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Browsing Статті КТМ by Author "Nadezhdin, Yurii L."
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Item Electric Pulse Treatment of Welded Joint of Aluminum Alloy(Дніпроопетровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпроопетровськ, 2013) Vakulenko, Ihor O.; Nadezhdin, Yurii L.; Sokirko, V. A.; Volchok, I. P.; Mitiaev A. A.EN: Purpose. Explanation of the redistribution effect of residual strengthes after electric pulse treatment of arc welding seam of the aluminum alloy. Methodology. Alloy on the basis of aluminium of АК8М3 type served as the research material. As a result of mechanical treatment of the ingots after alloy crystallization the plates with 10 mm thickness were obtained. After edge preparation the elements, which are being connected were butt welded using the technology of semiautomatic argon arc welding by the electrode with a diameter of 3 mm of AK-5 alloy. Metal structure of the welded joint was examined under the light microscope at a magnification of 200 and under the scanning electronic microscope «JSM-6360 LA». The Rockwell hardness (HRF) was used as a strength characteristic of alloy. Hardness measuring of the phase constituents (microhardness) was carried out using the device PМТ-3, with the indenter loadings 5 and 10 g. The crystalline structure parameters of alloy (dislocation density, second kind of the crystalline lattice distortion and the scale of coherent scattering regions) were determined using the methods of X-ray structural analysis. Electric pulse treatment (ET) was carried out on the special equipment in the conditions of the DS enterprise using two modes A and В. Findings. On the basis of researches the previously obtained microhardness redistribution effect in the area of welded connection after ET was confirmed. As a result of use of the indicated treatment it was determined not only the reduction of microhardness gradient but also the simultaneous hardening effect in the certain thermal affected areas near the welding seam. During study of chemical composition of phase constituents it was discovered, that the structural changes of alloy as a result of ET first of all are caused by the redistribution of chemical elements, which form the connections themselves. By the nature of the influence the indicated treatment can be comparable with the thermal softening technologies of metallic materials. Originality. The observed structural changes of alloy and related to them microhardness change in the areas near the welding seam after ET are conditioned by both the change of morphology of structural constituents and the redistribution of chemical elements. In case of invariability of chemical elements correlation in the phase constituents of alloy the reduction effect of gradient microhardness should be far less. Practical value. In practice, the negative effect of the wares embrittlement made using the casting technologies, excluding the pressure casting and quite difficult selection of chemical composition of alloy can be significantly reduced during the treatment of alloy with electric pulses.Item Influence of Grain Size Ferrite on Speed of Distribution Sonic Vibrations in Alloy Steel(China, 2016) Vakulenko, Ihor O.; Nadezhdin, Yurii L.; Sokyrko, V. A.; Yaremchuk, A.ENG: On the example of steel XI8TI after cold rolling and annealing influence of grain size ferrite and texture is investigational on speed of distribution sonic vibrations. Character influence of grain size and texture is set on correlation of hardness and speed of distribution sonic vibrations.Item Speed Dependence of Acoustic Vibration Propagation from the Ferritic Grain Size in Low-Carbon Steel(Дніпропетровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпропетровськ, 2015) Vakulenko, Ihor O.; Nadezhdin, Yurii L.; Sokirko, V. A.; Hai, Xu XiaoENG: Purpose. It is determining the nature of the ferrite grain size influence of low-carbon alloy steel on the speed propagation of acoustic vibrations. Methodology. The material for the research served a steel sheet of thickness 1.4 mm. Steel type H18T1 had a content of chemical elements within grade composition: 0, 12 % C, 17, 5 % Cr, 1 % Mn, 1, 1 % Ni, 0, 85 % Si, 0, 9 % Ti. The specified steel belongs to the semiferritic class of the accepted classification. The structural state of the metal for the study was obtained by cold plastic deformation by rolling at a reduction in the size range of 20-30 % and subsequent recrystallization annealing at 740 – 750 ° C. Different degrees of cold plastic deformation was obtained by pre-selection of the initial strip thickness so that after a desired amount of rolling reduction receives the same final thickness. The microstructure was observed under a light microscope, the ferrite grain size was determined using a quantitative metallographic technique. The using of X-ray structural analysis techniques allowed determining the level of second-order distortion of the crystal latitude of the ferrite. The speed propagation of acoustic vibrations was measured using a special device such as an ISP-12 with a working frequency of pulses 1.024 kHz. As the characteristic of strength used the hardness was evaluated by the Brinell’s method. Findings. With increasing of ferrite grain size the hardness of the steel is reduced. In the case of constant structural state of metal, reducing the size of the ferrite grains is accompanied by a natural increasing of the phase distortion. The dependence of the speed propagation of acoustic vibrations up and down the rolling direction of the ferrite grain size remained unchanged and reports directly proportional correlation. Originality. On the basis of studies to determine the direct impact of the proportional nature of the ferrite grain size on the rate of propagation of sound vibrations in the low-carbon alloy steel. The directly proportional nature of influence of ferrite grain size on the speed propagation of acoustic vibrations in low-carbon alloy steel on the basis of the conducted researches is defined. The paper is shown that at increasing in the size of the recrystallized ferrite grain the degree of influence the texture from the previous cold plastic deformation by rolling increases. Practical value. The received results on nature determination of influence of ferrite grain size on the speed propagation of acoustic vibrations can be the useful by development of techniques of non-destructive testing of metal materials quality. The special value the specified technique of measurement acquires in the conditions of line production of metal constructions.