Showing papers by "Dnipropetrovsk National University of Railway Transport named after Academician V. Lazaryan published in 2021"

Identification of Sleeper Support Conditions Using Mechanical Model Supported Data-Driven Approach

Abstract: The ballasted track superstructure is characterized by a relative quick deterioration of track geometry due to ballast settlements and the accumulation of sleeper voids. The track zones with the sleeper voids differ from the geometrical irregularities with increased dynamic loading, high vibration, and unfavorable ballast-bed and sleeper contact conditions. This causes the accelerated growth of the inhomogeneous settlements, resulting in maintenance-expensive local instabilities that influence transportation reliability and availability. The recent identification and evaluation of the sleeper support conditions using track-side and on-board monitoring methods can help planning prevention activities to avoid or delay the development of local instabilities such as ballast breakdown, white spots, subgrade defects, etc. The paper presents theoretical and experimental studies that are directed at the development of the methods for sleeper support identification. The distinctive features of the dynamic behavior in the void zone compared to the equivalent geometrical irregularity are identified by numeric simulation using a three-beam dynamic model, taking into account superstructure and rolling stock dynamic interaction. The spectral features in time domain in scalograms and scattergrams are analyzed. Additionally, the theoretical research enabled to determine the similarities and differences of the dynamic interaction from the viewpoint of track-side and on-board measurements. The method of experimental investigation is presented by multipoint track-side measurements of rail-dynamic displacements using high-speed video records and digital imaging correlation (DIC) methods. The method is used to collect the statistical information from different-extent voided zones and the corresponding reference zones without voids. The applied machine learning methods enable the exact recent void identification using the wavelet scattering feature extraction from track-side measurements. A case study of the method application for an on-board measurement shows the moderate results of the recent void identification as well as the potential ways of its improvement.

Influence of diamond–matrix transition zone structure on mechanical properties and wear of sintered diamond-containing composites based on Fe–Cu–Ni–Sn matrix with varying CrB2 content

Abstract: The influence of CrB2 additive (within the interval ranging from 0 to 8 wt%) on the formation of structure of the diamond–matrix transition zone and the matrix material, microhardness, elastic modulus, retention of diamond grains in Fe–Cu–Ni–Sn matrix material and wear resistance of sintered diamond-containing composites (DCCs) by the powder metallurgy method has been studied. Micro-mechanical and tribological tests were conducted using composite samples 10 mm in diameter and 5 mm thick. It has been established that the transition zone structure significantly depends on the CrB2 content in a composite and is of a different nature than that of the matrix material. The structure of DCCs transition zone based on 51Fe–32Cu–9Ni–8Sn matrix consists of Cu, α-Fe and Ni3Sn phases with graphite inclusions. The structure of DCCs transition zone based on 51Fe–32Cu–9Ni–8Sn matrix with CrB2 additives consists of the α-Fe phase and Fe3C, Cr7C3, Cr3C2 carbide layers without graphite inclusions. It has been shown that the hardness and the elastic modulus of sintered composite matrix material increase linearly as the concentration of CrB2 in their content increases while the wear rate decreases. The addition of 2 wt% of CrB2 to 51Fe–32Cu–9Ni–8Sn composite contributes to an increase in its hardness from 4.475 to 7.896 GPa and elastic modulus from 86.6 to 107.5 GPa thus reducing the wear rate from 21.61 × 10−6 to 10.04 × 10−6 mm3 N−1 m−1. The mechanism for enhancing the mechanical properties and wear resistance of DCCs samples containing CrB2 additives consists in refining of matrix phases of iron and copper from 25 μm to 10 μm and binding the carbon released during the graphitization of diamond grains to Fe3C, Cr7C3, Cr3C2 nanoscale carbides. This, in turn, increases the ability of matrix material to keep diamond grains from falling out during DCCs operation. Low values of mechanical properties and wear resistance of the initial (51Fe–32Cu–9Ni–8Sn) composite are attributed to the coarse-grained structure and formation of graphite inclusions in the diamond–matrix transition zone, causing its premature destruction and separation of diamond grains from the DCCs matrix.

