Residual Stresses in Flash Butt Welded Rail

The residual stresses on the surface of a rail joined by flash-butt welding are measured using a hole-drilling method and the thermal elastic-plastic deformation process considering the phase transformation are simulated using FEM code JWRIAN. The residual stresses measured by experiments and computed by FEM have an acceptable agreement in accuracy. The simulation results show that the phase transformation in the cooling stage has a significant effect on the residual stress distribution and its values. The tensile or compressive state for residual stresses near the welding section strongly depends on the phase transformation which occurred during the cooling process. The biaxial tensile stresses are produced at the web near the fusion line of the flash butt welded rail. The biaxial tensile stresses increase the risk of cracks. Although the Martensite phase transformation during the cooling process at top and bottom near the fusion line produces compressive stress, it increases the brittleness at the same time. Therefore, the proper heat treatment after welding is still necessary in order to improve the toughness.