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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.
The Influence Mechanism of Ferrite Grain Size on Strength Stress at the Fatigue of Low-Carbon Steel
(Дніпропетровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпропетровськ, 2014) Vakulenko, Ihor O.; Proidak, Svitlana V.
EN: Purpose. Explanation of the influence mechanism of ferrite grain size on the fatigue strength of low-carbon steel. Methodology. Material for research is the low-carbon steel with 0.1% of carbon contnent. The different size of ferrite grain was obtained due to varying the degree of cold plastic deformation and temperature of annealing. The estimation of grain size was conducted using methodologies of quantitative metallography. The microstructure of metal was investigated under a light microscope with increase up to 1 500 times. As a fatigue response the fatigue strength of metal – a maximal value of load amplitude with endless endurance limit of specimen was used. Fatigue tests were carried out using the test machine «Saturn-10», at the symmetric cycle of alternating bend loading. Findings. On the basis of research the dependence for fatigue strength of low-carbon steel, which is based on an additive contribution from hardening of solid solution by the atoms of carbon, boundary of the ferrite grain and amount of mobile dislocations was obtained. It was established that as the grainy structure of low-carbon steel enlarges, the influence of grain size on the fatigue strength level is reduced. For the sizes of grains more than 100 mcm, basic influence on fatigue strength begins to pass to the solid solution hardening, which is determined by the state of solid solution of introduction. Originality. From the analysis of the obtained dependences it ensues that with the increase of ferrite grain size the required amount of mobile dislocations for maintenance of conditions for spreading plastic deformation becomes less dependent from the scheme of metal loading. Practical value. The obtained results present certain practical interest when developing of recommendations, directed on the increase of resource of products work from low-carbon steels in the conditions of cyclic loading. Estimation of separate contribution of the studied processes of structural changes with fatigue load allows one to choose a rational solution – to use the hardening effect from the ferrite alloying or to change the grain size of ferrite.
Influence of Chemical Compounds on the Forming of Welding ARC
(Дніпропетровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпропетровськ, 2014) Vakulenko, Ihor O.; Plitchenko, Serhii; Makarevich, D. M.
EN: Purpose. The purpose of work is a comparative analysis of chemical compounds influence on the process of forming arc welding and condition of its burning. Methodology. A wire with diameter 3 mm of low carbon steel with contain of carbon 0.15% was material for electrode. As chemical compounds, which determine the terms of arc welding forming the following compounds were used: kaolin; CaCO3 with admixtures of gypsum up to 60%; SiO2 and Fe − Si with the iron concentration up to 50%. Researches were conducted using the direct electric current and arc of reverse polarity. As a source of electric current a welding transformer of type PSO-500n was used. On the special stand initial gap between the electrode and metal plate was 1-1.5 mm. The inter electrode space was filled with the probed chemical compound and the electric arc was formed. At the moment of arc forming the values of electric current and arc voltage were determined. After the natural break of electric arc, the final gap value between electrodes was accepted as a maximal value of arc length. Findings. Experimentally the transfer of metal in interelectrode space corresponded to the tiny drop mechanism. According to external signs the relation between maximal arc length and the power of electric current has the form of exponential dependence. Specific power of electric arc at the moment of arc forming per unit of its length characterizes the environment in the interelectrode space. Originality. 1) Based on the analysis of influence of the studied chemical compounds on the formation processes of electric arc the inversely proportional relationship between the power of the electric current and the maximum arc length until the moment of its natural break is defined. 2) Ratio between the maximal arc length and the power of electric current, with the sufficiently high coefficient of correlation is submitted to the exponential dependence. Influence of the compounds under study on the process of electric arc forming is determined using the indexes of degree of the above mentioned correlation. 3) The value of specific power of electric current at the moment of electric arc forming per unit of arc length can be accepted as the parameter, which characterizes the state of interelectrode space environment. Practical value. In the conditions of identical adjusting force of electric current the sequence of location of the studied compounds in the order of increase of their influence on the process of arcing is determined. Minimum influence is observed from kaolin, and maximal one – from Fe − Si .
Influence of Cooling Rate on the Strength of the Rims of Railway Wheel
(Springer Science, Business Media, New York, 2016) Vakulenko, Ihor O.
