| 1. |
- Abbasi, Saeed, et al.
(författare)
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Temperature and thermoelastic instability of tread braking friction materials
- 2012
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Ingår i: Proceedings 9th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems. ; , s. 606-607
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Konferensbidrag (refereegranskat)abstract
- Braking events in railway traffic often induce high frictional heating and thermoelastic instability (TEI) at the interfacing surfaces. In the present paper, two approaches are adopted to analyse the thermomechanical interaction in a pin-on-disc experimental study of railway braking materials. In a first part, the thermal problem is studied to find the heat partitioning between pin and disc motivated by the fact that wear mechanisms can be explained with a better understanding of the prevailing thermal conditions. The numerical model is calibrated using the experimental results. In a second part, the frictionally induced thermoelastic instabilities (TEI) at the pin-disc contact are studied using a numerical method and comparing them with the phenomena observed in the experiments. The effects of temperature on material properties and on material wear are considered. It is found from the thermal analysis that the pin temperature and the heat flux to the pin increase with increasing disc temperatures up to a transition stage. This agrees with the behaviour found in the experiments. Furthermore, the thermoelastic analysis displays calculated pressure and the temperature distributions at the contact interface that are in agreement with the hot spot behaviour observed in the experiments.
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| 2. |
- 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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| 3. |
- Teimourimanesh, Shahab, 1982
(författare)
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Railway tread braking temperatures - Numerical simulation and experimental studies
- 2012
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Licentiatavhandling (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 in rolling contact with the rail. The extensive use of tread brakes in metro and suburban applications has created a need for design guidelines or standards for wheels exposed to repeated stop braking. The thermal capacity of the wheels puts a limit to railway tread braking systems. With the exception of the drag braking cases described in the European standard EN 13979-1, there are no known standards or guidelines regarding the thermal capacity limits for wheels.In the present work, an extensive literature survey has been made with special focus on the braking capacity of wheels. Several aspects of the tread braking system, important for the dimensioning of railway wheels, have been assessed, such as brake block materials and residual stresses and temperature gradients through wheel rim and wheel disc. Additionally, two different railway wheel designs, with typical characteristics of freight and metro wheels, have been numerically studied with respect to design criteria for load cases of drag braking and stop braking.Brake rig experiments and a field test campaign were performed and aimed at measuring wheel and brake block temperatures during different service conditions for a metro line. It was concluded that even though the same nominal routes were simulated in the brake rig tests as those the field tests, the braking efforts are different. Therefore, simulation and calibration tools were employed in order to facilitate a comparison between measured temperatures. The results showed the importance of knowing the convection cooling parameters for different wagons if prolonged braking action is to be considered.Heat partitioning between wheel, block and rail has been numerically studied in a broad parametric study to investigate the influence of brake block materials, thermal parameters and brake pressure distribution. By use of a plane model, the implication of temperature variations around the wheel circumference (hot spots) is studied in detail. Even though the hot spots have a major impact on local temperatures, they were found to have only a minor influence on the global heat partitioning in the wheel-block-rail system. By use of an axisymmetric model, it was found that a presumed constant axial position of the wheel-rail contact towards the flange side of the tread leads to substantially higher maximum tread temperatures than a wheel-rail contact centred at the brake block position.
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| 4. |
- 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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| 5. |
- Teimourimanesh, Shahab, 1982, et al.
(författare)
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Thermal capacity of tread-braked railway wheels. Part 1: Modelling
- 2016
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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. ; 230:3, s. 784-797
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Tidskriftsartikel (refereegranskat)abstract
- Tread brakes are still a common frictional braking system used on metro and suburban trains. Here the wheels are safety-related components and there is a need to develop design specifications and guidelines to ensure that the wheels perform properly under the service conditions to which they are exposed. In the present paper, a model is proposed and developed that represents typical conditions in metro and suburban operations, in particular during sequential stop braking. The analysis also considers drag braking, mechanical loading, residual stresses and wheel-axle interference fit. Finite element modelling, with an advanced temperature-dependent material model, together with a fatigue analysis is employed to quantify the wheel's performance. An application example demonstrates the method for a typical metro wheel. In a companion paper, further applications are presented that demonstrate important aspects of the thermal capacity of tread-braked railway wheels.
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| 6. |
- Teimourimanesh, Shahab, 1982, et al.
(författare)
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Thermal capacity of tread-braked railway wheels. Part 2: Applications
- 2016
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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. ; 230:3, s. 798-812
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Tidskriftsartikel (refereegranskat)abstract
- Tread braking is a common friction-based braking system that finds use on metro and suburban trains. Here the wheels are safety-related components and there is a need to develop design specifications and guidelines to ensure that the wheels perform properly under the service conditions to which they are exposed. In the present paper, examples of applications are given that employ a modelling framework that was developed in a companion paper. The examples represent typical conditions in metro and suburban operations, in particular during sequential stop braking. Also results for drag braking, mechanical loading, residual stresses and wheel-axle interference fit are given. Parametric studies are performed to demonstrate the influence of load levels and other factors on the fatigue life of the wheels. The results should be useful for establishing design rules that consider the thermal capacity of tread-braked railway wheels.
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| 7. |
- Teimourimanesh, Shahab, 1982, et al.
(författare)
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Tread braking of railway wheels ─ state-of-the-art survey
- 2010
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Ingår i: Proceedings 6th European Conference on Braking (JEF2010 / 6ème Conférence Européenne du Freinage), Lille (France) 24-25 November 2010. ; , s. 293-302, s. 18 pp.-
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Konferensbidrag (refereegranskat)abstract
- An overview of design methods for tread braking systems is given with special focus on the braking capacity of the wheels. Several aspects of the tread braking system, important for the dimensioning of railway wheels, are assessed, such as brake block materials, residual stresses and temperature gradients through wheel rim and wheel disc. The influence of heat partitioning between wheel, brake block and rail on wheel temperatures for different braking cycles is considered. Two examples with numerical results on thermomechanical behaviour of tread braking systems are given regarding the freight and metro applications.
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| 8. |
- Teimourimanesh, Shahab, 1982, et al.
(författare)
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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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