Browsing by Author "Raksha, Serhii V."
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Item The Effect of Stress Pulses on the Cyclic Endurance of Steel Axle Wheel-Set(Nevsehir Haci Bektas Veli University, Cappadocia, Nevsehir, Turkey, 2019) Vakulenko, Ihor A.; Bülent, Kurt; Raksha, Serhii V.; Askerov, Hangardas; Hryshchenko, Mykola A.ENG: For different temperature and speed deformation conditions, the nature of the increase in the number of defects in the crystal structure and the achieved complex of properties are due to the peculiarities of the internal structure of the metallic material. Compared with unidirectional static loading, the violation of the monotonous nature of the effective stress is accompanied by qualitative changes in the internal structure of metals and alloys. Thus, the pulsating nature of the acting stresses in case of fatigue, depending on the degree of cyclic overload per cycle, can lead to significant changes in the development of the processes accumulation and redistribution of defects in the crystal structure and, above all, dislocations. Based on this, the rate of accumulation of dislocations per loading cycle can be considered as one factor that will allow the development of measures to increase the cyclic endurance of metallic materials during fatigue. Compared to thermal technologies, treatments that are based on the use of short stresses pulses for moving defects in a crystal structure have gained some fame. In addition to sufficiently strong magnetic fields or high-power pulses of electric current, treatments based on mechanical effects on the metal can be used.Item Energy-Efficient Excavation of the Soil of the Lower Track Structure by Bulldozers with a Combined Knife System(IOP Publishing, 2020) Hlavatskyi, Kazymyr Ts.; Raksha, Serhii V.; Gorbenko, Yu. О.ENG: The motivation of the research and further development of the new type combined knife system on the irreversible bulldozer blade and the results of the first series of laboratory studies of the process of digging the soil with the irreversible blade of the bulldozer with the first set of its physical models, which indicate the feasibility of continuing research in this direction. The proposed combined knife system makes it possible to realize oblique digging of the soil on the irreversible blade of the bulldozer and maximally complete its orientation in the prism of the soil before the blade in order to increase the productivity of the bulldozer with irreversible blade by reducing soil losses in the side rollers, reducing the time of filling and digging the soil by reducing the coefficient of specific soil resistance to digging. The paper substantiates the technology of more efficient use of bulldozers with non-return blade compared to their traditional counterparts, which is possible due to the use of the new combined knife system, and argues in favor of expanding the technological capabilities of the bulldozer with non-return blade, equipped with the proposed solutions new type with different digging angles and a spatial inclination of the cutting edges.Item Experimental Research of Ropeway Dynamics(Kaunas University of Technology, Kaunas, Lithuania, 2022) Kuropiatnyk, Oleksii S.; Raksha, Serhii V.; Krasnoshchok, Oleksandr L.ENG: Research of ropeways is carried out in several directions, one of which is the establishment of dynamic characteristics of rope systems under different operating conditions. In previous works, we proposed a mathematical model for calculating the frequency spectrum of ropeway, which is based on the representation of the ropeway traction circuit as a discrete-continuous dynamic system. The main purpose of the experimental studies is to confirm the adequacy of this model; its results are presented in this article. The considered single-span ropeway is usually used as a means of industrial transport for moving goods between production and storage facilities, in the mining industry – for transporting various materials from the place of extraction to railways and highways. Studies were carried out using experimental equipment developed by us. According to the results of the experiment, we drew the frequency diagrams, which show the change of eigenfrequencies of the ropeway traction circuit during the cars movement between stations. The total array of results includes information on the decoding of about a thousand oscillograms, which were obtained and studied according to the methodology developed by us.Item Frequency Analysis of Vehicle Drive with Cable Traction(Український державний університет залізничного транспорту, Харків, 2018) Raksha, Serhii V.; Kuropiatnyk, Oleksii S.; Anofriev, Pavlo G.; Onopreychuk, Dmytro V.; Kovalov, IhorENG: Abstract. The paper outlines the basic principles of