuations. It is proposed to use the dimensionless pressure drop on the throttle cavitation generator of pressure fluctuations as a cavitation criterion. The peculiarities of generation of the cavitation pressure oscillations by a throttle generator have been studied. The regularity of the influence of the pressure drop on the throttle cavitation generator of pressure fluctuations (mode of operation) on the range of cavitation pressure fluctuations and the amount of cavitation wear has been established. The influence of the geometric parameters of the throttle cavitation generator of pressure fluctuations on the intensity of the cavitation erosion was determined. Analytical dependences of the rate of cavitation erosion of test samples of materials on the pressure at the inlet to the throttle cavitation generator of pressure fluctuations were determined.

The results of the experimental research can be used to create highly efficient throttle cavitation generators of pressure fluctuations for the study of the cavitation erosion, cleaning the parts from contamination, intensification of technological processes in the chemical, oil production and other industries. On the other hand, the obtained results make it possible to create the hydraulic units that will have the high resistance to the cavitation erosion.

STRENGTHENING AND INCREASE OF WEAR RESISTANCE WORKING BODIES OF AGRICULTURAL MACHINERY

2023-12-11T04:07:30+02:00

The influence of the surfaces of the working organs of agricultural machines with a discrete structure coating, which has a relief in the form of hemispheres, on the destruction and grinding of grain raw materials is considered. It is shown that the working surface of cutting and crushing elements covered with a discrete structure and with a relief in the form of hemispheres can be more effective when grinding grain raw materials. The theoretical rationale and results of experiments in grinding wheat grain with cutting and crushing elements having a working surface covered with a discrete structure are presented. The article discusses the influence of the working surface of crushing elements with a coating of a discrete structure having a relief in the form of hemispheres located on a plane on the destruction and grinding of grain raw materials during its free impact. It is shown that the working surface of crushing elements coated with a discrete structure with a hemispherical relief, not yielding to a plane in a direct impact, can be much more effective in grinding grain raw materials if the angle of incidence of grain is increased. The theoretical justification and experimental results are given for grinding wheat grain by crushing elements with a working surface with discrete structure coatings. It is justified that in order to increase the wear resistance of the working surfaces of the grinding elements, the material of the discrete coating must have a hardness that is much higher than the hardness of the main material. The combination of the viscosity of the base material and the high hardness of the coating areas ensures the durability of the grinding elements.

ANALYSIS AND INTERPRETATION OF WEAR IN POLYMER MATERIALS BASED ON TRIBOLOGICAL INVESTIGATIONS

2023-12-11T03:44:17+02:00

The analyzed properties of polymer materials related to wear resistance and vibration absorption capabilities, utilized in the production of sliding pairs, have been explored. The perspective of employing polymer-metal friction pairs in industrial machinery, pharmaceuticals, and the food industry has been substantiated. To effectively control any mechanical system with sliding motion under optimal parameters, indicating tribological characteristics for materials in frictional contact is a convenient means for swiftly characterizing tribological behavior when operating conditions are variable. Through experimental investigation, factors influencing the wear of polymer specimens in contact with metal have been analyzed. The materials subjected to tribological analysis are polymer materials such as Sustamid 66 gray, Sustapei, and SusTamid 6G OL, manufactured by the Röchling Group, in contact with steel 30KhGSA. All selected polymer materials are designed for use in pairs with sliding contact.

