| 1. |
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| 2. |
- Fridell, Erik, 1963, et al.
(författare)
-
Emissions of particulate matter from railways – onboard and tunnel measurements
- 2009
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- There are increasing concerns about health risks associated with high levels of particulate matter in air. A major source of these particles is combustion engines but also particles originating from wear of material can be important. It is in this context of interest to study particle emissions from railways. A number of studies have reported high concentrations of particles in underground stations and subways. There are few studies reporting levels of particles in railway environments above ground and no studies reporting emission factors or the variability in emissions with driving pattern.In the report a number of measurements of particle emissions from railway are presented. In the first part of the report, results from tunnel measurements where abrasion particles from different types of trains are measured in two campaigns are reported. Further, emission factors are calculated from these measurements. In the second part of the project, measurements were done with instruments positioned under a train. This provided information on how the particle emissions vary with driving patterns.
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| 3. |
- Fridell, Erik, 1963, et al.
(författare)
-
On-board measurements of particulate matter emissions from a passenger train
- 2011
-
Ingår i: Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit. - 0954-4097 .- 2041-3017. ; 225:1, s. 99-106
-
Tidskriftsartikel (refereegranskat)abstract
- A number of measurements of particle emission from railways are presented. The measurements featured a particle instrument mounted in a compartment under a Regina train. The particles were probed in a volume between the coaches. The measurements were done in two campaigns and provide information on how the particle emissions vary with driving patterns. The measurements showed elevated particle concentrations when the train was running. Further, sharp peaks in the particle concentration were observed. It was noted that these peaks coincided with retardation of the train. However, there are also retardations where no peaks were observed. This can be explained from the two parallel breaking systems, one with regenerative breaking and one with mechanical breaks that are present on the Regina train. It is suggest that the observed peaks coincide with the use of the mechanical breaks. It was not possible to fully establish that increased particle concentration coincides with curvature of the rail, even though this was indicated in parts of the data. The size-resolved data showed maxima for the smallest fraction (350 nm) for the number distribution.
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| 4. |
- Fröidh, Oskar, et al.
(författare)
-
Färdplan för ökad forskning och innovation inom underhåll av järnvägsfordon
- 2015
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- KTH, Chalmers och Handelshögskolan vid Göteborgs universitet har av Trafikverket fått uppdraget att ta fram ett dokument om forskningen inom underhåll av järnvägsfordon. Det är föreliggande färdplan som ingår i Trafikverkets satsning Morgondagens depåer. Färdplanen ska ligga till grund för en strategi och förslag på utveckling för kostnadseffektivt fordonsunderhåll med de förutsättningar som råder i Sverige, med avreglering och många aktörer i branschen likväl som speciella klimatförutsättningar. Trafikverket har uppmärksammat att frågor om depåer och fordonsunderhåll inte alltid hanteras på ett bra sätt för att utveckla järnvägssystemet. Tidigare hade Banverket ett sektorsansvar men det avskaffades i och med att Trafikverket bildades. Det behövs dock ett övergripande systemansvar och incitament för att leda processen framåt mot en stabil utveckling genom forskning, utveckling och innovation i den fortsatta omreglering som sker av den svenska järnvägssektorn. Hur kan en effektiv samverkan mellan universitet, näringsliv och offentlig sektor utformas för att bidra till en säker och pålitlig tågtrafik i Sverige? En litteraturgenomgång har genomförts för att visa var den internationella forskningsfronten står. Det tycks dock som att det samlade greppet inom underhåll av järnvägsfordon inte är ett genomarbetat forskningsområde, utan det kan bli ett svenskt ”pionjärområde” där universitet, högskolor och institut i samarbete med branschen kan skapa forskningsresultat och kunskapsutveckling. Denna färdplan föreslår ett antal olika områden som skulle behöva ökad forskning för större kunskap och kompetens. Var ska depåer för person- respektive godsfordon mest effektivt lokaliseras, centralt eller perifert i jämförelse med trafiksystemet och respektive omlopp? Hur ska de utformas mest effektivt med tanke på fordonstyper, reservdelar och personalutnyttjande? Hur ska infrastrukturen till och internt i depåerna utformas för effektivt arbete? Detta ska ske i en avreglerad järnvägssektor med olika operatörer, vagnägare, depåägare samt underhållsleverantörer på olika långa kontrakt. Hur ska detta organiseras på ett stabilt sätt med långsiktig ekonomisk bärkraft för samtliga parter? Arbetet går att dela upp i avhjälpande och förebyggande underhåll; i depå eller mobilt, med säkerhets-, drifts- eller komfortrelaterat underhåll. På vilka olika sätt går det att utvärdera samt utveckla modeller för att prognostisera behovet av underhåll enligt ovan nämnda variabler? Målet är att ta fram vetenskapliga metoder för att effektivisera fordonsunderhåll för järnvägstrafiken på ett optimalt sätt. I färdplanen rekommenderas en strategi för fordonsunderhåll: Trafikverket ska verka för att efterfrågad funktion i det svenska järnvägssystemet uppnås, inkluderande kostnadseffektivt underhåll av både infrastruktur och fordon. Hög driftsäkerhet är attraktivt för resenärer och godskunder och har ett värde och motiverar ett samhällsekonomiskt synsätt på underhåll av järnvägsfordon. Tillståndsövervakning och relaterad prediktering