Biaxial tension-torsion fatigue properties of A588 steel weld joint for high-speed train bogie

The biaxial tension-torsion in-phase fatigue properties of the specimens taken from the welded joint and the base material of an A588 steel train bogie were investigated comparatively. The relation between the equivalent stress amplitude and the cyclic fatigue life of the specimens was obtained. The experimental results indicate that the fatigue life of the welded joint specimen is higher than that of the base material specimen at the higher applied stress amplitude, while the fatigue life becomes closer with decreasing the applied stress amplitude. There is a critical stress between 368 MPa and 396 MPa dominating the fatigue damage behaviors of welded joint specimens. The fatigue crack initiation is prone to occur at the boundary between the base material zone and the heataffected zone when the stress amplitude is higher than the critical stress, while the cracks originated from the weld metal zone when the stress amplitude is lower than the critical stress. The transition of fatigue damage behaviors was analyzed comprehensively based on the microstructure and the residual stress distribution of welded joint specimens. The present research may provide an important clue for the fatigue performance optimization of the welded metallic components.