Research on wheel rolling contact fatigue under traction and braking conditions for high-speed trains with a new fatigue factor

The wheel rolling contact fatigue (RCF) problems in high speed trains greatly reduce wheel service life. Previous studies have primarily focused on the trailer cars, without systematically considering the traction transmission system. Consequently, wheel contact fatigue issues in motor cars have not been thoroughly investigated. This paper establishes a vehicle dynamics model incorporating traction and braking systems. Based on the shakedown diagram, a fatigue factor combined with a damage function model is proposed to investigate the rolling contact fatigue of high-speed train wheels under traction and braking conditions, and to evaluate the risk, location, and safety margin of fatigue crack initiation. The influence of curve radius, traction torque, braking torque, braking level, and track grade on wheel fatigue was analyzed. The results show that wheel damage decreases as the curve radius increases, leading to an improved safety margin. Furthermore, the damage on the outer rail side is greater than that on the inner rail side. Both traction and braking conditions significantly exacerbate fatigue damage while increasing the creepage and adhesion coefficient, particularly in the longitudinal direction, thereby making stick-slip vibrations more likely to occur. In addition, excessive traction or braking torques substantially increase the risk of crack initiation. These findings can provide a theoretical basis for wheel maintenance and the prevention of RCF.