Fatigue Strength of Box-Section Beams under Torsion-Laser-Welded vs. Spot-Welded

Box-section beams in the automotive structures are usually produced by spot welding. How about the change in the fatigue strength if they are manufactured by laser welding? This paper will give a simple formula to estimate the fatigue strength ratio of the two kinds of box-section beams. The formula is obtained from a fracture mechanics analysis of the two beams and confirmed by the fatigue test data from the literature.