Crack initiation in wing rails of swing nose crossings in heavy haul railways

Swing nose crossings (SNXs) are widely used in heavy haul railways due to their favourable dynamic performance. However, field observations have reported significant damage to the wing rails of SNXs under heavy haul operating conditions, primarily caused by rolling contact fatigue (RCF) cracks. This study investigates the crack initiation behaviour in the wing rail of an SNX used in Australian heavy haul railways by examining its accumulated cyclic plastic deformation (ratcheting) response. Contact pressure and tangential stresses were extracted from dynamic finite element simulations and applied in cyclic loading analysis. The ratcheting strain under repeated loading was evaluated, and crack initiation location and life were predicted based on the stabilised ratcheting strain rate and material ductility. Critical plane method was adopted to estimate crack plane orientation. In addition, the influence of different wheel profiles, representing varying levels of tread hollowing, was assessed. The results show that crack initiation consistently occurs 1 mm below the centre contact patch, where the contact pressure reaches its maximum. The predicted crack plane is oriented nearly perpendicular to the rolling surface, and it's validated by field evidence from a service-operated wing rail. Our results also indicate that avoiding severely hollowed wheels can extend the life of crack initiation in the wing rails.