Browsing by Author "Vakulenko, Leonid I."
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Item Fractographic Analysis of the Destroyed Side Frame of the Truck of a Wreight Wagon(ПОСВІТ, Дрогобич, 2020) Vakulenko, Ihor O.; Kuzin, Nickolai O.; Vakulenko, Leonid I.EN: The initial inspection of damaged frame in fracture revealed two sections with characteristic structural features. The area with traces of slight corrosion, representing a smooth surface, corresponds to the gradual movement of fatigue crack. The rest of fracture surface with signs of a dynamic destroy has a qualitatively different structure. The fatigue part occupies approximately 30% of the total cross-sectional area. The propagation front of fatigue crack, after reaching the outer and inner surfaces of vertical wall from the side of wheel, reaches half the length lower horizontal wall. The focus of origin fatigue crack, located in lower inner corner, when moving from vertical wall to horizontal part of the side frame, is difficult obtain access when visually inspecting the frame trolley.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 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 Perlite Dispersion of Carbon Steel on the Fatugue Processes(Springer, 2018) Vakulenko, Ihor O.; Kawalek, Anna; Vakulenko, Leonid I.; Proidak, Svitlana V.EN: Using the example of carbon steel with perlite structure it was determined the influence nature of the ferrite layer thickness of perlite on the angular coefficient of tangent at a certain point of the fatigue curve. Based on the analysis of the obtained dependencies, it is determined that the value of angular coefficient of the tangent can be used to evaluate the resource of limited endurance of the metal under conditions of cyclic loading.Item Influence of Self-Tempering Temperature on Strength of Railway Wheel Disk after Accelerated Cooling(Дніпропетровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпропетровськ, 2016) Vakulenko, Leonid I.; Bolotova, Daria M.; Proidak, Svitlana V.; Gryshchenko, Mykola A.; Vakulenko, Ihor O.ENG: Purpose. The paper aims at estimation of resource of strength increase for railway wheel disk. Methodology. The material for research was carbon steel of railway wheel containing 0.57%C, 0.65%Si, 0.45%Mn, 0.0029%S, 0,014%P, 0,11%Cr. A railway wheel was heated to the temperatures above Ac3 and was held at this temperature until the completion of аustenite homogenization processes and then the disk was cooled at a growing rate to a certain temperature. A temperature interval of completion of the speed-up wheel disk cooling was 200-450 C. Structure was studied with the use of research methods under electronic and light microscopes. After accelerated cooling the estimation of metal structure imperfection degree was carried out with the use of X-ray structural analysis method. The stress and yielding limit of carbon steel were determined at tension, at a speed of deformation10− − 3 1 s. The microhardness of steel structural components was estimated using the microhardness tester of PMT-3 type. Findings. The properties complex of railway wheel carbon steel depending on the temperature of the accelerated cooling termination is determined by the correlation of soften and work-hardening processes development. The effect of work-hardening is based on blocking of mobile dislocations due to a precipitation carbon atoms and dispersion work-hardening from the formed particles of carbidic phase. At the temperatures of the accelerated cooling termination of carbon steel higher than 300-350 C the decrease rate of strength properties is determined by the exceeding of total soften effect (from disintegration of solid solution, acceleration of spheroidithation and coalescence of cementite particles) above the dislocations blocking by the carbon atoms and dispersion work-hardening. Originality Authors proved that the strength level of the railway wheel carbon steel from the temperature of accelerated cooling completion is determined by the influence ratio of the solid solution satiety degree and dispersion work-hardening from a carbidic phase. For the temperatures of accelerated cooling termination 200-300 C a decrease of solid solution satiety degree is a basic factor, which determines the level of the strength characteristic. Practical value. When making the whole-rolled railway wheel one can increase the strength limit of disk metal using the accelerated cooling to the middle interval of temperatures, which was successfully proven by authors.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 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 Softening of Hardened Medium-Carbon Steel During Heating(Дніпровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпро, 2019) Vakulenko, Ihor O.; Proidak, Svitlana V.; Vakulenko, Leonid I.; Grischenko, Nikolaj A.EN: Purpose. The work is aimed to clarify the softening mechanism during the heating of martensite hardened carbon steel, which is of practical importance, especially in the development of the production technology of rolled products with different levels of hardening. Methodology. The samples after martensite hardening were tempered at the temperatures of 300-500˚С. The microstructure was investigated under the electron microscope. Thin foils were made using the Bolman and tweezer methods in chlorous-acetic solution and Morris reagent. Phase distortions of crystalline lattice were determined by the methods of X-ray structural analysis, using the diffractometer. The cold-worked layer of metal after grinding was removed by electrolytic dissolution. Tensile strength brake of the metal was determined using the tensile diagrams of samples using the Instron type machine. Microhardness was measured using the PMT-3 device with indentation load 0.49 N. Findings. When heating the hardened steel to a temperature of 300˚C, the softening effect is mainly related to the rate of reduction of the accumulated as a result of martensitic transformation, density of the crystalline structure defects. The total result is caused by the development of dislocations recombination and strengthening because of the emergence of additional number of cementite particles during the martensitic crystals decomposition. Starting from the heating temperatures of 400˚C and above, the development of polygonization processes in the ferrite is accompanied by the emergence of additional sub-boundaries, which enhance the effect of metal strengthening. With increase in the heating temperature of the hardened steel, the level of strength properties is determined by the progressive softening from the decrease in carbon atoms saturation degree of the solid solution, dislocations density and increase in the size of cementite particles over the effect of strengthening from hindering of mobile dislocations by carbon atoms and the emergence of additional sub-boundaries. Originality. For the tempering temperature of 300-400˚C, the absence of the phase distortion change indicates the emergence of additional factor in strengthening the metal from the formation of sub-boundaries and the dispersion strengthening from the carbide particles. Practical value. The given explanation of the mechanism of structural transformations in the process of tempering in the average temperature range of the hardened carbon steel can be used to optimize the technology of thermal strengthening of rolled metal.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.