| 1. |
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| 2. |
- Caprioli, Sara, 1978, et al.
(författare)
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THERMO-MECHANICAL CRACKING OF RAILWAY WHEEL
- 2011
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Ingår i: Proceedings for Svenska mekanikdagar 2011. ; , s. 1-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Thermo-mechanical wheel tread damages are common in railway wheels. While the damagemagnitude is limited this is a rather benign phenomenon. However under harsher operationalconditions (winter conditions, poorly tuned damping/suspension, poorly matched wheel–railcontact profiles etc) the extent of the problem may increase dramatically and lead to epidemicsof wheel damages. Since this calls for wheel re-profiling, the result may be extensiveoperational disturbances.The presentation deals with thermo-mechanical damage. In practice one of the failuremodes, thermal cracking or rolling contact fatigue, usually dominates. However, it is mostlikely that the combined thermal and rolling contact loading will have an influence in increasingthe resulting damage as compared to both phenomena acting separately.In the literature there are a multitude of studies on both thermal and rolling contactloading. analyses of the combined load case are however scarce. One major reason for this isthat a combined loading makes a simplification to 2D very cumbersome (not to say futile).Here, a numerical study of the impact of simultaneous thermal and mechanical loading on arailway wheel tread as imposed by braking and rolling contact is presented. 3D finite element(FE) simulations of the thermo-mechanical problem featuring a material model which accountsfor thermal expansion and plastic deformations are carried out. Both pure rolling and tractiverolling are considered. The results indicate a significant influence of the thermal loading onthe resulting stress/strain response also in cases of relatively moderate temperature increases.In particular, a combination of thermal loading and high traction rolling is found to be verydetrimental.The resulting damage of the wheel tread is manifested by the formation of small surfacecracks. In cases of high thermal loading, these cracks will evolve to deep radial cracks thatcan, in a worst-case scenario, cause catastrophic wheel failures. Since this is a potential safetyproblem it is important to understand the driving mechanisms behind these cracks.To this end, a numerical study of thermal cracking of a wheel subjected to high thermalloading was carried out. The analysis features a computationally efficient approach where2D FE stress analysis owing to thermal loading during braking and subsequent cooling iscombined with an analytical evaluation of resulting stress intensity factors of a radially orientedsurface crack in the wheel tread. The analysis identifies critical sizes for when existingsurface cracks are prone to propagate under thermal loading and resulting crack lengths afterpropagation. The results imply that fully functional brake systems are not likely to inducethermal crack propagation under normal stop braking, but that with pre-existing defects asevere drag braking due to malfunctioning brakes may cause very deep cracking. Further theanalysis concludes the thermal cracking to be a (more or less) static phenomenon related tothe most severe brake cycle. In other words: later brake cycles of similar or lower severitywill not cause any significant propagation of existing cracks. To further validate the analysisof the semi-analytical analysis, preliminary 3D FE-simulations have been performed.
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| 3. |
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| 4. |
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| 5. |
- Ekberg, Anders, 1967, et al.
(författare)
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Identifying the root causes of damage on the wheels of heavy haul locomotives and its mitigation
- 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. ; 228:6, s. 663-672
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Tidskriftsartikel (refereegranskat)abstract
- The paper illustrates how damage patterns in the form of rolling contact fatigue (RCF) on wheels, can be employed to identify and improve underlying operational conditions. The focus is on RCF of locomotive wheels operating on the Iron Ore Line in northern Sweden and Norway. Seasonal changes and damage patterns are charted. Potential root causes for observed damage patterns are identified and investigated. Mitigating actions are proposed and the efficiency of implemented actions is quantified.
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| 6. |
- Ekberg, Anders, 1967, et al.
