KTH Engineering 899731/ آ  KTH Engineering Sciences ... Matin Shahzamanian Sichani Doctoral

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  • KTH Engineering Sciences

    On Efficient Modelling of Wheel-Rail Contact

    in Vehicle Dynamics Simulation

    Matin Shahzamanian Sichani

    Doctoral Thesis Stockholm, Sweden


  • Academic thesis with the permission of KTH Royal Institute of Tech- nology, Stockholm, to be submitted for public examination for the de- gree of Doctor of Philosophy of Engineering in Vehicle and Maritime Engineering on Wednesday the 24th of February 2016 at 13.15, in room F3, Lindstedsvägen 26, KTH Royal Institute of Technology, Stockholm, Sweden.

    TRITA-AVE 2016:02 ISSN 1651-7660 ISBN 978-91-7595-846-0

    c© Matin Sh. Sichani, 2016

    Postal address: Visiting address: Contact: Matin Sh. Sichani Teknikringen 8 matinss@kth.se Aeronautical and Vehicle Eng. 3rd floor KTH Royal Inst. of Tech. Room 6515 SE-100 44 Stockholm Stockholm


  • Abstract

    The wheel-rail contact is at the core of all research related to vehicle- track interaction. This tiny interface governs the dynamic performance of rail vehicles through the forces it transmits and, like any high stress concentration zone, it is subjected to serious damage phenomena. Thus, a clear understanding of the rolling contact between wheel and rail is key to realistic vehicle dynamics simulation and damage analysis.

    In a multi-body dynamics simulation, the demanding contact pro- blem should be evaluated at about every millisecond for several wheel- rail pairs. Hence, a rigorous treatment of the contact is highly time- consuming. Simplifying assumptions are therefore made to accelerate the simulation process. This gives rise to a trade-off between the accu- racy and computational efficiency of the contact model in use.

    Conventionally, Hertz+FASTSIM is used for calculation of the contact forces thanks to its low computational cost. However, the elliptic patch and pressure distribution obtained by Hertz’ theory is often not realistic in wheel-rail contact. Moreover, the use of parabolic traction bound in FASTSIM causes considerable error in the tangential stress estimation. This combination leads to inaccurate damage predictions.

    Fast non-elliptic contact models are proposed by others to tackle this issue while avoiding the tedious numerical procedures. The studies conducted in the present work show that the accuracy of these models is case-dependent.

    To improve the accuracy of non-elliptic patch and pressure estima- tion, a new method is proposed. The method is implemented in an al- gorithm named ANALYN. Comparisons show improvements in patch and, particularly, pressure estimations using ANALYN.

    In addition, an alternative to the widely-used FASTSIM is developed , named FaStrip. Unlike FASTSIM, it employs an elliptic traction bound and is able to estimate the non-linear characteristic of tangential stress distribution. Comparisons show more accurate estimation of tangential stress and slip velocity distribution as well as creep forces with FaStrip.

    Ultimately, an efficient non-elliptic wheel-rail contact model consis- ting of ANALYN and FaStrip is proposed. The reasonable computatio- nal cost of the model enables it to be used on-line in dynamics simula- tion and its accuracy can improve the damage predictions.

    Keywords: wheel-rail contact, non-elliptic contact, rail vehicle dynamics, rol- ling contact, vehicle-track interaction, wheel-rail damage


  • Sammanfattning

    Kontakten mellan hjul och räl är central i all forskning kring fordon- bana interaktion. Detta lilla gränssnitt styr spårfordons dynamiska pres- tanda genom de krafter det överför och, liksom andra spänningskoncen- trationer, är det utsatt för allvarliga skadefenomen. Således är en tydlig förståelse av den rullande kontakten mellan hjul och räl nyckeln till rea- listisk fordonsdynamisk simulering och skadeanalys.

    I simulering bör kontaktproblemet hjul-räl utvärderas varje millise- kund. Därför är en strikt behandling av kontakten mycket tidskrävande. Förenklande antaganden görs därför för att snabba upp simuleringspro- cessen. Detta ger upphov till en kompromiss mellan noggrannhet och beräkningseffektivitet för kontaktmodellerna.

    Konventionellt används Hertz+FASTSIM för beräkning av kontakt- krafter tack vare sin låga beräkningskostnad. Dock är kontaktytan och tryckfördelningen som erhålls genom Hertz teori ofta inte realistisk för hjul-räl kontakt. Dessutom kan användningen av parabolisk traktions- gräns i FASTSIM orsaka betydande fel i uppskattning av den tangen- tiella spänning. Denna kombination leder till en oprecis skadeanalys.

    Snabba icke-elliptiska kontaktmodeller har föreslagits av andra fors- kare för att lösa detta problem och undvika omfattande numeriska beräk- ningar. De studier som utförts i detta arbete visar att noggrannheten hos kontaktytan och uppskattningen av tryckfördelningen för dessa model- ler är skiftberoende. De studier som utförts i detta arbete visar att nog- grannheten hos dessa modeller är fullberoende.

