Influence of LCF overloads on combined HCF/LCF crack growth

Full scale tests of welded AL-6XN superaustenitic stainless steel I-beams were carried out to assess the fatigue behavior of three weld details. A total of 66 full-scale I-beams were tested under constant amplitude loading. The test program was developed to assess the effects of minimum stress, stress range, and residual stress on the fatigue behavior of the longitudinal fillet weld detail, transverse groove weld detail, and a simulated bulkhead attachment detail. Weld defects that initiated fatigue crack growth were characterized. Internal discontinuities included porosity, entrapped oxides, and lack of fusion sites located in the longitudinal fillet welds and the groove welds. Surface cracks initiated at microdiscontinuities at the toe of the attachment fillet welds and at the toe of the groove welds.