ges en viktigare roll för förebyggande underhåll. Öka synergin mellan infrastruktur- och fordonsbaserad tillståndsövervakning, inte minst av den dynamiska samverkan mellan infrastruktur och fordon. Utred hur ”intelligensen” hos infrastruktur och fordon bäst fördelas och utvecklas för ett mera kostnadseffektivt underhåll av järnvägssystemet. Detta innefattar att man vet vad man skall mäta och att uppmätta storheter kan länkas till framtida nedbrytning av fordon och infrastruktur. Utred flödet och ”flaskhalsar” i dagens system av fordonsunderhåll (kritiska aspekter). Utveckla distinktionen av säkerhetsnödvändigt underhåll och komfortrelaterat underhåll. Verka för tydliga och rimliga ”spelregler” för aktörer inom fordonsunderhåll. Förbättra nätverket bland dessa aktörer, inte minst kring tekniska frågor. Skapa ytterligare incitament för effektivt fordonsunderhåll genom att se över kostnader och intäkter i intressentkedjan mellan de primära kunderna och de som kan åtgärda problemen. Lyft fram goda exempel (best practice) på väl fungerande fordonsunderhåll. Låt universitet och högskolor få en viktig och neutral roll i den kunskapsbaserade utvecklingen. Detta bör ske genom att skapa ett forsknings- utvecklings- och demonstrations (FUD)-program inom området underhåll för järnvägsfordon. I denna färdplan föreslås även ett antal olika forskningsprojekt och -områden som skulle kunna utvecklas i ett sammanhållet forskningsprogram.
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| 5. |
- Fröidh, Oskar, et al.
(författare)
-
Färdplan för ökad forskning och innovation inom underhåll av järnvägsfordon
- 2015
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- KTH, Chalmers och Handelshögskolan vid Göteborgs universitet har av Trafikverket fått uppdraget att ta fram ett dokument om forskningen inom underhåll av järnvägsfordon. Det är föreliggande färdplan som ingår i Trafikverkets satsning Morgondagens depåer. Färdplanen ska ligga till grund för en strategi och förslag på utveckling för kostnadseffektivt fordonsunderhåll med de förutsättningar som råder i Sverige, med avreglering och många aktörer i branschen likväl som speciella klimatförutsättningar.Trafikverket har uppmärksammat att frågor om depåer och fordonsunderhåll inte alltid hanteras på ett bra sätt för att utveckla järnvägssystemet. Tidigare hade Banverket ett sektorsansvar men det avskaffades i och med att Trafikverket bildades. Det behövs dock ett övergripande systemansvar och incitament för att leda processen framåt mot en stabil utveckling genom forskning, utveckling och innovation i den fortsatta omreglering som sker av den svenska järnvägssektorn. Hur kan en effektiv samverkan mellan universitet, näringsliv och offentlig sektor utformas för att bidra till en säker och pålitlig tågtrafik i Sverige?En litteraturgenomgång har genomförts för att visa var den internationella forskningsfronten står. Det tycks dock som att det samlade greppet inom underhåll av järnvägsfordon inte är ett genomarbetat forskningsområde, utan det kan bli ett svenskt ”pionjärområde” där universitet, högskolor och institut i samarbete med branschen kan skapa forskningsresultat och kunskapsutveckling.Denna färdplan föreslår ett antal olika områden som skulle behöva ökad forskning för större kunskap och kompetens. Var ska depåer för person- respektive godsfordon mest effektivt lokaliseras, centralt eller perifert i jämförelse med trafiksystemet och respektive omlopp? Hur ska de utformas mest effektivt med tanke på fordonstyper, reservdelar och personalutnyttjande? Hur ska infrastrukturen till och internt i depåerna utformas för effektivt arbete? Detta ska ske i en avreglerad järnvägssektor med olika operatörer, vagnägare, depåägare samt underhållsleverantörer på olika långa kontrakt. Hur ska detta organiseras på ett stabilt sätt med långsiktig ekonomisk bärkraft för samtliga parter? Arbetet går att dela upp i avhjälpande och förebyggande underhåll; i depå eller mobilt, med säkerhets-, drifts- eller komfortrelaterat underhåll. På vilka olika sätt går det att utvärdera samt utveckla modeller för att prognostisera behovet av underhåll enligt ovan nämnda variabler? Målet är att ta fram vetenskapliga metoder för att effektivisera fordonsunderhåll för järnvägstrafiken på ett optimalt sätt.I färdplanen rekommenderas en strategi för fordonsunderhåll:Trafikverket ska verka för att efterfrågad funktion i det svenska järnvägssystemet uppnås, inkluderande kostnadseffektivt underhåll av både infrastruktur och fordon.Hög driftsäkerhet är attraktivt för resenärer och godskunder och har ett värde och motiverar ett samhällsekonomiskt synsätt på underhåll av järnvägsfordon.Tillståndsövervakning och relaterad prediktering ges en viktigare roll för förebyggande underhåll.Öka synergin mellan infrastruktur- och fordonsbaserad tillståndsövervakning, inte minst av den dynamiska samverkan mellan infrastruktur och fordon.Utred hur ”intelligensen” hos infrastruktur och fordon bäst fördelas och utvecklas för ett mera kostnadseffektivt underhåll av järnvägssystemet. Detta innefattar att man vet vad man skall mäta och att uppmätta storheter kan länkas till framtida nedbrytning av fordon och infrastruktur.Utred flödet och ”flaskhalsar” i dagens system av fordonsunderhåll (kritiska aspekter).Utveckla distinktionen av säkerhetsnödvändigt underhåll och komfortrelaterat underhåll.Verka för tydliga och rimliga ”spelregler” för aktörer inom fordonsunderhåll.Förbättra nätverket bland dessa aktörer, inte minst kring tekniska frågor.Skapa ytterligare incitament för effektivt fordonsunderhåll genom att se över kostnader och intäkter i intressentkedjan mellan de primära kunderna och de som kan åtgärda problemen.Lyft fram goda exempel (best practice) på väl fungerande fordonsunderhåll.Låt universitet och högskolor få en viktig och neutral roll i den kunskapsbaserade utvecklingen.Detta bör ske genom att skapa ett forsknings- utvecklings- och demonstrations (FUD)-program inom området underhåll för järnvägsfordon. I denna färdplan föreslås även ett antal olika forskningsprojekt och -områden som skulle kunna utvecklas i ett sammanhållet forskningsprogram.
