Plastic Deformation of Flash Butt Welds in High Strength Rail Steels in Heavy Haul Railway Systems

This doctoral study investigated the ratcheting (cyclic plasticity) behaviour and quantified cyclic plasticity of rail flash butt welds used in heavy haul railways. The experimental study including uniaxial and biaxial cyclic loading tests were first carried out, followed by the microstructure characterisation, to study the heterogeneities of ratcheting behaviour across the welds. Based on the calibrated ratcheting parameters from the experimental study, a cyclic plasticity constitutive model for welds was established. Finally, numerical simulations were performed to evaluate the ratcheting performance of welds under the practical wheel-rail weld cyclic rolling contact situation and further to predict the initiation of rolling contact fatigue damage in welds. The research outcomes can provide useful information about the optimisation of current flash butt welding techniques and the development of cost-effective rail maintenance strategies in order to mitigate rail degradation.