Browsing by Author "Vakulenko, Igor A."
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Item Improving the Performance Parameters of Railway Wheels with the Help of Optimal Design Technologies of their Electric Pulse Processing(Dnipro National University of Railway Transport named after Academician V. Lazaryan, 2019) Vakulenko, Igor A.; Kuzin, Nickolai O.; Vakulenko, Leonid I.; Raksha, Sergey V.; Proidak, Svetlana V.ENG: Abstract. The processing by pulses of electric current (PEC) of a fragment of the rim of a railway wheel was carried out on the DS10D equipment. When the density of the electric current is from 3 to 17 A/mm2, the processing cycle consisted of the action of a pulse with a duration of 2.5-3 s and a pause between pulses of 4 s. After 150 cycles of PEC, the hardness of cold-formed metal was reduced from 10 to 20%. Studies of the parameters of the metal structure of the wheels have determined that the processing of PEC leads to a decrease in the number of defects in the internal structure, which are accumulated as a result of cold deformation of the rim along the rolling surface of the railway wheel. It has been established that, according to the nature of the influence on the hardness distribution of carbon steel, the PEC treatment corresponds to changes during tempering in the average temperature range and allows to significantly increase the operating parameters of the wheels of railway equipment.Item Influence Factors on Electrophysical Parameters of Composite Varistors(Український державний університет науки і технологій, м. Дніпро, 2023) Ahadzade, Shafag; Vakulenko, Igor A.; Asgarov, HangardashENG: Purpose. The work is aimed to evaluate the influence of the structural state of polymer phase on the response voltage and nonlinearity coefficient of a multilayer varistor based on zinc oxide. Methodology. Zinc oxide consisted of 97% zinc oxide and 3% total oxides of Bi2O3, Co3O4, MnO2, B2O3, SbO3, ZrO2, Al2O3. To obtain the composite of thermoplastic polymers and zinc oxide, non-polar and polar polymers, high pressure polyethylene and polyvinyli-denefluoride were used. The composites were obtained by hot pressing at the melting temperature of the polymer phase and a pressure of 15 MPa. After that, using silver paste measuring electrodes 10 mm in diameter were applied to the surface of the synthesized samples and then current–voltage characteristics were measured. Modification of composites under the action of gas-discharge plasma was carried out in a special cell that creates a dielectric-gas-composite system. The composites structure was studied by X-ray diffraction analysis and IR spectroscopy. Findings. The obtained experimental results show that the size of inorganic phase particles significantly affects the cur-rent-voltage characteristics of the composite varistor: at a given thickness of the composite varistor, the operation voltage decreases markedly, and the nonlinearity coefficient increases. The influence of electric discharge plasma on the polymer zinc oxide-composite results in a significant change in the permittivity and the concentration of local levels at the separation boundary of the composite. The results research showed that electrical plasma effect on the response voltage depends on the polarity of polymer matrices. Moreover, plasma processing itself significantly changes the structure of the polymer phase in the composite. Originality. The magnitude of the potential barrier at the phase boundary is mainly determined by the volume fraction and size of the main structural element of ZnO ceramics. The change in the structural state of the polymer matrix allows adjusting the response voltage and nonlinearity coefficient of volt-ampere characteristic of the multilayer varistor. Practical value. The discovered development of electron-ion processes in the polymer phase of the varistor indicates the need of taking into account the change in its service characteristics from the duration and intensity of use. The result obtained shows not only the reason for the properties change, but also the need to develop the measures to increase the service life of varistor.Item Influence Ferrite Grain Size on the Development of Discontinuons Flow at Lowcarbon Steel(Nevsehir University, Turkey, 2021) Vakulenko, Igor A.; Kurt, Bulent; Erdogdu, Ahmet Emrah; Asgarov, KhangardashENG: On example of low-carbon steel, it is shown that development of strain hardening processes, starting from the moment initiation of plastic deformation, determines nature behavior of the metal at all subsequent stages of loading. The conditions formation of deformation bands and reasons for the disappearance of intermittent yield section on the deformation curves are considered. The use of the dependence characteristics of strain hardening on the size ferrite grain made it possible to explain evolution structure of low-carbon steel at region of intermittent flow.Item The Influence of Nonmetallic Inclusion