FATIGUE DESIGN CRITERION FOR WELDED STRUCTURES

— For continuously welded structures subjected to cyclic loading, the highly stressed zones where cracks initiate and lead to failure are usually located at weld toes. At these critical points, called hot‐spots, the very local stress states are difficult to determine so that standard fatigue criteria are very difficult to apply for fatigue life prediction. This work presents a fatigue design criterion for continuously welded thin sheet structures, based on a unique S‐N curve. The approach, which refers to the hot‐spot stress concept, defines the design stress S as the geometrical stress amplitude at the hot‐spot. In practice, the geometrical stress state is calculated by means of the finite element method (FEM) using thin shell theory. Meshing rules for the welded connection, which can be applied methodically to any welding situation, allow the hot‐spot location, and therefore the design stress of any structure, to be determined. Experimental data and FEM calculations show that a unique S‐N curve can be obtained whatever the geometry of the welded structure and the loading mode.