| 1. |
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| 2. |
- Ait Ali, Abderrahman, 1991-, et al.
(författare)
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Evaluating the mix of maintenance activities on railway crossings with respect to life-cycle costs
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Switches & crossings (S&Cs) are vital assets as they allow for increased railway capacity by introducing flexibility and connectivity in railway networks. At the same time, this makes them critical since they can cause costly delays and disruptions if they are not well maintained. This motivates studies to improve maintenance strategies of S&Cs, considering both the life-cycle costs (LCC) of the assets and socio-economic transportation costs for passengers and freight customers. In this paper, the interdependence between deterioration mechanisms, maintenance activities, and expected LCC (including transportation costs) is investigated using a combination of mechanical and econometric modelling. The interrelation between the degradation of contact geometry and track settlement is analysed using simulations of dynamic vehicle–turnout interaction. Long-term mechanical degradation of the S&C is simulated for different maintenance strategies that correspond to different timing of the associated maintenance measures (crossing repair welding and tamping). This provides the basis for analysing the interdependence between preventive and corrective activities using econometric modelling. Based on a case study of a common type of S&Cs in the Swedish infrastructure, the impact of different maintenance strategies on LCC and transportation costs is analysed. Opportunities and challenges in the development of more socio-economically effective maintenance strategies of S&Cs are discussed.
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| 3. |
- Ait Ali, Abderrahman, 1991-, et al.
(författare)
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Evaluating the mix of maintenance activities on railway crossings with respect to life-cycle costs
- 2024
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Ingår i: Sammanställning av referat från Transportforum 2024. - Linköping : Statens väg- och transportforskningsinstitut. ; , s. 405-406
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Switches and crossings (S&Cs) are critical assets in the Swedish rail infrastructure, with a density of 0.8 S&C per track-km and renewal costs of up to 4.5 million SEK/S&C. The efficiency of maintenance strategies for S&Cs is vital from a (socio-)economic perspective. The focus of this study is on the importance of the mix of maintenance activities performed on a S&C with respect to its life-cycle costs (LCCs). The study investigates the interdependencies between the deterioration mechanisms, preventive and corrective maintenance activities, and expected LCCs, including transportation costs due to traffic disruptions/delays. One or a combination of different approaches are often used in the literature, such as engineering or LCC methods. In this research, a novel approach is introduced that combines mechanical simulations, data analysis, econometrics, and LCC calculations to compare the efficiency of different maintenance strategies. The mechanical simulations consider one S&C on the Swedish railway network. The selection criteria were that the S&C is located on the main line, installed in 2014 (generates the longest observation period given the availability of data), and had no extreme values with respect traffic volume, maintenance activities and failures. The interrelation between the degradation of contact geometry and track settlement is analysed using simulations of dynamic vehicle–turnout interaction. Further, the relationship between frequency of preventive and occurrence of corrective maintenance activities is analyses using an econometric model. Implications of a specific mix of maintenance activities on the S&C lifetime and LCC are evaluated using different cost parameters. Results obtained from mechanical simulations reveal the correlation between poor crossing geometry and higher rates of ballast settlement. The econometric analysis finds a statistically significant impact of (cumulative) preventive maintenance on corrective maintenance, i.e., more preventive maintenance leads to fewer corrective activities. Based on a standard mix of maintenance activities (inferred using econometric regression across all S&Cs), the lifetime of the selected S&C is estimated to 10 years with a lower associated LCC than that resulting from the record of performed maintenance activities at the site. The LCC evaluations highlight the potential to improve the efficiency of S&C maintenance by adopting proactive strategies.
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| 4. |
- Ait Ali, Abderrahman, 1991-, et al.
(författare)
-
Evaluation of long-term maintenance of switches & crossings with respect to life-cycle costs and socio-economic impact
- 2022
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Switches & crossings (S&Cs) are vital assets as they allow for increased railway capacity by introducing flexibility and connectivity in railway networks. At the same time this makes them critical, and they can cause major delays and disruptions if they are not well maintained. This motivates studies to improve maintenance strategies of S&Cs, considering both life-cycle costs (LCC) of the assets and other additional socio-economic costs (e.g., transportation costs for passengers and freight customers). In this paper, the interdependence between deterioration mechanisms, maintenance activities, and expected LCC (including transportation costs) is investigated using a combination of mechanical and econometric modelling.The interrelation between the degradation of contact geometry and track settlement is analysed using simulations of dynamic vehicle–turnout interaction. Changes in the timing of the associated maintenance measures (crossing repair welding and tamping) are performed to investigate the impact on damage modes. This is then linked to LCC and transportation costs, which requires a distribution between preventive and corrective activities with respect to the simulated maintenance strategy. This relationship is investigated by means of regression modelling: ??????????=?(??????????,?)where Corrective and Preventive represent the number of failures and the scheduled actions to prevent these failures, respectively. ? holds variables related to the traffic (volume, type of traffic, axle load, etc.) and the infrastructure (type of S&Cs, etc.).
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| 5. |
- Ansin, Caroline, 1996, et al.
(författare)
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Influence of model parameters on the predicted rail profile wear distribution in a curve
- 2023
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- A sensitivity study is performed to determine the effect of model parameters on the predicted wear distribution on rail profiles. The numerical framework uses multibody simulations to evaluate dynamic vehicle-track interaction for different traffic scenarios, and FASTSIM and Archard's wear law to evaluate rail profile wear. Vehicle and track parameters as well as different approaches to contact modeling are considered. A previous study has shown good agreement between predictions and measurements in overall wear, but deviations in wear distribution. The objective of this study is to obtain a better agreement for the profile wear distribution under operational traffic conditions compared to rail profile measurements. The study shows that the inclusion of freight vehicles, different wheel profile samples, and the consideration of a different contact model are some of the most important parameters.
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| 6. |
- Ansin, Caroline, 1996, et al.
(författare)
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Simulation and Field Measurements of the Long-term Rail Surface Damage due to Plasticity, Wear and Surface Rolling Contact Fatigue Cracks in a Curve
- 2022
-
Ingår i: CM 2022 - 12th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, Conference Proceedings. ; , s. 591-601
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Konferensbidrag (refereegranskat)abstract
- A methodology that simulates the long-term rail surface damage in a cross-section of a curve for a given traffic scenario is presented. The numerical model considers plastic deformation, wear, and initiation of rolling contact fatigue (RCF) surface cracks. The models and simulations are calibrated and validated, respectively, against field profile measurement data.
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| 7. |
- Bezin, Yann, et al.