Development of mathematical models of energy conversion processes in an induction motor supplied from an autonomous induction generator with parametric non-symmetry

Abstract: The paper presents studies of the system "induction generator-induction motor" with parametric asymmetry on a mathematical model to determine the quality of generated electricity in load operating modes. A mathematical model of the "induction generator-induction motor" system has been developed taking into account losses in steel and parametric asymmetry. The analysis of the transient characteristics of an induction generator when a motor load is connected in symmetrical and asymmetrical modes of operation is carried out. The results of changes in the main characteristics of an induction motor at various degrees of parametric asymmetry in the generator are presented. The quality of the generated electricity was analyzed based on the calculations of the unbalance coefficients for each of the operating modes. The assessment of the thermal state in steady-state conditions was carried out using an equivalent thermal equivalent circuit. Thermal transients were investigated when starting an induction motor from an autonomous energy source based on an induction generator. On a thermal mathematical model, the study of the effect of the output voltage asymmetry on the heating of the connected induction motor was carried out. It is shown that the asymmetry of the output voltage of an induction generator reaches 3–10 % and causes overheating of the windings in excess of the permissible values. A regression model has been developed for studying the operating conditions of an induction motor when powered by an induction generator with an asymmetry of the stator windings. The use of the obtained equations will make it possible to determine the most rational combination of factors affecting the heating of the stator windings of induction machines, in which they will not overheat above the maximum permissible temperature values of the corresponding insulation classes

An optimization method of the multi-group train formation at flat yards

Abstract: Formation of multi-group trains is aimed at arranging their cars in a given order and is one of the mass operations performed at railway. In this regard, the reduction of the duration of shunting o...

Influence of Parameters of Electric Locomotive on its Critical Speed

Abstract: A high speed is one of the most important todays requirements for the rail transport. However, increasing the maximum speed brings also the problem of vehicle stability. The parameters of the vehicle suspension should be tuned in order to achieve vehicle stability in the entire speed range. The article presents the results of theoretical study of the impact of the suspension parameters of the mainline electric locomotive type DS3 on the magnitude of its critical speed. The stability and critical speed are assessed by eigenvalues calculation of the linear model of the vehicle. The study compares 9 variants of vehicle parameters. The sensitivity of the critical speed on the individual parameters is shown and discussed. At the same time, it is shown that by tuning vehicle parameters in order to achieve high critical speed, some other vehicle characteristics may deteriorate. As the result, the optimal range of the stiffness values of the connection of axle-boxes and bogie-frame is recommended.

Model of Propagation of Traction Current Harmonics from Trains to a Track Circuit Receiver

Abstract: The problem considered in the work is related to ensuring the electromagnetic compatibility of new types of rolling stock with track circuits. The article presents a mathematical model for propagation of traction current harmonics in asymmetric rail line from multiple rolling stock units to a track circuit receiver. To simulate the distribution of return traction current harmonics in longitudinally inhomogeneous and asymmetric rail lines, a large number of parameters are required that characterize a specific design of a traction network and track circuits, which makes the task difficult for practical implementation. The mathematical model proposed in this work can be conditionally divided into three parts. In the first part, the distribution of the total traction current harmonic in both rails from all rolling stock units located in a feeder zone is determined without considering rails asymmetry. In the second, the distribution of traction current harmonics in rails, considering their electrical asymmetry, is determined for the problem track section. And in the third part, the propagation of the traction current harmonics from the rails to the track circuit receiver is investigated. The adequacy of the developed model was verified by comparing the results of calculations and measurements

Determining the possibility of using removable equipment for transporting 20- and 40-feet-long containers on an universal platform wagon

Abstract: An important role in the market of transport services belongs to container transportation. Railroads, especially under the conditions of increased competition from road transport, must respond quickly to the needs of the market and the growing demand for container transportation, including interstate traffic. Demand for container transportation can vary significantly during the year, which testifies to the expediency of introducing removable equipment on universal railroad freight cars that are involved in the deliveries of containers. This paper reports the design of a removable frame structure for a universal platform that could carry two 20-ft or one 40-ft container. The proposed technical solution does not require changes in the structure of the car and changes in its model; with a decrease in the demand for container transportation, it would allow this car to be used for its main purpose. According to the current methodology, the efforts that operate on the frame during the transportation of containers have been determined. The strength of the proposed structure was estimated by a finite-element method. The maximum stresses arising in the proposed structure are 164.4 MPa; they occur in the corners of the stops attached to the stand-up staples of the platform. The resulting stress values do not exceed the allowable ones. The results of calculating the removable equipment indicate its sufficient strength. Requirements for placing cargo on the rolling stock assume a mandatory check to fit the dimensions, which confirmed that the container hosted by the frame does fit them. The proposed structure makes it possible to abandon disposable fastening parts, improve the safety of container transportation, and increase competitiveness in the container transportation market.