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| 6. |
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| 7. |
- Vesterlund, Anna, 1980, et al.
(författare)
-
Characterization of strong 241Am sources
- 2015
-
Ingår i: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043 .- 1872-9800. ; 99, s. 162-167
-
Tidskriftsartikel (refereegranskat)abstract
- Gamma ray spectra of strong 241Am sources may reveal information about the source composition as there may be other radioactive nuclides such as progeny and radioactive impurities present. In this work the possibility to use gamma spectrometry to identify inherent signatures in 241Am sources in order to differentiate sources from each other, is investigated. The studied signatures are age, i.e. time passed since last chemical separation, and presence of impurities. The spectra of some sources show a number of Doppler broadened peaks in the spectrum which indicate the presence of nuclear reactions on light elements within the sources. The results show that the investigated sources can be differentiated between by age and/or presence of impurities. These spectral features would be useful information in a national nuclear forensics library (NNFL) in cases when the visual information on the source, e.g. the source number, is unavailable.
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| 8. |
- Vesterlund, Anna, 1980, et al.
(författare)
-
Characterization of strong 241Am sources
- 2014
-
Ingår i: International Conference on Advances in Nuclear Forensics: Countering the Evolving Threat of Nuclear and Other Radioactive Material out of Regulatory Control, Vienna, IAEA; 07/2014.
-
Konferensbidrag (refereegranskat)
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| 9. |
- Aggestam, Emil, 1992, et al.
(författare)
-
Innovative requirements and evaluation methods for slab track design
- 2024
-
Ingår i: Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit. - 0954-4097 .- 2041-3017. ; 238:6, s. 651-661
-
Tidskriftsartikel (refereegranskat)abstract
- With increasing train speeds and reduced time windows for maintenance work, the interest in the application of slab track technology to increase the capacity of high-speed railways has grown. Slab track may still be considered a relatively young technology, but with several different designs available on the market. Current research on slab tracks commonly focuses on improved methods. In contrast, the formulation of requirements, and evaluation towards these, are seldom investigated. In this paper, state-of-the-art simulation models are employed to illustrate and address the needs for innovative requirements in terms of structural integrity and robustness, life cycle cost (LCC) and environmental footprint of new and existing slab track designs. Based on demonstration examples, it is argued that current standards may lead to overly conservative designs inducing higher LCC and environmental footprint than necessary. Extensions of the standards in terms of LCC and environmental footprint are suggested. The conflict of interest between structural integrity and robustness, LCC and environmental footprint is discussed, and suggestions for how to optimise slab track structures are proposed.
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| 10. |
- Aggestam, Emil, 1992, et al.
(författare)
-
Optimisation of slab track design considering dynamic train–track interaction and environmental impact
- 2022
-
Ingår i: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 254
-
Tidskriftsartikel (refereegranskat)abstract
- Modern railway tracks for high-speed traffic are often built based on a slab track design. A major disadvantage of slab track compared to conventional ballasted track is that the environmental impact of the construction is higher due to the significant amount of concrete required. In this paper, the dimensions of the rectangular cross-sections and the types of concrete used in slab tracks are optimised with the objective to minimise greenhouse gas emissions, while considering the constraint that the design must pass the static dimensioning analysis described in the European standard 16432-2. The optimised track design is also analysed using a three-dimensional (3D) model of vertical dynamic vehicle–track interaction, where the rails are modelled as Rayleigh–Timoshenko beams and the concrete parts are represented by quadratic shell elements. Wheel–rail contact forces and the time-variant stress field of the concrete parts are calculated using a complex-valued modal superposition for the finite element model of the track. For the studied traffic scenario, it is concluded that the thickness of the panel can be reduced compared to the optimised design from the standard without the risk of crack initiation due to the dynamic vehicle load. In parallel, a model of reinforced concrete is developed to predict crack widths, the bending stiffness of a cracked panel section and to assess in which situations the amount of steel reinforcement can be reduced. To reduce the environmental impact even further, there is potential for an extended geometry optimisation by excluding much of the concrete between the rails.