INFLUENCE OF MAGNETIC FIELD ON THE ANTIWEAR PROPERTIES OF DIESEL FUELS REFORMULATED BY BIOCOMPONENTS

2023-12-11T03:28:45+02:00

The article discusses the issue of antiwear properties of traditional and alternative diesel fuels. The main goal of this work was the theoretical and experimental studies on the effect of alternative biodiesel fuels (on a plant basis) on the change in the antiwear properties of traditional diesel fuels. Also, the goal was to study the effect of the magnetic field on the antiwear properties of diesel and alternative diesel fuels. Experimental studies have been conducted for the antiwear properties of traditional and alternative diesel fuels based on biocomponents obtained from rye oil. The studies showed that the addition of methyl esters of fatty acids of rye oil led to an increase in the amount of wear by 1.8 (10% esters) and 2.2 (20% esters) for the diesel samples and their mixtures with biocomponents, respectively. During the treatment of fuels with a magnetic field of 0.1 T and 0.4 T, it was established that the amount of wear is 1.2 and 1.5 times (10% esters, a magnetic field of 0.1 T and 0.4 T, respectively); 2.2 and 1.15 times (20% esters, magnetic field of 0.1 T and 0.4 T, respectively) times, respectively. It was established that the treatment with a magnetic field stabilizes the antiwear properties of diesel fuels in the case of addition a biological component to them. The results of studies can be applied in the chemical industry, the transport industry, in particular, in the operation of diesel vehicles. The article results can be useful to tribologists, chemical experts, as well as scientists involved in the development and implementation of alternative engine fuels.

EVALUATION OF THE EFFICIENCY OF THE LUBRICATION OF OILS WITH CARBONFLUORIDE ADDITIVES IN NON-STATIONARY FRICTION REGIMES

2023-12-11T03:02:57+02:00

The results of the study of the effect of carbonofluoride additives on the lubricating effect of aviation oils VNIINP-50-1-4u, IPM-10 are presented; MS-8p, industrial oils I-20A, IGP-18 and automotive oil M-10G2K in non-stationary friction modes. The introduction of KF additives into lubricating media significantly reduces, and in some cases completely eliminates, the temporary deterioration of the lubricating effect in non-stationary modes due to the high adsorption properties and chemical activity of carbonofluorides.

RESEARCH OF COMPOSITES FEATURES BY SOLVING THE DIRECT AND INVERSE PROBLEMS OF THERMAL ELASTICITY

2023-12-11T02:29:14+02:00

The article provides an analytical solution to the three-dimensional coupled problem of thermoelasticity for a composite whose structure and possible defects are given by trigonometric polynomials. Parameters of the temperature field arising as a result of defects in its structure are used in the diagnosis of defects in its structure. This is of great importance and practical value for non-destructive testing tasks. An expedient way of finding temperature values as a function of time and geometric coordinates is also the solution of inverse problems of thermoelasticity, i.e. determination of the temperature field based on the field of temperature stresses. The economy of this method lies in the fact that its application makes complex experimental studies of technical objects cheaper and eliminates the need to create computational and analytical methods that accompany these studies.

EVALUATION OF THE FRICTION PAIR RESOURCE OF DISC-PAD BRAKES OF VEHICLES

2023-12-09T23:08:52+02:00

Theoretical and experimental studies of the energy load of a disc-pad brake of a vehicle made it possible to propose a method for determining the components of generated electric currents in metal-polymer friction pairs, based on experimental and calculated data, which is implemented in five stages, at each of which the total electric currents: thermal; the current that arises due to the friction of sliding and contact-interacting macro sections of the surfaces; current arising due to sliding friction, formed by the movement of charged mass transfer particles; the current caused by sorption-desorption processes in the near-surface layers of the lining, which are at a temperature higher than the permissible for its materials, as well as their direction. Determine the total wear during the braking cycle of the friction disc treadmill as the sum of losses due to its oxidation (corrosion) with the involvement of mechanical wear. The components (mechanical, electrical, thermal) of the friction power and their calculated values were determined with the help of the obtained dependencies. Based on the found value of the energy balance of the brake friction unit, the volume intensity of wear of the working surface of the lining was determined based on the obtained dependence with the transition to the dependence of the actual resource, taking into account the width and permissible thickness of the wear of the lining. The projected service life of the pad is achieved due to its working area and length, as well as the specified radius of the microprotrusions of the friction track of the disc. This method made it possible to increase the resource of the friction pad by 1.25 times under different operational parameters of the disc-pad brake of the vehicle.