Devising a procedure for assessing the subgrade compaction degree based on the propagation rate of elastic waves

Abstract: This paper reports the analysis of the methods for estimating the technical condition of the subgrade underneath a constructed railroad track or road during its operation. The study results have proven that the issue related to monitoring and controlling high-quality compaction of a heterogeneous subgrade remains relevant and requires the construction of reliable experimental methods for assessing the subgrade degree of compaction. A procedure for determining the compaction of subgrade in the laboratory has been devised, based on inertial microcomputer technologies, which makes it possible to assess the degree of compaction of subgrade soils depending on the propagation rate of an impact's elastic waves. An experimental study has been performed into the propagation rate of elastic waves across a homogeneous subgrade made of coarse-grained sand and a heterogeneous subgrade made of coarse sand with a layer of clay in the middle of the prism. The study results established that the propagation rate of an elastic wave in a heterogeneous subgrade accepts a lower value than the rate of wave propagation in a homogeneous subgrade. Through the dynamic interpretation, by using a discriminant statistical analysis, the characteristic features have been defined in the distribution of accelerations in the body of the homogeneous and heterogeneous subgrade, depending on the degree of compaction, which would make it possible to monitor the state of the subgrade during operation. As the degree of the subgrade soil compaction affects the technical condition of roads

Development of a new suspension electrolyte based on methane-sulphonic acid for the electrodeposition of Cu–TiO2 composites

Abstract: Electrodeposition of composite coatings based on copper is a promising direction in the creation of advanced materials for multifunctional purposes. An important area of composites application is to use them in the treatment systems for gas emissions and wastewater. It is advisable to use semiconductor oxide materials, in particular titanium dioxide, as the photocatalysts in the photo destruction of organic pollutants of wastewater. The structural features of wastewater treatment equipment require that titanium dioxide particles should be fixed in a rigid matrix. Resolving the task of fixing photosensitive elements at the surface of a certain configuration implies the electrodeposition of coatings by composites, in particular Cu–TiO2. An important factor affecting the functional characteristics of composites and their manufacturing technology is the nature of the electrolyte. It has been shown that the electrodeposition of Cu–TiO2 composites from methane-sulfonate electrolytes makes it possible to reduce the coagulation of the dispersed phase and to obtain coatings with a high content of titanium dioxide from a suspension solution containing no more than 4 g/l of TiO2. It was established that the content of the dispersed phase in the composite made at a current density of 2 A/dm2 and the concentration of titanium dioxide in the electrolyte at the level of 4 g/l is 1.3 % by weight, which is twice as much as when using a sulfate electrolyte. It has been shown that the increase in the content of the dispersed phase in the coatings from 0.1 to 1.3 % by weight is accompanied by an increase in the degree of photo destruction of the colorant from 6 to 15.5 %. The micro-hardness of coatings increases, in this case, by 30 %. The proposed electrolyte to make the Cu–TiO2 composites is an important contribution to the development of the synthesis of wear-resistant high-performance photocatalysts for treating wastewater from organic pollutants

A comprehensive procedure for estimating the stressed-strained state of a reinforced concrete bridge under the action of variable environmental temperatures

Abstract: This paper reports the full-scale experimental measurements of temperature distribution over the surfaces of bridges' steel-concrete beams under the influence of positive and negative ambient temperatures. It has been established that the temperature is distributed unevenly along the vertical direction of a bridge's steel-concrete beam. It was found that the metal beam accepted higher temperature values. The maximum registered temperature difference between a metal beam and a reinforced concrete slab at positive ambient temperatures was +9.0 °C, and the minimum temperature difference was −2.1 °C. The mathematical models for calculating a temperature field and a thermally strained state of bridges' steel-concrete beams under the influence of variable climatic temperature changes in the environment have been improved, taking into consideration the uneven temperature distribution across a bridge's reinforced concrete beam. The possibility has been established to consider a one-dimensional problem or to apply the three-dimensional estimated problem schemes as the estimation schemes for determining the thermo-elastic state of reinforced concrete bridges. The temperature field and the stressed state of bridges' reinforced concrete beams were determined. It was found that the maximum stresses arise at the place where a metal beam meets a reinforced concrete slab. These stresses amount to 73.4 MPa at positive ambient temperatures, and 69.3 MPa at negative ambient temperatures. The amount of stresses is up to 35 % of the permissible stress values. The overall stressed-strained state of a bridge's reinforced concrete beams should be assessed at the joint action of temperature-induced climatic influences and loads from moving vehicles

Dynamic interaction of a freight car body and a three-piece bogie during axle load increase

Abstract: The article presents the results of theoretical studies of interaction process of a freight car body with a three-piece bogie, which are aimed at solving the relevant problem of increasing the perm...

