| 1. |
- Andersson, Robin, 1986, et al.
(författare)
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Numerical assessment of the loading of rolling contact fatigue cracks close to rail surface irregularities
- 2020
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Ingår i: Fatigue and Fracture of Engineering Materials and Structures. - : Wiley. - 8756-758X .- 1460-2695. ; 43:5, s. 947-954
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Tidskriftsartikel (refereegranskat)abstract
- Rolling contact fatigue damage of railway rails in the form of squats, characterised by local depressions and cracks located at the rail surface, has been linked to the occurrence of local rail surface irregularities. This study concerns rolling contact fatigue cracks in the vicinity of fairly smooth surface irregularities, here denoted dimples. The influence of factors such as dimple geometry, cluster effects, and crack size is evaluated. To this end, dynamic vehicle–track simulations featuring realistic wheel and rail profiles are employed to characterise the dynamic impact during a wheel passage. The contact load in the vicinity of the dimples is then mapped onto a 3D finite element model of a rail section containing a crack in the rail head. The crack loading is finally quantified by multimodal stress intensity factors. The analyses establish that also shallow dimples might have a significant impact on the crack loading. This effect is increased for larger or multiple irregularities but decreases as the crack grows.
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| 2. |
- Ekberg, Anders, 1967, et al.
(författare)
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Asset management – A brief introduction with focus on the ISO 55000 standard and mechanical deterioration of railway related assets
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The brief introduction focuses on railway related physical assets subjected to significant mechanical deterioration – that is wear and tear. This typically relates to track and railway vehicles that need to be regularly maintained. It discusses management of such assets in the light of the ISO 55000 series of standards. It sets out with an introduction to the ISO 55000 series. This overview is narrowed down to show how knowledge and predictive abilities regarding mechanical deterioration fits into asset management. It is followed by an overview of different modes of mechanical deterioration and failures, and how these can be assessed in risk analyses. A standardised and mandated way of performing risk analyses is the common safety method for risk analyses, which is described in chapter sec:Common-safety-method. The overview is then concluded with some brief comments on railway applications.
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| 3. |
- Ekberg, Anders, 1967, et al.
(författare)
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RAIL AND WHEEL HEALTH MANAGEMENT
- 2022
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Ingår i: CM 2022 - 12th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, Conference Proceedings. ; , s. 179-188
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Konferensbidrag (refereegranskat)abstract
- Rail and wheel health management is investigated with focus on deterioration phenomena in the wheel/rail contact interface – plastic deformation, wear, and rolling contact fatigue (RCF). How operational conditions affect deterioration, and how they can be included in track health predictions is discussed together with a more in-depth description of deterioration mechanisms. Here means of measuring, quantifying, and predicting deterioration is in focus. This provides the basis for the outline of a rail and wheel health management framework. As discussed in the paper, the proposed framework is well in line with the requirements in the ISO 55000 standard for asset management.
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| 4. |
- Ekberg, Anders, 1967, et al.
(författare)
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Rail and wheel health management
- 2023
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Ingår i: Wear. - 0043-1648. ; 526-527
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Tidskriftsartikel (refereegranskat)abstract
- Rail and wheel health management is investigated with focus on deterioration phenomena in the wheel/rail contact interface – plastic deformation, wear, and rolling contact fatigue (RCF). How operational conditions affect deterioration, and how they can be included in wheel/rail health predictions is linked to a more in-depth description of deterioration mechanisms. Here means of measuring, quantifying, and predicting deterioration is in focus. This discussion provides the basis for the outline of a rail and wheel health management framework. As discussed in the paper, the proposed framework is well in line with the requirements in the ISO 55000 standard for asset management.
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| 5. |
- Ekberg, Anders, 1967, et al.
(författare)
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Risk of fatigue of train car chassis due to pressure waves between meeting trains
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The report investigates consequences of modified track spacing on pressure waves induced by meeting high-speed trains. The aim is to investigate consequences in terms of an increased risk of fatigue of car body components and which potential counter-effects may have. The study is intended as a first investigation that should be valid under fairly generic conditions. Simplified analyses are employed due to the generic conditions considered. Under more specified conditions, refined analyses can be employed to improve the analysis and improve quantification of the various mitigating actions.
