Fatigue Crack Growth Studies on SA403 TP 304LN SS Elbows

Abstract In order to demonstrate fulfillment of LBB design criterion and have better understanding under cyclic loading of the fatigue crack growth behaviour of piping components, experimental investigations were carried out on four numbers of 168 mm Outer Diameter (OD) elbows made of SA403 Type 304LN stainless steel. The elbows had a machined part-through notch on the outer surface at different locations, i.e., crown, extrados or intrados. Fatigue crack growth during the experiments was continuously monitored using ultrasonic and alternate current potential drop techniques. Number of cycles to crack initiation and through-wall crack under in-plane bending moment were determined. Multiple cracks were observed in the elbow at various locations during fatigue crack growth studies. The two elbows with axial notch at crown location have shown less fatigue life compared to that of one elbow with circumferential notch at extrados and one elbow with circumferential notch at intrados.