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| 11. |
- Ahlström, Johan, 1969, et al.
(författare)
-
Temperature-dependent evolution of the cyclic yield stress of railway wheel steels
- 2016
-
Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 366:SI, s. 378-382
-
Tidskriftsartikel (refereegranskat)abstract
- The evolution of the cyclic yield stress for a railway wheel steel (UIC ER7T) during cyclic plastic straining has been characterized at different temperatures from -60 to 600 °C. Different constant strain amplitude levels were examined and for temperatures above 200 °C, hold periods were included to study stress relaxation during constant compressive strain. The results are of use in predicting material deformation and damage. This is demonstrated by the application to improve a criterion for surface initiated rolling contact fatigue damage.
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| 12. |
- Ahlström, Johan, 1969, et al.
(författare)
-
Temperature-dependent evolution of the cyclic yield stress of railway wheel steels
- 2015
-
Ingår i: Proceedings of the 10th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems (CM2015).
-
Konferensbidrag (refereegranskat)abstract
- The evolution of the cyclic yield stress for a railway wheel steel (UIC ER7T) during cyclic plastic straining has been characterized at different temperatures from -60 – 600°C. Two strain amplitude levels were examined and for temperatures above 200°C, hold periods were included to study stress relaxation during constant compressive strain. The results are of use in predicting material deformation and damage. This is demonstrated by the application to improve a criterion for surface initiated rolling contact fatigue damage.
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| 13. |
- Andersson, Robin, 1986, et al.
(författare)
-
Integrated analysis of dynamic vehicle-track interaction and plasticity induced damage in the presence of squat defects
- 2015
-
Ingår i: Proceedings of the 10th International International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, Colorado Springs, USA, August-September 2015.
-
Konferensbidrag (refereegranskat)abstract
- Despite significant efforts, the mechanisms behind the formation of squats – a form of rolling contact fatigue damage – are not fully understood. This study employs numerical simulations to investigate the propensity of squat initiation in the vicinity of small, isolated rail surface irregularities. Time domain dynamic vehicle–track interaction analysis is used to obtain wheel–rail contact stress distributions, which are mapped onto a continuum finite element model that accounts for plastic deformation of the rail material. The evaluated stress and strain fields are quantified using two RCF impact measures: accumulated effective strain and the Jiang-Sehitoglu multiaxial low cycle fatigue parameter. It is shown that the RCF impact increases with increasing size of the surface irregularity and that clustering of irregularities might strongly promote RCF. The friction coefficient is identified as a very influential parameter. Further, the effect of variations in friction along the rail is evaluated. It is shown that a short rail section of low friction results in fairly high RCF impact.
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| 14. |
- Andersson, Robin, 1986, et al.
(författare)
-
Integrated analysis of dynamic vehicle–track interaction and plasticity induced damage in the presence of squat defects
- 2016
-
Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 366-367:SI, s. 139-145
-
Tidskriftsartikel (refereegranskat)abstract
- Despite significant efforts, the mechanisms behind the formation of squats – a form of rolling contact fatigue (RCF) damage – are not fully understood. This study employs numerical simulations to investigate the propensity of squat initiation in the vicinity of small, isolated rail surface irregularities. Time-domain dynamic vehicle–track interaction analysis is used to obtain wheel–rail contact stress distributions, which are mapped onto a continuum finite element model that accounts for plastic deformation of the rail material. The evaluated stress and strain fields are quantified using two RCF impact measures: accumulated effective strain and the Jiang–Sehitoglu multiaxial low cycle fatigue parameter. It is shown that the RCF impact increases with increasing size of the surface irregularity and that clustering of irregularities might strongly promote RCF. The friction coefficient is identified as a very influential parameter and also the effect of variations in friction along the rail is evaluated.
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| 15. |
- Andersson, Robin, 1986, et al.
(författare)
-
Numerical assessment of the loading of rolling contact fatigue cracks close to rail surface irregularities
- 2020
-
Ingår i: Fatigue and Fracture of Engineering Materials and Structures. - : Wiley. - 8756-758X .- 1460-2695. ; 43:5, s. 947-954
-
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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| 16. |
- Andersson, Robin, 1986, et al.
(författare)
-
Numerical investigation of crack initiation in rails and wheels affected by martensite spots
- 2018
-
Ingår i: International Journal of Fatigue. - : Elsevier BV. - 0142-1123. ; 114, s. 238-251
-
Tidskriftsartikel (refereegranskat)abstract
- White etching layers (WELs) in the form of thermally induced martensite spots are often associated to so-called stud defects on rail surfaces and so-called rolling contact fatigue clusters on wheel treads. These defects might promote further material deterioration of rails and wheels and it is thus of importance to deepen the knowledge regarding their initiation mechanisms. The aim of this study is to gain insight into the problem by making qualitative assessments of different operational scenarios, involving various axle loads and amount of friction. To this end, this paper considers crack initiation, quantified through the Jiang–Sehitoglu low cycle fatigue criterion, in the vicinity of pre-existing WELs (in the form of martensite spots) subjected to varying contact load conditions. Three-dimensional finite element analyses are conducted to model phase transformations as well as the resulting residual stresses. It is seen that the contact pressure magnitude and WEL thickness affect the results only moderately, while the traction coefficient has a significant detrimental influence. It is furthermore seen that occasional wheel passages that are off-set in the lateral direction with respect to the WEL spot’s centre might be responsible for crack initiation on the gauge corner side of the rail surface.
