Evaluation of the Influence of a Rail Vehicle Running with Wheel-flat on the Railway Track (original) (raw)
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One of the most acute problems faced today by Railway Transport Companies is the rapid wear of locomotive wheel borders in the freight transport. Hence, the purpose of this article is to find ways to reduce the forces acting on the wheels of railway vehicles, generally during their movement in small radius turns. For means of simplification has been assumed that the train is moving at uniform speed during a curved path. Analyzing the scheme of action of forces on the pair of wheels, we see that one of the ways to reduce this consumption phenomenon is to reduce the parasitic moment of frictional forces. With reference to the practice of roller-contact studies, we modeled mathematically the redistribution of frictional forces at the point of contact of the wheel-rail pair and realized two computer models for two variants of wheel profiles: conical and curved.
Study of the Wheel-Rail Interaction
DEStech Transactions on Materials Science and Engineering, 2017
This article describes a measurement method whit strain gages, which allows measure the vertical force independently of the lateral force in the wheel-track interface of a railway. It also shows the obtained results from the implementation of this method to measure the forces in a commercial railway of the railway system.
An Investigation Into Effect of Train Curving on Wear and Contact Stresses of Wheel and Rail
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Some important papers concerning the studies on rail wear and wheel/rail contact stresses are briefly reviewed. The present paper utilizes a numerical method to analyze the effect of railway vehicle curving on the wear and contact stresses of wheel/rail. The numerical method considers a combination of Kalker's non-Hertzian rolling contact theory, a material wear model and a vertical and lateral coupling dynamics model of the vehicle/track. In the analysis, the important factors influencing on the wear and the contact stresses are, respectively, the curving speed, the curved track super-elevation and the rail cant. Compared to the present model, some concerned models and results in the published papers are in detail discussed. Through the detailed numerical analysis, it is found that the difference between the normal loads of the left and right of the wheelset increases linearly with increasing the vehicle curving speed. The material wear volume per length along the rail running surface has a tendency to grow. However, the variation of the maximum normal contact stress has a large fluctuation as the curving speed increases. The increase of the maximum contact stress depends greatly on not only the normal load but also the profiles of the wheel/rail. Increasing the track super elevation efficiently lowers the normal load difference of the left and right of the front wheelset, and the contact stresses and the wear. The rail cant has a great influence on the low rail wear of the curve track. An increase in rail cant results in a great increase in the low rail wear of the curved track, and a decrease in the outside rail wear. These conclusions are very useful in the maintenance of the track.
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Nowadays, one of the most sensible issues in the railway industry is the damage on vehicles caused by the track conditions and the infrastructure deterioration due to the trains' passage. Therefore, it is essential to acquire a better understanding on how the operation conditions influence the wear evolution of the railway wheels and the consequences of their changing profiles on vehicle-track interaction forces. In this work, a computational tool is used to simulate the dynamic performance of integrated railway systems and to predict the wear evolution of wheel profiles. The tool is applied to realistic operational scenarios with the purpose to evaluate the influence of the track conditions, defined by the track geometry and by its irregularities, on the wear progression of railway wheels. The loads imposed to the railway infrastructure by a trainset running at different velocities, on a track with and without irregularities, and equipped with wheelsets having new and worn profiles is also studied. The studies performed here show that the levels of track irregularities considered have a negligible influence on the wear progression. Furthermore, the loads imposed to the track during trainset operation are not affected by the wear state of the wheels. On the other hand, the track imperfections can affect significantly the vehicle-track interaction forces.
Some Aspects Concerning the Wheel Flat/Rail Interaction
The flat is a fault of the rolling surface of the railway wheel, which occurs when the wheel is blocked during braking process. When a wheel having a flat fault is rolling on the rail, a periodic impact force occurs, which is soliciting the rail and generates impact noise. The present work studies the interaction between a wheel having this particular fault and the rail, using a model in which the rail is considered to be a continuous supported beam on two elastic layers. The wheel is taken as a simple mass driven by the stationary load. The Green's functions method is applied in order to solve the equations of motion. The influences of the speed, flat geometry and wheel mass upon the maximal impact force are studied.
Computer-aided simulation of the wheel-rail interaction was performed with the help of the program code "Universal Mechanism» and its version "UMWear", the tribodynamic model, enabling to find wheel or rail profile evolution due to wear. Specific features of wheel and the rail profiles' evolution model are described. The objectives of simulation are to find the influence of various track and vehicles parameters on wheel/rail interaction characteristics, such as wheel/rail friction work and wheel wear, contact parameters, temperature and safety factor characterizing derailment risk. Some conclusions on a degree of the influence are made.
Reinvestigation into railway wheel-track interaction and suspension damage
Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, 2020
Without considering either velocity or acceleration effects, the current conventional method presented in literature applies the vertical deflection of a wheel centre caused by a flat defect to the Hertzian contact theory. This method has been numerically and theoretically proved to be inappropriate and can incorrectly predict a higher wheel-rail impact force for a low speed than a high speed. Therefore, under a hypothesis of no wheel bouncing and sliding, two new methods, the velocity-based and the acceleration-based have been proposed. The former method takes the wheel centre deflection change in each computational increment from the Hertzian contact theory while the latter applies the wheel centre acceleration caused by the flat in revolutions to the wheel as a force in dynamic simulation, which interprets the speed effects on impacts precisely. A sensitivity study proves that the velocity-based method is unreliable as opposed to the acceleration-based method. A beam/rigid FE mod...
The Study of the Wheel Diameter Influence over the Loading Capacity of a Railway Vehicle
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Considering the importance of aspects related to the wheel-rail contact, the work deals with issues related to tribology, mainly referring to the wear profile of the wheel. The detailed knowledge of contact phenomena in this area actually represents the fundamental issue ensuring the development of railway means of transport. The decrease in the diameter of the wheel causes that, at the same load per wheel, the surface of the contact ellipse decreases, appearing the danger of occurrence of plastic deformations. Therefore, this implies the limitation of the road per wheel depending on the diameter thereof. The form and dimensions of the contact area determine the reliability of wheels and rails, guidance safety and adherence features in traction and braking mode of the vehicle.