Abstract
Rolling contact fatigue defects are encountered in railway wheels used under high axle load conditions, in which substantial reductions in rail and wheel wear rates have been obtained through the previous introduction of higher strength materials and modified wheel and rail profiles. The metallurgical characteristics associated with defect initiation and growth are described. A fatigue initiation criterion based on exceedence of shakedown limits for the two wheel materials concerned has been assumed. An analysis of wheel-rail contact conditions in curved and tangent track was undertaken to identify which combinations of wheel load, wheel and rail profiles and vehicle dynamics result in stress levels which exceed shakedown limits. This analysis is supported by full-scale tests involving continuous monitoring of wheel-rail contact. Extreme dynamic loads, leading to the initiation of isolated defects, are more likely to occur on tangent track, while curved track conditions will favour fatigue crack growth, when contact geometry and vehicle tracking combine to concentrate higher stress cycles in the initiation zone. Additional field tests, using an instrumented vehicle, will be carried out to confirm these findings and allow appropriate remedial action to be identified.
Published Version
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