Effect of laser shock peening on fatigue properties of U75VG rail flash-butt welding joints

Rail-welded joints have an important impact on the safety of high-speed railways. Laser shock peening (LSP) is performed on these joints to improve their bending fatigue performance. This study examines the effect of LSP treatment on residual stress, surface microstructure, and surface morphology of the rail base of U75VG flash-butt welding joints. First, the characteristics of the LSP-treated and untreated specimens were evaluated, then the fatigue test was carried out. The results indicated that the LSP treatment generated compressive residual stress with an average value of-436.2 MPa on the surface, and the depth of the corresponding stress layer exceeded 1.5 mm. Both the surface dislocation density and hardness were increased. The fatigue S-N curves indicated that LSP treatment increased the fatigue life of the specimens, particularly under low bending stress conditions. The fatigue limit increased by 6.7% from 264.0 MPa. The fatigue fracture revealed that high-density dislocations enhanced the resistance to the fatigue crack growth, resulting in the crack propagation zone near the LSP-treated surface having a rough morphology with steps. The mass-produced pits on the LSP-treated surface and the induced compressive residual stress could be significant at the crack initiation phase.

Automated summary

This study examines the effect of laser shock peening (LSP) treatment on the bending fatigue performance of rail-welded joints. It was found that LSP treatment increases the fatigue life of the joints and enhances resistance to fatigue crack growth.