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| 6. |
- Kabo, Elena, 1972, et al.
(författare)
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Characterisation of track buckling resistance
- 2024
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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. ; in Press
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Tidskriftsartikel (refereegranskat)abstract
- This study sets out with a network-wide analysis of the risk for track buckling that concludes that track buckling relates to a few “weak points” along the track. To identify these, a numerical model to predict track buckling resistance is developed. The influences of key track parameters are evaluated and quantified using the innovative concept of an equivalent temperature. This allows to quantify the large influence of for example, curves and hanging sleepers in terms of an equivalent increase in temperature. Influence of less well-defined track parameters such as nearby fixed points or recent track work is estimated through statistical assessment of track buckling reports. Predicted influence generally agrees with empirical knowledge with some exceptions that are discussed in the report. Developed models and produced results should be valuable in identifying track sections at risk of track buckling and in assessing effectiveness of mitigating actions.
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| 7. |
- Maglio, Michele, 1993, et al.
(författare)
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Influence of railway wheel tread damage on wheel–rail impact loads and the durability of wheelsets
- 2023
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Ingår i: Railway Engineering Science. - 2662-4745 .- 2662-4753. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- Dynamic wheel–rail contact forces induced by a severe form of wheel tread damage have been measured by a wheel impact load detector during full-scale field tests at different vehicle speeds. Based on laser scanning, the measured three-dimensional damage geometry is employed in simulations of dynamic vehicle–track interaction to calibrate and verify a simulation model. The relation between the magnitude of the impact load and various operational parameters, such as vehicle speed, lateral position of wheel–rail contact, track stiffness and position of impact within a sleeper bay, is investigated. The calibrated model is later employed in simulations featuring other forms of tread damage; their effects on impact load and subsequent fatigue impact on bearings, wheel webs and subsurface initiated rolling contact fatigue of the wheel tread are assessed. The results quantify the effects of wheel tread defects and are valuable in a shift towards condition-based maintenance of running gear, and for general assessment of the severity of different types of railway wheel tread damage.
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| 8. |
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| 9. |
- Maglio, Michele, 1993, et al.
(författare)
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Prediction of axle fatigue life based on field measurements
- 2022
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- To facilitate the adoption of a condition-based maintenance approach for railway axles, more knowledge regarding operational loading is needed. In the present work, statistical distributions on axle stresses for revenue vehicles have been derived. To this end, raw strain spectra have been gathered during field measurements using an instrumented telemetry mounted on a powered axle running within the Swedish railway network. Strain spectra are transformed into bending stress spectra which are used to estimate the statistical distributions of axle stresses for different track sections. Both the derived stress spectra and the estimated statistical distributions are used as input to fatigue life analyses. In these analyses, Wöhler (stress–cycle) curves estimated for varying axle surface conditions (which can be related to different axle maintenance conditions) are used to predict axle lives. The proposed method allows to rapidly post-process data obtained during field tests, to quantify indications on the health status of track and of the wheelset from these, and to estimate resulting fatigue life. This would aid in asset management by enhanced status characterisation, improved inspection and maintenance planning, and enhanced possibilities to follow-up any non-conformities.
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| 10. |
- Maglio, Michele, 1993, et al.
(författare)
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Railway wheelset fatigue life estimation based on field tests
- 2022
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Ingår i: Fatigue and Fracture of Engineering Materials and Structures. - : Wiley. - 8756-758X .- 1460-2695. ; 45:9
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Tidskriftsartikel (refereegranskat)abstract
- Field tests using an instrumented powered wheelset were performed to investigate fatigue damage accumulation in railway axles. Axle bending strains were measured and post-processed to obtain axle stress spectra. Statistical analyses were used to investigate the variations of axle stress spectra due to changes in railway operation parameters. The study indicates that measured axle stress spectra can be modeled using truncated normal distributions, where the large majority of measured stress amplitudes are lower than 50 MPa. Stress cycles at higher amplitudes are affected by operation parameters such as track design, number of switches and crossings, and whether the wheelset is in a leading or trailing position. Variations in the obtained statistical distributions of axle stresses have been used as input for fatigue life analyses. It was concluded that fatigue damage can potentially initiate on axles suffering from corrosion or small surface cracks/scratches.
