| 1. |
- Teimourimanesh, Shahab, 1982, et al.
(författare)
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Modelling of temperatures during railway tread braking: Influence of contact conditions and rail cooling effect
- 2014
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Ingår i: Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit. - : SAGE Publications. - 0954-4097 .- 2041-3017. ; 228:1, s. 93-109
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Tidskriftsartikel (refereegranskat)abstract
- The temperature rise of wheels and blocks due to frictional heating during railway tread braking along with the transfer of heat through the wheel–rail contact is studied in this paper. In particular, heat partitioning between block, wheel and rail for stop braking cycles is considered. The wheels are of interest because they are a limiting factor for railway tread braking systems. Two types of thermal models are employed to investigate the maximum temperatures over the wheel tread. In a circumferential (plane) model of wheel, block and rail, the heat transfer problem is studied by use of a finite element formulation of the two-dimensional time-dependent convection–diffusion equation. The hot spot phenomenon is simulated by introducing a prescribed wheel-fixed contact pressure distribution between wheel and block. In an axisymmetric (axial) model of wheel, block and rail, the lateral movements of the wheel–rail contact are studied. A general result is that the cooling effect provided by the rail is important when local temperatures on the tread are considered, but not when studying bulk temperatures created in a single stop braking event. Furthermore, it is found from the lateral movements of the wheel–rail contact that slow oscillations result in maximum temperatures over the wheel tread that are somewhat lower than for travelling on straight track (rolling at the rolling circle).
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| 2. |
- Teimourimanesh, Shahab, 1982
(författare)
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Thermal Capacity of Railway Wheels - Temperatures, residual stresses and fatigue damage with special focus on metro applications
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Tread (block) braking is still one of the most common braking systems on railway vehicles.The action is carried out by pressing brake blocks against the tread of a wheel, which is also inrolling contact with the rail. The extensive use of tread brakes in metro and suburbanapplications has created a need for design guidelines or standards for wheels exposed torepeated stop braking. The thermal capacity of the wheels puts a limit to railway tread brakingsystems. With the exception of the drag braking cases described in the European standardEN 13979-1, there are no known standards or guidelines regarding the thermal capacity limitsfor wheels.In the present work, important aspects of the thermal capacity of tread braked railway wheelshave been assessed in a literature survey. Then two different railway wheel designs, withtypical characteristics of freight and metro wheels, have been numerically studied with respectto standard design criteria for load cases of drag braking and stop braking. The influence ofbrake block materials, thermal parameters and brake pressure distribution on the wheeltemperatures has been investigated. A general result is that hot spots only have a minorinfluence on the global heat partitioning in the wheel-block-rail system even though the hotspots have a major impact on local temperatures.Brake rig experiments and a field test campaign were performed and aimed at measuring wheeland brake block temperatures during different service conditions for a metro line. Simulationand calibration tools were employed in order to facilitate a comparison between measuredtemperatures. The results showed the importance of knowing the convection coolingparameters for different wagons if prolonged braking action is to be considered. In a pin-on-discexperimental study of railway braking materials, the heat partitioning characteristics betweenwheel and block material at controlled elevated disc temperatures were investigated by a finiteelement approach where a model was calibrated using measured temperatures.In the final part of the present thesis, a modelling framework was proposed and developed thatrepresents typical conditions in metro and suburban operations, in particular during sequentialstop braking. A parametric study was done for analysing the influence of various loading levelsand other important factors on temperatures, axial flange deflection, residual stresses and thefatigue life of the wheels. The model and the numerical results will be useful for assessing thethermal capacity of wheels and for developing new design rules and standards. It was foundthat the mechanical and thermal loadings have different influences on the web damage and onthe estimated fatigue life depending on load cases and wheel design.
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| 3. |
- Teimourimanesh, Shahab, 1982, et al.
(författare)
-
Tread braking of railway wheels – temperatures generated by a metro train
- 2014
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Ingår i: Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit. - : SAGE Publications. - 0954-4097 .- 2041-3017. ; 228:2, s. 210-221
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Tidskriftsartikel (refereegranskat)abstract
- Tread braking of railway wheels results in the kinetic energy of the train being dissipated into the wheel and blocks in the form of heat. This heat is further conducted into adjacent structures, notably the cold rail, and also transferred into the surroundings by convection and radiation. Heat partitioning between wheel and block is, for short time periods, controlled by local thermal interactions at the contact point and by the conductive properties of the bodies. However, for a metro train that performs longer periods of intermittent braking (or for drag braking) convective and radiation cooling properties of the components come into play. In the present study, results from brake rig tests and from in-field testing of a metro train are presented and used to calibrate a simulation model. It is found that the cooling level of the wheels of the metro train is substantially lower than for the wheels of a freight wagon. Moreover, it is found that the first axle on the metro train is exposed to higher cooling levels than the remaining axles. In a numerical example, temperatures of tread braked wheels are calculated using the new findings for a metro train, and the results obtained are compared with wheel temperatures as calculated assuming freight wagon conditions.
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