A multi-point contact detection algorithm combined with approximate contact stress theories
2012 (English)In: Proceedings of the first international conference on railway technology: Research, development and maintenance / [ed] J. Pombo, 2012Conference paper (Other academic)
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 . 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  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  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 , 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.
Place, publisher, year, edition, pages
, Civil-Comp Proceedings, ISSN 1759-3433 ; 98
switches, crossings, contact, stress, creepage, creep, force, damage
Research subject SRA - Transport
IdentifiersURN: urn:nbn:se:kth:diva-87829DOI: 10.4203/ccp.98.139ISBN: 978-1-62276-041-1OAI: oai:DiVA.org:kth-87829DiVA: diva2:501926
First International Conference on Railway Technology 2012 (RAILWAYS 2012), Las Palmas de Gran Canaria, Spain 18-20 April 2012
FunderTrenOp, Transport Research Environment with Novel Perspectives
QC 201301082012-02-142012-02-142013-01-08Bibliographically approved