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| 17. |
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| 18. |
- Baumann, Pia, et al.
(författare)
-
Outcome in a prospective phase II trial of medically inoperable stage I non-small-cell lung cancer patients treated with stereotactic body radiotherapy.
- 2009
-
Ingår i: Journal of clinical oncology : official journal of the American Society of Clinical Oncology. - 1527-7755 .- 0732-183X. ; 27:20, s. 3290-6
-
Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: The impact of stereotactic body radiotherapy (SBRT) on 3-year progression-free survival of medically inoperable patients with stage I non-small-cell lung cancer (NSCLC) was analyzed in a prospective phase II study. PATIENTS AND METHODS: Fifty-seven patients with T1NOMO (70%) and T2N0M0 (30%) were included between August 2003 and September 2005 at seven different centers in Sweden, Norway, and Denmark and observed up to 36 months. SBRT was delivered with 15 Gy times three at the 67% isodose of the planning target volume. RESULTS: Progression-free survival at 3 years was 52%. Overall- and cancer-specific survival at 1, 2, and 3 years was 86%, 65%, 60%, and 93%, 88%, 88%, respectively. There was no statistically significant difference in survival between patients with T1 or T2 tumors. At a median follow-up of 35 months (range, 4 to 47 months), 27 patients (47%) were deceased, seven as a result of lung cancer and 20 as a result of concurrent disease. Kaplan-Meier estimated local control at 3 years was 92%. Local relapse was observed in four patients (7%). Regional relapse was observed in three patients (5%). Nine patients (16%) developed distant metastases. The estimated risk of all failure (local, regional, or distant metastases) was increased in patients with T2 (41%) compared with those with T1 (18%) tumors (P = .027). CONCLUSION: With a 3-year local tumor control rate higher than 90% with limited toxicity, SBRT emerges as state-of-the-art treatment for medically inoperable stage I NSCLC and may even challenge surgery in operable instances.
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| 19. |
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| 20. |
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| 21. |
- Caprioli, Sara, 1978, et al.
(författare)
-
Influence of short thermal cracks on the material behaviour of a railway wheel subjected to repeated rolling
- 2014
-
Ingår i: Advanced Materials Research. - 1662-8985 .- 1022-6680. - 9783038350088 ; 891-892, s. 1139-1145
-
Konferensbidrag (refereegranskat)abstract
- An analysis of whether and how the occurrence of shallow (radial) thermal cracks promotes additional plastic deformation of a mechanically loaded wheel tread is carried out. The study employs numerical simulations of a 2D slice of an elastoplastic railway wheel tread containing thermal (radial) cracks. The cracked wheel material is subjected to repeated passes of a frictional rolling contact load. The effect of the existing thermal cracks on bulk deformation and subsequent rolling contact promoted growth is quantified. Results indicate that thermal cracks of a depth of 0.1 mm have a negligible effect, whereas 1.0 mm cracks significantly decrease the bulk resistance of the wheel material. Further, it is shown how the magnitude of stress, strain and deformation depends on the direction of applied traction.
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| 22. |
- Caprioli, Sara, 1978, et al.
(författare)
-
Numerical evaluation of the material response of a railway wheel under thermomechanical braking conditions
- 2012
-
Ingår i: Proceedings of the 9th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems (CM2012). ; , s. 460-467
-
Konferensbidrag (refereegranskat)abstract
- The material response of a railway wheel subjected to thermomechanical rolling contact is evaluated. Thermal and mechanical loads are combined in a three-dimensional sequentially coupled analysis where nodal temper- atures from a transient thermal analysis are applied as predefined fields in a structural analysis featuring an elastic-plastic material model. The mechanical contact load is prescribed as a moving Hertzian contact stress distribution with a surface shear stress distribution corresponding to full or partial slip conditions. Modelling aspects studied in detail are feasible model resolution at the contact patch, the influence of sequences of thermal and mechanical loads, and the influence of wheel–rail interfacial shear distributions. The study identifies fea- sible mesh sizes and load application strategies to obtain a good accuracy at reasonable computational efforts. Further, differences in predicted material response under full slip and partial slip conditions are assessed. It is found that for a given total tangential force, partial slip conditions result in larger plastic strain magnitudes in a thin layer near the contact surface.
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| 23. |
- Caprioli, Sara, 1978, et al.
