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Keywords: switches, crossings, contact, stress, creepage, creep, force, damage.

Summary

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.

References

1: I.J. Coleman, E. Kassa, R.A. Smith, "A new algorithm for Wheel-Rail Contact Detection at Railway Switches and Crossings", International Association of Vehicle System Dynamics, 1-7, 2011.
2: M. Burstow, M. Podesta, J. Pearce, "Understanding Wheel/Rail Interaction with Thermographic Imaging", International Association of Vehicle System Dynamics, 1-6, 2011.
3: H.R. Hertz, "Ueber die Beruehrung elastischer Koerper (On Contact Between Elastic Bodies)", Gesammelte Werke (Collected Works), Vol. 1, 1882.
4: A. Wickens, "Fundamentals of Rail Vehilce Dynamics", 2005.
5: J.J. Kalker, "Survey of Wheel-Rail Rolling Contact Theory", Veh. Syst. Dyn., 8, 317-358, 1979. doi:10.1080/00423117908968610
6: O. Polach, "A Fast Wheel-Rail Forces Calculation Computer Code", Veh. Syst. Dyn., 33, 728-739, 1999.
7: J.J. Kalker, "A Fast Algorithm for the Simplified Theory of Rolling Contact", Veh. Syst. Dyn., 1-13, 1982. doi:10.1080/00423118208968684
8: E.A.H. Vollebregt, P. Wilders, "FASTSIM 2: a Second-Order Accurate Frictional Rolling Contact Algorithm", Comput. Mech., 2010.

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 98 PROCEEDINGS OF THE FIRST INTERNATIONAL CONFERENCE ON RAILWAY TECHNOLOGY: RESEARCH, DEVELOPMENT AND MAINTENANCE Edited by: J. Pombo Paper 139 A Multi-Point Contact Detection Algorithm Combined with Approximate Contact Stress Theories I. Coleman^1,2, E. Kassa³ and R. Smith¹ ¹Imperial College London, United Kingdom ²Network Rail, London, United Kingdom ³Royal Institute of Technology KTH, Stockholm, Sweden doi:10.4203/ccp.98.139 purchase the full-text of this paper Full Bibliographic Reference for this paper I. Coleman, E. Kassa, R. Smith, "A Multi-Point Contact Detection Algorithm Combined with Approximate Contact Stress Theories", in J. Pombo, (Editor), "Proceedings of the First International Conference on Railway Technology: Research, Development and Maintenance", Civil-Comp Press, Stirlingshire, UK, Paper 139, 2012. doi:10.4203/ccp.98.139 Keywords: switches, crossings, contact, stress, creepage, creep, force, damage. Summary 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. References 1 I.J. Coleman, E. Kassa, R.A. Smith, "A new algorithm for Wheel-Rail Contact Detection at Railway Switches and Crossings", International Association of Vehicle System Dynamics, 1-7, 2011. 2 M. Burstow, M. Podesta, J. Pearce, "Understanding Wheel/Rail Interaction with Thermographic Imaging", International Association of Vehicle System Dynamics, 1-6, 2011. 3 H.R. Hertz, "Ueber die Beruehrung elastischer Koerper (On Contact Between Elastic Bodies)", Gesammelte Werke (Collected Works), Vol. 1, 1882. 4 A. Wickens, "Fundamentals of Rail Vehilce Dynamics", 2005. 5 J.J. Kalker, "Survey of Wheel-Rail Rolling Contact Theory", Veh. Syst. Dyn., 8, 317-358, 1979. doi:10.1080/00423117908968610 6 O. Polach, "A Fast Wheel-Rail Forces Calculation Computer Code", Veh. Syst. Dyn., 33, 728-739, 1999. 7 J.J. Kalker, "A Fast Algorithm for the Simplified Theory of Rolling Contact", Veh. Syst. Dyn., 1-13, 1982. doi:10.1080/00423118208968684 8 E.A.H. Vollebregt, P. Wilders, "FASTSIM 2: a Second-Order Accurate Frictional Rolling Contact Algorithm", Comput. Mech., 2010. purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £110 +P&P)
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