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Browsing Статті КТМ by Author "Lisnyak, Alex G."
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Item Influence of Hot-Reduction Parameters on the Steel Austenite Structure of a Railway Wheel(Politechniki Śląskiej, Poland, 2016) Vakulenko, Ihor O.; Bolotova, Daria M.; Perkov, Oleg N.; Lisnyak, Alex G.ENG: The formation of grain structures with boundaries similar to substructures is one of the factors contributing to grain refinement in hot-reduction carbon steel. At the forming of a rim, the slight cooling-down (100-150°C) of the surface volumes is sufficient to increase their strength characteristics. After that, an increase in the magnitude of the hot-hardening of metal in the central rim volumes will lead to the formation of a more uniform fine-grain austenite structure over the rim section.Item Influence of Shock Voltage from the Electric Discharge on the Fatigue Endurance of Carbon Steel in Water(Дніпропетровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпропетровськ, 2015) Vakulenko, Ihor O.; Lisnyak, Alex G.; Perkov, Oleg N.; Hai, Xu XiaoENG: Purpose. The research supposes the explanation of influence of stress impulses from an electrical discharge in water on the level of the limited endurance at a cyclic loading of the thermally work-hardened carbon steel. Methodology. Material for research was steel 45 (0,45 % carbon) with сoncentration of chemical elements within the limits of steel composition. Specimens for tests are made as plates in 1 thick, width 15 and length 120-180 mm. The structural state of steel corresponded to quenching on a martensite from the normal temperatures of annealing and tempering at 300 C, duration of 1 h. Microstructure was investigated with the use of electronic microscopy, the density of dislocations was estimated on the methods of X-ray analysis. Hardness was measured on the method of Rockwell (scale of «C»). A cyclic loading was carried out in the conditions of symmetric bend on a tester «Saturn-10» at a temperature +20 C. The treatment by shock voltage from the electrical discharge was carried out in water on setting of bath type «Iskra-23», used for cleaning of castings manufactures. Electric impulses were formed at 15-18 kV with energy of 10-12 kJ and amplitude of 1-2 GPа. Findings. As a result of processing pulses of a pressure wave of heat-strengthened steel 45 found the increase of endurance under the cyclic loading corresponds to an increased amount of accumulated dislocations on the fracture surface. The use of Coffin–Manson Equation allowed finding the decrease of deformation per cycle of loading as a result of arising stress from an electrical discharge in water. On the fracture surface (after pulse exposure) was found the increased number of dislocations, located in different crystallographic systems, that is a testament to the rather complicated development of dislocation transformations in the structure of steel, which provide an increase of endurance at a fatigue. The increase of the limited endurance became as a result of impulsive treatment largely related with the number change of mobile dislocations. For the area of low-cyclic fatigue the growth of amplitude of loading is accompanied with the decrease of distinction in the values of the limited endurance (before and after the treatment of shock voltage). Originality. For the field of high-cycle fatigue, the result of shock voltage of carbon steel with the structure of the improvements, the increase of limited endurance is accompanied with a decrease in deformation per cycle. As far as growth of amplitude of stress cycle the effect of increase of endurance from treatment of metal by the shock voltage declines. Practical value. Treatment of metal by the impulses of pressure waves from an electrical discharge in water can be used for the time extending of exploitation details of the rolling stock, which are subjects of the cyclic loading.Item Influence Voltage Pulse Electrical Discharge in the Water at the Endurance Fatigue of Carbon Steel(Magnolithe GmbH, Austria, Sankt Lorenzen, 2016) Vakulenko, Ihor O.; Lisnyak, Alex G.ENG: Effect of pulses of electrical discharge in the water at the magnitude of the limited endurance under cyclic loading thermally hardened carbon steel was investigated. Observed increase stamina during cyclic loading a corresponding increase in the number of accumulated dislocations on the fracture surface. Using the equation of Cofino-Manson has revealed a decrease of strain loading cycle after treatment discharges. For field-cycle fatigue as a result of processing the voltage pulses carbon steel structure improvement, followed by growth of limited endurance decrease per cycle of deformation. With increasing amplitude of the voltage loop gain stamina effect on metal processing voltage pulses is reduced. The results can be used to extend the life of parts that are subject to cyclic loading.Item Strength Properties of Carbon Steel of Railway Wheel After the Speed-Up Cooling(National Mining University, Dnipro, 2016) Vakulenko, Ihor O.; Lisnyak, Alex G.; Perkov, Oleg N.ENG: Purpose. The work is directed at elaboration of softening effect of carbon steel of a railway wheel after the speed-up cooling to the different temperatures. Methodology. Material for the research was carbon steel of a disk railway wheel with content of 0.57 % C, 0.65 % Si, 0.45 % Mn, 0.0029 % S, 0.014 % P, 0.11 % Cr. Specimens as plates 3 mm thick were exposed to heating up to the temperatures higher than Ac3, the subsequent speed-up cooling was halted after achieving certain temperatures (200–450 °C). A structure was studied with the use of electronic and light microscopes. The estimation of degree of the structure defect after the speed-up cooling was carried out with the use of method of x-ray analysis. The strength and yield stresses of carbon steel were determined under tension. Speed of deformation at mechanical tests was 10-3 s-1. The microhardness of structural constituents of steel was estimated using the apparatus a PMT-3 type. Findings. The research results of the structural state and properties of carbon steel of a railway wheel are presented depending on the temperature of self-tempering after the irregular cooling. Within the investigated temperature interval of self-tempering, permanent soften character of carbon steel with growth of the temperature of completion of the forced cooling of wheel is conditioned by the correlation of qualitatively different processes structural transformations. Originality. The net effect of softening the metal by reducing the degree of supersaturation of solid solution, reducing the dislocation density and coalescence of cementite particles exceeds the strengthening due to the presence of fine carbide particles in the structure. Practical value. According to studies it is determined that in order to increase fracture toughness, the discrolled railway wheel can be subjected to accelerated cooling to temperatures of 300–350°C without substantial metal embrittlement.