High cycle fatigue behavior and numerical evaluation of Alloy 690TT steam generator tube

High cycle fatigue behavior of Alloy 690TT steam generator (SG) tube under different maximum stresses was investigated at stress ratio R = 0.1 through experimental and numerical evaluation. The morphology of fatigue fracture surface was observed by SEM, and the crack initiation and propagation mechanism of Alloy 690TT SG tube was analyzed. The fatigue crack of Alloy 690TT SG tube initiated at the intrados surface edge, then propagated along the direction of maximum shear stress and penetrated through the side of the specimen, and finally transient fracture occurred in the direction perpendicular to the loading axis. With the increase of maximum stress, the number of fatigue crack initiation sources increased, but they were all distributed on the edge of the intrados surface, and a large number of persistent slip bands (PSBs) were formed on the intrados surface. The fracture mechanism of the tubular specimen was different from that of the bar specimen, and its fracture mode affected the life evaluation of the tubular specimen. The finite element analysis software ABAQUS and advanced fatigue durability analysis software FE-SAFE were first used to evaluate the fatigue life of Alloy 690TT SG tube. Compared with the experimental results, the error in predicting fatigue life by numerical method was acceptable.