| 1. |
- Ekberg, Anders, 1967, et al.
(författare)
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Stress gradient effects in surface initiated rolling contact fatigue of rails and wheels
- 2016
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Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 366-367, s. 188-193
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Tidskriftsartikel (refereegranskat)abstract
- The paper investigates gradient effects, which relate to how highly stressed regions should be dealt with in fatigue design analyses. In particular stress gradients in rolling contact are investigated with a focus on differences in response between full and partial slip conditions. To this end the multiaxial state of stress beneath a wheel–rail contact featuring full or partial slip is quantified using a multiaxial equivalent stress criterion. A comparative study shows that the significant differences in peak interfacial shear stress magnitudes between full and partial slip conditions are significantly reduced when translated to equivalent stress magnitudes. An innovative procedure to quantify the gradient effects by comparing the multiaxial contact stress field to uniaxial conditions is developed and employed. For the studied cases stress gradients beneath the frictional contact were found to be similar to stress gradients outside a uniaxially loaded large plate featuring a small hole with a radius in the order of 0.5–0.7 mm. The study concludes that the use of local magnitudes of interfacial shear stress in the analysis of surface initiated rolling contact fatigue under partial slip conditions is conservative. The analysis framework established in the current study can be used to estimate the level of conservativeness.
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| 2. |
- Ekberg, Anders, 1967, et al.
(författare)
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Stress gradient effects in surface initiated rolling contact fatigue of rails and wheels
- 2015
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Ingår i: Proceedings of the 10th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems (CM2015).
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Konferensbidrag (refereegranskat)abstract
- The paper investigates gradient effects, which relates to how highly stressed regions should be dealt with in fatigue design analyses. In particular stress gradients in rolling contact are investigated with a focus on differences in response between full or partial slip conditions. To this end the multiaxial state of stress beneath a wheel–rail contact featuring full or partial slip is quantified using a mulitaxial equivalent stress criterion. A comparative study shows that the significant differences in peak interfacial shear stress magnitudes between full and partial slip conditions are significantly reduced when translated to equivalent stress magnitudes. In addition, stress gradients beneath a frictional contact are compared to stress gradients outside a uniaxially loaded small hole in a plate and was found to correspond to hole radii in the order of 0.5– 0.7 millimetres for the cases studied. The study concludes that the use of local magnitudes of interfacial shear stress in the analysis of surface initiated rolling contact fatigue is conservative. The analysis framework established in the current study can be used to estimate the level of conservativeness.
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| 3. |
- Esmaeili, Ali, 1983, et al.
(författare)
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Thermomechanical cracking of railway wheel treads: a combined experimental and numerical approach
- 2015
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Ingår i: Proceedings of the 10th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems (CM2015). ; , s. 8-
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Konferensbidrag (refereegranskat)abstract
- In the present study, thermal cracking of railway wheel treads is studied by full-scale brake rig tests and finite element simulations. The focus is on thermomechanical rolling contact fatigue (RCF) life predictions. The wheel tread material is subjected to simultaneous mechanical and thermal loads due to rolling contact and stop braking, respectively. Full-scale tests featuring three series of repeated stop braking cases have been performed at the Railway Technical Research Institute (RTRI) in Japan in a brake rig featuring a tread braked wheel that is in rolling contact with a railwheel. The brake rig test conditions have been simulated numerically using the finite element method. To this end, the effect of “hot bands” on the tread is accounted for as indicated by the experimental findings. Thermomechanical stresses induced by braking as well as Hertzian contact loading on the tread including tractive loads based on a partial slip assumption are considered. The mechanical response of the wheel material ER7 is obtained from a viscoplastic Chaboche material model calibrated against data from cyclic experiments with hold-time from room temperatures up to 650 °C. Finally, a strategy for prediction of fatigue life with respect to ratcheting failure is discussed.
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| 4. |
- Fröhling, Robert, et al.
(författare)
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Preface: Special issue on heavy haul
- 2019
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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. ; 233:6, s. 595-595
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 5. |
- Ikeuchi, K., et al.
(författare)
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Wheel tread profile evolution for combined block braking and wheel-rail contact - Results from dynamometer experiments
- 2015
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Ingår i: 10th International Conference on Contact Mechanics of Wheel / Rail Systems, CM 2015, Colorado Springs, United States, 30 August - 3 September 2015.
