The Wheel-Rail Contact Problem in Vehicle
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THE WHEEL-RAIL CONTACT PROBLEM IN VEHICLE DYNAMIC SIMULATION MODELING OF TRAIN-TURNOUT INTERACTION THE WHEEL-RAIL CONTACT PROBLEM IN VEHICLE DYNAMIC SIMULATION MODELING OF TRAIN-TURNOUT INTERACTION Proefschrift ter verkrijging van de graad van doctor aan de Technische Universiteit Delft, op gezag van de Rector Magnificus prof. ir. K.C.A.M. Luyben, voorzitter van het College voor Promoties, in het openbaar te verdedigen op dinsdag 5 januari 2016 om 10:00 uur door Nico BURGELMAN Burgerlijk werktuigkundig ingenieur, Universiteit Gent, België MSc. Solid and fluid mechanics, Chalmers University of Technology, Sweden geboren te Gent, België. Dit proefschrift is goedgekeurd door de: promotor: Prof. dr. R.P.J.B. Dollevoet copromotor: Dr. Z. Li Samenstelling promotiecommissie: Rector Magnificus, voorzitter Prof. dr. ir. R.P.J.B. Dollevoet, Technische Universiteit Delft Dr. Z. Li, Technische Universiteit Delft Onafhankelijke leden: Prof. S. Iwnicki University of Huddersfield Dr. I.Y. Shevtsov ProRail Dr.ir. A.L. Schwab Technische Universiteit Delft Prof.dr.ir. D.J. Schipper Universiteit Twente Prof.dr. A. Scarpas Technische Universiteit Delft Prof. dr. ir. R.F.Hanssen Technische Universiteit Delft, reservelid This dissertation was supported by: Keywords: Railways, Wheel/rail Contact, Vehicle Dynamics, Non-Elliptical Con- tact Models, Turnouts Printed by: CPI Koninklijke Wöhrmann Cover: Front: The local slip in the contact area calculated with the FastSim method & Back: a visualization of the wheel profile and the contact locus Copyright © 2015 by Nico Burgelman ([email protected]). ISBN 978-94-6203-976-6 An electronic version of this dissertation is available at http://repository.tudelft.nl/. For science, for technology and last but not least, for better railway systems. Nico Burgelman SUMMARY One of the major costs incurred by railway companies is the maintenance of turnouts. This situation occurs because the large dynamic forces between the wheels of a train and the rails of a turnout cause excessive wear, rolling contact fatigue and rapid degradation of other components. A thorough understanding of the dynamic interaction between a train and a turnout could lead to a better design of the vehicle and track structures, deeper insight into the damage mechanisms and subsequently to smarter maintenance planning. To properly model the interaction between a train and a turnout, three important issues need to be considered: 1. Track flexibility: The rails, the fastening, the sleepers and the ballast are not rigid but can move and absorb or transmit vibrations. This factor is especially relevant when impact between the wheel and the rail occurs, which is always the case in a turnout. 2. Wheel/rail contact: In a turnout the rail geometry is complex at the switch blade and at the frog. Therefore, some of the assumptions commonly made in contact models used in vehicle dynamic software are no longer valid when considering those contacts. 3. Effect of train coupling: In a turnout the forces acting between the vehicles through the couplers have a significant effect on the vehicle dynamics. This is especially true when traction or braking is considered. The first issue has been extensively covered in the literature, and flexible track models are available in modern commercial software for vehicle dynamic simulation. Therefore, the issue is not further investigated in this dissertation. The second issue can be approached in two ways. One can use contact models online for the vehicle simulation, which are advanced while still being fast and robust. Alterna- tively, one can use a simple contact method to evaluate the contact forces online during the vehicle simulation. Then, a more sophisticated method can be employed offline re- solving the contact problems and obtaining a more accurate estimate of the local stress and slip distribution in the contact area. In the latter case, the balance of forces is not necessarily fulfilled as the contact force calculated with the more advanced method are not coupled back to the vehicle dynamic simulation; therefore generating an error. This error from the offline approach is investigated in this thesis for the determination of the contact point location and for the calculation of the tangential contact forces. A fast an- alytical method for calculating the longitudinal contact location was validated, but the effect of the contact point location on the wheelset’s yaw angle was found to be negligi- ble. vii viii SUMMARY To quantify the effect of different solution methods of the tangential contact forces, we compared four models: FastSim (the reference model, currently used most often in multibody simulations) and three non-elliptical models based on interpenetration: Kik- Piotrowski, Linder and Stripes. These models were applied in a co-simulation between the vehicle dynamic software and Matlab, simulating hunting motion and steady curv- ing. It was concluded that the interpenetration methods predict a better curving be- haviour (lower creepages and lower creep forces). The