(författare)
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Multibody simulation benchmark for dynamic vehicle-track interaction in switches and crossings: modelling description and simulation tasks
- 2023
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Ingår i: Vehicle System Dynamics. - : Informa UK Limited. - 1744-5159 .- 0042-3114. ; 61:3, s. 644-659
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the final description for the S&C Benchmark that was launched at the IAVSD 2019 conference held in Gothenburg, Sweden and completed by eighteen participants by the end of 2020. The purpose of this paper is to allow for the replication of the Benchmark exercise after publication for those who wish to do so in the future, and it includes a link to the repository containing all necessary input data. The original task description, including a description of the Benchmark submission, is presented in full. The results from the Benchmark are available in [Bezin Y, Pålsson BA, Kik W, et al. Multibody simulation Benchmark for dynamic vehicle-track interaction in switches and crossings: results and method statements. Submitted to VSD, 2021].
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| 8. |
- Bezin, Y., et al.
(författare)
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Multibody simulation benchmark for dynamic vehicle-track interaction in switches and crossings: results and method statements
- 2023
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Ingår i: Vehicle System Dynamics. - : Informa UK Limited. - 1744-5159 .- 0042-3114. ; 61:3, s. 660-697
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Tidskriftsartikel (refereegranskat)abstract
- A Benchmark of railway multibody dynamics software application to switches and crossings (S&C) is presented, comparing all major commercially available software and a few independent codes. Two different representative S&C have been implemented, using the Manchester Benchmark passenger vehicle. The final results show that all software offer a reliable and efficient way to understand the kinematic and dynamics forces between the wheels and the track elements. The highest challenges are found when modelling a combination of multiple rails in simultaneous contact with a wheel (check-stock or switch-stock), large longitudinal variations in rail shape (crossings) and high lateral steering forces (diverging cases in tight radius). In those cases, the codes able to account for the exact relative motion of each wheels with respect to each rails independently are the most apt. The most significant variations between software are found in the contact prediction with an influence on the detailed contact tangential and normal forces. The user variability is found to be very small, with the most time-consuming and error prone being the task of handling the input data for the variable rails definition. All software could benefit from improvements to assist the user and ensure higher reliability and efficiency generally.
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| 9. |
- Bolsman, Caspar T., et al.
(författare)
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The Use of Resonant Structures for Miniaturizing FMAVs
- 2007
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Ingår i: Proceedings of the 3rd US-European Competition and Workshop on Micro Air Vehicle Systems (MAV07) & European Micro Air Vehicle Conference and Flight Competition (EMAV2007), 17-21 September 2007, Toulouse, France. ; , s. 12-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The use of resonant structures in FMAVs is an idea inspired by nature. The application of resonancein an oscillating system requires a careful analysis of the involved structures in insects. The applicationof this concept in FMAVs yields opportunities for size reduction. As one moves away from standard constructionalprinciples. The latter become less feasible at the small scale. It is mandatory to include thecontrol mechanism in the design loop from the start. Control over wing kinematics in insects relies oncomplex wing root structures, for FMAVs other solutions are possible and needed. This article providesan overview on structures and their functions in insects and the engineering alternatives. Emphasis is ontechniques which are applicable in smaller designs. In particular, control mechanisms and thorax structuresare covered. Initial concepts are analyzed and presented based onmulti-body and FE representation.
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| 10. |
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| 11. |
- Carlberger, Andreas, 1992, et al.
(författare)
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Numerical prediction of rail corrugation growth on curves
- 2016
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Ingår i: Proceedings of the 19h Nordic Seminar on Railway Technology, September 14 - 15, Luleå, Sweden (2016).
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Rail corrugation (periodic surface irregularities at distinct wavelengths) is a problem experienced by many railway networks worldwide. Corrugation induces a pronounced dynamic wheel‒rail contact loading that leads to increased generation of noise and in severe cases even damage to vehicle and track components. The large magnitude creep forces and sliding between wheel and rail make corrugation especially prone to develop on curved track. The current work summarizes the results from a Master Thesis project performed in collaboration between Chalmers, ÅF Industry, Bombardier Transportation and Stockholm Public Transport. A time-domain model for the prediction of long-term growth of rail roughness has been developed, see Figure 1. Dynamic vehicle‒track interaction in a broad frequency range (at least up to 300 Hz) is simulated using the commercial software SIMPACK. Wheelset structural flexibility is accounted for by using modal parameters calculated for a finite element model. Non-Hertzian and non-steady wheel‒rail contact and associated generation of wear are calculated in a post-processing step in the software Matlab. Archard’s law is applied to model the sliding wear. A large number of train passages is accounted for by recurrent updating of the rail surface irregularity based on the calculated wear depth. The proposed prediction model is applied to investigate a curve on the Stockholm metro network exposed to severe corrugation growth.
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| 12. |
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| 13. |
- Ekberg, Anders, 1967, et al.
(författare)
-
Multiscale modelling of train–track interaction phenomena with focus on contact mechanics
- 2019
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Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 430-431, s. 393-400
-
Tidskriftsartikel (refereegranskat)abstract
- The paper examines possibilities for holistic modelling of the running gear/track interaction and related phenomena – in particular such that cause material deterioration in the form of wear and rolling contact fatigue. The required resolution, accuracy and challenges in understanding, describing and (in particular)modelling these phenomena are addressed. Particular focus is put on contact modelling, which commonly sets the limit for the level of accuracy that can be achieved in subsequent analyses. For all areas, simulation approaches that span from overview to very detailed are discussed. It is concluded that a simulation framework for the whole vehicle–track system needs to be based on modules of different levels of complexity and targeted towards different (aspects of)phenomena. Selecting a suitable level of detail for the task at hand, and to ensure that the employed simulations modules are able to interact are key challenges in this context.
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| 14. |
- Ekberg, Anders, 1967, et al.
(författare)
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The role of contact mechanics in multiscale modelling of train-track interaction phenomena
- 2018
-
Ingår i: Proceedings of the 11th International Conference on Contact Mechanics and Wear of Rail/wheel Systems, CM 2018. - 9789461869630 ; , s. 228-237
-
Konferensbidrag (refereegranskat)abstract
- The paper examines possibilities for holistic modelling of the running gear/track interaction and related phenomena-in particular material deterioration phenomena. The required resolution, accuracy and challenges in understanding, describing and (in particular) modelling these phenomena are addressed. Special focus is put on contact modelling, which commonly sets the limit for the level of accuracy that can be achieved in subsequent analyses.
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| 15. |
- Johansson, Anders, 1974, et al.