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Konferensbidrag (refereegranskat)abstract
- Wheel treads are subject to different types of damage such as wear, rolling contact fatigue (RCF), thermal cracks, plastic deformation and also flats caused by wheel sliding. Some of these phenomena is followed by a change in tread profile which results in frequent wheel reprofiling to keep rich comfort of the vehicle. In this study, a series of full-scale tread braking experiments, including wheel-rail rolling contact, were conducted in order to clarify the influencing factors of evolution of wheel tread profile. The experiments focused on plastic deformation and wear caused by rolling contact and tread braking. The presented results show that the maximum tread depression is 0.20 mm at the rolling contact center after 40 times stop braking actions. This is considered to be caused by plastic deformation of the wheel tread induced by high contact pressure and material softening due to high temperatures from tread braking. This result is supported by the observed protrusion of the tread near the rolling contact area and also by a difference of hardness between the rolling contact area and other tread area.
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| 6. |
- Ikeuchi, K., et al.
(författare)
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Wheel tread profile evolution for combined block braking and wheel–rail contact: Results from dynamometer experiments
- 2016
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Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 366-367:SI, s. 310-315
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Tidskriftsartikel (refereegranskat)abstract
- Wheel treads are subject to different types of damage such as wear, rolling contact fatigue (RCF), thermal cracks, plastic deformation and flats caused by wheel sliding. These types of damage cause changes in the tread profile of the wheel, which necessitates frequent wheel reprofiling in order to maintain the ride comfort of the vehicle. In this study, a series of full-scale tread braking experiments, including wheel–rail rolling contact, were conducted to clarify the factors influencing the wheel tread profile evolution. The experiments focused on plastic deformation and the wear caused by the rolling contact and tread braking. The results showed that the maximum tread indentation was 0.20 mm at the rolling contact center when the stop braking action was repeated 40 times. This was caused by the plastic deformation of the wheel tread, which, in turn, was the result of high contact pressure and material softening from high temperatures caused by tread braking. The results were supported by the observed tread protrusions near the rolling contact area and also by the difference in the rolling contact area hardness and that of the other wheel tread areas.
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| 7. |
- le Gigan, Gael, 1985, et al.
(författare)
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Disc brakes for heavy vehicles: An experimental study of temperatures and cracks
- 2015
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Ingår i: Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering. - : SAGE Publications. - 2041-2991 .- 0954-4070. ; 229:6, s. 684-707
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Tidskriftsartikel (refereegranskat)abstract
- A better understanding of the thermomechanical loading of brake discs is important for controlling material fatigue and crack propagation in the disc. In the present study, full-scale drag braking experiments were performed on brake discs made from eight different grey cast iron alloys. The well-performing materials were also tested with an alternative brake pad material. A testing procedure with repeated drag brakings was used. The disc and pad temperatures were registered by thermocouples embedded at selected locations, and the disc surface temperatures by a thermocamera. Extensive analyses of the measured temperatures were performed. The results for the thermocouples at the mid-radius of the disc and at the end of brake applications indicatd that the two sides of the disc have opposite deviations from the mean temperature. The temperature deviations are generally temporally alternating, but also stationary variations can be found. The thermocamera gives the possibility of identifying the phenomena behind the temperature variations found from the thermocouples. Banding of the disc–pads contact with alternating one band and two bands of high temperatures is observed for the studied brake discs exposed to severe braking load cases. Moreover, it was found that hot-spot patterns develop on the disc surface, which are spatially fixed during each brake application. However, they may be either slowly migrating or fixed relative to the disc during consecutive brake applications. Thermal images show that small cracks do not affect hot-spot migration as a hot spot migrates over the crack. However, at a critical length of the crack, the heat becomes localized at the crack and increases its growth, thus limiting the life of the disc. The tests indicate that a combination of hot-spot migration, alternating bands and small temperature differences over the disc are significant factors to be considered when improving the lifespan of the discs.
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| 8. |
- le Gigan, Gael, 1985, et al.
(författare)
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Modelling of grey cast iron for application to brake discs for heavy vehicles
- 2017
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Ingår i: Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering. - : SAGE Publications. - 2041-2991 .- 0954-4070. ; 231:1, s. 35-49
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Tidskriftsartikel (refereegranskat)abstract
- Cast iron brake discs are commonly used in the automotive industry, and efforts are being made to gain a better understanding of the thermal and mechanical phenomena occurring at braking. The high thermomechanical loading at braking arises from interaction between the brake disc and the brake pads. Frictional heating generates elevated temperatures with a non-uniform spatial distribution often in the form of banding or hot spotting. These phenomena contribute to material fatigue and wear and possibly also to cracking. The use of advanced calibrated material models is one important step towards a reliable analysis of the mechanical behaviour and the life of brake discs. In the present study, a material model of the Gurson-Tvergaard-Needleman type is adopted, which accounts for asymmetric yielding in tension and compression, kinematic hardening effects, viscoplastic response and temperature dependence. The material model is calibrated using specimens tested in uniaxial cyclic loading for six different temperatures ranging from room temperature to 650 °C. A special testing protocol is followed which is intended to activate the different features of the material model. Validation of the model is performed by using tensile tests and thermomechanical experiments. An application example is given where a 10° sector of a brake disc is analysed using the commercial finitie element code Abaqus under a uniformly applied heat flux on the two friction surfaces. The results indicate that the friction surface of the hat side and the neck can be critical areas with respect to fatigue for the uniform heating studied.
