Fatigue life prediction of laser welded 6156 Al-alloy joints based on crack closure

• The fatigue strength of butt joint is higher than T-joint for laser welded joints.
• Initial crack size was determined by the proposed approach.
• A fatigue life prediction approach based on crack closure was proposed.

The median S–N curves for laser beam welded 6156 Al-alloy butt joints and T-joints and crack growth rate curves for the base material were determined by fatigue experiments at stress ratio R = 0.5, 0.06, −1, respectively. The results showed that the fatigue strength of 6156 Al-alloy butt joint is obviously higher than that of T-joint. The fatigue limit and the crack growth threshold were proposed to determine the initial crack size for butt joint and T-joint. A fatigue life prediction approach based on crack closure was proposed, which can take into account the effect of welding residual stress. The predicted lives using the proposed approach agreed well with the experimental results.