constructing frequency diagrams and specifies the features of their application for the analysis of the dynamic state of the vehicle drive with cable traction on the example of a ropeway. To draw up the frequency diagrams, the ropeway traction circuit was presented as a dynamic system containing lumped masses and elements with distributed parameters. In this case, the moments of inertia of the rotating masses of the drive were brought to the traction pulley as a lumped mass. The traction cable segments are represented as elements with distributed parameters. The mathematical model describing the dynamic state of the drive consists of equations in the form of deformations of the traction cable segments using the positions of wave mechanics. Studies have shown that in most cases there is a fairly wide inter-resonance band, limited by the first and second eigenfrequencies. This phenomenon may be the basis for justifying the rational values of the rotational speed of the pulley as one of the kinematic parameters of the ropeway drive.Item Investigation of the Influence of Elastic-Mass Characteristics of the Axle Test Stand Links on Its Own Oscillation Frequencies(IOP Publishing Ltd, 2021) Raksha, Serhii V.; Anofriev, Pavlo G.; Kuropiatnyk, Oleksii S.; Plitchenko, SerhiiENG: The reliability of work according to the criteria of vibration stability of the stand for testing the axles of wheelsets for endurance is largely determined by the natural vibration frequencies of the stand. The work considers a stand with a lever structure for loading the tested axles. In order to determine the influence of the parameters of the cross-section of the links on the natural frequencies of the vibration stand, the frequency characteristics were obtained by the method of mathematical modeling for two variants of the design schemes of the stand. Studies have shown that increasing the cross-sectional area of the levers without measuring other linear dimensions leads to a simultaneous increase in their mass and cruelty. The rigidity of the levers is defined as for beams on two supports with a load of a transverse concentrated force. As a result, the calculated values of the natural frequencies of the stand vibrations change insignificantly. A deeper analysis of the Eigen frequency characteristics of the stand with the tools of the Matlab system made it possible to obtain linear regression equations with the coefficients of determination close to one. The obtained research results gave reason to expect a decrease in stresses in the metal structures of the stand with an increase in the cross-sectional area of the levers, however, the values of the natural frequencies of the stand vibrations vary within a few percent. The way to control the natural frequencies of the stand vibrations only by changing the profile parameters is ineffective.Item Justification of Criteria for Ropeways Energy Efficiency(Dnipro National University of Railway Transport named after Academician V. Lazaryan, 2019) Raksha, Serhii V.; Kuropiatnyk, Oleksii S.; Krasnoshchok, Oleksandr L.ENG: Purpose. The article is aimed to form and justify the energy efficiency indicators of ropeways of traditional design and ropeways with self-propelled wagons based on the determination and comparison of their values. The substantiation of the energy efficiency criteria of ropeway wagons allows us to determine fully the direction of further research in the field of development of alternative transport mode. Methodology. To obtain initial data, the authors reviewed the world trends in the development of ropeway wagons, proposed analytical formulas for determining criteria for ropeways` energy efficiency used to compare traditional ropeways and ropeways with self-propelled wagons. Herewith, we took into account the influence of the loading degree and rated power on the electric motor efficiency. In order to take into account the energy dissipation in the haul rope through its elastic properties, the concept of the efficiency coefficient of the haul rope was introduced. Findings. The authors formed a methodology for calculating the efficiency of ropeways, developed formulas for determining energy efficiency. We assessed the influence of the ropeway characteristics on their calculated values; constructed dependence graphs of the self-propelled ropeway efficiency coefficient on the rated electric motor power and the efficiency coefficient on the ropeway drive loading, as well as compared general efficiency coefficients for ropeways with self-propelled wagons and for ropeways of traditional design. The results are based on the averaged values of the electric motors parameters at their different loads. Originality. The authors first proposed and justified the energy-efficiency criteria for