(författare)
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Simulation of wheel-rail contact and damage in switches & crossings
- 2011
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 271:1-2, s. 472-481
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Tidskriftsartikel (refereegranskat)abstract
- A methodology for the simulation of degradation of rail profiles in switches & crossings (S&C) is presented. The methodology includes: simulation of dynamic vehicle-track interaction considering stochastic variations in input data (such as wheel profile, train speed and wheel-rail friction coefficient), simulation of wheel-rail contacts accounting for non-linear material properties and plasticity, and simulation of wear and plastic deformation in the rail during the life of the S&C component. The methodology is demonstrated by predicting the damage of a switch rail profile, manufactured from R260 steel, when exposed to freight traffic in the diverging route (facing move). In particular, the consequences of increasing the axle load from 25 tonnes to 30 tonnes are studied.
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| 16. |
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| 17. |
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| 18. |
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| 19. |
- Karlson, Björn, et al.
(författare)
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Arbetsplatsintervention vid utmattning-Dialog hjälper!
- 2007
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Ingår i: Bulletin från Centrum för yrkes- och miljömedicin, Universitetssjukhuset i Lund/Malmö akademiska sjukhus. - 1400-2833. ; :4, s. 2-2
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Tidskriftsartikel (refereegranskat)
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| 20. |
- Karlson, Björn, et al.
(författare)
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Return to work after a workplace-oriented intervention for patients on sick-leave for burnout : a prospective controlled study
- 2010
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Ingår i: BMC Public Health. - 1471-2458 .- 1471-2458. ; 10
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: In the present study the effect of a workplace-oriented intervention for persons on long-term sick leave for clinical burnout, aimed at facilitating return to work (RTW) by job-person match through patient-supervisor communication, was evaluated. We hypothesised that the intervention group would show a more successful RTW than a control group.METHODS: In a prospective controlled study, subjects were identified by the regional social insurance office 2-6 months after the first day on sick leave. The intervention group (n = 74) was compared to a control group who had declined participation, being matched by length of sick leave (n = 74). The RTW was followed up, using sick-listing register data, until 1.5 years after the time of intervention.RESULTS: There was a linear increase of RTW in the intervention group during the 1.5-year follow-up period, and 89% of subjects had returned to work to some extent at the end of the follow-up period. The increase in RTW in the control group came to a halt after six months, and only 73% had returned to work to some extent at the end of the 1.5-year follow-up.CONCLUSIONS: We conclude that the present study demonstrated an improvement of long-term RTW after a workplace-oriented intervention for patients on long-term sick leave due to burnout.TRIAL REGISTRATION: Current Controlled Trials NCT01039168.
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| 21. |
- Karlson, Björn, et al.
(författare)
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Return to work after work after a workplace-oriented intervention for patients on sick-leave for burnout - a prospective controlled study
- 2010
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Ingår i: BMC Public Health. - : BioMed Central. - 1471-2458. ; 10
-
Tidskriftsartikel (refereegranskat)abstract
- Background: In the present study the effect of a workplace-oriented intervention for persons on long-term sick leave for clinical burnout, aimed at facilitating return to work (RTW) by job-person match through patient-supervisor communication, was evaluated. We hypothesised that the intervention group would show a more successful RTW than a control group. Methods: In a prospective controlled study, subjects were identified by the regional social insurance office 2-6 months after the first day on sick leave. The intervention group (n = 74) was compared to a control group who had declined participation, being matched by length of sick leave (n = 74). The RTW was followed up, using sick-listing register data, until 1.5 years after the time of intervention. Results: There was a linear increase of RTW in the intervention group during the 1.5-year follow-up period, and 89% of subjects had returned to work to some extent at the end of the follow-up period. The increase in RTW in the control group came to a halt after six months, and only 73% had returned to work to some extent at the end of the 1.5-year follow-up. Conclusions: We conclude that the present study demonstrated an improvement of long-term RTW after a workplace-oriented intervention for patients on long-term sick leave due to burnout. Trial registration: Current Controlled Trials NCT01039168.
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| 22. |
- Li, Xin, 1985, et al.
(författare)
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Simulation of track settlement in railway turnouts
- 2014
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Ingår i: Vehicle System Dynamics. - : Informa UK Limited. - 1744-5159 .- 0042-3114. ; 52:SUPPL. 1, s. 421-439
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Tidskriftsartikel (refereegranskat)abstract
- A methodology for the simulation of track settlement in railway turnouts (switches and crossings, S&C) is presented. The methodology predicts accumulated settlement for a given set of traffic loads using an iterative and cross-disciplinary procedure. The different modules of the procedure include (I) simulation of dynamic vehicle-track interaction in a turnout applying a validated software for multibody vehicle dynamics considering space-dependent track properties, (II) calculation of load distribution and sleeper-ballast contact pressure using a detailed finite element model of a turnout that includes all of the rails (stock rails, switch rails, closure rails, crossing nose, wing rails and check rails), rail pads, baseplates and sleepers on ballast, (III) prediction of track settlement for a given number of load cycles and (IV) calculation of accumulated track settlement at each sleeper and the resulting vertical track irregularity along the turnout which is used as input in the next step of the iteration. The iteration scheme is demonstrated by calculating the track settlement at the crossing when the studied turnout is exposed to freight traffic in the facing move of the through route.
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| 23. |
- Manasian, Panagiotis, et al.
(författare)
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First Evidence of Acyl-Hydrolase/Lipase Activity From Human Probiotic Bacteria: Lactobacillus rhamnosus GG and Bifidobacterium longum NCC 2705
- 2020
-
Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X.
-
Tidskriftsartikel (refereegranskat)abstract
- Lactobacillus rhamnosus GG (ATCC 53103) and Bifidobacterium longum NCC 2705 are among the most studied probiotics. However, the first evidence of acyl hydrolase/lipase of two annotated proteins, one in each genome of these strains, is reported in this work. Signal peptide analysis has predicted that these proteins are exported to the extracellular medium. Both proteins were produced in Escherichia coli, purified and characterized. Molecular masses (without signal peptides) were 27 and 52.3 kDa for the proteins of L. rhamnosus and B. longum, respectively. Asymmetrical flow field-flow fractionation analysis has shown that both proteins are present as monomers in their native forms at pH 7. Both have shown enzymatic activity on pNP-laurate at pH 7 and 37°C. The enzyme from L. rhamnosus was characterized deeper, showing preference on pNP-esters with short chain fatty acids. In addition, a computational model of the 3D structure has allowed the prediction of the catalytic amino acids. The enzymatic activities using synthetic substrates were very low for both enzymes. The investigation of natural substrates and biological functions of these enzymes is still open.
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| 24. |
- Milosevic, Marko, 1991, et al.