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| 9. |
- Lundén, Roger, 1949, et al.
(författare)
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The influence of corrugation on frictional stress at the rail-wheel interface
- 2016
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Ingår i: Civil-Comp Proceedings. - 1759-3433. ; 110
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Tidskriftsartikel (refereegranskat)abstract
- The influence of rail and wheel corrugation on vertical and tractive forces is studied, in this paper, for high-speed trains with the aim of evaluating the risk for surface initiated rolling contact fatigue (RCF). A train-track interaction model for vertical dynamics, which accounts for a prescribed torque on the wheelset and for the highfrequency content of the induced force spectrum, is employed. Corrugation distributions according to ISO 3095 (smooth rail) and as obtained from field measurements (corrugated rail) are considered. A parametric study is carried out in which level of corrugation, tractive effort and vehicle speed are varied. Also the influences of axle load and unsprung mass are investigated. The results are interpreted in terms of rolling contact fatigue impact spectra and by using the Tgamma energy model. If is found that the two models give similar tendencies regarding the surface initiated RCF impact. As expected, the traction effort will dominate the development of RCF, but significant influences are also found for corrugation, speed, axle load and unsprung mass.
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| 10. |
- Singh Walia, Mandeep, 1987, et al.
(författare)
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Temperatures and wear at railway tread braking: Field experiments and simulations
- 2019
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Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 440-441
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Tidskriftsartikel (refereegranskat)abstract
- Field tests were carried out for a commuter train in revenue service equipped with cast iron and organic composite brake blocks. Temperatures for wheel tread, wheel web and brake blocks and wear of wheel treads and brake blocks were recorded. The measured temperatures are used for calibrating a thermal model for assessment of wheel and block temperatures. The wear of cast iron and organic composite brake blocks is estimated using simulated temperatures and temperature-dependent wear models based on pin-on-disc experiments. It is found that a wear rate adaption factor, tentatively motivated by the presence of thermoelastic instabilities at full-scale braking that cannot be found at small-scale testing, is required for producing a simulated wear that is in agreement with results from field tests. Wheel tread wear is assessed as change in flange height for both powered and trailing wheels and for the studied train it is found that the levels of annual total wear of these types of wheels are similar in magnitude. Modelling of the tread wear originating from block–wheel contact and wheel−rail contact, combined with a comparison with measured wear magnitudes, makes it possible to quantify the wear from these two tread contacts. It is found for the powered wheels that wear induced by the wheel-rail contact and the block-wheel contact have equal importance, whereas for the trailer wheels the wear emanating from the block-wheel contact is dominating.
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| 11. |
- 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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| 12. |
- 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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| 13. |
- Walia, Mandeep Singh, 1987, et al.
(författare)
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Temperatures and wear at railway tread braking: Field experiments and simulation
- 2018
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Ingår i: Proceedings of the 11th International Conference on Contact Mechanics and Wear of Rail/wheel Systems, CM 2018. - 9789461869630 ; , s. 1029-1036
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Konferensbidrag (refereegranskat)abstract
- Field tests were carried out for a commuter train in revenue service equipped with cast iron and organic composite brake blocks. Temperatures for wheel tread, wheel web and brake blocks and wear of wheel treads and brake blocks were recorded. The measured temperatures are used for calibrating a thermal model for assessment of wheel and block temperatures. In addition, the results from thermal and wear simulations are presented. Comparisons are made between measured and simulated temperatures and wear. The wear of the cast iron brake blocks estimated using simulated temperatures and a temperature-dependent wear model calibrated from pin-on-disc experiments is in agreement with measured wear results from field tests.
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| 14. |
- Walia, Mandeep Singh, 1987, et al.
