Thermal impact on rolling contact fatigue and capacity of railway wheels
Paper in proceedings, 2016
Tread braked railway wheels are subjected to complex loading due to combined rolling contact stresses and thermally induced stresses. The main objective of the present study is to find the limits for tread braking with respect to temperature impact on rolling contact fatigue (RCF) of the wheel tread. A wheel with an S-shaped web is studied for some different stop braking loads. Using 3D FE simulations, the effects of simultaneous thermal loading from braking and mechanical loading, with traversing wheel-rail rolling contact, are studied. In order to account for the elevated temperatures, the simulations utilise a temperature-dependent elastoplastic material model. The mechanical loads account for frictional rolling contact stress distributions induced by braking, using a novel method that is based on elastoplastic contact simulations. Partial slip is considered and interfacial shear stresses are introduced in the wheel-rail contact area. Evolution of damage in the vicinity of the wheel tread is studied for various brake loading cases. In order to assess limits for the tread braking, the calculated damage is compared to previously developed critical damage levels which were based on full-scale brake rig testing. Results are presented for a parametric study with thermomechanical loading based on different load cases. The influence from operational parameters such as axle loads, initial speeds, decelerations and block material is studied. The results show that the temperature has a strong influence on the rolling contact fatigue of the wheel treads and, hence, also on the thermal capacity of the wheels. The study gives preliminary limits for revenue traffic, described as combinations of tread temperatures and wheel-rail rolling contact loading, which should be respected to avoid thermal cracking of the wheel treads.