(författare)
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Identifying the root causes of damage on the wheels of heavy haul wheel damage phenomena
- 2013
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Ingår i: Proceedings of the 10th International Heavy Haul Conference (IHHA 2013), February 4–6, New Dehli, India. ; , s. 520-526
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Konferensbidrag (refereegranskat)abstract
- The paper illustrates how damage patterns, in particular in the form of rolling contact fatigue (RCF), can be employed to identify underlying operational conditions. In particular the focus is on RCF of wheel occurring at the Iron Ore line in north Sweden and Norway. The paper charts seasonal changes and damage patterns, and potential root causes are identified and investigated. Finally mitigating actions are proposed.
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| 7. |
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| 8. |
- Ekberg, Anders, 1967, et al.
(författare)
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Surface fatigue initiated transverse defects and broken rails -- an International Review
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The current report briefly compares some operational experience of cracked and broken rails from China, Russia, South Africa, Sweden, UK and USA. Four key questions are addressed:1. Is the critical crack length, i.e. the length of a surface initiated crack that causes a rail break (reasonably) constant in an international perspective?2. Is it (reasonably) constant over a line?3. Can the depth when a rolling contact fatigue crack deviates to a transverse propagation be estimated?4. Is it (reasonably) constant in an international perspective?The answers can briefly be summarized as1. No. Deviations in crack sizes from roughly 10% up to roughly 80% of the railhead area at fracture have been found.2. Not generally, but for some lines this seems to be the case if fractures at the same season are considered (i.e. climate effects are excluded).3. There are indications that this depth is in the order of 5 mm with a fair amount of scatter. However it is very difficult to identify from a photo whether an area of the fracture surface actually corresponds to inclined fatigue crack propagation.4. With a reservation in the considerable scatter, there seems to be some consistency also in an international perspective.Details on how these conclusions were reached are given in the report.
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| 9. |
- Ekberg, Anders, 1967, et al.
(författare)
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Wheel/rail rolling contact fatigue - probe, predict, prevent
- 2012
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Ingår i: Proceedings of the 9th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems (CM2012). ; , s. 29-41
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Konferensbidrag (refereegranskat)abstract
- With the aim of putting prediction and prevention of rolling contact fatigue of wheels and rails in context, the paper sets out with a description of the phenomena. This is followed by a discussion on predictive models with emphasis on influencing factors needed to be accounted for and how these can be incorporated in a predictive model. This forms the basis for a discussion on preventive measures. Finally a brief outlook of expected future trends is given.
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| 10. |
- Ekberg, Anders, 1967, et al.
(författare)
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Wheel/rail rolling contact fatigue – Probe, predict, prevent
- 2014
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Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 314:1-2, s. 2-12
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Tidskriftsartikel (refereegranskat)abstract
- With the aim of putting prediction and prevention of rolling contact fatigue of wheels and rails in context, the paper sets out with a description of the phenomena. This is followed by a discussion on predictive models with emphasis on influencing factors needed to be accounted for and how these can be incorporated in a predictive model of surface and subsurface initiated rolling contact fatigue (RCF). The focus is on predictive models fast enough to be integrated with multibody dynamic simulations of train–track interaction. In particular an attempt is made to highlight how current predictive models of surface initiated RCF can be extended to incorporate all affecting phenomena. The discussion on influencing factors then forms the basis for a discussion on suitable and efficient measures to maintain RCF under control. Finally the paper provides a brief summary on similarities and differences between wheel and rail damage, and an outlook of expected future trends in terms of expected damage patterns and possibilities to meet these.
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| 11. |
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| 12. |
- Kabo, Elena, 1972, et al.
(författare)
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A simplified index for evaluating subsurface initiated rolling contact fatigue from field measurements
- 2011
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 271:1-2, s. 120-124
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Tidskriftsartikel (refereegranskat)abstract
- A previous simplification of the Dang Van equivalent stress measure for assessment of subsurface initiated rolling contact fatigue (RCF) related to wheel-rail contact is modified. The new criterion is intended for real-time assessment of subsurface RCF from measured wheel-rail contact forces. The only needed parameters in the new expression for the equivalent stress are the vertical force and the wheel and rail radii. Comparisons between the new and the original criterion are carried out and show good agreement for the studied cases of tangent track operations. By employing principles of vehicle dynamics the criterion is further extended to the case of operations in curves. Reasonable consistency was found for curve radii down to approximately 2000 m.