FORMATION OF ANTIFRICTION SURFACE STRUCTURES UNDER FRICTION

2023-09-27T20:02:35+03:00

The results of the formation of anti-friction surface structures of the developed glass-composite self-lubricating nanocoatings, the structural components of which have a qualitative effect on the graphitization process and ensure the production of a surface layer of α-graphite that minimizes contact parameters, are presented.

The positive role of the glass phase in the form of aluminoborosilicate, which affects the tribotechnical properties of coatings, has been established. It is noted that the increase in adhesive strength is achieved due to the formation of a surface layer of vitreous sodium silicate during sputtering. It was established that the intercalation of the graphite layer with particles of the subsurface zone does not significantly affect the tribotechnical characteristics. The developed nanostructured glass composite coatings showed high anti-friction characteristics in the entire load-speed range of tests.

THE RESEARCH OF IMPROVEMENT WAYS FOR PYROLYSIS GAS COOLING AND BLOWING PROCESSES IN PYROLYSIS GAS POWER STATIONS USING CONVENTIONAL TECHNICAL SOLUTIONS

2023-09-27T19:52:09+03:00

The article is dedicated to describing the research of different ways, appliances and solutions for flammable gas supply, transportation and cooling, performed in terms of authors’ PhD theses, related to pyrolysis gas production and application for electric power production. The main idea of this research is the investigation of opportunities of application of modern simple generally used technological solutions on pyrolysis gas power plants for the above mentioned units design. The research is related to different ways of pyrolysis gas cooling and also to the ways of the gas supply from gas generator to the consumer. Another goal is to create a systematic approach to the automation of pyrolysis gas production and transportation onto future pyrolysis gas powered electric power plants.

SIMULATION OF TRANSPORT AND LOGISTICS SCHEMES OF TRUCK TRANSPORTATION UNDER THE CONDITIONS OF GLOBAL RISKS

2023-09-27T16:27:01+03:00

As a result of the increase in the number of factors that ensure the efficiency of transport flows, the methods of building mathematical models, which are based on the consideration of general laws, turned out to be ineffective. Therefore, it is promising to involve experimental methods of identification based on the formalization of the results of observations and analysis of the arrival of new information about changes in the situation that has developed with the use of new digital technologies.

The article shows that in the near future, road connections together with water transport will be of key importance, and therefore the task of mathematically ensuring the management of the preservation of traffic flows under the conditions of global risks will always be relevant. The method of work is the modeling of traffic flows under conditions of preservation of global risks.

A solution to the problem of maintaining the dynamics of traffic flows caused by the pandemic, military actions and extreme situations is proposed. Based on graph theory, Ford-Falkerson and Dinitz algorithms, a modified algorithm for determining the structure of transportation was developed. A feature of the algorithm is the synchronization of the capacity of transport flows with the moments of lifting and introducing restrictions on transport. The novel proposed algorithm is the possibility of adjusting transport routes. Also, a new use of the proposed modified algorithm is the synchronization of technologies using the methodology of determining the throughput capacity of the branches of the implementation of transport flows with moments of the concept and introduction of restrictions due to unforeseen situations and global risks. The modified algorithm for determining traffic flows in the conditions of unforeseen situations and global risks based on the maximum algorithms of Ford-Falkerson and Dinitz ensures the minimization of losses of carriers and traffic flow. Implementation of the algorithm ensures maximum traffic flow in extreme conditions and global risks.