Microstructural Features and Mechanical and Tribological Properties of Fe–Cu–Ni–Sn Composites Precipitation-Hardened with CrB2 Additions

Abstract: The structural features, hardness, elastic modulus, and wear resistance of Fe–Cu–Ni–Sn composites with different CrB2 contents, produced by cold pressing and subsequent sintering with additional hot pressing, were studied by X-ray diffraction, scanning electron microscopy, microindentation, and tribological testing. The micromechanical and tribological tests were performed on composite samples 10 mm in diameter and 5 mm thick in dry friction conditions. The test results showed that the mechanical and tribological properties of the composites depended on the CrB2 content. The microhardness and elastic modulus of the samples varied from 1.2 to 9.2 GPa and from 110 to 245 GPa, respectively, depending on their composition, resulting from the uneven distribution of α-Fe, Cu, Cu9NiSn3, NiSn3, and CrB2 phases. The addition of 2 wt.% CrB2 to the 51Fe–32Cu–9Ni– 8Sn composite increased its hardness from 1.2–2.8 GPa to 2.0–4.5 GPa and the elastic modulus from 110–190 GPa to 130–200 GPa and decreased the wear rate from 22.93 ∙ 10–3 to 10.19 × 10–3 mm3 ∙ N–1 ∙ m–1. The mechanism of increasing the wear resistance of the composite sample containing 2 wt.% CrB2 in comparison with the starting composite was associated with the refinement of iron and copper grains from 5–40 μm to 2–10 μm and the presence of discrete areas of greater hardness and higher elastic modulus. A further increase in the CrB2 content from 2 to 8 wt.% in the composite was accompanied by a simultaneous increase in hardness from 2.0–4.5 GPa to 4.8–9.2 GPa, elastic modulus from 130–200 GPa to 150–245 GPa, and wear rate from 10.19 ×10–3 to 16.68 ∙10–3 mm3 ∙ N–1 ∙ m–1. The higher wear rate of these composites was due to excessive brittleness caused by excessive CrB2 content.

Devising a procedure to form the diagnostic parameters for locomotives using a principal components analysis

Abstract: Modern diagnostic systems are characterized by that the flow of diagnostic information requires significant computational resources to process. In order to improve the reliability of the object to be diagnosed and reduce operating costs, it is necessary to improve procedures for analyzing diagnostic results. This paper suggests a procedure to form the diagnostic features of locomotive nodes based on the use of a principal components analysis. The proposed approach is distinguished by a decrease in the dimensionality of the input set of diagnostic features in order to select the sets of interconnected diagnostic parameters. Based on the selection of the sets of interconnected diagnostic features, constructing new latent diagnostic parameters has been proposed. A latent diagnostic parameter contains information that combines data from several initial diagnostic features. The result of the method is a set of latent diagnostic parameters that do not correlate with each other and reflect the behavior of the object to be diagnosed from different technical points. The application of a sufficient number of latent diagnostic parameters involved the scree test method. This paper reports the results from using the proposed approach for treating the results from diagnosing the hydraulic transmissions in locomotives. The result from applying the procedure has made it possible to propose using three latent diagnostic parameters to assess the technical condition of a locomotive’s hydraulic transmission during bench tests. The suggested parameters contain 90 % of the original information and reflect losses in the transmission, as well as the load at the input and output of the transmission.

Quantum-Mechanical Modeling of the Interaction between Carbon Nanostructures and Metal Ions

Abstract: Quantum-mechanical models for the formation of metal–carbon complexes of Co, Ni, Cu, and Zn ions with С60 fullerene molecules and single-wall С48 carbon nanotubes (SWCNTs) are proposed. The results of calculations show that, in aqueous solutions of electrolytes, Co, Ni, Cu, and Zn ions can be adsorbed into the С60 fullerene and С48 SWCNT surfaces with the formation of stable carbon-nanomaterial—metal (CNM—M) complexes; in this case, the minimum energy of the С60–М complex for Co and Cu ions corresponds to the position above the С6 cell center; for a Ni ion, above the single С–С bond in the С6 cell; and for a Zn ion, above the C atom. The optimized states of the С48–М complexes correspond to the position of metal ions above the С6 cell center.

