Dnipropetrovsk National University of Railway Transport named after Academician V. Lazaryan

About: Dnipropetrovsk National University of Railway Transport named after Academician V. Lazaryan is a education organization based out in Dnipro, Ukraine. It is known for research contribution in the topics: Track (rail transport) & Bogie. The organization has 736 authors who have published 655 publications receiving 1468 citations. The organization is also known as: Institute of Railway Transport Engineers.

Power quality complex estimation at alternating current traction substations

Abstract: Purpose. At alternating current traction substations are used three-winding transformers. This scheme comes to significant costs from power quality disturbances at each supplier. The most significant power quality indices at alternating current traction substation are voltage deviation, voltage unbalance and harmonic distortion. The purpose of this article is power quality complex estimation at two traction substations that work on the one district of traction network. Methodology . The measurements were made according to accepted program during 24 hours with 1 sec discretization. A few power quality analyzers PM175 are used to record data with time synchronization. The scheme of measurements means that devices are connected through current and potential transformers at the each level of voltage. Findings . Voltage level at different substation is various due to power losses in primary network. The voltage in one phase of 1-st substation is bigger than in other phases. Voltage THD values according to standard requirements are below norm only for primary 154 kV networks. For another traction and regional networks voltage THD values are above norm value. The voltage unbalances in 154 kV networks are below voltage unbalance in 35 kV networks. Besides the voltage unbalance in 154 kV network is below 2 % that complies with the requirements of standard. At the same time we can consider that voltage and current spectrums consist from discrete harmonics with frequencies that multiples of the fundamental frequency. Originality . Voltages at the connection points of traction substations to supply lines are complex stationary random process that determines the voltage mode of the external power supply system of each traction substation. The flows of active and reactive power of the higher harmonics at AC traction substation are directed opposite power of the fundamental harmonic. The power flows on higher harmonics create the disturbing impact on related devices. The total power at AC traction substation consists of 61,8 % of the active power, 32,5 % of the reactive power of the 1st harmonic and 5,7 % of the distortion power in the quadrature components. Practical value . Analysis of the quadrature components suggests that traditional approaches to reactive power compensation at the fundamental frequency will be sufficiently effective. But the influence of the distortion power on reducing energy losses must be also researched. Besides reactive power compensation should be considered with the issue of reducing the basic power quality indices to standardized values.

Stress-strain state of beam staged connection point of the railway bridge track-way

Abstract: Purpose. The staged connections of the beams of railway bridge track-way have the simplest design, but some design flaws result in numerous defects. The purpose of the given work is to research the actual stress-train state of the point of connection of the stringers with the floor beams on condition of their staged interposition. It is also necessary to determine possible effect of coupled work of deck beam grid and booms on their stress-strain state. Methodology. To reach the purpose of the study the testing of the existing bridge was conducted. To measure strains (stresses) in the span elements we used the strain gages glued to flange angles of stringers and floor beams and to fillets of lower flange angles of stringers in the points of their support on floor beams. To measure deflections of the truss, stringers and floor beams from static loads we used Aistov’s and Maksimov’s deflectometers, that were installed on lower boom in the middle of span 0-1, as well as on both stringers and floor beams in the middle of the span. Deflectometers were fastened to the span and, by wire communication, to the ground surface. Findings. Stress-strain state of the point of connection of the stringers with the floor beams on condition of their staged interposition was obtained and analyzed. Analysis indicates that, apart from vertical bending of the stringers and beams, there is a significant effect of horizontal bending of floor beams and their torsion, that occur due to the coupled work of track-way beams and top booms, both for P0 beam and for other beams. Originality. Research of stress-strain state of metal track-way staged beams while considering their coupled work with bearing trusses. Practical value. While testing the span under the train load, there are significant additional stresses from horizontal bending of floor beams and their torsion in the floor beam flanges. The appearance of these stresses is caused by inclusion of stringers into coupled work with top booms. Appearing flaws in stringers are caused by local stress concentration due to design features of staged track way.