(författare)
-
Condition Monitoring of Railway Crossing Geometry via Measured and Simulated Track Responses
- 2022
-
Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 22:3
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents methods for continuous condition monitoring of railway switches and crossings (S&C, turnout) via sleeper-mounted accelerometers at the crossing transition. The methods are developed from concurrently measured sleeper accelerations and scanned crossing geometries from six in situ crossing panels. These measurements combined with a multi-body simulation (MBS) model with a structural track model and implemented scanned crossing geometries are used to derive the link between the crossing geometry condition and the resulting track excitation. From this analysis, a crossing condition indicator Cλ1-λ2,γ is proposed. The indicator is defined as the root mean square (RMS) of a track response signal γ that has been band-passed between frequencies corresponding to track deformation wavelength bounds of λ1 and λ2 for the vehicle passing speed (f = v/ λ). In this way, the indicator ignores the quasi-static track response with wavelengths pre-dominantly above λ1 and targets the dynamic track response caused by the kinematic wheel-cross-ing interaction governed by the crossing geometry. For the studied crossing panels, the indicator C1-0.2 m,γ (λ1 = 1 and λ2 = 0.2) was evaluated for γ = u, v, or a as in displacements, velocities, and accelerations, respectively. It is shown that this condition indicator has a strong correlation with vertical wheel–rail contact forces that is sustained for various track conditions. Further, model calibrations were performed to measured sleeper displacements for the six investigated crossing panels. The calibrated models show (1) a good agreement between measured and simulated sleeper displacements for the lower frequency quasi-static track response and (2) improved agreement for the dynamic track response at higher frequencies. The calibration also improved the agreement between measurements and simulation for the crossing condition indicator demonstrating the value of model calibration for condition monitoring purposes.
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| 25. |
- Milosevic, Marko, 1991, et al.
(författare)
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Demonstration of a Digital Twin Framework for Model-Based Operational Condition Monitoring of Crossing Panels
- 2022
-
Ingår i: Lecture Notes in Mechanical Engineering. - Cham : Springer International Publishing. - 2195-4356 .- 2195-4364. ; , s. 95-105
-
Konferensbidrag (refereegranskat)abstract
- The wheel transition area in railway crossings is subjected to impact loads that cause an accumulation of structural degradation in crossing panels over time. This degradation leads to high maintenance costs and possibly traffic disturbances. There is therefore a demand from infrastructure managers to monitor the condition and predict maintenance needs for these assets without the need for regular on-site inspections. One solution for operational condition monitoring is to observe the structural response of the crossing under traffic loading via embedded accelerometers. From these measurements, relative changes in track dynamics over time can be observed. To derive a condition or predict maintenance needs, however, these measured accelerations need to be related to the status of the asset. A framework for this where measurement data, simulation models and maintenance history are combined to build an online model that can assess the status and predict future maintenance needs for a material asset is often called a Digital Twin. This paper will present a Digital Twin framework that uses measured accelerations, climate data, scanned running surface geometry and a multi-body simulation (MBS) model to estimate the status and degradation rate of crossing panels. Method developments for this framework are demonstrated for two in situ crossings.
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| 26. |
- Milosevic, Marko, 1991, et al.
(författare)
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Model-Based Remote Health Monitoring of Ballast Conditions in Railway Crossing Panels
- 2023
-
Ingår i: Lecture Notes in Civil Engineering. - Cham : Springer International Publishing. - 2366-2565 .- 2366-2557. ; 253 LNCE, s. 502-512
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Konferensbidrag (refereegranskat)abstract
- Railway crossing panels accumulate damage due to impact loads induced in the wheel transition area. To reduce the need for labour-intensive visual inspections of crossing panels, railway administrations are evaluating solutions for remote health monitoring. One such solution is to measure the track response that follow from the wheel–crossing impact using embedded accelerometers mounted on the sleeper at the crossing transition. The challenge that remains is to determine the health of the asset from these measured signals. In this paper, a procedure is developed to identify the ballast condition under a crossing panel via the calibration of a multibody simulation model to measurement data. This model considers the complex wheel–rail interaction in the crossing transition area, while also capturing the dynamic response of the track using a Finite Element representation of the track structure. The calibration procedure has been developed using data from six in situ crossing panels where the crossing geometry and the track response are known via laser-scanned crossing geometries and measured accelerations. Parameters associated with the physical state of the ballast are identified by minimizing the least-squares discrepancy between the measured track response and the corresponding response from simulations of dynamic vehicle–track interaction. The utilised ballast parameterization has been motivated from sensitivity analysis to ensure that each parameter has a clear and observable influence on the track response. The performance of the developed calibration procedure is demonstrated and its suitability for implementation in condition monitoring solutions is discussed.
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| 27. |
- Milosevic, Marko, 1991, et al.
(författare)
-
On tailored signal processing tools for operational condition monitoring of railway switches and crossings
- 2020
-
Ingår i: Proceedings of ISMA 2020 - International Conference on Noise and Vibration Engineering and USD 2020 - International Conference on Uncertainty in Structural Dynamics. ; , s. 2639-2653
-
Konferensbidrag (refereegranskat)abstract
- Railway switches and crossings (S&C, turnout) connect different track sections and create a railway network by allowing for trains to change between tracks. This functionality comes at a cost, however, as load-inducing rail discontinuities in the switch and crossing panels cause much larger degradation rates for S&C compared to regular track. As there are hundreds of thousands of S&C in Europe, railway administrators are interested to advance solutions for reliable and resilient maintenance of these assets via remote condition monitoring. One such solution is to measure accelerations using embedded sensors mounted on the sleeper that lies underneath the crossing transition. With the adoption of this solution, this paper addresses the development of tailored signal processing tools for specifically analysing and evaluating the given acceleration signals. In particular, the methodology addresses both temporal and frequency characteristics of measured accelerations, and their integration to displacements. In this work, measured accelerations from 41 train passages and two different crossing panels have been used.
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| 28. |
- Milosevic, Marko, 1991, et al.
