Fatigue Life Prediction of Spot-Welded Box-Section Beams under Repeated Torsion

Torsional fatigue tests of: spot-welded box-section beams were conducted to explain fatigue fracture phenomena, and a technique to predict fatigue life of spot welds in beams was developed. When a torsional moment acts on box-section beams that are hat beams with their flanges spot-welded to form closed sections, shearing force is transmitted through the spot welds. Based on theoretical analysis of stress distribution in the vicinity of spot welds and using strain values measured on the outer surface of spot welds, fatigue life of beams was successfully predicted. A technique to predict fatigue life of beams was developed by computing the load acting on spot welds in a beam and using fatigue strength data of a single-point spot-welded joint of the same load coponent.