Fault Detecting of Turnouts Using DWT and ANN

Abstract: The problem considered in the work is concerned to fault detection of turnouts. Turnouts are one of the most safety-critical components of the railway infrastructure, faults of which lead to significant delays in train movement and can also cause serious accidents. To ensure the safe operation of the turnouts, they need to be maintained periodically, which is mainly done manually and is very expensive. For fault detection in turnouts, it is convenient to use the dependences of their operating current on time. The development of a reliable method for diagnosing turnouts consists in the need to obtain a sufficiently large number of measured dependences of the operating current on time for all possible malfunctions of turnouts necessary to find statistically patterns or train artificial neural network. The paper proposes to preprocess the time-dependences of the turnouts operating current using a discrete wavelet-packet transform, which allows to extract simple and clear features of turnouts faults and, accordingly, reduce the size of the required dataset for training artificial neural network and accelerate the learning process. The results confirmed effectiveness of using the discrete wavelet-packet transform and an artificial neural network-based classifier for detecting turnouts faults

Use of Container and Piggyback Services in International Railway Traffic

Abstract: A modern cargo owner imposes rather strict requirements on transport services in terms of delivery time, cargo safety, quality of forwarding services. In the current conditions, it is necessary to explore the possibility of developing new additional types of carriage on rail transport, in close cooperation with the road transport. In the interaction of rail and road transport the reliability, speed and carrying capacity of the first one is combined with the flexibility and efficiency of the other. However, many issues within the framework of interaction between rail and road carriers still require scientific solutions – from the selection of criteria to a comprehensive assessment of the effectiveness of piggyback transportation. Principles of transport service quality management were formulated and evaluation criteria were determined. Piggyback traffic in the direction of Odessa-Klaipeda will allow Ukraine, Belarus and Lithuania to maintain roads, ensure purity of environment, make it possible to save fuel, as well as allow owners and carriers to significantly reduce operating costs and improve the quality of services provided.

Numerical model for air pollution simulation from road transport

Abstract: The problem of air pollution modelling near road which is situated in complex terrain is under consideration. To simulate wind flow pattern in case of complex terrain Navier-Stokes’s equations were used. NavierStokes’s equations were written using Helmholtz variables. Numerical finite difference schemes of splitting were used for numerical integration of Navier-Stokes’s equations. Equation of connective-diffusive pollutant transfer was used to simulate air pollution. Finite difference scheme of splitting was used for numerical integration of convectivediffusive equation of pollutant transfer. Computer code was developed on the basis of created numerical model. The results of a numerical experiment are presented.

Development of Analytical Methods for Calculating Time Standards for Shunting Operations

Abstract: Purpose. The article is aimed to conduct a historical analysis of the development of analytical methods for standardizing the duration of shunting operations, as well as assessing their compliance with the existing operating conditions of railway transport. Methodology. The research in this article was carried out on the basis of an analysis of literary sources and methods of the theory of the organization of the operational work of railways. Findings. The standardization of the duration of shunting operations is one of the most important tasks of the theory of operational work of railways. The existing method of standardizing the duration of shunting operations developed in the first half of the 20th century and is used to this day. The performed analysis shows that the scientific principles underlying it generally correspond to the modern conditions of the railway transport. Additional research in this area can be associated with assessing the influence of the initial location of cars on the tracks on the average duration of shunting operations, taking into account the influence of length restrictions of the cars groups being moved, as well as monitoring the implementation of established norms by statistical methods. The article also shows that the values of modern time standards for shunting operations, in many cases, are set for technical means and technologies that were used in railway transport in the 50–70s of the 20th century and do not correspond to the operating conditions of real stations and sidings of industrial enterprises. Therefore, they require revision. Originality. In this paper, based on historical analysis, the process of development of methods for setting the time for shunting operations is described and the factors influencing the current value of norms are established. Practical value. The research results make it possible to identify the reasons for the discrepancy between the existing time standards for performing shunting operations and the real operating conditions of stations and sidings of industrial enterprises, as well as to establish the main elements of the methodology for standardizing the duration of shunting operations that require revision.

The Optimal Thickness of the Surface Plasma Hardening Layer of Functional-Gradient Parts with Symmetrical Stress Concentrators

Abstract: Based on the approaches of continuous mathematical modeling, a computational methodology is proposed for establishing one of the most important operational parameters of surface engineering technologies, which determines the life of parts - the thickness of the hardened layer. For the first time, using non-local models of mechanics and the Fenics finite element analysis package, a scheme for finding the optimal hardening depth of parts depending on the load parameters and characteristics of stress concentrators has been built. Using the example of wheel rims of locomotives, it is shown that in the presence of stress concentrators, the increase in the life cycle of parts is achieved by plasma strengthening to a depth of 2.5… 3.5 times larger than the radius of the concentrators. The methodology proposed in the work is necessary for describing the behavior of the material of parts under the action of force loads in the presence of stress concentrators for selecting the optimal technological modes of hardening the surface layers. The established relationship between the change of properties of local volumes of wheels of locomotives at operational loadings and characteristics of concentrators of tension is used to obtain products with the defined life cycle, computer designing of the technological process of plasma strengthening of surfaces of contact interaction of details.

