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- Coleman, Ian, et al.
(author)
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A multi-point contact detection algorithm combined with approximate contact stress theories
- 2012
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In: Proceedings of the first international conference on railway technology. - Stirlingshire, UK : Civil-Comp Press. - 9781622760411
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Conference paper (other academic/artistic)abstract
- The wheel-rail contact condition highly influences both the dynamics of the wheelset and the location and severity of rail surface damage. Complex rail geometries, as found within railway switches and crossings (S&C), require a sophisticated contact detection procedure to account for any general state of the wheelset.A generic wheel-rail contact detection tool suitable for railway S&C has been developed [1]. Nominal and measured wheel and rail profiles can be handled and automatically positioned within a common track coordinate system. Flange-back detection, wheelset yaw angles and track irregularities are all accounted for. An elastic deformation multi-point contact detection scheme has also been developed, enabling any number of contact points to be found for both conformal and non-conformal contact conditions. The total applied load is then distributed proportionately between all contact points through a new iteration scheme.Contact detection results have been compared with both established contact models (theoretical) and a new experimental technique [2] using thermal imaging technology (measured). A vehicle-track dynamics analysis was completed to provide realistic input parameters to the contact detection model. Excellent alignment with both the theoretical and measured points of contact was made.Established contact stress theories have also been integrated within the tool. The Hertzian normal elastic contact model [3] has been included to provide an approximation to the shape and size of each individual contact patch. Numerous tangential solutions have been implemented to calculate wheel-rail creepage [4], linear and non-linear creep forces [5,6] and three-dimensional tractions and slip [7,8].Wear depth predictions were made by adapting Archard's wear law to accept results from the Fastsim algorithm. An indication of rolling contact fatigue (RCF) has also been included through calculation of the wear number (damage index) T-gamma. To demonstrate the entire methodology, a simple switch rail contact scenario is presented.
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| 4. |
- Cornish, Andrew, et al.
(author)
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Field Experimental Studies of Railway Switches and Crossings
- 2012
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In: First International Conference on Railway Technology 2012 (RAILWAYS 2012). - Stirlingshire, UK : Civil-Comp Press.
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Conference paper (other academic/artistic)abstract
- Switches and crossings are the weakest point in the rail infrastructure, with a high rate of failure in comparison with plain lines arising from the amplified dynamic forces that occur as vehicles negotiate through their complex rail geometries. The switch and crossing assets require heavy investment to maintain and renew within the rail infrastructure. Maintenance strategies tend to include a routine inspection followed by corrective maintenance to correct failures or the damage as necessary.This paper shows a methodology for switches and crossings (S&C) maintenance moving towards a predictive maintenance using condition monitoring. Several sites have been instrumented around the United Kingdom to follow the condition of the assets and different components. The instrumentation method, design of experiments and the results for a single site are shown in the investigation. The various 'design of experiment' parameters and levels are described, with the analysis based on the recorded data at a single site. Strain data and the velocity data are included in the investigation.Data analysis was completed in two phases, firstly collecting field data, which included strains through the rail, and the velocity of the adjoining structure. This data has given a good understanding of the material degradation over time, and under certain loading conditions. The analysis will continue into the second phase, which will include signal processing to understand the general responses of the structure to the dynamic loading of the wheel-rail contact.Preliminary instrumentation results of the field experimentation are shown. There are high peaks of strain arising from the vehicle entering the higher magnitude zone of the S&C, shown in the peak to peak and mean strain levels. The mean values of strain are maximum vertically at the switch tips (with the switch blade closed against the stock rail) for the through route.Investigation of strains and velocities are important to determine the trends and current values that are being seen within the infrastructure under loading. The use of this data will continue to develop through trend analysis. Current limits and tolerances are being recorded for future research to develop triggers for condition monitoring limits and maintenance guidelines.
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| 6. |
- Gebretsadik, Elias Kassa, 1975-, et al.
(author)
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Dynamic interaction between train and railway turnout : full-scale field test and validation of simulation models
- 2008
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In: Vehicle System Dynamics. - : Taylor & Francis Group. - 0042-3114 .- 1744-5159. ; 46:1, s. 521-534
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Journal article (peer-reviewed)abstract
- Results from an extensive field test performed in a UIC60-760-1:15 turnout on Svealandsbanan in Sweden are reported. Lateral and vertical wheel-rail contact forces were measured by a wheelset instrumented with strain gauges on the wheel discs. The test train with axle load 25 tonnes passed through the turnout in the main and diverging routes and in the facing and trailingmoves. The influences of train speed and moving direction on the magnitude and the position of the maximum lateral contact force in the diverging route of the switch panel, and the influences of train speed, moving direction and route on the maximum vertical contact force in the crossing panel, are investigated. Measured contact forces are compared with calculated forces for a validation of two previously developed numerical models. The magnitude and position of the calculated maximum lateral contact forces are in good agreement with the corresponding measured values. Both measurements and numerical simulations show an increase in maximum lateral contact force with increasing train speed in both the facing and trailing moves. The facing move of the diverging route leads to the highest lateral contact forces in the switch panel. The maximum vertical contact force is not influenced significantly by whether the train is moving in the facing or trailing moves. However, the train route (main or diverging) has a large influence on the maximum vertical contact force at the crossing.
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| 7. |
- Gebretsadik, Elias Kassa, 1975-, et al.
(author)
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Dynamic train-turnout interaction in an extended frequency range using a detailed model of track dynamics
- 2009
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In: Journal of Sound and Vibration. - : Elsevier BV. - 0022-460X .- 1095-8568. ; 320:4-5, s. 893-914
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Journal article (peer-reviewed)abstract
- A time domain solution method for general three-dimensional dynamic interaction of train and turnout (switch and crossing) that accounts for excitation in an extended frequency range (up to several hundred Hz) is proposed. Based on a finite element (FE) model of a standard turnout design, a complex-valued modal superposition of track dynamics is applied using the first 500 eigenmodes of the turnout model. The three-dimensional model includes the distribution of structural flexibility along the turnout, such as bending and torsion of rails and sleepers, and the variations in rail cross-section and sleeper length. Convergence of simulation results is studied while using an increasing number of eigenmodes. It is shown that modes with eigenfrequencies up to at least 200 Hz have a significant influence on the magnitudes of the wheel-rail contact forces. Results from using a simplified track model with a commercial computer program for low-frequency vehicle dynamics are compared with the results from using the detailed FE model in conjunction with the proposed method.
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| 8. |
- Gebretsadik, Elias Kassa, 1975-, et al.
(author)
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Geometry and stiffness optimisation for switches & crossings, and simulation of material degradation
- 2010
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In: 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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Journal article (peer-reviewed)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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| 9. |
- Gebretsadik, Elias Kassa, 1975-, et al.
(author)
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Investigation of failure statistics for switches and crossings in the UK
- 2011
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Conference paper (peer-reviewed)abstract
- Switches and crossings (S&Cs) failure statistics for the UK rail industry are investigated for the various types of S&C in the network with varying geometry, switch length and allowable speed limit. The analysis is based on recorded delay and failure rectification costs for a single (financial) year. The overall cumulative delay cost and the cost per unit have been included in the investigation. Wear has been shown to be the common damage type in all lengths of S&C in terms of delays and rectifications costs, since one of the rectification procedures for such failure type is replacement of the asset. Mid speed switches, such as C length and D length switches, have high industrial relevance due to the high costs in terms of failure delays. The normalised delay per total population showed a highest delay cost for the high speed G+ length switch.
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