薄鋼板レーザ重ね溶接継手の強度特性

抄録

Laser welding has the advantage of high welding speed and provides low heat distortion. Thus, laser welding is very attractive process for joining thin steel sheets. In this study, static and fatigue strength of laser welded lap joints were investigated.
Tensile strength of the lap joints was determined by the weaker one between the strength of base metal and that of weld metal. The strength of the base metal was estimated with the tensile strength and thickness, and the strength of the weld metal was estimated with the hardness and width of the weld metal. Thus, the calculated strength coincided with the experimental strength of the joint with different tensile strength and thickness of the base metal.
Fatigue crack initiated at the edge of weld metal, and propagated along the fusion line to the free surface. We employed fracture mechanics to evaluate the fatigue strength of the lap joint with different thickness. Stress intensity factor of the lap joint was calculated with the analysis of J. Chang and R. Muki.
We employed criterion of Erdogan and Sih to evaluate the fatigue strength. By this criterion, the fatigue strength was well characterized.
As a result, this approach, which was originally developed to evaluate fatigue strength of spot welded lap joints, was also effective for fatigue strength of laser welded lap joints.