(författare)
-
Numerical evaluation of the material response of a railway wheel under thermomechanical braking conditions
- 2014
-
Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 314:1-2, s. 181-188
-
Tidskriftsartikel (refereegranskat)abstract
- The material response of a railway wheel subjected to thermomechanical rolling contact is evaluated. Thermal and mechanical loads are combined in a three-dimensional sequentially coupled analysis where nodal temperatures from a transient thermal analysis are applied as predefined fields in a structural analysis featuring an elastic-plastic material model. The mechanical contact load is prescribed as a moving Hertzian contact stress distribution with a surface shear stress distribution corresponding to full or partial slip conditions. Modelling aspects studied in detail are feasible model resolution at the contact patch, the influence of sequences of thermal and mechanical loads, and the influence of wheel--rail interfacial shear distributions. The study identifies feasible mesh sizes and load application strategies to obtain a good accuracy at reasonable computational efforts. Further, differences in predicted material response under full slip and partial slip conditions are assessed. It is found that for a given total tangential force, partial slip conditions result in larger plastic strain magnitudes in a thin layer near the contact surface
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| 24. |
- Caprioli, Sara, 1978, et al.
(författare)
-
Thermal Cracking of a Railway Wheel Tread due to Tread Braking – Critical Crack Sizes
- 2011
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Ingår i: Proceedings 2011 International Heavy Haul Association Conference. ; , s. 8-
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A numerical study of tread cracking due to thermal loading induced by tread braking is carried out. The analysis features a computationally efficient approach combining 2D FE-simulations with an analytical evaluation of resulting stress intensity factors. The analysis identifies critical sizes for when existing surface cracks are prone to propagate under thermal loading and resulting crack lengths after propagation. The results imply that fully functional brake systems are not likely to induce thermal crack propagation under normal stop braking, but that with pre-existing defects a severe drag braking due to malfunctioning brakes may cause very deep cracking. Further the analysis concludes the cracking to be a static phenomenon related to the most severe brake cycle, i.e. later brake cycles of similar or lower severity will not cause any significant propagation of existing cracks. Preliminary 3D FE-simulations that have been performed indicate the presented results to be conservative.
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| 25. |
- Caprioli, Sara, 1978, et al.
(författare)
-
Thermal cracking of a railway wheel tread due to tread braking -- critical crack sizes and influence of repeated thermal cycles
- 2013
-
Ingår i: Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit. - : SAGE Publications. - 0954-4097 .- 2041-3017. ; 227:1, s. 10-18
-
Tidskriftsartikel (refereegranskat)abstract
- A numerical study of tread cracking due to thermal loading induced by tread braking is carried out. The analysis features a computationally efficient approach combining two-dimensional finite-element simulations with an analytical evaluation of resulting stress intensity factors. The analysis identifies critical sizes for when existing surface cracks are prone to propagate under thermal loading and resulting crack lengths after propagation. The results imply that fully functional brake systems are not likely to induce thermal crack propagation under normal stop braking, but that with pre-existing defects, a severe drag braking due to malfunctioning brakes may cause very deep cracking. Furthermore, the analysis concludes the cracking to be a static phenomenon related to the most severe brake cycle, i.e. later brake cycles of similar or lower severity will not cause any significant propagation of existing cracks. Additional three-dimensional finite-element simulations are used to validate the model, and they indicate two-dimensional results to be on the conservative side.
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| 26. |
- Caprioli, Sara, 1978, et al.
(författare)
-
Thermal cracking of a railway wheel tread due to tread braking – critical crack sizes and influence of repeated thermal cycles
- 2011
-
Ingår i: International Heavy Haul Association Special Technical Session (IHHA STS 2011). ; , s. 8-
-
Konferensbidrag (refereegranskat)abstract
- A numerical study of tread cracking due to thermal loading induced by block braking is carried out. The analysis features a computationally efficient approach combining 2D FE-simulations with an analytical evaluation of resulting stress intensity factors. The analysis identifies critical sizes for when existing surface cracks are prone to propagate under thermal loading and resulting crack lengths after propagation. The results imply that fully functional brake systems are not likely to induce thermal crack propagation under normal stop braking, but that with pre-existing defects a severe drag braking due to malfunctioning brakes may cause very deep cracking. Further the analysis concludes the cracking to be a static phenomenon related to the most severe brake cycle, i.e. later brake cycles of similar or lower severity will not cause any significant propagation of existing cracks. Finally it should be noted that preliminary FE-simulations that have been performed indicate the presented results to be conservative.
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| 27. |
- Caprioli, Sara, 1978, et al.
(författare)
-
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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| 28. |
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| 29. |
- Deuce, Roger, et al.
(författare)
-
Mechanical deterioration of wheels and rails under winter conditions – mechanisms and consequences
- 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. 640-648
-
Tidskriftsartikel (refereegranskat)abstract
- This study focuses on identifying and understanding the core phenomena behind winter-related issues with regard to railways. State-of-the-art knowledge regarding the mechanical deterioration of wheels and rails is employed to obtain a first estimation of the influence of the different phenomena and to find out under which circumstances they are influential. The interaction between these different phenomena is discussed, as this additional level of complexity is necessary to develop a complete understanding.
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| 30. |
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| 31. |
- Dirks, Babette, et al.