    För att förbättra noggrannheten av den icke-elliptiska kontaktytan och tryckuppskattningen, föreslås en ny metod. Metoden är implemen- terad i en algoritm kallad ANALYN. Jämförelser visar på förbättringar för kontaktytan och, i synnerhet, tryckuppskattningen med ANALYN.

    Dessutom har ett alternativ till den välkända FASTSIM utvecklats, kallad FaStrip. Till skillnad från FASTSIM, används en elliptisk trak- tionsgräns och metoden kan prediktera en icke-linjära tangentiell spän- ningsfördelning. Jämförelser visar på förbättrad noggrannheten för spän- ning och glidhastighetsfördelning samt krypkrafter med FaStrip.

    Sammanfattningsvis förslås en effektiv icke-elliptisk kontaktmodell som består av ANALYN och FaStrip. Den rimliga beräkningskostnaden för modellen gör det möjligt att använda den odirekt i dynamisk simu- lering och dess noggrannhet kan förbättra skadeanalysen. Nyckelord: hjul-räl kontakt, icke-elliptisk kontakt, spårfordons dynamik, rul- lande kontakt, fordon-bana interaktion, hjul-räl utmattning


  • Preface

    The work presented in this doctoral thesis was carried out at the Depart- ment of Aeronautical and Vehicle Engineering, KTH Royal Institute of Technology in Stockholm, between January 2011 and January 2016.

    The financial support from KTH Railway Group sponsors, namely the Swedish Transport Administration (Trafikverket), Bombardier Transpor- tation, Interfleet Technology, Stockholm County Council (Stockholms Läns Landsting), SJ, and Sweco, is gratefully acknowledged.

    I would like to thank my supervisors, Prof. Mats Berg and Dr. Roger En- blom, for their invaluable support and guidance throughout the project. Mats your professional standards and uninterrupted care and support backed me till the end. Roger your in-depth knowledge enlightened me and the discussions we had guided me towards the right path. Thanks both of you for believing in me.

    To my colleagues at the division of Rail Vehicles and at KTH, thank you for making such a friendly and pleasant atmosphere. Besides enjoying fruitful discussions, it is a lot of fun working with you.

    To my family, Maman, Baba, Danial and Amin, whose support and en- couragement made this work possible, you truly deserve my deepest gratitude and love. Maman if it wasn’t for you, I would never manage this. Thank you!

    Finally, I would like to thank all my friends and fellows for standing by me even when I have a rough day. You are truly the best.

    Matin Sh. Sichani Stockholm, January 2016


  • Dissertation

    This thesis comprises two parts. Part I offers an overview of the research area and a summary of the present work. Part II consists of the following scientific papers written during the PhD work:

    Paper A M. Sh. Sichani, R. Enblom, M. Berg, Comparison of Non-elliptic Contact Models: Towards Fast and Accurate Modelling of Wheel-Rail Contact, Wear 314 (2014) 111-117.

    Paper B M. Sh. Sichani, R. Enblom, M. Berg, A Novel Method to Model Wheel-Rail Normal Contact in Vehicle Dynamics Simulation, Veh. Syst. Dyn. 52 (12) (2014) 1752-1764.

    Paper C M. Sh. Sichani, R. Enblom, M. Berg, Non-Elliptic Wheel-Rail Contact Mo- delling in Vehicle Dynamics Simulation, Int. J. Railway Tech. 3 (3) (2014) 77-94.

    Paper D M. Sh. Sichani, R. Enblom, M. Berg, An Alternative to FASTSIM for Tan- gential Solution of the Wheel-Rail Contact, submitted for publication.

    Paper E M. Sh. Sichani, R. Enblom, M. Berg, A Fast Wheel-Rail Contact Model for Detailed Damage Analysis in Dynamics Simulation, submitted for publica- tion.

    Division of work between authors Sichani initiated the studies, performed the analyses and wrote the pa- pers. Enblom and Berg supervised the work and reviewed the papers.


  • Publication not included in this thesis N. Burgelman, M. Sh. Sichani, R. Enblom, M. Berg, Z. Li, R. Dollevoet, Influence of Wheel-Rail Contact Modelling on Vehicle Dynamic Simulation, Veh. Syst. Dyn. 53 (8) (2015) 1190-1203.

    Presentations at international conferences M. Sh. Sichani, R. Enblom, M. Berg, Comparison of Non-elliptic Contact Models: Towards Fast and Accurate Modelling of Wheel-Rail Contact, 9th Int. Conf. on Contact Mechanics and Wear of Rail-Wheel Systems, Chengdu 2012.

    M. Sh. Sichani, R. Enblom, M. Berg, Towards Fast and Accurate Model- ling of Wheel-Rail Contact, 17th Nordic Sem. on Railway Tech., Tammsvik 2012.

    M. Sh. Sichani, R. Enblom, M. Berg, A Fast Non-Elliptic Contact Model for Application to Rail Vehicle Dynamics Simulation, 2nd Int. Conf. on Rail- way Tech., Ajaccio 2014.

    M. S