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| 13. |
- Kabo, Elena, 1972, et al.
(författare)
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Järnvägen igår, idag, imorgon – hur forskning kan användas
- 2014
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Ingår i: Reflexen. - 0284-0707. ; 2014:3, s. 15-17
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- edan 1850-talet har järnvägen varit en viktig del in samhällets transportsystem. Under den tiden har krav på kapacitet och prestanda ökat radikalt. I denna artikel beskrivs hur forskning har möjliggjort järnvägens utveckling och några framtida krav den ställs inför.
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| 14. |
- Kabo, Elena, 1972, et al.
(författare)
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Rolling contact fatigue prediction for rails and comparisons with test rig results
- 2010
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Ingår i: Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit. - 0954-4097 .- 2041-3017. ; 224:F4, s. 303-317
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Tidskriftsartikel (refereegranskat)abstract
- Tests in a full-scale roller rig, a full-scale linear test rig, and a twin-disc machine are numerically evaluated and compared in terms of rolling contact fatigue loading. From previously evaluated contact patch sizes, a Whler curve relationship is established and matched towards experimentally established fatigue lives. In addition, non-linear finite-element simulations are carried out. Key data needed for the numerical evaluations, as well as difficulties in translating experimental data to numerical models are highlighted. A key parameter here is the interfacial wheel-rail friction. Additional simulations were carried out to establish the latter. However, the conformal contact in the linear test rig makes such simulations very uncertain.
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| 15. |
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| 16. |
- Karttunen, Kalle, 1976, et al.
(författare)
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A numerical study of the influence of lateral geometry irregularities on mechanical deterioration of freight tracks
- 2012
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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. ; 226:F6, s. 575-586
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Tidskriftsartikel (refereegranskat)abstract
- Optimisation of railway track maintenance requires knowledge of how a deteriorated track geometry will affect subsequent loading and damage of the track. This is the scope of the current study where, in particular, the influence on track shift forces and rolling contact fatigue is investigated through numerical simulations. To this end, track geometries are obtained from field measurements. Lateral irregularities are extracted and scaled to represent different levels of geometry deterioration. Multibody simulations of dynamic train-track interaction featuring two freight wagon types are performed under different operational conditions. Track shift forces and rolling contact fatigue damage are further evaluated from simulation results. It is found that track shift forces tend to follow a normal distribution for moderate levels of lateral track geometry irregularities, and that an approximate linear relationship between standard deviations of lateral irregularities and track shift forces can be established. The relation between lateral track irregularity magnitude and rolling contact fatigue is more complex. Increasing levels of lateral irregularities will decrease the fraction of curve length affected by rolling contact fatigue for sharp curves, whereas for shallow curves it increases. As detailed in the article, this is caused by the lateral movement of the contact point as imposed by the track irregularities. Furthermore, the influence of wheel/rail friction and wear is investigated.
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| 17. |
- Karttunen, Kalle, 1976, et al.
(författare)
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Numerical assessment of the influence of worn wheel tread geometry on rail and wheel deterioration
- 2014
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Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 317:1-2, s. 77-91
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Tidskriftsartikel (refereegranskat)abstract
- Current maintenance criteria of railway wheel geometries consider mainly flange thickness, flange height, flange gradient, and depth of tread wear. These geometrical quantities are relatively simple to evaluate, but do not fully describe neither the worn profile nor its influence on subsequent deterioration of wheel and rail. With increased use of automatic wheel profile measurements there is a potential to plan maintenance from measures that provide a more elaborate description of the wheel profile and its operational capabilities. To this end, the paper first outlines a procedure to parametrise worn wheel profiles. This procedure is linked to multibody simulations of a curve negotiating freight wagon to identify parameters of the worn wheel profile with the largest influence on rolling contact fatigue (RCF) and wear. To limit the number of parameter combinations, nearly orthogonal and space filling Latin hypercube sampling is employed. Regression analysis is then utilised to derive simple relationships (meta-models) between geometry parameters and deterioration measures. The derived meta-models of RCF and wear deterioration are shown to produce good agreement to results from fully fledged multibody simulations. The end result is identified geometrical quantities that provide an improved categorisation of the deteriorated wheel tread geometry for improved maintenance decisions.
