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| 2. |
- Enblom, Roger, 1950-
(författare)
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On Simulation of Uniform Wear and Profile Evolution in the Wheel - Rail Contact
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Numerical procedures for reliable wheel and rail wear prediction are rare. Recent development of simulation techniques and computer power together with tribological knowledge do however suggest computer aided wear prediction as possible. The present objective is to devise a numerical procedure able to simulate profile evolution due to uniform wear sufficiently accurate for application to vehicle dynamics simulation. Such a tool should be useful for maintenance planning, optimisation of the railway system and its components as well as trouble-shooting. More specifically, the field of application may include estimation of reprofiling frequency, optimisation of wheel – rail profile match, optimisation of running gear suspension parameters, and recognition of unfavourable profile evolution influencing the dynamic response of the vehicle. The research contribution accounted for in this thesis includes, besides a literature review, modelling of the wheel – rail interface, benchmarking against traditional methods, and validation with respect to full-scale measurements. The first part addresses wheel – rail contact conditions in the context of wear simulation as well as tribological environment and tractive forces. The current approach includes Archard’s wear model with associated wear maps, vehicle dynamics simulation, and railway network definition. One objective is to be able to include variations in operation conditions in the set of simulations instead of using scaling factors. In particular the influence of disc braking and varying lubrication conditions have been investigated. Both environmental factors like moist and contamination and deliberate lubrication need to be considered. As part of the associated contact analysis the influence of tangential elastic deformation of the contacting surfaces has been investigated and found to be essential in case of partial slip contact conditions. The influence on the calculated wear of replacing the Hertzian contact by a non-elliptic semi-Hertzian method has been investigated, showing relocation of material loss towards increased profile curvature. In the second part comparisons have been carried out with traditional methods, where the material loss is assumed to be directly related to the energy dissipated in the contact. Attention has been paid to the understanding of the principle differences between the investigated methods, comparing the distribution of friction energy, sliding velocity, and wear depth. As a prerequisite, contact conditions with dependence on wheelset guidance and curving performance as well as influence of tractive forces have been investigated. In the final part validation of the developments related to wheel wear simulation is addressed. Disc braking has been included and a wear map for moist contact conditions based on recent tests has been drafted. Good agreement with measurements from the reference operation, is achieved. Further a procedure for simulation of rail wear and corresponding profile evolution has been formulated. A simulation set is selected defining the vehicles running on the track to be investigated, their operating conditions, and contact parameters. Trial calculations of a few curves show qualitatively good results in terms of profile shape development and difference in wear mechanisms between gauge corner and rail head. The wear rates related to traffic tonnage are however overestimated. The impact of the model improvements accounted for in the first part of the thesis has been investigated, indicating directions for further development.
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| 3. |
- Gebretsadik, Elias Kassa, 1975-, et al.
(författare)
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Geometry and stiffness optimisation for switches & crossings, and simulation of material degradation
- 2010
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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. ; 224, s. 279-292
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Tidskriftsartikel (refereegranskat)abstract
- A methodology for simulatingwear, rolling contact fatigue, and plastic deformation for a mixed traffic situation in switches and crossings (S&C) has been developed. The methodology includes simulation of dynamic vehicle-track interaction considering stochastic variations in input data, 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. To find means of improving the switch panel design, the geometry of a designed track gauge variation in the switch panel has been represented in a parametric way. For traffic in the facing and trailing moves of the through route, an optimum solution was identified and then validated by evaluating a wide set of simulation cases (using different wheel profiles). The optimum design includes a 12 mm maximum gauge widening. Several crossing geometries were investigated to find an optimal geometric design for the crossing nose and wing rails. The MaKuDe design showed the best performance for moderately worn wheel profiles in both running directions (facing and trailing moves). In connection with reduced support stiffness (e. g. elastic rail pads), this crossing design is predicted to lead to a significant reduction of impact loads and consequently provide a high potential of life-cycle cost reduction.
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| 4. |
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| 5. |
- Iwnicki, Simon, et al.
(författare)
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Advances in vehicle-track interaction tools
- 2009
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Ingår i: Railway Gazette International. - 0373-5346. ; 165:9, s. 47-52
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Forskningsöversikt (övrigt vetenskapligt/konstnärligt)abstract
- In this article, the authors discuss how computer modeling is enabling researchers to improve their understanding of vehicle-track interaction. This in turn allows for more accurate predictions to be made regarding rail damage on plain lines as well as turn-outs. The authors discuss track interaction models, multi-body system modeling, surface roughness models, and train-turnout interactions. The article concludes with the authors noting that numerous parameters related to design and conditions influence dynamic train-turnout interactions.
