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  • Author: Prentkovskis Olegas x
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Abstract

The main regularities in fatigue fracture of the railway axle material - the OSL steel - are found in this paper. Micromechanisms of fatigue crack propagation are described and systematized, and a physical-mechanical interpretation of the relief morphology at different stages of crack propagation is proposed for fatigue cracks in specimens cut out of the surface, internal and central layers of the axle.

Abstract

Dynamically changing economic conditions influence the growing demand of various freights transportation. Inevitably, the demand for heavy and oversized freight transportation is increasing, which is quite problematic. In many cases, it is very difficult to standardize the technology of heavy and oversized freight transportation. Decisions are necessary, which would allow to deliver heavy or oversized freight to the destination place, allocating fewer funds as possible for infrastructure improvements, choosing the most appropriate mode of transport for such freight transportation or using advantages of multimodal (combined) transport. In this article there will be selected methodology of heavy and oversized freight transportation system, carrying heavy and oversized freight by road transport. There will also be made an approval of this methodology, based on a hypothetical route within Lithuanian territory.

Abstract

This study proposes a hybrid multiple criteria decision making (MCDM) methodology for evaluating the performance of the Indian railway stations (IRS). Since the customers are heterogeneous and their requirements are often imprecise, the evaluation process is a critical step for prioritizing the IRS. To improve the existing approaches, an efficient evaluation technique has been proposed by integrating rough numbers, analytic hierarchy process (AHP) and multi-attribute border approximation area comparison (MABAC) methods in rough environment. The relative criteria weights based on their preferences given by experts is determined by rough AHP whereas evaluation of the alternatives based on these criteria are done by the modified rough MABAC method. A case study of prioritizing different railway stations in India is provided to demonstrate the efficiency and applicability of the proposed method. Among different criteria “proactively” is observed to be the most important criteria in our analysis, followed by ‘Railfanning’ and ‘DMO’ is found to be the best among the forty IRS in this study. Finally, a comparative analysis and validity testing of the proposed method are elaborated and the methodology provides a standard to select IRS on the basis of different criteria.

Abstract

The melting conditions of the electrode wires and the structure of coatings, obtained by the electric arc spraying method depending on the pressure of the spraying air flow, are analysed in the current paper. The effect of air pressure on the spraying angle of the flow of melted metal droplets is demonstrated. It is established that due to the decrease in this spraying angle, the temperature of the droplets increases. In addition, high-speed airflow is more easily captured by smaller molten metal droplets and during the contact with the substrate surface their deformations were more strongly. Due to such phenomenon, the porosity of the coatings was reduced and the number of lamellae, welded to each other, increased. With the increasing pressure of the air flow, the thicknesses of the lamellae were decreased, however, the amount of the oxide phase in the coatings has increased. As a result, the hardness, wear resistance and cohesive strength of the coatings, obtained at a higher pressure of the air flow, have increased, and the level of residual stresses of the first kind in them decreased.