(författare)
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Reconstruction of sleeper displacements from measured accelerations for model-based condition monitoring of railway crossing panels
- 2023
-
Ingår i: Mechanical Systems and Signal Processing. - : Elsevier BV. - 0888-3270 .- 1096-1216. ; 192
-
Tidskriftsartikel (refereegranskat)abstract
- Railway switches and crossings (S&C, turnouts) connect different track sections and create a railway network by allowing trains to change tracks. This functionality comes at a cost as the load-inducing rail discontinuities in the switch and crossing panels cause much larger degradation rates for S&C compared to regular plain line tracks. The high degradation rates make remote condition monitoring an interesting prospect for infrastructure managers to optimise maintenance and ensure safe operations. To this end, this paper addresses the development of tailored signal processing tools for condition monitoring using embedded accelerometers in crossing panels. Multibody simulations of the dynamic train–track interaction are used to aid the interpretation of the measured signals in a first step towards building a model-based condition monitoring system. An analysis is performed using sleeper acceleration measurement data generated by 100 000 train passages in eight crossing panels. Based on the given data, a novel frequency-domain displacement reconstruction method is developed and the robustness of the method with respect to encountered operational variability of the measured data is demonstrated. The separation of the track response into quasi-static and dynamic domains based on deformation wavelength regions is proposed as a promising strategy to observe the ballast condition and the crossing geometry condition, respectively.
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| 29. |
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| 30. |
- Nielsen, Jens, 1963, et al.
(författare)
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Switch panel design based on simulation of accumulated rail damage in a railway turnout
- 2016
-
Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 366-367:SI, s. 241-248
-
Tidskriftsartikel (refereegranskat)abstract
- A methodology for numerical prediction of accumulated rail damage in railway turnouts is presented. Based on simulation of dynamic vehicle-track interaction followed by a discretisation of the conditions in each wheel-rail contact, distributions of rail wear are calculated by the Archard model of sliding wear, while surface initiated rolling contact fatigue (RCF) damage is evaluated by the Palmgren–Miner rule and an index building on shakedown theory. Partial slip in the wheel-rail contacts and variable amplitude loading are considered. For freight traffic in the diverging route, the influence of rail inclination and switch rail elevation on damage in the switch panel is investigated in a demonstration example. Two-point contact situations with one contact on the switch rail and one on top of the stock rail induce relative motion and slip between wheel and rail leading to high energy dissipation. In agreement with field observations, it is concluded that wear is the dominating damage mechanism on the gauge side of the switch rail while the risk for RCF is higher on the crowns of the switch and stock rails. For accurate prediction of rail life for given combinations of wheel/rail materials and traffic conditions, the methodology needs to be calibrated by field measurements.
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| 31. |
- Nielsen, Jens, 1963, et al.
(författare)
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Switch panel design based on simulation of accumulated rail damage in a railway turnout
- 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
- A methodology for numerical prediction of accumulated rail damage in railway turnouts is presented. Based onsimulation of dynamic vehicle‒track interaction followed by a discretisation of the conditions in each wheel‒railcontact, distributions of rail wear are calculated by the Archard model of sliding wear, while surface initiated rollingcontact fatigue (RCF) damage is evaluated by the Palmgren-Miner rule and an index building on shakedown theory.Partial slip in the wheel‒rail contacts and variable amplitude loading are considered. For freight traffic in the divergingroute, the influence of rail inclination and switch rail height on damage in the switch panel is investigated in ademonstration example. Two-point contact situations with one contact on the switch rail and one on top of the stock rail induce relative motion and slip between wheel and rail leading to high energy dissipation. In agreement with fieldobservations, it is concluded that wear is the dominating damage mechanism on the gauge side of the switch rail whilethe risk for RCF is higher on the crowns of the switch and stock rails. For accurate prediction of rail life for givencombinations of wheel/rail materials and traffic conditions, the methodology needs to be calibrated by fieldmeasurements.
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| 32. |
- Oghazi, Pejman, et al.
(författare)
-
Traceability by multivariate analysis on morphology data from grinding circuit
- 2008
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Ingår i: Conference in Minerals Engineering. - Luleå. ; , s. 81-95
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- LKAB has started a new pelletization plant at Malmberget, the raw material is a mix from Kiruna and Malmberget. To achieve good products it is important to have a good control over the input material in the concentrators that is why the traceability of the process is a crucial factor. However, creating traceability in continuous processes imply vast challenges: process flows can be parallel, serial and reflux; sub processes can be continuous as well as batch-wise; large buffers; no interruptions in product handling. These challenges imply that loads of data from the material is needed for creating traceability. In this case the grinding sections have been in focus and the data are collected from the old and the new grinding sections. The main task is to find a way to make the traceability easy and practical. One way to reach good traceability would be to find a process mineralogical signature or identification. For having a good traceability we need information from the system. It is important to analyze and look into the variables that have a crucial importance to the process. By using Particle Texture analysis a good overview of how magnetite is liberated or associated to others minerals is shown. More important is that morphological data is produced for each mineral in the process. The number o variables made it difficult to compare the result, and by using multivariate analysis such as Principal Component Analysis (PCA) it is possible to have a better insight from the collected data.
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| 33. |
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| 34. |
- Pålsson, Björn, 1981, et al.
(författare)
-
A comparison of track model formulations for simulation of dynamic vehicle–track interaction in switches and crossings
- 2023
-
Ingår i: Vehicle System Dynamics. - : Informa UK Limited. - 1744-5159 .- 0042-3114. ; 61:3, s. 698-724
-
Tidskriftsartikel (refereegranskat)abstract
- This paper compares different track model formulations for the simulation of dynamic vehicle–track interaction in switches and crossings (S&C, turnouts) in a multi-body simulation (MBS) environment. The investigations are an extension of the S&C simulation Benchmark with the addition of a finite element model of a 60E1-760-1:15 turnout. This model constitutes a common reference from which four different track formulations are derived: co-running, modal superposition, finite element incorporated into the MBS model and finite element coupled to MBS using a co-simulation approach. For the different track models, the difference in modelling technique, results, simulation time, and suitability for different simulation tasks is compared. A good agreement is found between the different track model formulations for wheel–rail contact forces and rail displacements. This study found a better agreement between co-running and structural track models compared to previous studies in the prediction of wheel–rail contact forces. This appears to be due to the increased complexity of co-running track model used in this study together with a tuning of the co-running track model to the reference model in a wider frequency range. For the reader interested to reproduce the results in this paper, the reference track model is available for download.
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| 35. |
- Pålsson, Björn, 1981
(författare)
-
A linear wheel–crossing interaction model
- 2018
-
Ingår i: Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit. - : SAGE Publications. - 0954-4097 .- 2041-3017. ; 232:10, s. 2431-2443
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents the derivation of a linear model for wheel–rail interaction kinematics at railway crossings. The purpose of this model is to demonstrate the fundamental constraints imposed on a crossing geometry if it should be compatible with a given range of wheel profile shapes. In this model, the contact point locations on the wing rail and on the crossing nose are described using linear functions, and the wheel profiles are modelled as conical. Based on these assumptions, a method is developed to adjust the vertical position and longitudinal inclination of the wing rail and the crossing nose in order for the crossing geometry to be compatible with a given range of equivalent wheel profile cone angles. In particular, an expression is derived for the average impact angle. The derived relation highlights the potential of tailoring crossing geometries for a given spread in wheel profile shapes in traffic for minimized loading and damage. Further, the properties of the model are compared to the results of quasi-static multibody simulations for a range of wheel profiles.
