Science and Transport Progress

7-15

Authors: K. I. Yashchuk

Purpose. To conduct the study of the potentials and currents propagation along the rails to evaluate the potential difference and the current asymmetry in the rails that may have an impact on the work of railway automatics and supervisory systems. Methodology. To compass the purpose, the author applies methods of analysis and synthesis of track circuit electrical engineering calculations, mathematical modeling and methods of homogeneous and heterogeneous ladder circuits. Findings. TheconductedtheoreticalstudiesindicatethatinthemountainoussectionsofDCtractionrailwaysthereareveryhigh-levelcurrents,wherebyevenatnominalasymmetryratio theasymmetrycurrentwill beunacceptablyhigh.The re-equipment of running line with the automatic blocking system with tonal rail circuits resulted in reduction of the number of impedance bonds, the equalizing functions of which required further advanced research, that allowed obtaining the potential railwise propagation curves when installing the impedance bonds every 6 and 5 km. The resulting potential difference was too high for railway automation systems, so the potential propagation study was conducted with impedance bonds placed every 3 and 3.5 km, which greatly improved the operation conditions of track circuits. Originality.The proposed method for calculating the propagation of potentials and currents in the rail network of DC traction line is characterized by the representation of the common ladder circuit of each rail as a series of T-shaped four-poles connected in cascade, taking into account the grounding of the contact-line supports on the nearer rail. It has allowed estimating the levels of asymmetry currents that branch into the equipment of track circuits and have a negative impact on their operation. Practicalvalue. The obtained results can be used in designing and re-equipping the running lines with new railway automatics and supervisory systems, as well as for evaluating the influence of high asymmetry currents on the railway automation systems operation.

23-28

Authors: M. M. Biliaiev, O. S. Slavinska, R. V. Kyrychenko

Purpose. The scientific paper solves the question of 2D numerical model development, which allows quick computation of air pollution in streets from vehicles. The aim of the work is numerical model development that would enable to predict the level of air pollution by using protective barriers along the road. Methodology. The developed model is based on the equation of inviscid flow and equation of pollutant transfer. Potential equation is used to compute velocity field of air flow near road in the case of protection barriers application. To solve equation for potential flow implicit difference scheme of «conditional approximation« is used. The implicit change – triangle difference scheme is used to solve equation of convective – diffusive dispersion. Numerical integration is carried out using the rectangular difference grid. Method of porosity technique («markers method») is used to create the form of comprehensive computational region. Emission of toxic gases from vehicle is modeled using Delta function for point source.Findings. Authors developed 2D numerical model. It takes into account the main physical factors affecting the process of dispersion of pollutants in the atmosphere when emissions of vehicle including protection barriers near the road. On the basis of the developed numerical models a computational experiment was performed to estimate the level of air pollution in the street. Originality. A numerical model has been created. It makes it possible to calculate 2D aerodynamics of the wind flow in the presence of noises and the process of mass transfer of toxic gas emissions from the motorway. The model allows taking into account the presence of the car on the road, the form of a protective barrier, the presence of a curb. Calculations have been performed to determine the contamination zone formed at the protective barrier that is located at the motorway. Practical value. An effective numerical model that can be applied in the development of environmental protection measures for the operation of road transport in the city is considered. The developed model allows estimating sizes, the form and intensity of a zone of pollution at a motorway.