STUDY OF THE PROCESS OF RECOVERY OF IRON OXIDES BY HIGH-TEMPERATURE HYDROGEN-CONTAINING GAS IN AN ELECTROTHERMAL PSEUDO-FLUIDIZED LAYER

2023-09-27T08:26:37+03:00

Hydrogen metallurgy involves the replacement of a carbon reducing agent with a hydrogen one. One of the promising opportunities for the use of hydrogen in metallurgy is the recovery of iron ore pellets that consist of iron oxides. However, there is a problem of heating the hydrogen-containing gas to the recovery temperature. One of the possible solutions to this problem is the use of an electrothermal fluidized bed. The purpose of the article was to determine the principle possibility of recovery of iron oxides in the form of iron ore pellets by high-temperature hydrogen-containing gas in an electrothermal fluidized bed. The authors considered the generation of hydrogen by pyrolysis of natural gas. Conducted thermodynamic calculations of the process of reduction of iron oxides with the obtained hydrogen indicate the optimal temperature range of the process: 900 ... 1500 K. To study this process, a laboratory installation with an electrothermal fluidized bed with a combined heating method was created. This installation is divided into two reaction zones. In the first, natural gas is decomposed into hydrogen and pyrocarbon. Carbon dioxide, which is a valuable material, remains in the first reaction zone. The formed hydrogen with a high temperature enters the second reaction zone where it restores the iron ore pellets. During the process of recovery of iron pellets with high-temperature hydrogen-containing gas, no flame accompanying the process of hydrogen formation by pyrolysis of hydrocarbons was detected. The release of water vapor at the reactor outlet was observed. This means that the hydrogen produced reacted with the iron pellets and reduced them to pure iron. The surface microstructure of the original iron pellet is darker and matte, while the surface microstructure of the processed iron pellet has a lighter color and a shiny surface, which is characteristic of pure metals. This additionally indicates the fundamental possibility of restoring iron pellets to pure iron with high-temperature hydrogen produced by pyrolysis of natural gas in an electrothermal fluidized bed. Research results can be applied in the energy sector, the transport sector, in particular, in the operation of space vehicles. The results of the article can be applied in practice by energy engineers, expert chemists, as well as scientists involved in the development of the latest technologies for obtaining hydrogen.

COMBINED METHOD OF SURFACE HARDENING OF HIGH-SPEED STEELS

2023-09-27T02:44:55+03:00

The structure, phase and chemical composition, microhardness, and microbrittleness of the surface zones of P6M5 steel after chemical and thermal treatment: nitriding followed by titanium and chromium plating are considered. Metallographic and micro-X-ray spectral analyzes of wear surfaces of P6M5 steel with different types of coating were carried out. It is shown the dependence of physical and mechanical properties of complex coatings and discrete laser treatment on wear-resistance. The analysis of the obtained data showed that azochromic coatings with additional strengthening by laser treatment of steel, which serves as a substrate for coatings, increase its performance in extreme operating conditions, excluding its crushing, chipping and peeling.

RESEARCH OF THE WEAR RESISTANCE OF ELECTRO-SPARK COATINGS UNDER ABRASIVE CONDITIONS

2023-09-27T02:18:47+03:00

The reasons for the destruction of parts of the friction units of aircraft and ground aviation equipment, which are made of iron-based alloys, were analyzed, and it was established that during operation, various processes develop on their working surfaces, namely: abrasive wear, seizure, fretting - corrosion, fatigue wear. The analysis of modern technological methods of surface strengthening of machine parts was carried out, the prospects of electrospark alloying of iron-based alloys were determined. Research on the wear resistance of coatings was carried out using a complex methodology, which includes metallographic, electron microscopic, durometric, and other methods of analysis of physical and mechanical methods. The influence of electrode materials on the wear resistance of ESD coatings has been established. Practical recommendations for surface strengthening of parts of automatic transmission systems operating under conditions of abrasive wear are indicated.

