The paper is devoted to a theoretical study of the car movement stability when exposed to longitudinal forces of a quasistatic nature. The authors obtained the expressions for calculating the resistance coefficient of the car lift by the longitudinal compressive force acting on the car as part of a freight train. The influence of some factor’s combination on the longitudinal forces, at which the car movement stability is still maintained, was analyzed using the analytical dependencies to assess the longitudinal loading of cars in trains. The study was carried out by analytical method for assessing the freight car stability when moving at different speeds along curved track sections. The calculations were made in a curve of small radius taking into account the inertia forces from the unbalanced acceleration. In a theoretical study, the influence of quasistatic longitudinal compressive forces depending on changes in speed and force value, as well as the influence of friction in the wheel flange and rail contact and the eccentricity of fastening the automatic coupler shank on the stability were considered. When applying the results obtained, the stability of freight rolling stock can be increased, which in turn will remove some existing restrictions on the permissible speeds and increase the technical speed of train movement. Using the described methodology for determining the lift resistance coefficient will make it possible to justify the cause of derailment, as well as to develop and put into practice technical measures to prevent the lift of carriages, thrusts and shears of the track.
The authors of the article analyzed existing software systems that are used to study the dynamic behavior of rolling stock, and also emphasized the importance of using a computer experiment to implement this task. An improved spatial mathematical model of the dynamic behavior of a freight wagon when it interacts with a rail track is considered, and it is proposed to study it using an object-oriented approach using the Maple software package. To accomplish this task by writing procedures, separate modules (subprograms) were created that included differential equations of motion for the individual components of the object under study. Based on existing procedures, the main module was created, which reflected the sequence of performing certain functions (calling up the necessary information, especially the use of logic, methods for solving the problem, as well as visualizing the results). Using the created modules in the Maple software package, a computer experiment was used to study the dynamic behavior of a freight car when it interacted with a rail, and also showed the possibility of taking into account the influence of individual parameters of its technical condition on its dynamic behavior.
It was developed a computational model to evaluate the body strength of short base hopper models 19-758-01, 20-471, and 20-4015 when unloading them on the car dumper VRS–134M. Modeling of the stress-strain state of the car design was made using the finite element method. It was established that in terms of strength, bodies of the hopper models 19-758-01, 20-471, and 20-4015 are suitable for unloading on car dumper. The results of experimental studies showed sufficiently high accuracy of the chosen computational model for estimating the stress-strain state of design and confirmed the possibility of hopper car unloading on the car dumper VRS–134M.
The analysis of cases of rolling stock derailment from the track at PJSC «Ukrzaliznytsia» over the past 5 years has been carried out and their main types are given. It is noted that the rapid development and improvement of computer technology allows the use of computer and mathematical modelling in the study of cases of rolling stock derailment from the rail track, which makes it possible to take into account a combination of factors that have the main influence on the behavior of rolling stock when moving along the track. It has been established that the first step is the construction of a mathematical model of an object using a selected type of mathematical description: algebraic, differential, integral equations, discrete mathematics, set theory, and others. And the second step is the choice of a method for solving these models. The simulation methods are given, which, depending on the programming style, are divided into: procedural-oriented, object-oriented, logical-oriented, rule-oriented, and oriented to constraints. An object-oriented programming of a freight car has been developed, which will make it possible to evaluate its main dynamic indicators, in particular, indicators of stability from derailment. This in turn will facilitate the establishment of the main causes of rolling stock derailment from the rail track.
JSC “Ukrzaliznytsia” purchased the first of three planned regional three-car (two main motor cars and one intermediate) diesel train DPKr-3 manufactured by PJSC “Kryukovsky railway car building works”. To confirm the declared characteristics and safety indicators of the DPKr-3 diesel train, specialists department of Cars of Dnipro National University of Railway Transport named after Academician V. Lazaryan conducted complex certification tests, which confirmed the compliance of the stated parameters. One of the points of the Terms of Reference was to determine the brake pressure of the linings per 100 weight of the train in terms of cast iron brake pads. For this purpose, according to the methodology adopted in the territory of the former CIS, force sensors, which were installed in the tick mechanisms instead of the brake linings, measured the magnitudes of the forces of pressing the brake linings on the disks. However, during the tests it was found out that the current standards for calculating the provision of train brakes cannot be applied to modern rolling stock. It is recommended for rolling stock where the use of brake pads, and even more cast iron, is not provided by the design, to develop normative documents that would determine the standards for brakes by the results of calculations and tests.
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