simulations performed using the Kik-Piotrowski method resulted in a slightly shorter hunting wavelength. Although the above-mentioned interpenetration methods are more advanced than FastSim, they still make a number of assumptions that may not be satisfied under some certain contact conditions. Therefore, a new contact method is introduced based on Kalker’s full theory with the addition of varying spin creepage. This new method was ap- plied offline in a multibody simulation of a wheel-rail contact in a turnout. The resulting stress and slip distributions were realistic. Moreover, the method converged even in the most difficult contact cases. Thus the method is suitable for online application. The question regarding how the contact models can be validated through measure- ments is a difficult one, as the local stress and slip in the contact area cannot be measured directly. Many methods measuring the consequences of the stress and slip in the con- tact area have been proposed in the literature. One possibility is to measure the energy dissipated in the wheel/rail contact. This dissertation presents and compares several methods calculating the dissipated energy, it then compares the results obtained from vehicle dynamic simulations with measured energy values. It is concluded that although the approach is promising, there is room for improvement for both the simulations and the measurements. The third issue is especially relevant for long trains with a braking locomotive at the front or a tractive locomotive at the rear. In these configurations the couplers will be compressed. Because of the curvature of the track in a curve or a turnout, there will be a misalignment between the couple and the adjacent carbodies. This misalignment produces an outwards lateral force, which combines with the lateral centripetal force to create a large force on the wheels. The magnitude of this force needs to be below a certain limit for derailment safety. In this dissertation, an existing method for calcu- lating the coupler angles in curves with a constant radius is extended to calculate the coupler angle in curve transients and turnouts. With the knowledge of the coupler an- gle, quasi-statics can be used to estimate the lateral wheel rail force and thus the risk of derailment. The results obtained from the quasi-static approach are compared to results obtained from vehicle dynamic simulations. This comparison allows for the definition of a dynamic multiplication factor to be applied to the quasi-static results to obtain a first estimate of the dynamic lateral forces. Such a fast method could be useful when a quick and dirty estimate of the derailment risk is required for a non-daily train configuration or in the early stages of a new vehicle/track design. The analysis of the contact models in this dissertation will help researchers choose between the different models and between implementing the model offline or online. This should enable researchers to accurately model the contact in turnouts so that the deterioration mechanisms underlying the excessive wear and RCF in turnouts can be un- derstood. In turn, this understanding should lead to better maintenance and associated SUMMARY ix cost savings. SAMENVATTING Het onderhoud van spoorwissels is een belangrijke kostenpost voor spoorweguitbaters. Dit komt doordat de hoge krachten tussen wielen van de trein en de spoorstaaf in het wissel hoge slijtage en vermoeiing veroorzaken. Een diepgaand inzicht in de dynami- sche interactie tussen de trein en het wissel kan een beter ontwerp van het wissel mo- gelijk maken. Ook zorgt een beter inzicht in de dynamische interactie voor een beter begrip van de slijtagemechanismen, wat op zijn beurt weer leidt tot een slimmere on- derhoudsplanning. Om de dynamische interactie tussen trein en wissel accuraat te modelleren moeten de volgende drie factoren in acht genomen worden: 1. de elasticiteit van het spoor: de spoorstaven, de dwarsliggers en het ballastbed kunnen bewegen en zo trillingen absorberen of doorgeven. Dit is zeker van belang als er sprake is van impact tussen het wiel en de spoorstaaf, wat in een wissel altijd het geval is. 2. het wiel/spoorstaafcontact: in een wissel is de spoorstaafgeometrie complex, zo- wel bij de tong als bij het puntstuk. Hierdoor zijn sommige veronderstellingen die vaak gemaakt worden in de contactmodellen voor voertuigsimulaties niet langer geldig. 3. de invloed van de treinkoppeling: in een wissel hebben de krachten in de kop- peling tussen de wagenbakken een significante invloed op de voertuigdynamica. Dit wordt nog belangrijker als ook rekening gehouden wordt met de tractie of het remmen van het voertuig. Het eerste punt, de elasticiteit van het spoor, is uitvoerig beschreven in de vaklitera- tuur. Verscheidene modellen voor het modelleren van deze elasticiteit zijn beschikbaar in commerciële software voor voertuigsimulaties. Daarom wordt dit punt niet verder behandeld in dit proefschrift. Het tweede punt, het wiel/spoorstaafcontact in het wissel, kan op twee manieren benaderd worden. Ofwel wordt een tamelijk geavanceerd contactmodel gebruikt, on- line in de voertuigsimulatie.