(författare)
-
The development of a crack propagation model for railway wheels and rails
- 2015
-
Ingår i: Fatigue and Fracture of Engineering Materials and Structures. - : Wiley. - 8756-758X .- 1460-2695. ; 38:12, s. 1478-1491
-
Tidskriftsartikel (refereegranskat)abstract
- Rolling contact fatigue (RCF) and wear of railway wheels and rails are the main phenom-ena that affect their m aintenance costs. When crack propagation and wear rates can bepredicted, maintenance planning can be optimised, and cost-effective measures can bedeveloped. Several RCF models exist, but none which can be used in combination withvehicle dynamics simulations and can predict the actual crack depth. This study showsthe development of a crack propagation model that can be applied for both railwaywheels and rails. Two unknow n material parameters in the model were calibrated againstcrack measurements in a curve on the Dutch railways over a period of 5 years. Two dif-ferent RCF models were used to calculate the stress magnitudes for the propagationmodel. The propagation model can be used in combination with vehicle-track dynamicssimulations and shows promise in predicting the actual crack depth and/or surface length.Further research is needed to determine the model’s validity for other operationalconditions.
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| 32. |
- Draganis, Andreas, 1984, et al.
(författare)
-
An Arbitrary Lagrangian Eulerian Formulation For Simulation Of Wheel-Rail Contact
- 2010
-
Ingår i: Proceedings of NSCM-23: the 23rd Nordic Seminar on Computational Mechanics, Anders Eriksson, Gunnar Tibert, 21-22 Oktober, 2010, KTH, Stockholm. - 0348-467X. ; 2010, s. 173-176
-
Konferensbidrag (refereegranskat)abstract
- A novel ALE-formulation of a rolling wheel is presented in the context of finite element simulations. Numerical examples illustrate the proposed strategy for a two-dimensionalproblem.
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| 33. |
- Draganis, Andreas, 1984, et al.
(författare)
-
Finite element analysis of transient thermomechanical rolling contact using an efficient arbitrary Lagrangian-Eulerian description
- 2014
-
Ingår i: Computational Mechanics. - : Springer Science and Business Media LLC. - 1432-0924 .- 0178-7675. ; 54:2, s. 389-405
-
Tidskriftsartikel (refereegranskat)abstract
- A theoretical and computational framework for the analysis of thermomechanically coupled transient rolling contact, based on an arbitrary Lagrangian-Eulerian (ALE) kinematical description, is developed. A finite element formulation featuring 2D cylinder-plate rolling contact is implemented. The implementation features penalty-type contact formulations for mechanical and thermal contact. It is noted that the ALE formulation allows for a simplified time description, a compact computational domain and localized mesh refinement. Numerical simulations considering stationary and transient rolling conditions are presented. Highlighted aspects include the influence of variations in thermal contact conductivity, rolling speed and external mechanical load on the contact interface heat flow. The model is shown to give predictions in qualitative agreement with results in the literature. For the velocity range studied, numerical issues such as spurious numerical dissipation/oscillations in the temperature field are noted to have a prominent influence. These phenomena are addressed using a Streamline-Upwind Petrov-Galerkin stabilization scheme together with a bubble function approach.
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| 34. |
- Draganis, Andreas, 1984, et al.
(författare)
-
Finite element modelling of frictional thermomechanical rolling/sliding contact using an arbitrary Lagrangian-Eulerian formulation
- 2015
-
Ingår i: Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology. - : SAGE Publications. - 1350-6501 .- 2041-305X. ; 229:7, s. 870-880
-
Tidskriftsartikel (refereegranskat)abstract
- A theoretical and computational framework for the analysis of thermomechanically coupled, frictional, stationary (steady-state) rolling contact based on an Arbitrary Lagrangian-Eulerian (ALE) kinematical description is presented. The finite element method is employed in a numerical implementation featuring two-dimensional cylinder-plate rolling contact, with a contact formulation incorporating mechanical and thermal frictional interaction. The ALE formulation is noted to allow for linearization of the governing equations, localized mesh refinement, a time-independent description of stationary dynamics, velocity-independent contact interface modelling and so on. Numerical simulations show the model to be able to capture, for example, stick/slip behaviour and a range of thermal phenomena, including the effect of convective cooling of the cylinder due to the contact with the plate.
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| 35. |
- Draganis, Andreas, 1984, et al.
(författare)
-
Modelling the thermomechanical wheel–rail interface during rolling contact
- 2012
-
Ingår i: Proceedings of the 9th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems (CM2012).
-
Konferensbidrag (refereegranskat)abstract
- A theoretical and computational framework for the analysis of thermomechanically coupled transient rolling contact based on an arbitrary Lagrangian–Eulerian (ALE) kinematical description is developed. A finite element formulation featuring 2D cylinder–plate rolling contact is implemented. The implementation features penalty- type contact formulations for normal/tangential mechanical and thermal contact. It is noted that the ALE formulation allows for a simplified time description, a compact computational domain and localized mesh refinement. Numerical simulations considering stationary rolling conditions featuring full slip are presented.
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| 36. |
- Draganis, Andreas, 1984, et al.