ropeways that make it possible a comparative analysis of traditional ropeways and those with self-propelled wagons. We determined the dependence of these indicators on the ropeway parameters. Practical value. The results of the comparative analysis of traditional construction of ropeways and the ropeways with self-propelled wagons, based on the proposed energy efficiency indicators, can be used to substantiate the feasibility of using certain type of rope-ways for the implementation of individual transport processes. The construction diagram of a self-propelled wagon can be used in the development of energy efficient passenger ropeway projectsItem Justification of Parameters of Wheelset Axle Fatigue Strength Test-Bench for Railway Rolling Stock(Dnipro National University of Railway Transport named after Academician V. Lazaryan, 2019) Kuropiatnyk, Oleksii S.; Raksha, Serhii V.; Anofriev, Pavlo G.ENG: Abstract. The operation safety of the railway rolling stock depends directly on the strength of the base part of the wheelset – its axle. Therefore, in recent years numerous studies of theoretical and experimental nature, both for means of rail transport, and for machines containing rail track equipment are carried out. This paper substantiates the main parameters of the fatigue test bench for axles for wheelsets of railway rolling stock. We performed an analysis of the load schema for bench tests, determined the dependence of the bench work force on the parameters of the wheelset axle. In addition, we substantiated the design and parameters of vibrator. For the research, we adopted the following criteria of rationality: work force, energy consumption and longitudinal dimension of the test bench. The design is considered the best, if these criteria acquire the smallest values. The results of the research indicate that the load scheme “cantilever beam” is rational for the fatigue bench tests of the axles for wheelsets of railway rolling stock. The best design of the vibrator have to provide the test bench work force by rotating the unbalanced mass around the stationary wheelset axle. The rational vibrator contains a sectoral eccentric mass rotating at an angular velocity of about 150 s-1. In this case, the eccentric mass value is about 80 kg, and its eccentricity is 135 mm.Item Justification of the Parameters of the Life-Test Bench for Railway Wheelsets(IOP Publishing Ltd, England, 2021) Raksha, Serhii V.; Anofriev, Pavlo G.; Kuropiatnyk, Oleksii S.ENG: One of the tasks that need to be solved in order to predict the life of wheelsets is to assess the contact strength and wear of their parts. Thus, the purpose of this work is to develop a scheme and justification of the parameters of the life-test bench for railway wheelsets in conditions close to real operating ones. This bench simulates a contact of “wheel-rail” pair as a contact of “wheel-roller” pair. To ensure compliance of the bench tests conditions with the real wheelsets operation conditions we took that the maximum contact pressure in the “wheelroller” pair is equal to the maximum contact pressure in the “wheel-rail” pair. As results of this study we obtained the dependences of the values of the roller diameter and the working force of the bench on the characteristics of the tested wheelset and proved the mutual influence of these quantities. For railway wheelsets with an axle load of 230.5 kN and wheels with a tread diameter of 957 mm, we obtained the following values of the bench parameters: roller diameter is 75 mm; working force of the bench is 8,375 kN; wheel speed is 500 rpm; number of rollers is 8; test duration is about 220 h.Item Mathematical and S-Models of Cargo Oscillations During Movement of Bridge Crane(Національний гірничий університет, Дніпро, 2019) Raksha, Serhii V.; Anofriev, Pavlo G.; Bohomaz, Volodymyr M.; Kuropiatnyk, Oleksii S.ENG: The effectiveness of research on the basis of mathematical models (linear, nonlinear) describing the dynamics of bridge cranes and cargo oscillations during transitional modes of movement, increases significantly with the use of numerical methods and simulation models created by visual programming tools.Item The Optimum Design of Compressed Thin-Walled Columns of Open Cross-Section(2000) Manevich, Arkadiy I.; Raksha, Serhii V.ENG: The structural optimization problem for compressed thin-walled columns of open cross-section (channel and lipped channel) is considered on the base of the linear stability theory and the nonlinear interactive buckling theory. Optimal dimensionless parameters are presented as a function of a single leading parameter of load and geometry P* and imperfection amplitudes.Item Research of the Dependence of Pneumatic Conveyor Compressors Power on Project Parameters of Transport Machines(Ukrainian