ENG: It is shown that the intense cooling (with rates of 2-9°C/sec) of wheel rims after their hot rolling in a rolling mill increases the yield limit and the ultimate strength of the metal. It is also established that, in the absence of supersaturation of the solid solution with carbon atoms in the course of this kind of cooling, the mechanical properties of carbon steel are determined solely by the internal stresses caused by the phase hardening of ferrite in pearlite and the state of ferrite-cementite boundaries.
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.
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.
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.
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 Xiao
ENG: 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.
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.
Investigation of Slide Mechanism of Tread During Operation of Railway Wheel
(Silesian University of Technology, Gliwice, Silesia, Poland, 2016) Vakulenko, Ihor O.; Proidak, Svitlana V.; Perkov, Oleg N.
ENG: Causes of reasons and explanation of mechanism forming damages of railway wheels tread were investigated. At slipping on contact surfaces wheel-rail a between by simultaneous development of processes of work-hardening and softening metal determines the terms of origin damages of railway wheels tread were fixed.
The Process of Formation of Railway Wheel Damages and Tires in Operation
(Дніпропетровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпропетровськ, 2015) Gryshchenko, Nikolay A.
ENG: Purpose. The dependence analysis of structural changes in the metal of railway wheels and tires from indicated influences in operation, for the further development of strategy of service reliability growth. Methodology. Test materials are the details selected from railway wheels which were taken out of operation beforehand because of various damages. Micro-structural researches were made with the use of light microscope Epiquant and electron microscope. The sizing of structural elements was done by using the methods of quantitative metallography. Findings. Over the past few decades the rapid development of industry was supported by the steady growth of intensity of using railway transport. In this case simultaneous increase of load at wheel set axle, with the increase of speed was accompanied by natural increase of the amount of cases of premature wheels and tires’ withdrawing out of operation. Railway wheel, except the formation of metal layer at rolling surface with the high defects concentration of crystal structure and first of all dislocations, falls under thermal influence from interaction with break blocks. The nature of joint influence (cold deformation and heating) on the metal rim of a wheel is conditioned by the appearance of sufficiently high gradients of structural changes that can be considered as the influence on the level of internal residual stresses. In case of the rise of volume part of carbide phase at a constant ferrite grain size, it is achieved only by the increasing of dislocation nucleation sources without changing the number of annihilation positions. In this case the accumulation of dislocations at the initial stages of plastic deformation (in metal volume in front of delta arm crack) will lead to the formation of cementite globes around certain interlocked dislocation density. In contrast the sharp increase of deformation hardening carbon steel parameters is observed. Originality. During the braking of locomotive the speed rise of metal heating at rolling surface is provided with the increase of temperatures that is enough for the beginning of phase transformations. Under the further cooling there is the formation of a number of structures formed from sliding to diffusive mechanisms. As a result the chosen areas become the centers of future metal deformations on wheels’ rolling surface and tires. Practical value. Based on the study of patterns of damages’ formation in railway wheels and tires from the peculiarities of internal metal structure and the working conditions «Classifier of defects» was developed аnd «Technical tips for determination of causes of cracks in solid-rolled railway wheels and destruction in general», which have been implemented on Ukrzaliznytsia.
Roles and functions of asphalt sub-ballast in the modern maintenance of the European railways
(Tongji University and Tongji University Press, 2025) La Placa, A.; Autelitano, F.; Neduzha, Larysa O.; Tiutkin, Oleksii L.; Giuliani, F.
ENG: The railway network is increasingly becoming central to the socio-economic development and the decarbonisation of transport, supporting its growth in compliance with the emission reduction targets set by the 2050 European Green Deal. Thus, several programmes for the major network renewals and the construction of safe, resilient and efficient high-speed lines have been implemented. In this scenario, some construction solutions have been introduced to enhance the durability and functionality of the railway infrastructure, particularly for the ballasted track one. Among these design techniques, the asphalt or bituminous sub-ballast has emerged as a proven technology capable of improving the railway performance and durability. Derived from the road construction approach, asphalt sub-ballast has been used in the European high-speed and high-capacity lines since the 1970s, providing both structural and functional benefits. This article offers a critical review of the current knowledge on the asphalt sub-ballast applications, highlighting its technical characteristics and long-term performances. Functional, structural and economic advantages have been assessed and analysed based on laboratory scale and on-field experiences. Experimental data indeed confirm the effectiveness of asphalt sub-ballast in improving the track stability and load distribution, in providing better water drainage and in reducing fatigue induced phenomena. These enhanced properties lead to lower maintenance costs and operations, particularly those related to ballast tamping, as well as to an extended service life of the whole infrastructure. From the circular economy perspective, the re-use or recycle of wastes and by-products in these mixes amplifies the cost-benefit ratio, also improving their sustainability.
