Abstract
For the purpose of defining the initial crack size used in estimating the fatigue life of fillet welded joints, fatigue tests of fillet welded joints with a longitudinal attachment were carried out under constant and computer-simulated highway variable amplitude loadings, and the initiation and early-stage propagation behavior of fatigue cracks at the fillet weld toe was investigated. Facet-like fracture surfaces were observed where fatigue cracks initiated and the depth of them was independent of stress range and welding material. Fatigue life analyses applying the fracture mechanics concept were performed on the assumption that such a fracture surface is the initial crack. Good agreement was obtained between the estimated fatigue life and the experimental one.