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| 36. |
- Pålsson, Björn, 1981
(författare)
-
A Parameterized Turnout Model for Simulation of Dynamic Vehicle-Turnout Interaction with an Application to Crossing Geometry Assessment
- 2020
-
Ingår i: Lecture Notes in Mechanical Engineering. - Cham : Springer International Publishing. - 2195-4356 .- 2195-4364. ; , s. 351-358
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a parameterized structural track model for the simulation of dynamic vehicle-turnout interaction in a multi body simulation environment. The model is demonstrated by performing simulations for different vehicle speeds, crossing geometries and fixations between crossing rail and sleepers with different stiffness. Results are presented for dynamic wheel-rail contact forces, bending moments in crossing rail and sleepers and sleeper-ballast contact pressure. The main conclusions are that (a) the peak dynamic bending moment in the sleeper under the crossing transition is significantly higher with a stiff direct fixing compared to a softer indirect fixing and (b) the structural loading in terms of bending moment in the crossing rail, bending moment in the underlaying sleeper and sleeper-ballast contact pressure increases proportionally and significantly with increased impact angle and vehicle speed for wheels passing over the crossing transition.
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| 37. |
- Pålsson, Björn, 1981, et al.
(författare)
-
Calibration of a model for dynamic vehicle – track interaction in crossing panels to comprehensive field measurements
- 2022
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A so-called Whole System Model (WSM) for railway switches and crossings (S&C) is currently under development within the European research program Shift2Rail. The objective of the WSM is that it should allow for holistic simulation-based evaluation of S&C designs and ultimately provide input for Life Cycle Cost analysis and virtual homologation. At the centre of the WSM is a multibody simulation (MBS) model that evaluates the dynamic vehicle-track interaction for a given S&C design and traffic situation and generates wheel-rail contact quantities and structural responses for the following damage calculations. This paper is focused on the MBS model and present developments for a finite element track model of an S&C crossing panel. The developments concern the model itself and a calibration to measurement data from a comprehensively instrumented S&C demonstrator installed as a part of Shift2Rail activities in the Austrian railway network. The presented track model demonstrates an overall good agreement between measurements and simulation after minor and physical track parameter adjustments. A very good agreement is obtained at the center of the crossing panel at the crossing transition while discrepancies are found across the track along the sleeper that goes underneath the crossing transition. It is hypothesized that this discrepancy is due to variations in ballast stiffness distribution under the investigated sleeper. It is concluded that the presented track model can represent the track dynamics well enough to fulfil its function within the Whole System Modelling scheme.
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| 38. |
- Pålsson, Björn, 1981, et al.
(författare)
-
DAMAGE IN SWITCHES AND CROSSINGS CONSIDERING STOCHASTIC SPREAD IN RAILWAY TRAFFIC PARAMETERS
- 2010
-
Ingår i: Proceedings of RASD 2010 - 10th International Conference on Recent Advances in Structural Dynamics, Southampton, England, July 12-14 2010.
-
Konferensbidrag (refereegranskat)abstract
- Dynamic interaction between a railway freight vehicle and a track switch is studied by simulations of stochastic vehicle dynamics. In particular, the influence of the spread (scatter) in traffic parameters on the damage in S&C is assessed. The considered stochastic parameters are wheel profile and wheel–rail friction coefficient. To form a database for sampling, 120 wheel profiles from freight wagons in traffic have been measured and categorized with respect to wear. It is shown that hollow worn wheels lead to the highest normal contact forces and contact stresses at the crossing.
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| 39. |
- Pålsson, Björn, 1981
(författare)
-
Design optimisation of switch rails in railway turnouts
- 2013
-
Ingår i: Vehicle System Dynamics. - : Informa UK Limited. - 1744-5159 .- 0042-3114. ; 51:10, s. 1619-1639
-
Tidskriftsartikel (refereegranskat)abstract
- Inspired by a manufacturing process of switch rails for railway turnouts, a method for the optimisation of switch rail profile geometry is presented. The switch rail profile geometry is parameterised with four design variables to define a B-spline curve for the milling tool profile, and two design variables to prescribe the deviation from the nominal vertical path of the milling tool. The optimisation problem is formulated as a multi-objective minimisation problem with objective functions based on the contact pressure and the energy dissipation in the wheel–rail contact. The front of Pareto optimal solutions is determined by applying a genetic type optimisation algorithm. The switch rail profile designs are evaluated by simulations of dynamic train–turnout interaction. It is concluded that the obtained set of Pareto optimal solutions corresponds to a rather small variation in design variables where increased profile height and increased profile shoulder protuberance are preferred for both objectives. The improvement in the objectives comes at the cost of an earlier wheel transition to the switch rail and thus increased vertical loading at a thinner rail cross-section. The performance of the optimised geometry is evaluated using a set of 120 measured wheel profiles, and it is shown that the optimised geometry reduces damage also for this large load collective. It is concluded that accurate limits on switch rail loading need to be established to determine the feasible design space for switch rail geometry optimisation.
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| 40. |
- Pålsson, Björn, 1981, et al.
(författare)
-
Design Optimization of Switch Rails in Railway Turnouts
- 2012
-
Ingår i: 9th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, CM 2012.
-
Konferensbidrag (refereegranskat)abstract
- Inspired by the manufacturing process of switch rails for railway turnouts, a method for the optimization of switch rail profile geometry is presented. The switch rail profile geometry is parameterized with four design variables to define a B-spline curve for the milling tool profile, and two design variables to prescribe the deviation from the nominal vertical path of the milling tool. The optimization problem is formulated as a multi-objective minimization problem with objective functions based on the contact pressure and the energy dissipation in the wheel–rail contact. The front of Pareto optimal solutions is determined by applying a genetic type optimization algorithm. The switch rail profile designs are evaluated by simulations of dynamic train–turnout interaction using a commercial code for multi-body dynamics. The vehicle model is a freight wagon with Y25 bogies and 25 metric tonnes axle load. Traffic is simulated in both travelling directions in the diverging route of a 60E1-760-1:15 turnout. It is concluded that the obtained set of Pareto optimal solutions corresponds to a rather small variation in design variables where increased profile height and increased profile shoulder protuberance are preferred for both objectives.
