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.

Constructive Modeling of the Software Development Process for Modern Code Review

Abstract: The preeminent point of this work is to construct a model of the software development process for automatic analysis. Utilizing constructive-synthesizing modeling (CSM) tools, a code-writing history constructor was proposed. This research provides an innovative method for code and development process review in the preparation of teaching programs. This work aims to encourage the use of code review and monitoring the coding practice in educational institutions. The standard approach to evaluation, which takes into consideration only the result, no longer complies with the modern specifications for teaching programming. Practically, it is supposed to be utilized in programming training, particularly in initial stages.

Selection of rational parameters of the nominal mode electric trains with asynchronous traction drive

Abstract: Purpose. Parameters of the nominal mode are related to the most important performance indicators of traction means, therefore, the problems of choosing their optimal values always inevitably arise when forming technical requirements for a new rolling stock. The paper describes the features of solving the above-mentioned problems for electric trains with an asynchronous traction drive in the case of two-zone and three-zone frequency control of power. Methodology. Power of nominal mode of the rolling stock should be chosen in such a way that it would be possible to realize a predetermined travel time along in the section or the movement speed. On that basis, and also taking into account the fact that the important operational characteristics of electric trains include the acceleration value during the start-up and acceleration at the design speed , we will formulate the problem of determining the nominal power. In the task for a given range of traction, it is necessary to find such a value of the nominal mode power and the corresponding force value to ensure the ability to carry out transportations with the given level of average speed with minimal energy consumption for traction. At the same time, it is necessary to fulfill the following conditions: a) the speed of the electric train on the section does not exceed the established limits; b) it is possible to realize the given values of accelerations. A more detailed consideration of the problem shows that in real conditions, when the starting acceleration and the mass of the train are given, the problem of determining electric train power is practically reduced to determining the optimal value of the nominal mode speed. Findings. The task of choosing the optimal values of the nominal mode speed is solved by determining the electric power consumption with the variation of the possible values of starting speed. Therefore, only those values that ensure the implementation of the given starting and residual accelerations should be taken into account. The work shows that the traction force value increases with the design speed increase and other equal conditions, if the starting speed is increased. Originality . Authors developed the methodology for determining the optimal values of the nominal mode parameters of electric trains with an asynchronous traction drive, with two-zone and three-zone frequency power regulation. Practical value . The above mentioned methodology can be the basis when forming technical requirements for new rolling stock for Ukraine’s railways.

Determination of the optimal parametersof the structure of functional gradientmaterials using mathematical modellingapproaches

Abstract: Purpose: Functioning of mechanical friction systems largely depends on the characteristics of the structure of their surface layers. By controlling these parameters, it is possible to significantly adjust the reliability and durability of parts under the conditions of contact interaction. Design/methodology/approach: he proposed approach, which is based on the principle of nonlocality of the operational properties of materials, allows determining the optimal microhardness values of the surface layers and the gradient of this parameter, at which the contact durability of friction pair elements significantly increases. Findings: It is established that by adjusting the ratios of the surface strength of materials and its gradient, it is possible to achieve a significant increase in the operational parameters of friction units. Practical implications: The engineering relationship considered in the work allows to establish functional distributions of microhardness in the structure of surface layers, at which their wear reaches minimum values. Originality/value: Mathematical approaches are proposed, which allow determining the parameters of the structure of the surface layers of parts to increase their durability under conditions of friction contact loads.

Problem of the definition the «reliability» term. methodology of construction and study the reliability of freight cars

Abstract: Purpose . Scientific paper is aimed at disclosing the existing problem of the «reliability» definition and provides a reasoned definition of the term. The study assumes the development of a complex that includes the methodology and appropriate terminology that will be true. Methodology . Currently there is reliability theory in the special case of the probabilistic and statistical theory, which is used to determine or predict the occurrence of object failures. Within the existing theories the term «reliability» is formulated, the parameters related to it are described. Findings . On the basis of the conducted analysis of the research within the existing theory of reliability and personal considerations of the authors, they formulated a definition of the term «reliability». The methodology and study of the object reliability on the example of a freight car was proposed. Originality . The authors proposed a new definition of the «reliability» term. Namely: reliability is an assessment of the ability of an object to maintain the original property within the established limits and temporary space, in the conditions of storage and transportation, as well as to perform the required functions in predetermined modes of operation with maintenance and repair facility. The reliability parameters include: reliability, durability, maintainability and safety that characterize the object. Also a methodology for developing and study the reliability of a freight car was developed, which comprises: 1) design, technological and operational reliability; 2) scientific experiment, including the modeling of the freight car in different conditions and operating modes; 3) the reliability theory is presented as combined or modified, covering the mathematical and physical foundations; 4) Bayesian statistics that describe the different states of a freight car with a breakdown of its basic components and with the appropriate probability for each component to describe the overall reliability. Practical value . The results of the study allow to provide a full and accurate picture with a corresponding failure of a freight car and to improve approaches to the construction and study of the reliability of the car overall.

About the evaluation of the longitudinal forces level effecting the track displacement at transient modes of train movement

Abstract: Purpose . Study the transient modes effect of movement on the track displacement for the freight train safety control is supposed in this paper. For this it is necessary to investigate the longitudinal dynamics of a train on the track displacement. Simultaneously to assess the longitudinal forces level of a track and rolling stock interaction. Methodology . The level of the longitudinal forces, effecting the track displacement, was evaluated using mathematical modeling of longitudinal vibrations of the trains at transient modes of motion caused by braking. It was considered that each train vehicle consists of a body (solid) and the wheel sets, connected with the body by friction bearings (inelastic link). It was believed that during the movement of each train vehicle the vertical plane of its symmetry coincident with the vertical plane of symmetry of the assembled rails and sleepers. At simulation it was also supposed that in the process of translational motion of the vehicle body wheels make pure rolling along the rail without slipping on it. Findings . In the results of calculations the values of the longitudinal forces at different types of braking were obtained (it is regenerative braking and pneumatic one) under quasi-static and shock transients. For this various initial state of clearances in the inter-car connections up to beginning of transient was considered. The level of dynamic additives to longitudinal forces of interaction between wheel and rail that are substantially depending on vehicle accelerations was assessed. Originality . The transient regimes effect of trains movement caused by braking on the level of the longitudinal forces of track and rolling stock interaction was investigated. The longitudinal load of freight trains with regenerative and pneumatic braking was researched. The effect of the initial state of the train and different modes of braking on a dynamic additive to the longitudinal forces of the interaction between the track and rolling stock, which may effect the displacement of assembled rails and sleepers, was estimated. Practical value . The obtained results can be used to select rational modes of braking of freight trains, especially on lengthy down grade, from the positions prevent possible track displacement.