Research of Mathematical Model of Movement of Six-Axle Locomotives with Controllable Wheelsets Installation

Abstract: Research of mathematical model of movement of six-axial locomotive with controllable wheelsets installation. Based on the general system of nonlinear variable coefficient differential equations of the vehicle movement in a rail track with inequalities in plan, the mathematical model of movement dynamics of locomotive of improved design with the axial formula 30-30 as an object of automatic control of the wheelsets position in the rail track is considered. Movement simulation is performed on the example of a six-axle locomotive at the speeds of movement and parameters of the curvilinear track sections, which coincide with the conditions of the experiment presented in the thesis work of V. N. Yazykov. The article presents research results of the mathematical model of movement of the improved locomotive bogie with controllable wheelsets installation in the curvilinear track sections using the Matlab/Simulink software package. The results of experimental studies of the All-Russian Scientific-Research and Design Technological Institute of Rolling Stock and the performed theoretical studies show that the efficiency of the improved system for controlling the wheelset position is higher than that of the serial design, in all modes of movement. The improved system of automatic control of wheelsets position makes it possible to reduce guiding forces by 35%. The possibility of using the mathematical model of locomotive movement of the axial formula 30-30 of improved bogie design with axle-box links of adjustable length, taking into account the dynamics of the automatic control system of the wheelsets installation in the rail track, is theoretically substantiated. The theoretical research found out the reduction of lateral forces in the improved bogie design during the passage of curvilinear track sections. The use of the explored mathematical model of locomotive movement reduces the volume and complexity of research works, as well as increases the reliability of engineering calculations when designing new and improving existing designs of the locomotive underframe.

Determination of Energy and Electric Capacity of On-Board Supercapaci-tor Regenerative Energy Storage

Abstract: Purpose. Development of a method for determining the main functional parameters of on-board supercapacitor recuperative energy storage based on the asymptotic theory of extreme statistics by Gumbel, taking into account stochastic nature of changes in recuperated voltage and current. Methodology. To achieve this purpose, methods, devices and computer systems for temporary registration of recuperated voltages and currents on operating electric locomotives, methods of the theory of random processes and methods of probabilistic and statistical processing of registrograms of voltages and currents were used. Findings. A computational and experimental method for estimating recuperative energy has been proposed and practically applied. A probabilistic method has been developed for determining the energy and electric capacity of on-board supercapacitor recuperative energy storage units. Numerical probabilistic and statistical calculations of the energy and electric capacity of on-board storage for the VL8 and VL11M6 electric locomotives during their operation in the sections of Prydniprovska railway have been carried out. It was found that the energy and electric capacity of on-board storage devices are distributed according to an exponential law with a clear prevalence of their minimum values and in compliance with direct proportionality between them. Originality. For the first time, an autonomous phase of recuperative braking mode of an electric rolling stock has been developed, which makes it possible to significantly reduce the mass and dimension of a supercapacitor storage. The asymptotic theory of extreme statistics by Gumbel was adapted to the method for calculating energy and electric capacity of an on-board storage device, which made it possible to take into account the influence of stochastic nature of changes in the recuperated voltage and current. The probabilistic influence regularities of the change nature in the recuperation energy on the capacity of on-board storage in the phase of recuperative braking have been established. Further development was obtained by a computational-experimental method for assessing the recuperative energy, based on monitoring and using the time dependences of voltage and current obtained in real modes of recuperative braking. For the first time in electric traction systems, it was proposed to carry out the transition from the recuperative braking mode to the recuperative regeneration mode. Practical value. The developed method and technique based on it make it possible to evaluate functional parameters of on-board storage device of all types of electric rolling stock, considering stochastic nature of recuperated voltages and currents. Numerical-graphic dependences of the energy intensity and capacity of the on-board storage are recommended for predicting and evaluating these parameters for various modes of recuperative braking. Since the task of designing an on-board storage unit (in terms of mass and dimensions) is ambiguous, therefore, in each specific case of the type of electric locomotive and recuperation modes, it must be solved individually, taking into account the probability of the corresponding capacitance values.

Research of Interference in the Operational Current of DC Motors of Railway Switch Points

Abstract: This paper deals with the research of interference in the current curve of DC motors of railway switch points and the diagnostics of using harmonic analysis of it during the operation. The current spectral composition of the DC motor with the series excitation was evaluated experimentally and theoretically. The influence of DC motors interferences on the adj acent railway automatics devices was investigated.