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| 6. |
- Iwnicki, Simon, 1966-, et al.
(författare)
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The "SUSTRAIL" High Speed Freight Vehicle : Simulation of Novel Running Gear Design
- 2013
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Konferensbidrag (refereegranskat)abstract
- As part of the European Commission project ‘SUSTRAIL’ the authors together with other industry and academic partners are designing a freight vehicle optimised for the carriage of high value, low density, time sensitive products. A review of potential engineering innovations has been carried out and a vehicle is being designed based on optimised parameters for this combination of innovative technologies including radial steering, disk braking and optimised bogie frame structure. The results of the selection and optimisation of the running gear are presented heretogether with an assessment of the potential improvement in running behaviour and its impact on the railway system.
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| 7. |
- Iwnicki, Simon, et al.
(författare)
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Wheel-rail contact mechanics
- 2009
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Ingår i: Wheel-rail interface handbook. - Cambridge, UK : Woodhead Publishing Ltd. - 9781845694128 - 9781845696788 - 9781439801468 ; , s. 58-92
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Bokkapitel (refereegranskat)
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| 8. |
- Link, Heike, et al.
(författare)
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Cost allocation Practices in the European Transport Sector
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This deliverable D1, Cost Allocation practices in the European Transport Sector, is one of two reports from WP1 - State of the art methodology and survey of existing practice. It summarises the existing practice of cost estimation and cost allocation in all modes of transport. Its purpose is to identify gaps and open issues in allocation methods which currently prevent the use of marginal cost figures in pricing, and to analyse the methodological background of available studies. As the whole CATRIN project, the focus is on infrastructure costs, e.g. on the costs of providing, maintaining, renewing and operating infrastructure. The second deliverable from WP1 provides the internal blueprint for the case studies to be conducted in CATRIN.
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| 9. |
- Persson, Rickard, 1958-
(författare)
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Tilting trains : Enhanced benefits and strategies for less motion sickness
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Carbody tilting is today a mature and inexpensive technology that allows higher train speeds in horizontal curves, thus shortening travel time. This doctoral thesis considers several subjects important for improving the competitiveness of tilting trains compared to non-tilting ones. A technology review is provided as an introduction to tilting trains and the thesis then focuses on enhancing the benefits and strategies for less motion sickness. A tilting train may run about 15% faster in curves than a non-tilting one but the corresponding simulated running time benefit on two Swedish lines is about 10%. The main reason for the difference is that speeds are set on other grounds than cant deficiency at straight track, stations, bridges, etc. The possibility to further enhance tilting trains’ running speed is studied under identified speed limitations due to vehicle-track interaction such as crosswind requirements at high speed curving. About 9% running time may be gained on the Stockholm–Gothenburg (457 km) mainline in Sweden if cant deficiency, top speed, and tractive performance are improved compared with existing tilting trains. Non-tilting high-speed trains are not an option on this line due to the large number of 1,000 m curves. Tilting trains run a greater risk of causing motion sickness than non-tilting trains. Roll velocity and vertical acceleration are the two motion components that show the largest increase, but the amplitudes are lower than those used in laboratory tests that caused motion sickness. Scientists have tried to find models that can describe motion sickness based on one or more motion quantities. The vertical acceleration model shows the highest correlation to motion sickness on trains with active tilt. However, vertical acceleration has a strong correlation to several other motions, which precludes vertical acceleration being pointed out as the principal cause of motion sickness in tilting trains. Further enhanced speeds tend to increase carbody motions even more, which may result in a higher risk of motion sickness. However, means to counteract the increased risk of motion sickness are identified in the present work that can be combined for best effect. Improved tilt control can prevent unnecessary fluctuations in motion sickness related quantities perceived by the passengers. The improved tilt control can also manage the new proposed tilt algorithms for less risk of motion sickness, which constitute one of the main achievements in the present study. Local speed restrictions are another means of avoiding increased peak levels of motion sickness when increasing the overall speed. The improved tilt control and the proposed tilt algorithms have proven to be effective in on-track tests involving more than 100 test subjects. The new tilt algorithms gave carbody motions closer to non-tilting trains. Rather unexpectedly, however, the test case with the largest decrease in tilt gave a greater risk of motion sickness than the two test cases with less reduction in tilt. It is likely that even better results can be achieved by further optimization of the tilt algorithms; the non-linear relation between motions and motion sickness is of particular interest for further study.
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| 10. |
- Polach, Oldrich, et al.
