Advanced local concepts for assessing the fatigue durability of welded joints

Some recently developed variants of local concepts for assessing the fatigue strength and structural durability of welded joints are reviewed. These comprise structural stress, notch stress or strain and fracture mechanics concepts. New variants of the structural stress concept are Dong´s gradient stress approach and Xiao-Yamada´s `one millimetre stress´ approach. FE meshing rules have been developed for welded joints in thin sheet structures. The concept of fictitious notch rounding is now better substantiated for aluminium alloys. The small-size notch concept is applicable to thin sheet lap joints. The new notch stress intensity factor concept is based on the singular stresses at the sharp weld toe notch. Advanced fracture mechanics concepts combine crack initiation at the seam weld root or nugget edge and crack propagation over the plate thickness resulting in endurable ()K values as function of cycles per unit thickness, N/t.