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Effect of Laser Shock Peening on Fatigue Fracture Behaviour of Laser Welded Butt Joints with Different Surface Conditions
Z-W. Cao, J. Yang, W. Lu and B. Wang

The effect of laser shock peening (LSP) with a Nd:YAG laser on fatigue fracture behaviours of butt joints was investigated on thin wall Ti6Al4V Nd:YAG laser welded plates with two different surface conditions which were processed respectively by single-side remelting and dual-side remelting after laser welding. The results show that LSP could obviously improve the fatigue life of all laser welded joints, but there were significantly different fatigue fracture characteristics between the two types of laser welded joints. The fatigue cracks initiated at undercuts in the single-side remelting specimens, no matter LSP was applied or not, but LSP retarded the initiation and propagation of cracks. While in the dual-side remelting specimens, the fatigue crack sources shifted from welded spatters on surface to weld pores inside of specimen after LSP, due to the balance between compressive residual stresses on surfaces and tensile residual stresses around weld pores.

Keywords: Nd:YAG laser, Ti6Al4V, laser welding, laser shock peening (LSP) butt joints, thin wall, undercut, spatter, weld pore, fatigue life,

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