41-49

Authors: O. P. Datsyshyn, H. P. Marchenko, A. Y. Glazov

Purpose. The formation of crack-like defects in rails of railway tracks is a serious problem for engineering practice because of the danger of creating emergency situations. The purpose of this work is to establish theoretically the characteristic angle of propagation of surface cracks in the rail heads of railway rails, which is basic in the formation of typical surface contact fatigue damages, such as pitting, «checks» and «squat». It is also necessary to find the conditions for determining this angle. Methodology. The investigations were carried out on the basis of the method of singular integral equations. The rail damaged by the surface crack was modeled with a half-plane with an edge cut, and the action of the wheel on the rail by unidirectional repeated translational movement along the edge of the half-plane of the Hertzian contact forces with the tangential component. The problem of determining the stress intensity factors in the vicinity of the crack tip in the rail head was reduced to a system of two real singular integral equations which were solved numerically by the Gauss-Chebyshev mechanical quadrature method. The complexity of the problem consists in the fact that the boundaries of the contact areas and the opening of the crack faces are unknown beforehand and they change when the model contact forces move. These boundaries were determined simultaneously with solving the integral equations of the problem from additional conditions by the iteration method. Findings. The presence of the characteristic angle of propagation of mode II surface cracks in the rail head has been established theoretically and the conditions for its determination have been put down. The results obtained are in good agreement with engineering and experimental data. Originality. For the first time, the values of the characteristic angle were theoretically determined, under which at the initial stage, the surface contact fatigue cracks propagate in the head of the railway rail under the action of the wheels. Conditions for determining this angle have been also put down. Practical value. The received data are of great importance for engineering practice, since they reveal the nature of surface contact fatigue defects under various operating conditions and allow to predict their contact strength and durability.

60-70

Authors: V. V. Netrebko, I. P. Volchok

Purpose. The article is aimed to determine effect of the chemical composition of Fe-C-Cr-Mn-Ni cast iron on the chromium content in the metallic base, carbides and the coefficient of interphase distribution of chromium after annealing at 690 ° С (КРСr690). Methodology. Cast irons containing 1.09–3.91% C; 11.43–25.57% Cr; 0.6–5.4% Mn; 0.19–3.01% Ni and 0.8–1.2% Si were investigated. The analysis of chromium distribution was carried out using mathematical statistics methods. Cast iron was melted in induction furnace with a capacity of 60 kg. Findings. The use of methods of active planning of the experiment 24-1 allowed us to establish regression dependencies of the chromium concentration in the base and carbides, as well as its interphase distribution coefficient on the С, Mn, Cr and Ni content in the cast iron. Chromium, after annealing, was mainly concentrated in carbides. The chromium content of the base varies from 3.94% at 3.23% C, 5.4% Mn, 11.43% Cr and 3.01% Ni to 17.43% at 1.09% C, 0.60% Mn, 25.57% Cr and 1.32% Ni. The minimum value of the distribution coefficient of CRC690 was 2.1 in cast iron, of composition 1.09% C, 0.6% Mn, 11.43% Cr and 0.19% Ni, maximum 9.4 at 3.91% C, 0, 6% Mn, 11.43% Cr and 3.01% Ni. The distribution of chromium was determined by the amount and type of carbides formed. During annealing, the carbides’ composition was formed as a result of carbide-forming elements contention and replacement of iron and manganese atoms by chromium atoms. Originality. Authors obtained regression dependences of the chromium content in the base, carbides and its interfacial distribution coefficient on the chemical composition of Fe-C-Cr-Mn-Ni cast iron after annealing at 690 ° C. Practical value. The obtained dependencies allow predicting the chromium content in the metallic base and may be used during the elaboration of the new wear resistant cast irons compositions, as well as in the choice of heat treatment regimes.

80-88

Authors: Y. M. Korol, O. M. Kornelyuk

Purpose.The study involves: 1) formation of 3D propeller models under study; 2) studying of the effect of profiling the blade of the propeller on its hydrodynamic characteristics; 3) development of a methodology for specifying optimal project parameters for modeling the operation of a propeller in free water, which in the future could be recommended when simulating similar tasks in the CFD package Flow Vision. Methodology. The technology of design of propellers of new series was developed. For the first time, the project methodology was proposed in the CFD package Flow Vision for studying the operation of a propeller in free water. Findings. On the example of solving a practical problem for studying the influence of blade profiling on the efficiency of a propeller, the expediency of developing the proposed methodology for setting a propeller design in the CFD package Flow Vision is justified. The using of this technique makes it possible to obtain reliable values of the propeller hydrodynamic characteristics for constructing its action curves, and also to reduce the estimated time. This approach makes it possible to optimize the process of designing propellers. Originality. Through numerous experiments and based on the analysis of the obtained results, it was found that the profiling of the propeller mainly affects its hydrodynamic characteristics. The choice and calculation of the propeller for the projected vessel occurs in the early stages of design. Therefore, the rationale for choosing one or another geometry of the marine propeller is a topical task. A method for specifying project parameters for conducting numerical experiments in studying the operation of propellers in free water was proposed and justified. Thus, it is possible to design not only the serial screws, but also the new series propellers, minimizing the costs of carrying out the research along with the reliability of the resulting calculation results. Practical value. Authors established that the influence of the propeller blade profiling on its hydrodynamic characteristics is greater than the influence of its other general and blade characteristics. The developed design methodology for the calculation of propellers in the CFD package Flow Vision can be used to design the marine propellers of both new series and existing ones, and also in the case of optimizing the shape of the propeller to ensure the greatest efficiency. The application of the technique will allow reducing the time for conducting a numerical experiment due to the convergence of the solution in a relatively short time.