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| 18. |
- Karttunen, Kalle, 1976, et al.
(författare)
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The influence of lateral track irregularities on track shift forces, rolling contact fatigue and component fatigue
- 2011
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Ingår i: 22nd IAVSD Symposium on Dynamics of Vehicles on Roads and Tracks, 14-19 August, Manchester, UK.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Optimised maintenance of railways requires a knowledge of how a deteriorated track geometry will affectsubsequent loading and damage of the track. In the current study its influence on track shift forces, rolling contactfatigue and component fatigue is investigated through numerical simulations. Multibody simulations incorporatinga track with scaled lateral track irregularities are combined with fatigue evaluations using criteria from the literatureto quantify the progressively increasing track deterioration as lateral irregularities grow.
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| 19. |
- Karttunen, Kalle, 1976, et al.
(författare)
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The influence of track geometry irregularities on rolling contact fatigue
- 2014
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Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 314:1-2, s. 78-86
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Tidskriftsartikel (refereegranskat)abstract
- Optimised maintenance of railway tracks requires knowledge of how a deteriorated track geometry will affect subsequent damage of the track. In this study the influence on rolling contact fatigue (RCF) is investigated through numerical simulations featuring a freight wagon run on tracks with a single track irregularity or with a track irregularity spectrum generated from a power spectral density. Evaluated RCF impact is correlated to the track geometry to identify intrinsic properties of track geometry and irregularities that promote surface initiated RCF. On tangent track, simulations predict a single lateral irregularity with amplitude of 6 mm and length less than 20 m to be sufficient to cause RCF. For operations in shallow curves the simulations indicate that the most efficient RCF mitigation measure is to reduce the longwave content of the lateral irregularities. Furthermore, a study of the relation between track irregularity geometries and resulting wheel forces found a fairly weak correlation.
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| 20. |
- Karttunen, Kalle, 1976, et al.
(författare)
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The influence of track geometry irregularities on rolling contact fatigue
- 2012
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Ingår i: Proceedings of the 9th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems (CM2012). ; , s. 540-546
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Konferensbidrag (refereegranskat)abstract
- Optimised maintenance of railway tracks requires knowledge of how a deteriorated track geometry will affect subsequent damage of the track. In this study the influence on rolling contact fatigue (RCF) is investigated through numerical simula- tions. The numerical simulations employ a vehicle model of a freight wagon run on tracks with a single track irregularity or with irregularities generated from a power spectral density. Evaluated RCF impact is correlated to the track geometry to identify intrinsic properties of track geometry and irregularities that promote surface initiated rolling contact fatigue. On tangent track simulations predict a single lateral irregularity with amplitude of 6 mm and wavelength less than 20 m to be sufficient to cause RCF. For curves with a radius of 1250 metres simulations employing generated lateral irregularities indicate that the most efficient RCF mitigation measure is to reduce the longwave content of the lateral irregularities.
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| 21. |
- Sandström, Johan, 1978, et al.
(författare)
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Deterioration of insulated rail joints – a three-year field study
- 2012
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Ingår i: Proceedings of the 9th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems (CM2012). ; , s. 301-308
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Konferensbidrag (refereegranskat)abstract
- Four operational joints at the Swedish West Coast Line have been monitored in field from installation and during three years of operation to follow degradation. Even though operational loads were comparatively low, material damage was found to occur early after installation. All joints showed a similar damage pattern with dominating deformation on the side towards a nearby station. In addition some joints showed “cavity-like” damage on the off-station side. The paper reports observations on continuing degradation of the joints as well as hardness evolution and increased joint dip over time.