State University of Railway Transport, Kharkiv, 2018) Raksha, Serhii V.; Bohomaz, Volodymyr M.; Shcheka, Ihor M.; Stefanov, Volodymyr O.; Nesterenko, AlexENG: Abstract. The paper considers the algorithm for calculating the pneumatic transport systems of the main constructions: with high vacuum and with different pressures. The analysis of the dependence of all calculation elements on the design data of the transport system of the considered structures was carried out. In order to accelerate the calculation of such systems, the analytical dependence of the power of the compressor drive on the type of cargo, the coefficient of concentration of the transported mixture, the design productivity, and the geometric parameters of the route, the number and types of auxiliary devices (ells and shutters) are constructed. A graphical analysis of the dependence of compressor drive power of the pneumatic transport systems with high vacuum and with different pressures on the design data: the mixture concentration coefficient, the length of transportation, the design productivity for the transportation of cement with a given route configuration. The directions for further research have been determined.Item Simulation Modelling of the Rolling Stock Axle Test-Bench(EDP Sciences, 2019) Raksha, Serhii V.; Anofriev, Pavlo G.; Kuropiatnyk, Oleksii S.ENG: Abstract. Wheelset axles are essential parts of railway and mine site rolling stock. For fatigue testing of axles, various test-benches are designed to implement the cyclic loads. The effectiveness of test-bench vibration analysis grows with the use of numerical approach and simulation models created with the aid of visual programming tools. The purpose of the work is to develop and assess the proposed simulation models of test-bench dynamics created with the aid of visual programming tools. Based on mathematical models, the test-bench simulation models of the lever system vibration have been developed. Simulation models are created with the aid of Simulink visual programming tools running under Matlab system. For modelling the components of Simulink, the SimMechanics and DSP System Toolbox Libraries are used. The comparative analysis of proposed models has been made. For the first time, with the aid of Simulink visual programming tools, the set of test-bench vibration simulation models has been obtained in steady-state and transient motion modes for linear task formulation. The proposed S-models allow automation and visualization of the motion dynamics study for test-bench components in order to determine their rational elastic-weight, kinematic and dynamic behavior. Simulation of vibrations was carried out using design parameters of the test-bench metal framework.Item Stand for Accelerated Tests of Rail Vehicles Wheelsets(IOP Publishing, 2020) Raksha, Serhii V.; Anofriev, Pavlo G.; Kuropiatnyk, Oleksii S.ENG: Tests and research can be greatly accelerated by applying a multi-point load to the test wheel. The aim of this work is to substantiate rational parameters of the stand for accelerated life tests of railway wheelsets, in which a multi-point load applies to the rolling surface of the test wheel. On the basis of the laws of the theory of elasticity, we performed analytical calculations of the contact stresses created by the rolling bodies of the load mechanism of the test stand. Research has shown that the dependence of the contact stresses on the wheel rolling surface on the ball’s diameter is nonlinear. The decrease in stress is due to an increase in the contact area. We obtained the analytical and graphical dependencies, which make it possible to evaluate the influence of the parameters of the stand for accelerated life tests of railway wheelsets on contact stresses on the wheel rolling surface, taking into account the shape and dimensions of this surface. The authors have proposed a stand design for accelerated life tests of railway wheelsets. The use of a stand with the parameters justified in this work will reduce the test duration by 10-15 times.Item Substantiation of the Parameters of the Bench for Testing of Railway Wheels for Contact and Fatigue Strength(Technologija, Kaunas, 2022) Raksha, Serhii V.; Anofriev, Pavlo G.; Kuropiatnyk, Oleksii S.; Glavatskij, Kazimir Ts.; Bohomaz, Volodymyr M.; Posmitiukha, Oleksandr P.; Volkova, Svetlana A.ENG: Strength indicators are important parameters of the railway wheels, as they determine the allowable service life of both the wheel itself and the wheelset as a whole. Therefore, the development of bench equipment that allows in the laboratory to reproduce or simulate the real conditions of the wheel load in order to conduct strength tests, is an urgent scientific and practical task. The purpose of this work is to substantiate