(författare)
-
Numerical evaluation of the transient response due to non-smooth rolling contact using an arbitrary Lagrangian–Eulerian formulation
- 2012
-
Ingår i: Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology. - : SAGE Publications. - 1350-6501 .- 2041-305X. ; 226:J1, s. 36-45
-
Tidskriftsartikel (refereegranskat)abstract
- A theoretical and numerical framework to evaluate rolling contact using an arbitrary Lagrangian–Eulerian (ALE) formulation is established. A finite element formulation is imple- mented featuring cylinder–plate contact, automated mesh refinement, non-reflecting boundary conditions, and the ability to incorporate surface roughness through user-defined gap functions. Presented examples include rolling contact on a corrugated surface and negotiation of a surface discontinuity. Sensitivity and validation analyses are presented and show the model to be robust and the trends in parametric responses to be reasonable as compared to results in literature. Owing to the ALE formulation, the model can be kept very compact and the computational demands very modest.
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| 37. |
- Ekberg, Anders, 1967, et al.
(författare)
-
Alarm limits for wheel–rail impact loads – part 2: analysis of crack growth and fracture
- 2009
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The crack growth and subsequent fracture of rails is governed by the imposed rolling contact load from operational vehicles. This study focuses on the growth of longer cracks. In contrast to shorter cracks that are mainly driven by the influence of the contact stress field in combination with the effect of trapped liquid, these cracks are mainly driven by the global bending of the rail. In addition there is, for all-welded rails, a major influence of the rail temperature.The aim of the study is to find a scientific basis for regulations regarding allowed wheel de- fects. These defects generate wheel–rail impact loads that in severe cases may promote fracture from pre-existing cracks in the rail. Present wheel removal criteria relate wheel defect alarm limits to the size (length) of a wheel flat. This is not an optimal situation since it may be both difficult and dangerous to locate and measure the length of a wheel flat. Further, a given size of a wheel flat will result in different impact loads if present on different types of vehicles due to differences in train speed, axle load, etc, and on different tracks with differences in track proper- ties. In this study, the focus is instead on the wheel–rail impact load magnitude and its influence on the risk of rail breaks.
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| 38. |
- Ekberg, Anders, 1967, et al.
(författare)
-
Allowable wheel loads, crack sizes and inspection intervals to prevent rail breaks
- 2015
-
Ingår i: Proceedings of the 11th International Heavy Haul Association Conference (IHHA 2015).
-
Konferensbidrag (refereegranskat)abstract
- Cost-efficient and reliable heavy haul operation requires a minimum of operational disturbances. To this end, the current study focuses on wheel load management with the aim to establish wheel load monitoring and mitigation actions (in terms of limits on allowable wheel defects) that minimize traffic disruptions.As a first step, the relation between wheel impact load magnitudes (resulting from the out-of-round wheels) and critical rail crack sizes that would result in rail breaks is established. Variations in parameters such as track stiffness, rail temperature, impact load characteristics and hanging sleepers etc. are investigated and a “bad case scenario” that implies severe, but realistic operational conditions is established. In this manner allowable wheel impact load magnitudes can be linked to pertinent critical crack sizes that must be identified during inspections. An interesting finding is that thermal stresses have such a major effect that a seasonal variation in allowable wheel load limit seems justified.Predicted critical crack sizes (presuming allowed wheel load magnitudes) are then contrasted to critical crack sizes at operational rail breaks. A large scatter in operational critical crack sizes is found and reasons for this fact are discussed. Finally operational aspects of implementing the suggested limit values are discussed.
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| 39. |
- Ekberg, Anders, 1967, et al.
(författare)
-
An engineering model for rolling contact fatigue
- 2002
-
Ingår i: Fatigue and Fracture of Engineering Materials and Structures. - 8756-758X .- 1460-2695. ; 25, s. 899-909
-
Tidskriftsartikel (refereegranskat)
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| 40. |
|
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| 41. |
- Ekberg, Anders, 1967, et al.
(författare)
-
Asset management – A brief introduction with focus on the ISO 55000 standard and mechanical deterioration of railway related assets
- 2021
-
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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| 42. |
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| 43. |
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| 44. |
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| 45. |
- Ekberg, Anders, 1967
(författare)
-
Fatigue of railway wheels
- 2009
-
Ingår i: Wheel-rail interface handbook. - : Elsevier. - 9781845694128 ; , s. 215-244
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Wheel fatigue – the formation of cracks on wheel tread, in wheel rim or on the wheel disk, is a crucial phenomenon in assuring safe and reliable rail transportations. In the current chapter a background to the phenomenon is given. The appearance and mechanisms of different forms of wheel fatigue are discussed and predictive models are presented. The influence of some operational factors and interacting deterioration phenomena are then discussed before the chapter ends with concluding remarks and an outlook on future trends.
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| 46. |
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| 47. |
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| 48. |
- Ekberg, Anders, 1967, et al.
(författare)
-
Guest editorial
- 2005
-
Ingår i: Wear. ; 258:7-8, s. 953-954
-
Tidskriftsartikel (refereegranskat)
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| 49. |
- Ekberg, Anders, 1967
(författare)
-
Guest editorial
- 2010
-
Ingår i: Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit. - : SAGE Publications. - 0954-4097 .- 2041-3017. ; 224:4, s. i-iii
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 50. |
- Ekberg, Anders, 1967, et al.
(författare)
-
Identifying the root causes of damage on the wheels of heavy haul locomotives and its mitigation
- 2014
-
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
-
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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