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 Xiao
ENG: 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.
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.
Аналіз діаграм циклічного навантаження металевих матеріалів
(Дніпропетровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпропетровськ, 2009) Вакуленко, Ігор Олексійович
UK: Розглянуто питання оцінки характеру зміни співвідношення між амплітудою та кількістю циклів навантаження до руйнування зразків з вуглецевої сталі.
Аналіз причин виникнення дефектів на поверхні кочення залізничних коліс
(Дніпропетровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпропетровськ, 2008) Вакуленко, Ігор Олексійович; Перков, Олег Миколайович; Анофрієв, Василь Григорович; Крот, В. С.
UKR: Виникнення руйнування залізничного колеса обумовлено формуванням високих локальних напружень від неоднорідної пружно-пластичної деформації за рахунок циклічної зміни температур під час гальмування.
Аналіз структурних змін в металі залізничних коліс при їх експлуатації
(Дніпропетровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпропетровськ, 2008) Вакуленко, Ігор Олексійович; Грищенко, Микола Анатолійович
UKR: Виникнення руйнування залізничного колеса обумовлено формуванням високих локальних напружень від неоднорідної пружно-пластичної деформації за рахунок циклічної зміни температур під час гальмування.
Аналітичний опис кривої циклічного навантаження вуглецевої сталі
(Дніпропетровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпропетровськ, 2009) Вакуленко, Ігор Олексійович
UK: У статті викладено результати досліджень з метою математичного опису кривої циклічного навантаження вуглецевої сталі.
Визначення механізму зношування вуглецевої сталі з мартенситною структурою
(Дніпропетровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпропетровськ, 2013) Вакуленко, Ігор Олексійович
UK: Мета. Метою роботи є оцінка ступеню зміни твердості металу залізничного колеса з структурою мартенситу підчас кочення. Методика. В якості характеристики міцності була використана твердість за Роквеллом. Випробування на зношування проводили за умов нормального навантаження, з просковзуванням (10%) і без просковзування, на випробувальному устаткуванні СМЦ-2. Параметри тонкої кристалічної будови (ступінь тетрагональності кристалічної решітки, густина дислокацій, розмір областей когерентного розсіювання, величина викривлень кристалічної решітки другого роду) визначали з використанням методик рентгенівського структурного аналізу. Результати. При експлуатації залізничних коліс різного рівня міцності виникнення ушкоджень на поверхні кочення обумовлене від одночасної дії сил тертя та циклічно змінних навантажень. Вважаючи, що формування осередків руйнування в значній мірі визначається станом об'ємів металу поблизу з поверхнею кочення залізничного колеса, слід очікувати відмінностей в розвитку процесів тертя при високій контактній напрузі для коліс з різним рівнем міцності і структурним станом. Наукова новизна. В процесі випробувань на зношування був отриманий ефект пом’якшення вуглецевої сталі з структурою після гартування на мартенсит. Зниження твердості склало значення від 3,5 до 7 % від рівня стану металу після гартування. Ефект пом’якшення супроводжувався зниженням ступеню тетрагональності кристалічної решітки мартенситу, подрібненням областей когерентного розсіювання, збільшенням густини дислокацій і викривлень кристалічної решітки другого роду. Практична значимість. Отримані результати указують на необхідність продовження досліджень стосовно уточнення механізму отриманого ефекту пом’якшення.
Визначення об’ємної частки зміцненого шару в прокаті з вуглецевої сталі
(Дніпропетровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпропетровськ, 2005) Вакуленко, Ігор Олексійович; Грищенко, Микола Анатолійович; Раздобрєєв, В. Г.
UKR: Розглянуто вплив об’ємної частки зміцненого шару та параметрів магнітної фази на рівень міцностних характеристик термозміцненого прокату.

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