98-105

Authors: R. P. Pogrebnyak

Purpose. The article is aimed to determine the conditions of a dynamic error formation of contour machine cutting of surface of the real railway wheel flange by the cup-tip tool and propose the ways of reducing the errors. Methodology. The problem was solved by the creation of dynamic nonlinear and elastic calculation model with further modeling of its loading by the external force factors. The values of forces were obtained by analytical and experimental methods. The calculation scheme of the equilibrium support is a nonlinear two-mass system, a dynamic model of slide - single-mass with one degree of freedom. The basis of the mathematical description of technological loads is the results of factory experiments, as well as analytical generalizations obtained as a result of the comparison of several schemes of the formation of the wheel flange. Analytical determination of the components of the cutting force takes into account the changes in the kinematic parameters of the cutting mode when the profiling is done using a shaped tool. Findings. During processing of the wheel flange the radial and axial components of the cutting forces that load slide and slide-block of machine are alternating. There are conditions in drive of slide and slide-block when the gaps appear, and it is possible at any profile geometry of the wheel. The peculiarities of loading of the slide and slide-block forming a flange (with biharmonic allowance) cause the occurrence of the processing areas where the gaps increase many times in drives of mechanical transmissions and error of forms increases. The dynamic system of the drive is quite tough and high-frequency and it is sensitive to the presence of gaps. Originality. The author created elastic nonlinear dynamic models of support and slide. In accordance with the model it is written and solved equations of motion of the masses and loading of the connections. The conditions of the stable motion were found. Practical value. It is determined by modeling the qualitative and quantitative terms of stable motion without gaps. It is recommended to change the weight of counterweight.

117-128

Authors: O. V. Fomin, O. M. Gorobchenko, N. S. Kocheshkova, V. V. Kovalenko

Purpose. The article is aimed to systematize and structure representation of theoretical grounds for the optimization designing of railway car components and practical ways of its implementation. Methodology. The study is based on analysis of several well-known articles on the subject, as well as on authors' researches, some mathematical foundations and computer modeling. The rolling stock components structural analysis was made by applying modern and acknowledged methods. Findings. In the study the authors systematized the set of methodological approaches to the freight car design processes; they also analyzed every application phase of the designing process and its conditions. The article presents the developed mathematical model of the car component implementation. This model takes into account all the calculated cases of the car life cycle. Moreover, the model also can be applied to other transport modes accounting their specific operation modes. The possibility to generate different construction options for equally strong car component with minimum material intensity was also shown in the article. There were several methods developed for finding optimal solutions that make it possible to calculate the sought characteristics of construction elements with the reliable accuracy. The presented variety of different approaches significantly extends engineering apparatus by increasing the synthesis and analysis abilities of the car design. Originality. The authors proposed the methodological foundations of the car components design aimed at creating their optimal structural parameter execution and the operating features based on the results of the detailed research. Practical value. Expediency and effectiveness of the presented methods has been confirmed by positive experience of its application when constructing the general-purpose gondola cars, models 12-9904 and 12-9904-01, as well as when upgrading existing constructions of freight cars, model 12-9745 and the hoper car 20-9749.