Numerical simulation of dust pollution of working place near coal dump

Abstract: The problem of estimating the level of air pollution in the working areas near the coal pile is considered. The task is to develop a CFD model that allows to predict the level of air dust pollution, taking into account the process of wetting the surface of the coal pile. To model the process of coal dust transfer in the air, a twodimensional mass transfer equation is used, which takes into account coal dust transfer due to convection and diffusion. The Navier-Stokes equations are used to calculate the air flow field near the coal pile. Finite-difference schemes of splitting are used for numerical integration of modeling equations. Computer code is developed on the basis of created CFD model. The developed code can be used to analyze the effectiveness of the coal surface wetting to reduce dust pollution of work areas near coal piles. The results of a computational experiment are presented.

Оцінювання ризику термічного ураження працівників при пожежі на азс

Abstract: The problem of assessing the risk of thermal hitting of employees in case of fire at the gas station is considered. The task is to develop a mathematical model that allows quickly determining the dynamics of temperature changes and, on this base, forecasting the risk of thermal injury to workers in work areas. The energy equation to calculate the dynamics of thermal air pollution during burning is used. An aerodynamic model of potential motion (Laplace equation for velocity potential) to calculate the airflow velocity field in building conditions is used. Numerical integration of the equation for the velocity potential using the Richardson method and the conditional approximation method is carried out. Differential splitting schemes for numerical integration of the energy equation are used. The computer program is developed on the basis of the constructed numerical model. The results of a computational experiment to determine the risk of thermal injury to workers in a fire at a gas station are presented.

Determining a Train Location at Level Crossing Approach Section by Track Circuit Input Impedance Processing Using ANN

Abstract: The possibility of determining a train location at level crossing approach section by measuring the input impedance of the track circuit with subsequent processing of the results using an artificial neural network has been carried out. The need to measure the coordinates and speed of the train at the section approaching the level crossing is associated with the need to improve traffic safety at the level crossing and reduce the waiting time for a train (especially for a slow moving one) for vehicles. The investigations of the track circuit input impedance dependences on factors such as the train coordinate on it, the resistance of the ballast layer of the track and the frequency of the signal current were carried out by modeling and experimental measurements on a real track circuit. The monotonic dependences of the track circuit input impedance on the train location make it possible to use these dependences to monitor the train location on the track circuit. However, the strong influence of the ballast resistance on the input impedance makes it impossible to directly use the input impedance for positioning the train. Two methods have been considered for determining the coordinates of a train on a track circuit by using its input impedance. The error in determining the train coordinates at the level crossing approach section by processing the track circuit input impedance using ANN shows that this method is promising for practical use.

Use of Fine-Grained Heat-Strengthened Steels to Increase the Operation Qualities of Bunker Capacities from Thin-Walled Galvanized Profiles

Abstract: Purpose. The work is aimed to study the use efficiency of fine-grained heat-strengthened steels (mainly 10G2FB) for steel bunker capacities. At the same time, the structural scheme of such a structure using corrugated steel sheets is considered as the main variant. Methodology. To achieve this purpose, a series of numerical calculations was carried out for a steel bunker capacity of a pyramidal-prismatic type with overall dimensions in plan view of 6×5.2 m and a total height of 4.5 m. The capacity was designed for complicated working conditions, in particular, increased loads, including long-term dynamic ones. The potential possibility of operating the container under conditions of high or low temperatures was also taken into account. At the same time, both the traditional structural scheme of a bunker capacity with horizontal stiffening ribs and the developed structural scheme based on corrugated steel sheets were analyzed. The calculations were carried out by the finite element method based on the SCAD for Windows project complex. Findings. Based on the results of the analysis and comparison of the data obtained in numerical calculations, it was found that the use of fine-grained heat-strengthened high-strength steels (for example, steel 10G2FB) for bunker capacities, both the traditional structural scheme with stiffening ribs and the developed structural scheme based on corrugated sheets, allows reducing material consumption by about 30% in both cases. At the same time, due to the good performance of fine-grained heat-strengthened steel 10G2FB, both at high and at low temperatures, it can be effectively used for steel bunker capacities that work in difficult conditions. Originality. The possibility and efficiency of the use of fine-grained, heat-strengthened high-strength steels for the construction of a steel bunker capacity is estimated. At the same time, such an estimation was given not only for structures of the traditional structural scheme with horizontal stiffening ribs, but also for bunkers with a developed structural scheme based on corrugated sheets. Practical value. From a practical point of view, quantitative parameters of the stress-strain state were obtained during investigations of various design variants for a steel bunker capacity. The data are presented in a compact form that is easy to evaluate and compare. They allow us to state about the improvement of the operation characteristics of capacities and the potential reduction of the risks of their failures and accidents during operation.

