High-Cycle Fatigue of Welded Joints

This chapter addresses advanced methodologies for the high-cycle fatigue assessment of welded tubular and plate joints, introducing an extrapolation-based approach for determining the ENS of CHS X-joint under various loading conditions, which simplifies FE modeling by avoiding the need for finely meshed rounded local notches. Additionally, a volume-based hot-spot energy indicator is proposed to account for stress gradient effects in both surface and thickness directions, offering improved fatigue life predictions compared to traditional point-based Hot-Spot Stress methods. Experimental and numerical investigations on concrete-filled tubular X-joints with full-capacity welds confirm the applicability of existing S-N curves. The chapter also examines the life-extending effect of ultrasonic impact treatment (UIT) on prefatigued welded joints, introducing a two-reduction-factor model to quantify UIT effectiveness under prior fatigue damage. These approaches collectively enhance the accuracy and practicality of fatigue life evaluation for welded structures.