(författare)
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Simulation
- 2006
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Ingår i: Handbook of Railway Vehicle Dynamics. - : Taylor & Francis Group. - 9780849333217 ; , s. 359-421
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Bokkapitel (refereegranskat)
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| 11. |
- Smith, Andrew, et al.
(författare)
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Estimating the relative cost of track damage mechanisms : combining economic and engineering approaches
- 2017
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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. ; 231:5, s. 620-636
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a new, two-stage methodology to estimate the relative marginal cost of different types of vehicles running on the rail infrastructure. This information is important particularly where the infrastructure managers wish to differentiate the track access charges by vehicle type for the purpose of incentivizing the development and use of more track-friendly vehicles.EU legislation requires that the European infrastructure managers set the access charges based on the incremental (marginal) cost of the running trains on their networks. The novelty of the approach derives from the combination of: (1) engineering simulation methods that estimate the track damage caused by the rail vehicles; and (2) econometric methods that estimate the relationship between the actual maintenance costs and the different damage mechanisms. This two-stage approach fills an important gap in the literature, given the limitations of the existing single-stage engineering or econometric approaches in obtaining the relative marginal costs for different types of damage.The authors demonstrate the feasibility of the method using 45 track sections from Sweden, for which the data on maintenance costs are available together with relevant track and vehicle data for 2012 (supplied by the Swedish Transport Administration). The authors demonstrate the feasibility of producing summary, section-level damage measures for the three damage mechanisms (wear, rolling contact fatigue, and track settlement), which can be taken forward to the second stage. The econometric results of the second stage indicate that it is possible to obtain sensible relationships between cost and the different damage types, and thus produce relative marginal costs by the damage mechanism and in turn the vehicle type. Based on this feasibility study, tracksettlement has been found to be the most expensive (in terms of maintenance cost) of the three mechanisms, followed by the rolling contact fatigue and then the wear. Future applications should focus on larger datasets in order to produce the required degree of precision on the estimation of the marginal cost.
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| 12. |
- Smith, Andrew S. J., et al.
(författare)
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Estimating the damage and marginal cost of different vehicle types on rail infrastructure : Combining economic and engineering approaches
- 2015
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Ingår i: Stephenson Conference Research for Railways 2015. - : Institution of Mechanical Engineers. - 9781510855830 ; , s. 265-274
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Konferensbidrag (refereegranskat)abstract
- EU legislation requires that European infrastructure managers set access charges based on the marginal cost of running trains on their networks. Two methods have been used in the literature for this purpose. Top-down methods relate actual costs to traffic volumes. Bottom-up methods use engineering models to simulate damage and then translate damage into costs based on assumptions about interventions and their unit costs. Whilst top down methods produce sensible results for marginal cost overall, they have struggled to differentiate between traffic types. The challenge for bottom-up approaches is how to translate damage into cost, with numerous assumptions being required which may be invalid. This paper proposes a new, two stage approach to estimating the marginal cost of rail infrastructure usage. The first stage uses engineering models to simulate damage caused by vehicles on the network. The second stage seeks to establish a statistical relationship between actual costs and damage. It is thus possible to convert damage estimates into costs using actual cost data, rather than through a set of potentially invalid assumptions as in previous approaches. Only the first stage is implemented in this paper. We show that it possible to produce total (annualised) damage measures for three damage mechanisms on five actual track sections in Sweden. Once extended, it will be possible to model the relationship between damage and actual costs for the first time; and thus better understand the relative costs of the different damage mechanisms and in turn inform the level and structure of track access charges.
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| 13. |
- Stichel, Sebastian, Professor, 1966-, et al.
(författare)
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Estimating the marginal maintenance cost of different vehicle types on rail infrastructure
- 2021
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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.
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we combine engineering and economic methods to estimate the relative maintenance cost of different types of damage on the Swedish rail infrastructure. The engineering method is good at predicting damage from traffic, while the economic method is suitable for establishing a relationship between damage and cost. We exploit the best features of both methods in a two-stage approach and demonstrate its applicability for rail infrastructure charging, based on a sample of 143 track sections comprising about 11,000 km of track. The paper implements for the first time the method previously proposed in Smith et al., whilst also enhancing the method in several respects. We demonstrate how the estimated relative maintenance costs related to different damage mechanisms can be used to calculate the marginal cost of different vehicle types. The results are relevant for infrastructure managers in Europe who wish to differentiate their track access charges such that each vehicle pays its short run-marginal damage cost, which can support more efficient use of the rail infrastructure and influence vehicle design to minimize system costs.
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