on Strain Hardening Carbon Steel(Silesian University of Technology, Katowice, Poland, 2019) Vakulenko, Igor A.; Vakulenko, Leonid I.; Proydak, Svetlana V.EN: Summary. On a fragment of the rim of a railway wheel removed from service, the volume of the metal with non-metallic inclusions located near the tread surface was investigated. The use of the microhardness measurement technique made it possible to establish the nature of strain hardening of carbon steel near non-metallic inclusions. It showed that with a normal orientation of the plastic flow relative to the inclusion surface, the metal volumes undergo hardening. In proportion to the appearance of a fraction of the tangential component of the deformation near the nonmetallic inclusion, a decrease in the degree of hardening of the metal was observed.Item Influence of Plastic Deformation Carbon Steel on the Process of Burning lectric ARC(Silesian University of Technology, Poland, 2021) Vakulenko, Igor A.; Plitchenko, Sergey; Kurt, Bulent; Askerov, Hangardas; Proydak, Svetlana V.; Erdogdu, Ahmet EmrahEN: During a study of the combustion process of a direct polarity electric arc, a directly proportional dependence of the electric current value on the degree of cold plastic deformation of carbon steel used as an electrode was found. To calculate the value of the electric current during arc burning, in the indicated ratio, it was proposed to replace the surface tension force of the liquid metal with the surface tension of ferrite of plastically deformed carbon steel. Calculation of the ferrite’s surface tension value on the deformation degree of the steel under study through the size of the coherent scattering regions was used to explain the observed dependence of the electric current during arc burning. From the analysis of the considered correlation ratios, it was found that with an increase in the cold deformation degree, the refinement of the coherent scattering regions results in the ferrite’s surface tension increase and consequently, to an increase in the electric current during arc burning. Comparative analysis of the obtained results of calculating the value of electric current during arc burning through the surface tension of ferrite of cold-deformed carbon steel showed a fairly good coincidence with experimental data. The differences did not exceed 9%.Item Influence Structure on the Plasticity of Carbon Steel of the Railway Wheel Rim in Operation(Silesian University of Technology, Poland, 2022) Vakulenko, Igor A.; Vakulenko, Leonid I.; Bolotova, Dariy M.; Kurt, Bulent; Asgarov, Hangardash; Çölova, ÖmerENG: Summary. When simulating the operating conditions of the rim of a railway wheel, an analysis of change in the structural state from the possible degree of plastic deformation and the heating temperature of steel near the rolling surface was carried out. The development processes of spheroidization and coalescence of cementite during heating of the cold-worked steel change its ability to strain hardening. Substructure changes during heating to temperatures of 500-550°C deformed steel are accompanied by a simultaneous decrease in its ability to strain hardening and the level of plasticity. When heated above 500-550°C, the development of ferrite recrystallization processes provides a gradual transition of the metal from substructure hardening to hardening from grain boundaries with large angles of disorientation. It is shown that regardless of the nature of the main structural element, the ability of steel to strain hardening and the level of plasticity after heating are related by a proportional relationship.Item Influense of the Shock Wave Treatment on Fatigue Carbon Steel(Print ABC, Netanya, Israel, 2017) Vakulenko, Igor A.; Lisnyak, Alexander G.; Griaznova, Ludmila; Bolotova, Daria M.EN: The process of introducing additional number of dislocations in the heat-hardened steel after shock wave pulse treatment apparently is not accompanied by the development of dislocation annihilation. Furthermore, implementation of the deformation per cycle for the area of high-cycle fatigue is ensured by the participation of more dislocations. Thus, in the process of shock wave pulse treatment, the vast number of introduced dislocations is mobile and able to interact with further cyclic loading or it takes place additional unlock of previously fixed dislocations after hardening and tempering. Overall, on the destruction surface after treatment with shock wave pulses it is found increased number of dislocations that are located in different crystallographic slip systems. They can be seen as evidence of the development of quite complex dislocation reactions that increases the metal limited endurance during cyclic loading.Item Insights into Factors of Damage of Surface Rolling of Railway Wheels During Operation(The Silesian University of Technology, 2019) Askerov, Hangardas; Vakulenko, Igor A.; Grischenko, NikolajiEN: The systematization results of