(författare)
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Thermal impact on rolling contact fatigue and capacity of railway wheels
- 2016
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Ingår i: Proceedings Eurobrake 2016 (Milan). ; , s. 10-
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Konferensbidrag (refereegranskat)abstract
- Tread braked railway wheels are subjected to complex loading due to combined rolling contact stresses and thermally induced stresses. The main objective of the present study is to find the limits for tread braking with respect to temperature impact on rolling contact fatigue (RCF) of the wheel tread. A wheel with an S-shaped web is studied for some different stop braking loads. Using 3D FE simulations, the effects of simultaneous thermal loading from braking and mechanical loading, with traversing wheel-rail rolling contact, are studied. In order to account for the elevated temperatures, the simulations utilise a temperature-dependent elastoplastic material model. The mechanical loads account for frictional rolling contact stress distributions induced by braking, using a novel method that is based on elastoplastic contact simulations. Partial slip is considered and interfacial shear stresses are introduced in the wheel-rail contact area. Evolution of damage in the vicinity of the wheel tread is studied for various brake loading cases. In order to assess limits for the tread braking, the calculated damage is compared to previously developed critical damage levels which were based on full-scale brake rig testing. Results are presented for a parametric study with thermomechanical loading based on different load cases. The influence from operational parameters such as axle loads, initial speeds, decelerations and block material is studied. The results show that the temperature has a strong influence on the rolling contact fatigue of the wheel treads and, hence, also on the thermal capacity of the wheels. The study gives preliminary limits for revenue traffic, described as combinations of tread temperatures and wheel-rail rolling contact loading, which should be respected to avoid thermal cracking of the wheel treads.
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| 15. |
- Walia, Mandeep Singh, 1987, et al.
(författare)
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Thermomechanical capacity of wheel treads at stop braking: A parametric study
- 2018
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Ingår i: International Journal of Fatigue. - : Elsevier BV. - 0142-1123. ; 113, s. 407-415
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Tidskriftsartikel (refereegranskat)abstract
- During tread braking, the treads of railway wheels are subjected to a complex loading due to combined rolling contact and thermally induced stresses. In revenue traffic the running mode of the train varies and the operational parameters will influence the life of the wheels. To prevent excessive damage, it is therefore important to understand at which operational conditions wheel damage becomes unacceptable. The current study aims to find limits for tread braking with respect to the influence of thermal stresses on rolling contact fatigue (RCF) of the wheel tread when subjected to repeated stop braking. A parametric study, using 3D FE simulations and involving operational parameters such as axle load, maximum vehicle speed, deceleration, brake block material and initial wheel temperature, is carried out for a new wheel with an S-shaped web. Additional analyses investigate impact from wheel geometry by studying a wheel with a straight web and a wheel with a thin (worn) rim. The effects of simultaneous thermal loading from wheel–block frictional contact during braking and mechanical loading, due to the traversing wheel–rail rolling contact, are studied in an uncoupled thermomechanical analysis. In the wheel–rail contact simulations, frictional rolling contact stress distributions induced by braking are accounted for. Interfacial shear stresses and partial slip are also included in the model. A temperature-dependent elastoplastic model is utilised to characterise changes in material behaviour during braking. In the vicinity of the wheel tread, damage evolutions for the studied brake load cases are evaluated. The results show that high tread temperatures, in particular temperatures above 450 °C, have a strong detrimental influence on the RCF formation and, hence, also on the thermomechanical capacity of the wheel. On the other hand, it is found that for braking temperatures between 300 °C and 375 °C, the fatigue resistance is increased due to strain hardening effects. In addition, the parametric study points towards actual braking load cases that can give such temperatures in terms of initial speeds, axle loads, etcetera. Specifically, the study shows that the train axle load, that controls the normal wheel–rail contact force, has a substantial impact on the life of the wheel treads. Wheels having straight webs and S-shaped wheel web exhibit the same fatigue life of their treads, whereas a reduction in wheel rim thickness promotes ratchetting due to increased flexural stresses from the mechanical wheel–rail contact loading.
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| 16. |
- Walia, Mandeep Singh, 1987, et al.
(författare)
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Wear and plastic deformation of the wheel tread at block braking : Results from brake rig experiments and simulations
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In the present work, results from a series of full-scale tread braking experiments that include a wheel–railwheel rolling contact, are compared to the results from FE simulations with focus on tread plasticity and wear. Brake rig tests have been performed to reveal tread plasticity and tread wear in the form of sequences of constant temperature rolling at 200 °C, 250 °C, and 300 °C, all for a wheel–railwheel contact load of 60 kN. The evolution of the tread profile is measured during the experiments and is compared to estimations from the FE simulations and wear calculations. Finally, calculated tread wear introduced by braking and specific influence from rolling contact plasticity on the tread profile evolution are estimated and compared to the measured wear.
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