Thermal cracking of railway wheels: Towards experimental validation

Abstract

Thermal cracking of railway wheel treads is investigated using a combined experimental and numerical approach. Results from controlled brake rig tests of repeated stop braking cycles for a railway wheel in rolling contact with a so-called railwheel are presented. Test conditions are then numerically analysed using finite element (FE) simulations that account for the thermomechanical loading of the wheel tread. For the studied stop braking case, thermal cracks are found in the wheel tread after few brake cycles. Results from thermal imaging reveal a frictionally excited thermoelastic instability phenomenon called “banding” where the contact between brake block and wheel occurs only over a fraction of the block width. This condition results in locally high temperatures. The numerical analysis assesses ratcheting response of the wheel tread material under operational conditions corresponding to two types of banding patterns and also a case of uniform heating. Fatigue life predictions are estimated from the evaluated ratcheting response using a simplified accumulation rule. Predicted lives are found to be in reasonable agreement with experimental results.