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| 22. |
- Shahzamanian Sichani, Matin
(författare)
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Wheel-rail contact modelling in vehicle dynamics simulation
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The wheel-rail contact is at the core of all research related to vehicle-track interaction. This tiny interface governs the dynamic performance of rail vehicles through the loads it transmits and, like any high stress concentration zone, it is subjected to serious damage phenomena. Thus, a clear understanding of the rolling contact between wheel and rail is key to realistic vehicle dynamic simulation and damage analyses.In a multi-body-system simulation package, the essentially demanding contact problem should be evaluated in about every millisecond. Hence, a rigorous treatment of the contact is highly time consuming. Simplifying assumptions are, therefore, made to accelerate the simulation process. This gives rise to a trade-off between accuracy and computational efficiency of the contact models in use.Historically, Hertz contact solution is used since it is of closed-form. However, some of its underlying assumptions may be violated quite often in wheel-rail contact. The assumption of constant relative curvature which leads to an elliptic contact patch is of this kind. Fast non-elliptic contact models are proposed by others to lift this assumption while avoiding the tedious numerical procedures. These models are accompanied by a simplified approach to treat tangential tractions arising from creepages and spin.In this thesis, in addition to a literature survey presented, three of these fast non-elliptic contact models are evaluated and compared to each other in terms of contact patch, pressure and traction distributions as well as the creep forces. Based on the conclusions drawn from this evaluation, a new method is proposed which results in more accurate contact patch and pressure distribution estimation while maintaining the same computational efficiency. The experience gained through this Licentiate work illuminates future research directions among which, improving tangential contact results and treating conformal contacts are given higher priority.
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| 23. |
- Vernersson, Tore V, 1968, et al.
(författare)
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Wheel fracture - Sensitivity to extreme loads for two generic wheel designs
- 2013
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Ingår i: Proceedings 17th International Wheelset Congress (IWC17). ; , s. 38-47
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Konferensbidrag (refereegranskat)abstract
- The web (disc) of railway wheels is generally designed with respect to mechanical loading by use of standardized load cases. These are assessed using fatigue criteria aiming towards an infinite life. This system of design loads and implemented fatigue criteria has successfully been used over the years and has resulted in that only a very limited number of web failures are reported. Nevertheless, wheel webs are occasionally subjected to fatigue related problems. These are many times associated to substantial wheel tread damage which causes excessive forces. At other occasions, root causes are more unclear. In the present paper, the sensitivity to excessive mechanical loading of two generic wheel designs is studied. Evaluation of fatigue sensitivity shows that wheels of low-stress design can be sensitive to tread damage located towards flange side and/or field side of tread. Study of fatigue crack growth in the web of the wheels indicates slow crack growth for normal running conditions. Moreover, a substantial widening of the crack (in the circumferential direction) is required for the crack to grow deeper into the web.
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| 24. |
- Vernersson, Tore V, 1968, et al.
(författare)
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Wheel tread damage – a numerical study of railway wheel tread plasticity under thermomechanical loading
- 2010
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Ingår i: Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit. - 0954-4097 .- 2041-3017. ; 224:5, s. 435-443
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Tidskriftsartikel (refereegranskat)abstract
- A numerical study is presented where the impact of simultaneous thermal and mechanical loading on a railway wheel tread, as imposed by braking and rolling contact, is reported. A comparison is made of two-dimensional (2D) and 3D finite-element simulations of the thermomechanical problem featuring a material model that accounts for thermal expansion and plastic deformations. It is found that 2D simulations give unrealistic predictions of plastic deformations. The 3D simulations demonstrate a significant influence of the thermal loading also in cases of rather moderate temperature increases. In particular, the combination of thermal loading and high traction is found to be very detrimental.
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