Problems of Friction and Wear

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

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

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

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

FORCED COOLING OF BRAKE FRICTION UNITS (part 2)

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

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

FORCED COOLING OF BRAKE FRICTION UNITS (part 1)

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

LOCAL CHARACTER OF THE STRESS-STRAIN STATE DURING LASER PROCESSING

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.