the parameters of the bench for testing railway wheels for fatigue and contact strength. As the bench has to test railway wheels for fatigue and contact strength at the same time, the requirements of various normative and methodological documents, which determine the procedure for conducting such tests on separate benches, were combined when determining the parameters of the bench. We determined that the working force of the bench should vary from 10% to 100% of the wheel endurance limit, the duration of the tests should correspond to five million load cycles with a frequency of 5 to 10 Hz. To reduce the duration of the tests, pushing on the wheel was carried out by several rollers, which were evenly distributed around the wheel. For the proposed bench, we obtained the dependence that connects the parameters of the test wheel, the parameters of the bench, the wheel pair axle load and the wheel material endurance limit. The results of this study can be used as a basis for the development of new schemes of benches for railway wheels tests.Item Three-Criteria Optimization of Compressed and Bend Thin-Walled Beams-Columns(Poland, 2003) Raksha, Serhii V.ENG: A three-criteria optimization problem for thin-walled members of open cross-section with one axis of symmetry (of channel type) subjected to compression or/and bending in two planes under stability constraints is solved. The objective function vector components are the compressive force and the bending moments in two planes. Optimal configurations of the cross-section for marginal cases of loading – axial compression or bending in both planes – are obtained, Pareto-optima are constructed and «compromise» optimal projects parameters are derived as a function of a single leading non-dimensional parameter of weight.Item The Transformation of Structure Steel with Thermal Strengthening of the Disk Railway Wheel(Karabuk University, Karabuk, Turkey, 2019) Vakulenko, Ihor A.; Proidak, Svitlana V.; Raksha, Serhii V.; Akay, M.; Cug, Harun; Askerov, KhangardasENG: On the example of the carbon steel, issues of structuring in the process of accelerated cooling are considered. The emerging gradient of structures at different distances from the surface of the heat transfer is presented in the form of a dependence, which is adequate to the effect of the temperature of individual heating during the release of steel after the quenching. It is shown that after the forced cooling is stopped, the increase of distance from the cooling surface accompany higher the tempering temperature of the metal. In the volumes of the metal, the microstructure close to the middle of the disk wheel is formed by the diffusion mechanism.Item Two-Criteria Optimization of H-Section Bars Under Bending and Compression(2006) Manevich, Arkadiy I.; Raksha, Serhii V.ENG: The two-criteria optimum design problem for thin-walled members with two axes of symmetry (of h-type) subjected to compression and bending is solved. Components of the objective function vector are the compressive force and the bending moment in the web plane. Pareto-optima and «compromise» optimal projects have been obtained and compared with standard profiles.Item Two-Criteria Optimization of H-Section Bars-Beams Under Bending and Compression(2007) Manevich, Arkadiy I.; Raksha, Serhii V.ENG: The two-criteria optimum design problem for thin-walled members with two axes of symmetry (of h-type) subjected to compression and bending is solved. Components of the objective function vector are the compressive force and the bending moment in the web plane. Pareto-optima and «compromise» optimal projects have been obtained and compared with standard profiles.Item Two-Criteria Optimization of Thin-Walled Beams-Columns Under Compression and Bending(2001) Manevich, Arkadiy I.; Raksha, Serhii V.ENG: A two-criteria optimization problem for thin-walled members of open cross-section with one axis of symmetry (of the channel type) subjected to compression or / and bending in the symmetry plane under stability constraints is solved. The objective function vector components are the axial compressive force and the bending moment. Optimal configurations of thin-walled members for marginal cases of loading – axial compression or pure bending – are obtained? Pareto-optima are constructed and «compromise» optimal projects are derived as a function of a single leading nondimensional parameter of weight. The obtained optimal projects are universal? In distinction from the optimal projects for special loading cases, and applicable under arbitrary combination of compression and bending. Comparison of standard profiles (specified by the design codes) with the optimal projects enables us to indicate «bad» standard profiles which are far from optimal ones under any loads.