Study on the mechanism of rolling contact fatigue in the central section of wheel treads for metro vehicles

Rolling contact fatigue (RCF) is a common form of wheel damage of metro vehicles, which has significant impacts on operational safety and maintenance of wheels. This paper focuses on the RCF observed in wheels used on a metro line in China. On-site investigations and simulation analyses were conducted to examine the influence of various wear patterns on the RCF of wheel treads. The results showed that about 42% of the wheels rolling on this line experienced RCF on the central section of their treads, with oblique cracks forming at angles of approximately 40° to 50° relative to the horizontal plane. Moreover, these wheels exhibiting RCF typically displayed W-shaped wear patterns. Increased contact position concentration was noted at the low rail side wheels with a radius of less than 600 m when W-shaped tread wear on wheels, resulting in creep force resultants roughly perpendicular to the fatigue cracks on the wheel treads, and a significant increase in contact stress. As a result, the wheel material in the contact area was more likely to fall into the ratcheting zone. The damage values for these wheels were about two times higher than those with LM treads. To sum up, W-shaped wear on wheels is identified as the primary cause of RCF in the central section of wheel treads for vehicles operating on this line.