Showing papers by "Dnipropetrovsk National University of Railway Transport named after Academician V. Lazaryan published in 2012"

Improving hardness and tribological characteristics of nanocrystalline Cr–C films obtained from Cr(III) plating bath using pulsed electrodeposition

Abstract: Effect of pulsed electrodepostion on the nanocrystal size, composition, hardness, coefficient of friction and wear resistance was investigated for the Cr–C electrodeposits obtained from a trivalent chromium bath. The electrodeposits were shown to contain about 9% of carbon. Pulsed electrodeposition does not virtually affect the carbon content. At the same time, an increase in the off time duration leads to a decrease in the nanocrystals size. The hardness and wear parameters of the electrodeposits may be sufficiently improved when using pulsed current. For instance, at ton = toff = 1 s, the hardness reaches the values of ~ 1200 ÷ 1300 HV (meanwhile, it is close to 850 ÷ 950 HV at a steady-state electrolysis).

Electrodeposition of nanocrystalline chromium-carbon alloys from electrolyte based on trivalent chromium sulfate using pulsed current

Abstract: The effect of the parameters of pulsed electrolysis on the current efficiency, nanocrystal size, composition, hardness, friction coefficient, and wear resistance of nanocrystalline Cr-C coatings obtained from electrolyte based on Cr(III) sulfate containing carbamide and formic acid is studied. It is shown that coatings contain ∼9 wt % of carbon; the current density and pulse ratio produce practically no effect on their composition. It is found that a maximum appears on the dependence of current efficiency on pulse ratio in the case of the pulse ratio of ∼1.05–1.1. Thereby, current efficiency greatly exceeds the value implemented in the steady-state current mode. It is shown that, if the microhardness of Cr-C deposits obtained at constant current is close to 850–900 HV, the microhardness may increase to ∼1200−300 HV when pulsed electrolysis is used in certain modes. It is found that application of pulsed electrolysis allows a significant decrease in the friction coefficient of chromium-carbon coating (steel counterbody) both under the dry friction conditions and in the case of boundary lubrication and also results in an increase in the deposit wear resistance.

Impact of rail transport in the development of the national economy of Ukraine

Abstract: In the article considers the job the railroad industry in the light of implementation of economic reforms in Ukraine for 2010-2014, the stages of reform and the principles for reforming the railway industry for the implementation of government programs.

Statistics and probability analysis of the voltage on the pantograph of dc electric locomotive in the recuperation mode

Abstract: The statistical analysis and probability characteristics of voltage random variation on the pantograph of DC electric locomotive in the recuperation mode are presented in the article.

Cognitive dynamics of historical and anthropological studies at the хх and early ххі centuries

Abstract: We study the logical and methodological aspects of historical and anthropological studies in the twentieth and the beginning of the XXI century

Financial resources management during major overhaul of main facilities of railway transport in the process of its reforming

Abstract: In the article some directions of financing the programs of updating and modernizing the main facilities of the railways of Ukraine in the conditions of reforming the railway transport are considered.

Comparative analysis of modulation and demodulation methods of the control signals of rail line

Abstract: Introduction: One of the ways of increasing the noise stability rail circuit is the use more informative waveform of control signal. Use in rail circuit modulated signals gives several informative selective traits in relatively narrow spectrum. The study of features of various modulation and demodulation methods with considering operating conditions of rail circuits is urgent. Purpose: the search for more informative forms of rail line control signal, the search for improved methods of signal processing of control current. Methods: For carrying out researches the method of signals decomposition in Fourier series and the simulation with the method of statistical tests have been sed. Results: Spectrum of frequency shift signal is wider than the spectrum of amplitude shift and phase shift signals by an amount equal to twice the frequency deviation. The research of correlation coherent and incoherent reception methods of rail line control signal has been carried out. In this case, we used the following models of interferences: white Gaussian noise, random pulse sequence and sinusoidal interference. It has been found that the transition from amplitude to frequency shift keying reduces signal/noise ratio by 2...4 dB, depending from the signal level and the type of noise. Losing amplitude shift keying receiver compared with the phase shift keying receiver is 5...6 dB. Conclusions: The use of more advanced methods of modulation and demodulation improves noise stability of rail circuit. When using correlation methods reception phase shift keying provides the best noise stability, and amplitude – the worst.

Analysis of influencing of terms of coupling on the factor of wear of combs of the wheel pairs of locomotives

Abstract: Analysis of influencing of terms of coupling on the factor of wear of combs of the wheel pairs of locomotives

Reduced operating costs by train traffic optimization

Abstract: The paper conducted research to reduce the cost of electricity for traction power in the wholesale electricity market. Our calculations show that the previously known criteria for evaluating energy consumption in the market conditions are irrelevant.

Improving the estimation of track condition using standard deviations of its geometrical parameters

Abstract: It is shown that estimation of the rail track by means of the standard deviations of track geometric parameters provides obtaining a more objective picture than using the existing criteria. This will allow better planning of the track repairs.

Methods of nonseparable diagnostics of diesel engines in operation of rolling stock

Abstract: Methods of nonseparable diagnostics of diesel engine and an analysis of method for diagnostics on uneven angular speed of the crankshaft are reviewed.

Structural - functional analysis of rolling stock repair of industrial enterprises

Abstract: The analysis of the existing system repair rolling stock industry and proposed to use structural and functional models that allow to create effective communication system repairs.

Directions of development of transport infrastructure of Ukraine

Abstract: The trends of the transport infrastructure development as a basic factor of national security, the stable and dynamic economic growth, its integration into the European and world economic space are considered. The most important element of the transport infrastructure in the modern economy is a network of logistic providers, which reduce transaction costs and improve the quality of transport service. And the main direction of government policy according to infrastructure should be a gradual transition of activities for establishing and operating the infrastructure objects, that is a burden for the State, from a cost sphere to an efficient business based on the state-private partnership.

Estimation of economic efficiency from restrictions elimination of speed movement of trains

Abstract: The technique which allows to receive at level of engineering calculations preliminary results of economic efficiency from elimination of restrictions for speed movement of trains is resulted.

Use of technology of friction stir welding for aluminum alloys

Abstract: This paper presents experimental data on the effect of mode of friction stir welding of aluminum alloy on the distribution of hardness over the cross section of the weld

Results of experimental research of the modes of short circuit in a traction network

Abstract: In the article the results, namely oscillograms of the transitional feeder electric values obtained by the experimental tests of the short circuit modes in case of setting off different types of substation fast-acting switches are presented. The experiments were conducted on the operating electrified track sections of the Prydniprovs’ka Railway.

Strucrural complexity of systems

Abstract: The structure of system complexity is introduced; and the linked complexity of systems is determined according to it.

Structure formation in modified concretes

Abstract: We studied the stages of structure formation in modified concretes, the impact of technological peculiarities of production on the morphology of the structural components of cement crystal hydrate, are shown ways to develop new formulations of concrete with improved physical and mechanical characteristics.