Strain Hardening of Low-Carbon Steel in the Area of Jerky Flow

Abstract: Purpose. The aim of this work is to assess the effect of ferrite grain size of low-carbon steel on the development of strain hardening processes in the area of nucleation and propagation of deformation bands. Methodology. Low-carbon steels with a carbon content of 0.06–0.1% C in various structural states were used as the material for study. The sample for the study was a wire with a diameter of 1mm. The structural studies of the metal were carried out using an Epiquant light microscope. Ferrite grain size was determined using quantitative metallographic techniques. Different ferrite grain size was obtained as a result of combination of thermal and termo mechanical treatment. Vary by heating temperature and the cooling rate, using cold plastic deformation and subsequent annealing, made it possible to change the ferrite grain size at the level of two orders of magnitude. Deformation curves were obtained during stretching the samples on the Instron testing machine. Findings. Based on the analysis of stretching curves of low-carbon steels with different ferrite grain sizes, it has been established that the initiation and propagation of plastic deformation in the jerky flow area is accompanied by the development of strain hardening processes. The study of the nature of increase at dislocation density depending on ferrite grain size of low-carbon steel, starting from the moment of initiation of plastic deformation, confirmed the existence of relationship between the development of strain hardening at the area of jerky flow and the area of parabolic hardening curve. Originality. One of the reasons for decrease in Luders deformation with an increase of ferrite grain size of low-carbon steel is an increase in strain hardening indicator, which accelerates decomposition of uniform dislocations distribution in the front of deformation band. The flow stress during initiation of plastic deformation is determined by the additive contribution from the frictional stress of the crystal lattices, the state of ferrite grain boundaries, and the density of mobile dislocations. It was found that the size of dislocation cell increases in proportion to the diameter of ferrite grain, which facilitates the development of dislocation annihilation during plastic deformation. Practical value. Explanation of qualitative dependence of the influence of ferrite grain size of a low-carbon steel on the strain hardening degree and the magnitude of Luders deformation will make it possible to determine the optimal structural state of steels subjected to cold plastic deformation.

An Overview of Tools for Collecting Data on Software Development and Debugging Processes from Integrated Development Environments

Abstract: Purpose. This paper presents the findings of a review of the literature published in the twenty-first century in order to identify and analyze the current state of tools that track developer interactions with integrated development environments, as well as to recommend future research directions based on the actual state. Methodology. By systematically searching in five digital libraries we conducted a systematic review of the literature on data collection tools from integrated development environments published in the twenty-first century. Fifty-five papers were selected as primary studies. Findings. 55 articles were analyzed and the findings show that using an integrated development environment to collect usage data provides more insight into developer activities than it was previously possible. Usage data allows us to analyze how developers spend their time. With usage data, you can learn more about how developers create mental models, investigate code, conduct mini-experiments through trial and error, and what can help everyone improve performance. The research community continues to be highly active in developing tools to track developer activity. The findings indicate that more research is needed in this area to better understand and measure programmer behavior. Originality. For the first time, systematization and analysis of tools for tracking programmer's behavior in an integrated development environment have been carried out. Practical value. Our study contributes to a better understanding of the current state of research on programmer behavior in integrated development environments. An analysis of the study can help define a research agenda as a starting point for the creation of a novel practical tool.

Application of «tx active» surfaces on buildings to reduce the level of chemical air pollution in working areas

Abstract: This paper is devoted to the problem of numerical modeling of TX ACTIVE surfaces on buildings to reduce air contamination. Numerical model was developed. To compute the process of pollutant dispersion in air the mass transfer equation is used, which takes into account the pollutant transfer due to convection and diffusion. Two-dimensional model of potential flow is used to determine wind flow over buildings. An explicit difference scheme is used to solve numerically the equation for velocity potential. The splitting method is used for numerical integration of the mass transfer equation. A computer program based on the developed numerical model was developed. The results of a computational experiment are presented.

Investigation of the Acoustic Emission Field in a Half-space from the System of Coplanar Cracks

Abstract: The solution of the dynamic problem of the acoustic-emission field displacements in an elastic half-space generated by steady-state displacements of the surfaces of a circular cracks system is obtained. The solutions are obtained by the boundary integral equations (BIEs) method. For the case of mode III cracks, the dependences of elastic displacements on the surface of the half-space on the wave number, the number of defects and the depths of their location are analyzed.