Investigation of welding residual stress in flash-butt joint of U71Mn rail steel by numerical simulation and experiment

Highlights: • An advanced FEM was developed to simulate welding residual stress in high carbon joint. • Phase transformation significantly affects welding residual stress distribution in U71Mn steel joint. • The residual stresses predicted by FE model with consideration of phase change match the measurements. - Abstract: U71Mn rail steel has been widely used in high speed railway construction, and it is commonly jointed by flash welding process. It is inevitable to produce very high residual stress in the welded joint. In this study, residual stresses in a rail steel flash-butt joint were measured by hole-drilling method. Meanwhile, an in-house finite element programme JWRIAN was developed to simulate welding residual stresses in the flash-butt joint. To effectively and accurately predict welding residual stress, a fast computing algorithm named iterative substructure method and an advanced material model with consideration of the influence of solid-state phase transformation were included in the computational approach. By comparing the calculated results with the experimental data, the validity of the developed computational approach was verified. Both experimental and numerical results suggest that the solid-state phase transformation plays a very important role in the course of formation of welding residual stress. In addition, simulation results indicate that the welding residual stress distribution in the flash-butt joint is very complex, and the peak values of tensile residual stress are relatively high. The residual stress distributions of the rail steel joint obtained by numerical simulation will be helpful in assessing the structural integrity.