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.

Stability of motion of railway vehicles described with lagrange equations of the first kind

Abstract: Purpose. The article aims to estimate the stability of the railway vehicle motion, whose oscillations are described by Lagrange equations of the first kind under the assumption that there are no nonlinearities with discontinuities of the right-hand sides. Methodology. The study is based on the Lyapunov’s stability method of linear approximation. The equations of motion are compiled in a matrix form. The creep forces are calculated in accordance with the Kalker linear theory. Sequential differentiations of the constraint equations reduced the equation system index from 2 to 0. The coefficient matrix eigenvalues of the system obtained in such a way are found by means of the QR-algorithm. In accordance with Lyapunov's criterion of stability in the linear approximation, the motion is stable if the real part of all eigenvalues is negative. The presence of «superfluous» degrees of freedom, which the mechanical system does not have (in whose motion equations there are left only independent coordinates) is not trivial. Herewith the eigenvalues and eigenvectors correspond to these degrees of freedom and have no relation to the stability. In order to find a rule that allows excluding them, we considered several models of a bogie, with rigid and elastic constraints of high rigidity at the nodes. In the limiting case of high rigidities, the results for a system without rigid constraints must coincide with the results for a system with rigid constraints. Findings. We carried out the analysis and compared the frequencies (with decrements) and the vibration modes of a three-piece bogie with and without constraints. When analysing the stability of the system with constraints, only those eigenvalues are of interest whose eigenvectors do not break the constraints. The values of these numbers are limits for the eigenvalues of the system, in which rigid constraints are replaced by elastic elements of high rigidity, which allows us to leave the Lyapunov’s criterion unchanged. Originality consists in the adaptation of Lyapunov's stability method of linear approximation to the case when the equations of railway vehicle motion are written in the form of differential-algebraic Lagrange equations of the first kind. Practical value. This written form of the equation of motion makes it possible to simplify the stability study by avoiding the selection of a set of independent generalized coordinates with the subsequent elimination of dependent ones and allows for the coefficient matrix calculation in an easily algorithmized way. Information on the vehicle stability is vitally important, since the truck design must necessarily exclude the loss of stability in the operational speed range.

Rational design of short-span industrial building roof for reconstruction conditions

Abstract: Purpose. Recently, the demand for reuse of industrial buildings that have not been in operation for some time has been increasing in Ukraine. Herewith, quite often the design of their roof requires the complete replacement and renovation by using modern roofing materials to meet the requirements of new government standards. Therefore, the choice and justification of the rational design of steel roof on the example of a short-span industrial building (18-24 m span), which is planned to be returned to exploitation after idle time, is the main goal of this publication. The object of the analysis is an unheated building equipped with bridge cranes of a small capacity (up to 10 tons). Me -thodology. To achieve this purpose, the comparison of structural variants of a roof steel collar tie was performed. Such variants include two types of collar tie cross-section –a lattice truss and a solid I-girder. The first type was analyzed for four possible types of section of elements – double angles, a roll-welded square profile, an electric-welded round tube and a rolled round tube. The second type was analyzed for two possible types of section – rolled I-section made of normal strength steel and fabricated sections of thin-gage high-strength steel. The design variants were compared on the basis of a numerical analysis of their work using the finite element method based on the software complex SCAD for Windows. Findings. According to the research results it should be stated that for the conditions of the city of Dnipro the most cost-effective variant of the steel collar tie cross section for the short-span industrial building is the truss made of electric-welded round tubes. Also the construction of collar tie made of roll-welded square profiles or fabricated section of thin-gage high-strength steel is considered quite effective. Originality. The research presented in the publication allows estimating the possibility and economic efficiency of usage for various types of cross-sections for the collar tie of a steel non-insulated roof of the industrial building for the reconstruction conditions in the Dnipro-city. Practical value. A practical estimation of mass and cost parameters for steel collar ties of various types has been carried out, and the methodology for conducting such estimation has been substantiated.

Study of car traffic flow structure on arrival and departure at the marshalling yard x

Abstract: Purpose. The paper is aimed to analyse the existing car traffic organization at the marshalling yard aimed to reduce downtime of cars. Methodology. The methods of mathematical statistics allowed building the histogram of car traffic flow distribution at the marshalling yard and assessment of their parameters. The key quantitative and qualitative indicators of the station operation were analyzed. In order to analyze the effect of rehandling volume on the rehandled transit car downtime elements at the station we plotted the dependence graph of the car downtime elements on the rehandling volume. The curve variation on the graph clearly shows the effect of rehandling volume on two downtime elements: during formation and in expectation of operations. Findings. The question of reducing the average downtime of all car categories at the station should be solved by reducing unproductive downtime was proved. The correct determination of the average time spent by a rehandled transit car at the station is essential, especially in the conditions of new system of economic incentives. But still there is no separate methodology for determining the car downtime, which would allow to objectively consider the equipment and operation technology and exclude the possibility for subjective decisions. Originality. One of the main kinds of unproductive downtime during the carriage of goods by rail is a downtime on the marshalling yards in expectation of technological operations because of the system congestion. Reduction of this indicator is possible due to rational use of the marshalling yard capacity provided the rational distribution and car – and train flows between the major marshalling yards of Ukrzaliznytsia. Practical value. The analysis of changes in downtime elements, depending on the rehandling volume allows not only to identify the car downtime reduction methods, but also to make a correct assessment of station staff work, as well as to adjust the rate of idle wagons.

Strucrural complexity of systems

Abstract: The structure of system complexity is introduced; and the linked complexity of systems is determined according to it.

Reactive power devices in systems of electric traction

Abstract: A comparative characteristic of different concepts and expressions for determination of reactive power in the circuits with non-sinusoidal electric values has been given. For the first Ukrainian electric locomotives of DE1 type with the system of DC electric traction, the values of reactive power after Budeany, Fryze, and also the differential, integral and generalized reactive powers have been determined. Some measures on reducing its consumption by the DC electric rolling stock have been suggested.