EROSIONAL WEAR OF THE LOAD CARRYING CANVAS OF BURNING MACHINES UNDER THE INFLUENCE IRON ORE PELLETS

2023-09-27T01:54:33+03:00

The load-carrying belt of conveyor machines for clods of iron ore concentrate operates in a complex, aggressive dust and gas environment and cyclic "heating-cooling" modes. At the same time, the constituent elements of the load-bearing fabric - gratings also work under the influence of shock and abrasive loads, which leads to their intensive wear, as well as an increase in the regulated working gaps between adjacent gratings, and, therefore, to their premature replacement. In order to predict the degree of wear of the working surfaces of parts (grills), numerical models have been developed at the micro, macro, and meso levels. These models work in various combinations, but in the given conditions of operation of burning machines, due to the specifics of their work, meso- and micro-models rarely appear. The results of the analysis of the defects of the grates, which have failed, indicate the manifestation of macro-models, the schematization of which takes place mainly in the form of an erosive wear model. On the basis of macro models, Bitter's dependences were modified to calculate the degree of erosive wear of grates, and it was also established that to significantly reduce the degree of wear of pallets, it is recommended to use drum-type loading devices that ensure unloading of material with an angle of attack α=35÷45°. At the same time, the best recommended material for grates is steel 30Х14Г8Ю2Л.

DEFINING TESTS OF HEAT-RESISTANT YTTRIUM-CONTAINING SEALING COATINGS FOR HIGH-TEMPERATURE GAS-EROSION RESISTANCE

2023-09-27T01:35:16+03:00

This article describes the testing of heat-resistant yttrium-containing sealing coatings for high-temperature gas-erosion resistance. The study includes careful visualization and characterization of the geometry of the cut-in profile, observation of changes in surface color, and analysis of the internal structure of powder coatings. The first important conclusion is that there are no obvious changes in the geometry of the flute profile and the configuration of the edges, bottom and sides. This indicates the absence of significant mechanical wear of the surface of the coating materials under the influence of high-temperature gas flow. Further analysis suggests that the modeled mechanical pressure and velocity of the flare jet were not large enough to cause destruction of the coating surfaces. A noticeable change in the color of the surfaces was noted. This phenomenon may be the result of the formation of oxides on the surface of materials under the influence of elevated temperature. The exact chemical composition and nature of these oxides require further research to fully understand. Studies indicate the presence of deformation of the internal structure of powder coatings, as well as the accumulation of zones with high and low microstresses. These phenomena indicate the possibility of micro-wear of the coating materials and the formation of additional cohesive bonds. it was found that the yttrium content affects the rate of mass gain of coatings. The weight gain depends on the yttrium concentration and the method of coating application. This relation can have important practical applications in the development of tribological materials with improved properties.

ELECTION OF GEAR OILS BY PHYSICO-CHEMICAL CHARACTERISTICS

2023-09-27T01:09:41+03:00

A comparative analysis of the performance of mineral and synthetic gear oils according to the main (standard) physical and chemical characteristics was carried out. The main requirements for gear oils, which are formulated today by leading gear manufacturers and are reflected in international specifications and standards, are given. Conclusions were made regarding the compatibility of mineral and synthetic gear oils.

ANALYSIS OF MODELS AND METHODS FOR ASSESSING THE STRENGTH CHARACTERISTICS OF POLYMER COMPOSITE MATERIALS

2023-09-27T00:04:40+03:00

The expediency of combining complex design systems and conducting standardized mechanical tests in the development of new composite materials in order to increase the reliability of products and structures is substantiated. The analysis of modern software complexes of finite element analysis SolidWorks, ANSYS, Abaqus and Patran/Nastran for modeling the properties of composite materials was carried out. The peculiarities of predicting various forms of destruction of polymer composite materials are determined, estimates of potential mechanisms of destruction, PCM damage models depending on the software complex used in the design of products from composite materials are given. The application of the edge effects model in layered composites, displacement compatibility models, adhesion models, linearized three-dimensional fracture criteria and other fracture models with the rate of energy release, the method of virtual crack closure in calculating the damage resistance of laminated composite structures at the design stages is considered. The main aspects of methods of research and determination of mechanical properties of composite materials under tension and compression according to ISO and ASTM standards are considered. The procedure for creating a regulatory and technical base in the field of production and application of PCM is analyzed from the standpoint of bringing the national standardization system closer to international and European norms and rules.