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| 11. |
- Maglio, Michele, 1993, et al.
(författare)
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Relating the influence of track properties to axle load spectra through onboard measurements
- 2024
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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. ; 238:1, s. 3-13
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Tidskriftsartikel (refereegranskat)abstract
- This work aims at investigating how variations in measured stresses are affected by track conditions and, if possible, extract information on track conditions from onboard measurements. Axle bending strains measured in extensive field tests are employed to evaluate axle stress spectra. Correlation between stress spectra and parameters describing track design and condition for three sections of the Swedish mainline “Västra stambanan” have been investigated. The study shows how switches and other discontinuities in the track running surface increase the scatter of the stress spectra and increase the number of overloads. Circular and transition curves mainly increase stress amplitudes with magnitudes close to quasistatic conditions load. A decrease in track quality leads to both a shift of stress spectra towards higher values and a higher number of overloads. The influence of bridges/tunnels and decreased track stiffness were found to be difficult to distinguish from effects of curves, switches and crossings and track quality. If effects exist, they are likely to be small. Results from the study aids future track condition monitoring, maintenance planning of track and running gear, and the estimation of stress spectra for track stretches with known characteristics.
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| 12. |
- Salahi Nezhad, Mohammad, 1993, et al.
(författare)
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NUMERICAL PREDICTION OF ROLLING CONTACT FATIGUE CRACK GROWTH IN A RAILHEAD
- 2022
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Ingår i: CM 2022 - 12th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, Conference Proceedings. ; , s. 428-435
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Konferensbidrag (refereegranskat)abstract
- The influence of crack face friction on predicted crack paths in a 2D rail model is investigated numerically. A surface-breaking inclined rolling contact fatigue crack is propagated under a moving contact load, combined thermal and contact load, and combined (rail) bending and contact. Coulomb crack face friction is included. The growth direction is predicted using an accumulated vector crack tip displacement criterion. Frictional cracks are found to grow deeper into the rail under pure contact load and combined bending and contact while friction has a moderate influence under combined thermal and contact loads. Furthermore, friction reduces crack growth rates.
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| 13. |
- Salahi Nezhad, Mohammad, 1993, et al.
(författare)
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Numerical predictions of crack growth direction in a railhead under contact, bending and thermal loads
- 2022
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Ingår i: Engineering Fracture Mechanics. - : Elsevier BV. - 0013-7944. ; 261
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Tidskriftsartikel (refereegranskat)abstract
- The effect of different operational loading scenarios on predicted crack growth direction for a propagating inclined railhead crack is assessed by 2D finite element simulations. Studied load scenarios include a moving Hertzian contact load, a temperature drop, rail bending due to a passing wheelset, and combinations thereof. The direction of the unbiased crack propagation is predicted using an accumulative vector crack tip displacement criterion. The numerical model is validated for the individual load scenarios. Restraints due to crack face locking are imposed by a threshold parameter, whose influence is also assessed. For combinations of thermal and contact loads, the predicted crack path is found to diverge gradually from transverse growth, corresponding to pure thermal loading, to shallow growth, corresponding to a pure contact load. For combined bending and contact loading, there is a discrete jump in the predicted crack direction as the contact load increased while the bending load is kept constant. These results are well aligned with empirical experience.
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| 14. |
- Steyn, Erika, 1990, et al.
(författare)
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Rail machining - current practices and potential for optimisation
- 2024
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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. ; 238:2, s. 196-205
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Tidskriftsartikel (refereegranskat)abstract
- Current practices on rail machining show large variations in strategies and amount of grinding and milling. To identify reasons for this and suggest strategies to further optimise rail machining, objectives of machining are scrutinised and consequences of not fulfilling objectives are investigated. This leads to a discussion on potentially detrimental effects of rail machining and how to minimise these. With this background, general aspects of rail machining optimisation are discussed. The study shows several means to improve rail machining, but also how the potential is restricted by the current lack of knowledge and predictive models. This prevents quantifying benefits of innovative solutions, and complicates transfer of knowledge between different operational conditions and translations of (scaled and controlled) test results to (full-scale, uncontrolled) operational conditions.
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