Abstract: Continuously distributed rolling contact fatigue (RCF) has been observed in recent years on wheels of a type of Chinese EMU trains with a designed speed of 250 km/h. To understand its initiation mechanism, a monitoring test covering 2~3 periods of wheel re-profiling are performed in three depots. The results show that the RCF usually occurs in a band of 15~30 mm outside the nominal rolling circle after a mileage of 100 000~150 000 km, the cracks propagate on the tread surface with an angle about 45° or -45° to the lateral direction and down to a depth of 0.25~1.2 mm within a re-profiling period, and the RCF does not influence the operation of the EMU trains due to the absence of severe damages resulted from it, e.g., shelling. With the parameters collected during the monitoring test, a vehicle-track interaction model is developed with SIMPACK, based on which the occurrence of RCF is further estimated using the shakedown map and Tγ model. It is found that the poor geometry match between wheels and low rails on curves dominates the occurrence of the RCF, and the root causes include unsound rail profiles for grinding and wheel hollow wear. Detailed analyses show that the severe wheel-rail mismatch leading to RCF only occurred on specific curves, which explains the one side occurrence of RCF on the EMU trains that do not turn around during return services and run on lines with similar numbers of left and right curves. At the end discussions are given on the limitations of existing RCF prediction methods and future research objectives on RCF.

Key words: Tγ model, curving, high-speed EMU, rolling contact fatigue, shakedown map