RELATIONSHIP OF WEAR-FRICTION PROPERTIES AND ENERGY-LOAD OF FRICTION COUPLES OF BRAKE DEVICES

2023-09-26T23:13:34+03:00

The relationship between wear and friction properties and the energy load of friction pairs of braking devices during external friction of different friction pairs of a belt-pad brake is considered. The decisive influence on the dynamic coefficient of friction (f) and the intensity of wear (I_n) of the maximum surface temperature ( ) on discrete contacts of friction pairs is shown. Graphical dependences of the form f=f(p_a, )and I_n =I(p_a, ), λ = λ( ), а = а( ) and НВ = НВ( ) were analyzed (p_a – impulse specific loads; λ and а – coefficients heat and temperature, HB – Brinell hardness) and establish their interdependence with the temperatures of the friction surfaces. In a correctly designed metal friction element of any type of braking device, the values of the ratio of the areas of matte and polished (working) surfaces must be maintained. At the same time, the increase in the area of the matte surface is achieved by the introduction of external constructive elements. In drum and belt-pad brakes, this is the implementation of ribs, deflectors, grooves, protrusions, etc.), in disc-pad brakes, internal developed surfaces are used in self-ventilated disks (protrusions, half ribs, ribs, channels, etc.). This approach is connected with the need to intensify the forced cooling of metal friction elements, which are heat energy accumulators in any type of braking device. Therefore, the second and third subsystems of various types of braking devices are considered from the point of view of the interaction of metal friction elements with high-speed flows of the washing medium, which reduce their energy load. When evaluating the intensity of cooling simultaneously with forced cooling in a belt and drum-pad brake, it is necessary to take into account the conductive type of heat exchange in the couplings "pulley rim – fastening protrusion and "drum rim - side wall". The presence of a fastening protrusion significantly affects the intensity of circulation of the main and additional heat flows in the rim of the pulley. The side wall of the drum plays a significant role in forming the thermo-stabilization state of its rim. A comparative analysis of changes in the main operating parameters was made and their interdependence was established on a model belt-pad brake during the operation of friction pairs in pulse and three-shaft braking modes.

INTEGRAL ASSESSMENT OF THE RISKS OF THE EMERGENCY OF EMERGENCY SITUATIONS IN MARINE CARGO TRANSPORTATION

2023-06-07T18:44:09+03:00

The work provides a methodology for calculating risks based on the use of a model of the safety of cargo transportation by various types, including sea, transport, and a general model of the emergency development scenario. The considered theory of statistical decisions is intended for the development of recommendations on the rational application of actions in conditions of uncertainty and associated risk.

Given that accidents and the risk of emergency situations have a pronounced random nature, the methods of probability theory and mathematical statistics are used to assess risks. Therefore, the article deals with the issue of vehicle accidents and related cases of cargo loss/damage, which are rare events distributed according to the Poisson law. Predicted estimates of the probability of failure of technical means can be determined using the theory of Markov processes.

The practical use of the integrated risk assessment methodology allows already at the stage of the initial design of transport and technological schemes of sea freight transportation to evaluate alternative options according to risk criteria and to develop measures to reduce the level of risk in order to increase the safety of transportation and preserve cargo. At the same time, risks are assessed not only under normal conditions of transportation, but also in cases of accidents, which is a mandatory condition when choosing methods and means to minimize losses and negative consequences of accidents and disasters.

The results of research on the development, development and improvement of the methodology of integrated risk assessment and ways of managing them in emergency situations to increase the safety of sea cargo transportation are also given.