Implementation of the dynamic, competitive and fuzzy models for planning of the multi-product flows in transport networks

Abstract: Purpose . The purpose of the article is to develop a new unified procedure for planning of the fuzzy multi-product, dynamic and competitive flows in the transport networks and in the information network systems. The procedure is based on the use of the parallel synchronous algorithms for inhomogeneous maximum flows calculating. Methodology . The paper proposes the mathematical models’ classification of the tasks for planning the flows in transport networks. The possibilities of using the unified procedure and the parallel synchronous algorithm for calculating the maximum inhomogeneous flows for implementation of the tasks for planning multi-product, fuzzy, dynamic and competitive flows are investigated. The efficiency and universality of the proposed methods for the planning inhomogeneous flows is established by comparing the results of the calculations obtained in the article with the known results. Findings . The article proposes classification of the mathematical models for the planning inhomogeneous flows in the transport networks. The unified procedure and the parallel synchronous algorithm for planning fuzzy multi-product, dynamic and competitive flows in the transport networks have been developed. The tasks of the optimal distribution of the fuzzy multi-product, dynamic and competitive flows in the transport networks are realized. Originality. The article describes the new unified procedure for planning fuzzy multi-product, dynamic and competitive flows in the transport and information systems, using the parallel synchronous algorithms for calculating maximum flows. The procedure allows us to calculate the local extrema of the optimal flows distribution models. Practical value. The practical value of the obtained results is determined by the unified capabilities and the procedure efficiency, as well as the parallel synchronous algorithm designed to calculate the maximum multi-product flows in transport networks. The developed procedure provides the possibility to solve the analysis and planning problems of the multi-product flows in the networks for dynamic, fuzzy and competitive models for the distribution of the transport and information flows.

Experimental studies of static behavior of granular media in the capacitive structure

Abstract: In the paper the main results of experimental investigations made by the author on distribution of static pressure from granular material in a covered capacity structure are presented. The investigations were conducted on the small-sized steel constructions and provided for the variation both a row of constructive parameters of the experimental installation and the types of granular material.

Formation of Carbon Steel Structure During Hot Plastic Deformation

Abstract: Purpose. The main purpose of the work is to determine the peculiarities of the development of recrystallization processes of carbon steel austenite depending on the degree of hot plastic deformation and to develop proposals for improving the structural state of the metal of the railway solid-rolled wheel. Methodology. Two carbon steels of a railway wheel with a minimum and maximum carbon content of 0.55 and 0.65 % and other chemical elements within the grade composition of the steel 60 were used as research material. Samples in the form of cylinders with a diameter of 20 mm and a height of 40 mm were heated in a muffle furnace, exposed for a certain time to equalize the temperature across the cross section of the sample. After that, the samples were subjected to hot compression on Instron type test machine. The temperature interval of hot compression of the samples was 950–1100 oС, with deformation degrees in height in the range of 10–40%. The strain rate was 10-3–10-2sec-1. A standard etching was used to detect the boundaries of the austenite grains. Structural studies were performed using Epikvant type light microscope at magnifications sufficient to determine the structure of austenite grains. The grain size of austenite was determined by the methods of quantitative metallography. Findings. In the case of hot compression of the railway wheel blank, increasing the concentration of carbon atoms only within the grade composition of the steel is sufficient to increase the average austenite grain size, which confirms the proposals to limit the carbon content in the metal of railway wheels. The formation of a certain degree of austenite structural heterogeneity at the cross section of the rim or hub of the railway wheel is due to a change in the development mechanism of recrystallization processes depending on the deformation value. Under conditions of the same degree of hot plastic deformation, the replacement of one-time compression by fractional one is accompanied by a violation of the conditions of formation of the recrystallization nucleus. As a result of the specified replacement of the scheme of hot plastic deformation we obtain reduction in the austenite grain size. Originality. Based on a study of the development of collective recrystallization processes during the hot compression of carbon steel of the railway wheel, it was determined that the increase in carbon content contributes to the austenite grain increase. After hot compression of the wheel blank, the structural inhomogeneity of austenite that occurs is determined by a change in the mechanism of recrystallization processes development. During deformations above the critical degree, the recrystallization nuclei are formed and successively grow, which leads to the structure refinement. In the case of deformations below the critical value, the growth of austenite grains occurs according to the coalescence mechanism, according to which fragments of boundaries with large disorientation angles consistently disappear. Practical value. For austenite grain refining in massive elements of solid-rolled railway wheel we offer to replace one-time hot compression by fractional one.