Browsing by Author "Reidemeister, Oleksii H."

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    Determination of Characteristics of Throttling Device for Pneumatic Spring
    (Дніпропетровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпро, 2018) Reidemeister, Oleksii H.; Laguza, Anastasiia V.
    EN: Purpose. This paper focuses on determination of the dependence of the working medium flow on the capacity of the throttling device, its geometric features and the pressure difference in the pneumatic spring cylinder and in the auxiliary reservoir. Methodology. Calculation of the dependence of the working medium and pressure drop is performed in two ways: 1) by numerical simulation of a stationary gas flow through a throttling element; 2) its analytical calculation expression using empirical relationships (control calculation to evaluate the reliability of numerical simulation results). For the calculation, three models of throttling devices were chosen. Dependence of the flow rate of the working medium on the capacity of the throttling device and its geometric features was determined based on the approximation of the dependency graphs of the pressure drop against the mass flow rate of the working medium. Findings. We obtained graphical dependencies between the pressure drop and the mass flow rate of the working medium from the two calculation options. Based on the results of calculations performed with the help of a software package with visualization of the results, we calculated a proportionality coefficient that describes the dependence of the working medium flow on the throttling device capacity and its geometric features for each of the throttling elements considered, with three degrees of closure. The air flow values, obtained by numerical simulation, are greater than the flow rates obtained from semi-empirical formulas. At the same time, they are in good qualitative agreement, and the quantitative difference averages 25%, which can be regarded as confirmation of the reliability of the numerical model. Based on the calculation results, we plotted the proportionality coefficient graphs against the degree of closure of the throttling device. Originality. The work allows determining the degree of influence of the frictional component on the variation of the pressure difference in the pneumatic cylinder and the auxiliary reservoir of the pneumatic suspension system. Also, the work proposes a method to determine the dependence of the working medium on the capacity of the throttling device and its geometric features. Practical value. The ability to predict the operating parameters of the pneumatic system depending on the pneumatic resistance of the throttling device will improve the car running characteristics, increase the comfort of passenger transport, and also reduce the wear of the rolling stock and track gauge due to vehicle-track interaction.
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    Method of Constructing the Dynamic Model of Movement of the Multi-Mass System
    (Дніпропетровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпро, 2017) Reidemeister, Oleksii H.; Kalashnyk, Volodymyr O.; Shykunov, Oleksandr A.
    EN: Purpose. The scientific work is intended to develop a methodology for describing the structure of the railway vehicles (they are considered as a system of rigid bodies connected by rigid, elastic and dissipative elements), which would allow us to obtain the equations of motion in an easily algorithmized way. Methodology. When constructing the model, authors tend to ensure that its structure reflects the structure of the mechanical system, that is, parts of the model must correspond to parts of the car. In this case, the model takes the form of a hierarchically organized graph whose vertices correspond to the bodies, attachment points of the connecting elements and to the connecting elements themselves, and the edges describe the sets of processes that are related to the incident vertexes. As a rule, these are movements and forces: for the edge between the body and the attachment point they are generalized movements of the body and the general forces acting on it; for the edge between the attachment point and the connecting element - the movements of the point and the forces arising in the element. To each vertex there corresponds a group of equations describing the motion of the system. The nature of the equations depends on the type of the vertex. For the body it is the equations of body motion; for the point - the expressions for the point displacements through generalized displacements of the body and generalized forces acting on the body, through the forces arising in the connecting element; for the connecting element - the expression for the forces arising in it through the deformation of the element. The graph can be regarded as oriented. The direction of the edge is chosen in such a way that for each vertex the values on the right-hand side of the vertex-associated equation would correspond to the incoming edge, and in the left-hand side - to the outgoing edge. Findings. A technique for constructing a dynamic model of oscillations of railway vehicles as a system of rigid bodies is developed on the basis of their description using hierarchically organized graphs. The technique was tested to construct a model of spatial oscillations of a 4-axle freight car with an axial load of 25 tons in Simulink package. Originality. For the first time, a technique has been developed for describing the structure of a railway vehicle using a hierarchical graph, which makes it possible to obtain equations of motion in an easily algorithmized manner. Practical value. The proposed methodological approach will allow, after creating a library of bodies and connecting elements, to significantly reduce the time spent on modeling the oscillations of different vehicles.