microstructure studies of carbon steel has made it possible to explain the mechanism of formation of certain damages to the rolling surface of railway wheels during operation. The evaluation ability of metal to strain hardening was used to explain the nature of the influence compactly located non-deformable dispersed particles on the strength properties steel during cold plastic deformation. In the process of the interaction of a railway wheel with a rail, successively occurring heterogeneities in the distribution of the plastic flow metal are one of the main reasons for the formation of defects on the rolling surface of the wheel.Item Reason of Destruction Side Frame of the Trolley(Фізико-технологічного інститут металів та сплавів Національної академії наук України, Київ, 2019) Vakulenko, Igor A.; Vakulenko, Leonid I.; Proidak, Svetlana V.EN: The metallographic and fractographic analysis methods were used to study the influence of the cast metal quality on the causes of the destruction of a railway carriage under high dynamic and cyclic loads. As a result of study structure fracture surface of the side frame freight car truck, the detected elements indicate simultaneous presence of fatigue and static fracture. The focus of nucleation fatigue crack was a surface defect of casting origin such as a blockage. Volumes with a concentrated arrangement of gas bubbles and non-metallic inclusions of various nature was found in the individual elements of the side frame. As a result of acceleration of moving fatigue crack, there are achievements of continuous decrease of construction of strength side frame. The meeting of the fatigue crack with volumes metal with an increased concentration of gas bubbles and non-metallic inclusions accelerated the transition to the phase of static fracture. Improving the operational safety of the side frame is possible by improving the foundry technology of its manufacture and changing the regulatory documentation to limit non-metallic inclusions and pores in the metal.Item Structural Changes at Metal of a Railway Wheel Along Rolling Surface(Nevsehir University, Turkey, 2021) Vakulenko, Igor A.; Kurt, Bulent; Bolotova, Daria M.; Colova, O.ENG: As a result rolling of the hardened carbon steel without slipping, only due to normal loading, a decrease in hardness is observed. The observed decrease in hardness is due to the development of softening processes during plastic deformation. Additional slippage at the contact points of the samples accelerates development of softening effects in the hardened metal. It has been found that softening during rolling of a quenched metal is accompanied by a refinement of the coherent scattering regions, increase in internal stresses, and increase at number of crystal structure defects.Item Structure and Properties of the Steel Railway Wheel Disc After Forced Cooling(The Faculty of Transport The Silesian University of Technology, Katowice, Poland, 2018) Vakulenko, Igor A.; Grischenko, Nikolaji; Vakulenko, Leonid I.; Efremenko, Vasily G.; Proiydak, Svetlana V.; Perkov, Oleg N.EN: The technological use of accelerated cooling makes it possible to improve the carbon steel properties of the all-rolled railway wheel disc. The properties’ complex depends on the temperature of the accelerated cooling termination. This is determined by the ratio of the carbon atoms emitted from the supersaturated solid solution to the crystal structure defects and dispersion strengthening from carbide phase particles. If the cooling stops at a temperature above 350°C, the decline rate of the strength properties increases. This is caused by the excessive softening effect of the solid solution breakdown and cementite spheroidization during the processes of dispersion hardening.Item Transformation of Structure During Friction Stir Welding(Silesian University of Technology, Poland, 2021) Vakulenko, Igor A.; Plitchenko, Sergey; Kurt, Bulent; Proydak, Svetlana V.; Askerov, HangardasEN: In comparison with low carbon steels, there is increased interest in the use of aluminium-based alloys as materials for the manufacture of welded structures rolling stock of railway transport. During friction stir welding aluminium-based alloy, against the background of the analysis structural transformations, issues of development hardening processes are considered. Under conditions of existence, a temperature gradient at zone of weld formation, shown degree approximation alloy to the conditions of superplastic flow and influence from presence particles of the second phase on grain size of matrix is estimated. Evaluation of the separate influence grain size of matrix and state of solid solution at total hardness of the weld showed dependence of their contributions on temperature of hot plastic deformation. As the temperature of plastic deformation of alloy at area of the weld increases, contribution to the total hardness from grain size increase and on state of the solid solution decreases.