Damage tolerances of a railway axle in the presence of wheel polygonalizations

• A coupled vehicle/track dynamic model is developed to study the wheel polygonalization-induced impacts.
• Dynamic stresses developed in a railway axle due to wheel polygonalization-induced impacts are evaluated.
• Wheel polygonalization-induced load cycles are identified.
• Damage tolerance of a railway axle in the presence of wheel polgyonalization – is assessed in term of residual lifetime.

Damage tolerances of a railway axle in the presence of wheel polygonalization are investigated using a comprehensive coupled vehicle/track dynamic model. The model is formulated through coupling a typical high-speed train model and a slab track model, in which the wheelset, axle box and the slab track are treated as flexible bodies using the modal approach to account for the flexible deflections and dynamic stresses caused by the wheel ploygonalization-induced impact forces. The validity of this model is validated by using axle box vertical accelerations obtained from field tests. The dynamic stress in a railway axle is evaluated by using the modal stress recovery method in the proposed dynamic model, which is validated by the Finite Element Method (FEM). Using this comprehensive coupled/slab track dynamic model, the dynamic stresses developed in a railway axle due to the wheel polygonalization-induced impact forces are predicted, and subsequently used in the damage tolerance analyses to determine the residual lifetime of a railway axle in case of initial cracks. The results indicate that the wheel polygonalization can generate high magnitude impact forces at wheel/rail interfaces leading to remarkable increases in the stress states of a railway axle, and subsequently contribute to the propagations of cracks in the axle shaft. Consequently, a reasonable inspection interval for a high-speed train axles should be employed in the presence of wheel polygonalization.