Management and understanding of rolling contact fatigue: WP1 mechanisms of crack initiation: final report

As part of RSSB's research programme, AEA Technology Rail have been developing a model of rolling contact fatigue (RCF) crack initiation. The existing model was developed following a number of detailed RCF site surveys and subsequent vehicle dynamics modelling of vehicles passing each site. It uses the forces and creepages developed in the contact patch, characterised by the energy parameter (also called the wear number), Tγ, to quantify the RCF fatigue damage generated at each contact position. The model was developed largely empirically, but has been found to give good predictions of the locations where RCF cracks develop in normal grade rails. The objective of the research was to increase the understanding of the mechanisms of crack initiation and to underpin and improve the existing energy-based fatigue model of RCF. Work was also undertaken to analyse the effect of material properties on the RCF resistance so that a similar function could be developed for other rail materials. These objectives were achieved through utilisation of fundamental ratchetting and fracture mechanics fatigue models of wear-fatigue interaction developed at the University of Newcastle upon Tyne