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| 41. |
- Pålsson, Björn, 1981, et al.
(författare)
-
Dynamic vehicle-track interaction in switches and crossings and the influence of rail pad stiffness - field measurements and validation of a simulation model
- 2015
-
Ingår i: Vehicle System Dynamics. - : Informa UK Limited. - 1744-5159 .- 0042-3114. ; 53:6, s. 734-755
-
Tidskriftsartikel (refereegranskat)abstract
- A model for simulation of dynamic interaction between a railway vehicle and a turnout (switch and crossing, S&C) is validated versus field measurements. In particular, the implementation and accuracy of viscously damped track models with different complexities are assessed. The validation data come from full-scale field measurements of dynamic track stiffness and wheel-rail contact forces in a demonstrator turnout that was installed as part of the INNOTRACK project with funding from the European Union Sixth Framework Programme. Vertical track stiffness at nominal wheel loads, in the frequency range up to 20 Hz, was measured using a rolling stiffness measurement vehicle (RSMV). Vertical and lateral wheel-rail contact forces were measured by an instrumented wheel set mounted in a freight car featuring Y25 bogies. The measurements were performed for traffic in both the through and diverging routes, and in the facing and trailing moves. The full set of test runs was repeated with different types of rail pad to investigate the influence of rail pad stiffness on track stiffness and contact forces. It is concluded that impact loads on the crossing can be reduced by using more resilient rail pads. To allow for vehicle dynamics simulations at low computational cost, the track models are discretised space-variant mass-spring-damper models that are moving with each wheel set of the vehicle model. Acceptable agreement between simulated and measured vertical contact forces at the crossing can be obtained when the standard GENSYS track model is extended with one ballast/subgrade mass under each rail. This model can be tuned to capture the large phase delay in dynamic track stiffness at low frequencies, as measured by the RSMV, while remaining sufficiently resilient at higher frequencies.
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| 42. |
- Pålsson, Björn, 1981, et al.
(författare)
-
Dynamic vehicle–track interaction and loading in a railway crossing panel–calibration of a structural track model to comprehensive field measurements
- 2024
-
Ingår i: Vehicle System Dynamics. - 1744-5159 .- 0042-3114. ; In Press
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a finite element model of a railway crossing panel for use in multibody simulations (MBS). It is a two-layer track model with rails and sleepers represented by beam elements that use linear bushings for rail fastenings and non-linear bushings for ballast. The model is calibrated and validated to measurement data from a comprehensively instrumented switch and crossing demonstrator installed in the Austrian railway network as a part of the European research programme Shift2Rail. The validation concerns the capability of the model to capture the structural response of the crossing panel under traffic loading after calibration of physical track parameters to realistic values. The structural response is measured in the form of displacements, strains, and sleeper-ballast contact forces. It is shown that the developed model can represent the measured track responses well and that it was necessary to account for a varying sleeper-ballast gap distribution along the crossing transition sleeper to obtain good agreement. The calibration uses Latin hypercube samples to explore the parameter space in a sensitivity analysis before a parameter optimisation is performed using a gradient-based method on a response surface built from a polyharmonic spline.
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| 43. |
- Pålsson, Björn, 1981, et al.
(författare)
-
Editorial for S&C benchmark special issue
- 2023
-
Ingår i: Vehicle System Dynamics. - : Informa UK Limited. - 1744-5159 .- 0042-3114. ; 61:3, s. 639-643
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 44. |
- Pålsson, Björn, 1981, et al.
(författare)
-
Kinematic Gauge Optimization of Switches Using Genetic Algorithms
- 2011
-
Ingår i: International Symposium on Dynamics of Vehicles on Roads and Tracks, Manchester, August 2011.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A methodology for minimizing rail profile degradation in the switch panel of a railway turnout (switch &crossing, S&C) through kinematic track gauge widening is presented. A holistic approach is applied using agenetic algorithm for multi-objective optimization, where both routes and both moves (travel directions) areconsidered simultaneously. The dynamic vehicle–turnout interaction and rail profile wear as a function of gaugeconfiguration are evaluated using a multi-body simulation tool. In the obtained set of Pareto optimal solutions,the trade-off between wear in the two routes is highlighted. A stochastic spread in wheel profile and wheel–railfriction coefficient is accounted for.
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| 45. |
- Pålsson, Björn, 1981
(författare)
-
Optimisation of railway crossing geometry considering a representative set of wheel profiles
- 2015
-
Ingår i: Vehicle System Dynamics. - : Informa UK Limited. - 1744-5159 .- 0042-3114. ; 53:2, s. 274-301
-
Tidskriftsartikel (refereegranskat)abstract
- A numerical method for robust geometry optimisation of railway crossings is presented. The robustness is achieved by optimising the crossing geometry for a representative set of wheel profiles. As a basis for the optimisation, a crossing geometry is created where rail cross-sectional profiles and longitudinal height profiles of both wing rails and crossing nose are parameterised. Based on the approximation that the two problems are decoupled, separate optimisations are performed for the cross-sectional rail profiles and the longitudinal height profiles. The rail cross sections are optimised to minimise the maximum Hertzian wheel-rail contact pressure. The longitudinal height profiles are optimised to minimise the accumulated damage in the wing rail to crossing nose transition zone. The accumulated damage is approximated using an objective criterion that accounts for the angle of the wheel trajectory reversal during the transition from the wing rail to the crossing nose as well as the distribution of transition points for the utilised wheel profile set. It is found that small nonlinear height deviations from a linear longitudinal wing rail profile in the transition zone can reduce the objective compared to the nominal design. It is further demonstrated that the variation in wheel profile shapes, lateral wheel displacements and the feasible transition zone length of the crossing will determine the longitudinal height profiles of the wing rail and crossing nose if all wheel profiles are to make their transition within the transition zone.
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| 46. |
- Pålsson, Björn, 1981
(författare)
-
Optimisation of railway crossing geometry considering a set of representative wheel profiles
- 2013
-
Ingår i: Proceedings 23rd International Symposium on Dynamics of Vehicles on Roads and Tracks, Qingdao, China, 2013.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A parameter study and grid search optimisation is performed on a parameterised crossing geometry. Crossing designs are evaluated with respect to the maximum Hertzian wheel‒rail contact pressure recorded during simulated freight traffic. Each crossing design is evaluated by running five simulation runs in each traffic direction (facing and trailing moves of the through route) with different combinations of wheel profile and friction coefficient. The sensitivity of nine design variables is estimated using regression analysis on the damage estimates for the different crossing designs. Two different categories of design variables are investigated: parameters related to the cross-sectional rail profiles of the wing rail and crossing nose, and parameters controlling the longitudinal height profiles of the wing rail and crossing nose. Parameter settings are found that provide lower objectives than the nominal design, but the improvements are typically small.
