Wyniki wyszukiwania - BazTech

1

Train control system for railway vehicles running at operational speed

Jakimovska K., Vasilev V., Stoimenov N., Gyoshev S., Karastoyanov D.

Journal of Achievements in Materials and Manufacturing Engineering

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2015

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Vol. 69, nr 2

86--92

EN

Purpose: Bulgaria's accession to the transport system in European Union as well as the strategic geographic location of the country suggests a high level of operational reliability in the rail sector. This paper contains a detailed study aimed to investigate the advantages and disadvantages of the Checkpoint Systems implemented by leading railway administrations. Design/methodology/approach: The basic principles of the construction of Checkpoint Systems are examined and the purpose of corresponding regional system for control of the train technical state in motion in Bulgaria is defined. The possibilities for the application of different types of sensors in order to achieve necessary and sufficient features for reliable implementation at a relatively low price were analysed. Findings: A model for values comparison of the most important parameters is proposed. The Recognition System is based on intelligent optical sensors that operate through cameras mounted on certain height which scans the numbers of wagons and after subsequent software image processing it compares them to the numbers from database. Practical implications: Application of these systems increases safe movement of trains and regulates the superintendence between the infrastructure operators and managing infrastructure state institutions. Originality/value: The novelty in this authors’ approach is the use of accelerometer sensors measurements that examines the magnitude of acceleration acquired by the rail under the effect of shock cyclical loads. Thanks to achievements of modern communication and information technologies, the key aspects of creating technical connections are marked. This research indicated the guidelines for the development of a nationwide unified network of diagnostic points which will help the future studies.

2

Static and kinetic friction of electroless Ni composite coatings

Vencl A., Jakimovska K., Ivanova B., Ruzic J., Simeonov S., Kandeva M.

Journal of Achievements in Materials and Manufacturing Engineering

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2015

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Vol. 70, nr 1

13--21

EN

Purpose: The aim of this study was to examine the static and kinetic friction of electroless Ni coatings of different surface roughening, in unlubricated contact with various counter-body materials. In particular, difference between static and kinetic coefficient of friction was analysed. Design/methodology/approach: The Ni coatings deposition was done with electroless plating process. Samples of electroless Ni coatings without and with SiC nanoparticles were heat treated at 300°C for 6 hours. The microstructure of all samples was characterized by optical microscopy. Microhardness of samples and counter-bodies were also examined. The static and kinetic coefficient of friction was measured for each coating with initial and working surface roughness. Three typical materials used in industry were chosen as a counter-body material. The possibility of stick-slip occurrence was analysed through the static and kinetic coefficients of friction difference. Findings: Obtained results show that coatings hardness has strong influence on coefficient of friction, and that slip-stick phenomenon is unlikely to occur, since the differences between static and kinetic coefficient of friction are small. Research limitations/implications: The SiC nanoparticles were added to Ni coating in order to improve the abrasive wear resistance. In the same time, presence of SiC nanoparticles slightly increases the coefficient of friction in unlubricated conditions. Originality/value: The SiC nanoparticles were added to standard electroless Ni coating, and their properties are investigated. Heat treatment was applied to achieve crystalline structure and to improve mechanical and tribological properties. Coefficient of friction testing was performed by simply and easy to operate test rig.

3

Influence of mechanical alloying time on particle size of copper matrix composite

Ruzic J., Jakimovska K., Stoimenov N., Gyoshev S., Karastoyanov D.

Journal of Achievements in Materials and Manufacturing Engineering

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2015

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Vol. 68, nr 2

53--58

EN

Purpose: The aim of this study was to determine the influence of mechanical alloying time on particle size of copper matrix composites. Particle size distribution is very important parameter in many research areas such as powder metallurgy, particle-based computational modelling, advanced nanocomposite materials, etc. Hence, knowledge of relations between particle size and applied technique is essential for many studies, especially for selection of further manufacturing procedures. Design/methodology/approach: Starting powders (94.78 wt.% copper, 4.1 wt.% zirconium and 1.12 wt.% boron) were mechanically alloyed (MA) for 1, 10 and 20 hours. The structural characterization of copper and MA powders were performed by X-ray powder diffraction (XRPD) and morphology of MA powders were examined by using scanning electron microscopy (SEM). Particle size distribution as a function of milling time was determine by advanced laser nanoparticle sizer. Findings: Obtained results show that with increasing milling time the particle size is decreasing and morphology is changing. Also, identification of nanoparticles was achieved. Analysis of particle size distribution point out that after 1 hour of mechanical alloying the particle diameter is decreasing until 10 hours after which it starts to increase. Research limitations/implications: Identification of correlations between particle morphology/size distribution and milling time is of great importance in powder-based techniques and computational models. Originality/value: Copper matrix composites reinforced with ceramic nano and micro particles are relatively new materials. Obtaining these kind of composite materials by powder metallurgy is new approach in its production. Optimization of mechanical alloying parameters for production of MA powders will provide control of final material properties.

4

Application of principal component and hierarchical cluster analysis in classifying defects of trolleybuses

Bartłomiejczyk M., Połom M., Jakimovska K.

Przegląd Elektrotechniczny

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2013

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R. 89, nr 8

48--51

EN

The failure rate of vehicles is a relevant task, which is strictly connected with the reliability of transportation systems. Methods of data analysis allow us to find similarity and differences between failure rates of several parts of trolleybuses. This paper deals with the statistic of failure of trolleybuses from the municipal transport company of Gdynia (Poland).

PL

Częstotliwość występowania awarii pojazdów jest ważnym zagadnieniem związanym z niezawodnością systemów transportowych. Metody wielowymiarowej analizy porównawczej umożliwiają znalezienie wspólnych cech I różnic pomiędzy częstotliwością występowania uszkodzeń poszczególnych podzespołów trolejbusów. W artykule przedstawiono awaryjność niezawodności trolejbusów eksploatowanych w Gdyni.