INFLUENCE OF GAS THERMAL PROCESS PARAMETERS SPRAYING OF COATINGS FOR THEIR WEAR RESISTANCE AND ADHESION STRENGTH

2023-06-07T18:09:00+03:00

On principle of equivalent tensions of adhesive connection, the estimation of remaining tensions is conducted in coverage. For this purpose, graphic differentiation of experimental dependence of adhesive durability is utilized from the thickness of coverage. Functional connection is set between adhesive durability, thickness of coverage, critical deformation of basis and remaining tensions. It allows choosing the parameter When using electrical contact treatment after gas-thermal spraying of coatings, positive results were obtained: the value of residual stresses does not exceed 200 MPa; parts with gas-thermal coatings that have undergone electrocontact treatment are characterized by a smooth change in hardness from the coating to the surface of the part and an increased diffusion zones of the system «basis-coverage» at finish treatment and exploitation. the amount of pressure and the technological scheme of the electrical contact treatment process significantly affect the level of residual stresses and the adhesion strength of the coatings. From this point of view, preference should be given to the application of coatings by gas-thermal spraying with subsequent electrical contact treatment with a gradual increase in temperature and pressure of the process.

The method of graphic differentiation of the experimental dependence of the adhesive strength on the thickness of the coating was used to determine the residual stresses in the coatings obtained by gas-thermal spraying with subsequent electrical contact treatment. According to the principle of equivalence of residual stresses and critical deformation of the part during peeling of the coating, a functional relationship of adhesive strength, thickness of the coating, critical deformation of the part and residual stresses was established. This dependence allows you to determine the characteristics of coated parts for their operating conditions.

INFLUENCE OF HEAT TREATMENT ON TRIBOTECHNICAL PROPERTIES OF EUTECTIC ELECTROSPARK COATING

2023-06-07T12:59:41+03:00

The article considers the efficiency of applying electric spark coatings with the aim of studying the effective influence on the tribological properties of eutectic alloys. Friction and wear tests of electrospark coatings made of the developed eutectic alloy on a steel substrate were performed. In order to compare the effectiveness of the influence on the tribotechnical properties of eutectic alloys, both the coatings in the initial state and the coatings annealed under two different modes were tested.

Based on the results of the study of the chemical composition of the films formed in the process of friction, regularities were established by qualitative assessment. The dependences of tribotechnical properties for the initial and heat-treated coatings were determined. These studies indicate the feasibility of using electrospark coatings for different friction conditions.

THE EFFECT OF FRICTION MODIFIERS ON THE PERFORMANCE CHARACTERISTICS OF LUBRICANTS

2023-06-07T10:04:19+03:00

The analysis of antifriction and antiwear additives to lubricants has been carried out and the mechanisms of formation of protective films on tribocombination elements have been considered. An increase in the antifriction and antiwear characteristics of lubricants due to their additional modification with graphite, molybdenum disulfide, fullerenes, nanotubes or a repair composition has been established. The mechanism for increasing the efficiency of lubricants with friction modifiers is to create a protective surface layer in the process of tribosystem self-organization during friction. It has been established that by empirical analysis it is possible to choose the optimal concentration of the repair and restoration compound RVS, the addition of which to the gear oil provides an increase wear resistance of steel under rolling conditions with slippage. Reducing the wear of contact surfaces is facilitated by mechanical chemical processes that manifest themselves during structural adaptability of finely dispersed components of the geomodifier friction RVS, boundary lubricating films and metal surface layers at friction under dynamic loading conditions. For the main indicators providing an increase in the wear resistance of friction pairs are microhardness of metal surface layers and its gradient depth distribution, microgeometry of the surface layer, formed during friction, and the formation of boundary lubricating layers on friction-activated contact surfaces. These processes are a manifestation of structural adaptability structural materials under study, the consequence of which is qualitative and quantitative change in the microgeometry of surfaces friction. Fullerenes and nanotubes are elementary objects of nanotechnologies, on the basis of any possible macro-objects, which may be of practical importance, - materials and outbuildings. The potential of using these structures (especially nanotubes) exceeds potential of other nanostructures.