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| 47. |
- Pålsson, Björn, 1981
(författare)
-
Optimisation of Railway Switches and Crossings
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Methods for simulation-based optimisation of the design of railway turnouts (switches & crossings, S&C) are developed and demonstrated. Building on knowledge of dynamic wheel–rail interaction in turnouts, it is investigated how rail profile degradation can be reduced by the optimisation of geometry and component stiffness of the track superstructure. It is assumed that reduced rail profile degradation will reduce the Life Cycle Cost (LCC) of turnouts.In order to obtain robust optimised designs that perform well in situ, the influence of spread in traffic parameters, such as wheel profile and wheel–rail friction coefficient, is accounted for in the optimisations. For this purpose, studies of the correlation between wheel profile characteristics and damage in S&C are performed to allow for an efficient parameter sampling using the Latin Hypercube Sampling method. Track gauge optimisation in the switch panel is performed using a multi-objective optimisation approach to highlight the design trade-off in performance between different traffic routes and moves. The objective is to minimise rail and wheel wear as estimated by the energy dissipation in the wheel‒rail contacts. As track gauge widening affects the switch rail design, the switch rail geometry is linked to the gauge widening in the parameterisation. It is found that gauge configurations with a large maximum gauge widening for the straight stock rail are optimal for both the through and diverging routes, while the results for the curved stock rail show a more significant route dependence. A method for the optimisation of switch rail profile geometry is presented, where the geometry parameterisation is inspired by a manufacturing process for switch rails. It is found that increased profile height and increased profile shoulder protuberance are preferred to reduce the energy dissipation and wheel‒rail contact pressures when a nominal S1002 wheel profile is used as input. It is concluded that accurate constraints on allowable switch rail loading need to be established to determine the feasible design space for switch rail geometry optimisation.A method for the optimisation of crossing geometry is also introduced. The rail cross-sections are optimised for minimum wheel‒rail contact pressure. Further, the longitudinal height profiles of the wing rails and crossing nose are optimised to minimise an estimate of the accumulated damage in the transition zone. The optimisation is computationally efficient which makes it possible to account for very large samples of wheel profiles. An investigation and demonstration of the constraints imposed on the crossing design by the spread in profile and lateral displacement of passing wheels is presented. Supplementary to the optimisation studies is the comparison of simulation results to field measurement data to evaluate and validate the accuracy of the utilised model of dynamic vehicle‒track interaction, as well as a demonstration of a methodology that simulates rail profile degradation for a given mixed traffic situation.
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| 48. |
- Pålsson, Björn, 1981
(författare)
-
Robust evaluation of rail damage and track forces using representative load collectives
- 2015
-
Ingår i: 24th Symposium of the International Association for Vehicle System Dynamics, IAVSD 2015; Graz; Austria; 17 August 2015 through 21 August 2015. - : CRC Press. - 9781138028852 ; , s. 841-850
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a method for robust evaluation of rail damage and lateral wheel–rail contact force spectra for rail traffic in curves. To this end the Manchester Benchmarks passenger vehicle model is used and scatter in vehicle, suspension and wheel profile properties is accounted for in the generation of load collectives that are used for rail damage assessment. Rail wear and RCF damage are evaluated at different curve radii for load collectives of different size using Archard’s wear law and the Tγ RCF damage model. Variance in damage estimates are investigated and it is shown that variance is reduced at smaller curve radii for both damage criteria. It is also found that the variance is larger for the RCF damage estimate than for the wear calculations.
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| 49. |
- Pålsson, Björn, 1981
(författare)
-
Towards Optimization of Railway Turnouts
- 2011
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The turnout (Switch & Crossing) is a vital component in railway networks as it provides flexibility to traffic operation by allowing trains to switch between tracks. The flexibility comes at a cost as the common lack of a transition curve in the diverging route together with the variation and discontinuities in rail profiles result in higher rail degradation rates than in regular track. In this thesis, dynamic interaction between vehicle and turnout is studied using numerical tools for multibody dynamics with focus on laying a foundation for robust optimization of turnout geometry. Considering a stochastic spread in traffic parameters, quantitative and qualitative estimates of rail profile degradation are computed. The influence of wheel profile wear on wheel–rail interaction in a turnout is studied, and it is concluded that equivalent conicity is the wheel profile characterization parameter with the best correlation to rail damage of the investigated parameters. In addition, the influence of hollow worn wheels on rail damage is investigated and it is found that such wheel profiles display a significantly different and potentially more harmful running behaviour at the crossing. The influence of wheel–rail friction coefficient is studied and it is shown that friction correlates strongly to lateral contact forces and wear in the diverging route. Wheelset steering, considering the turnout specific configuration of rail profiles and the presence of check rails, is discussed. One of the track models studied is a discretized mass-spring-damper model with nine degrees-of-freedom. This track model can be tuned to capture the large phase delay at low frequencies found in measurements of dynamic track stiffness, while remaining sufficiently resilient at higher frequencies. Good agreement between the simulation model and field measurement data has been observed. It is concluded that the use of more resilient rail pads can reduce wheel–rail impact loads during the crossing transition.
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| 50. |
- Pålsson, Björn, 1981, et al.
(författare)
-
Track gauge optimisation of railway switches using a genetic algorithm
- 2012
-
Ingår i: Vehicle System Dynamics. - : Informa UK Limited. - 1744-5159 .- 0042-3114. ; 50:SUPPL. 1, s. 365-387
-
Tidskriftsartikel (refereegranskat)abstract
- A methodology for the optimisation of a prescribed track gauge variation (gauge widening) in the switch panel of a railway turnout (switch and crossing, S&C) is presented. The aim is to reduce rail profile degradation. A holistic approach is applied, where both routes and travel directions (moves) of traffic in the switch panel are considered simultaneously. The problem is formulated as a multi-objective minimisation problem which is solved using a genetic-type optimisation algorithm which provides a set of Pareto optimal solutions. The dynamic vehicle-turnout interaction is evaluated using a multibody simulation tool and the energy dissipation in the wheel-rail contacts is used for the assessment of gauge parameters. Two different vehicle models are used, one freight car and one passenger train set, and a stochastic spread in wheel profile and wheel-rail friction coefficient is accounted for. It is found that gauge configurations with a large gauge-widening amplitude for the stock rail on the field side are optimal for both the through and diverging routes, while the results for the gauge side show a larger route dependence. The optimal gauge configurations are observed to be similar for both vehicle types.
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