Assessment of a creep-fatigue crack initiation and crack propagation for a welded cylindrical shell

An assessment of the creep-fatigue crack bahaviour for a cylindrical structure with weldments has been carried out by using a structural test and an evaluation with an assessment procedure. The structural specimen with a diameter of 600 mm and thickness of 7 mm is a welded cylindrical shell made of 316L stainless steel (SS) for one half of the cylinder and 304 SS for the other half. Eight artificial defects were machined and the defect behaviours were examined. In the creep-fatigue test, the hold time was 1 h at 600 °C and the primary nominal stress was 45 MPa. The evaluation results for the creep-fatigue crack initiation and crack propagation were compared with those of the observation images from the structural test. The assessment results for the creep-fatigue crack behaviour by using the French A16 procedure showed that the A16 guide is reasonably conservative but overly conservative for the creep-fatigue crack propagation in the case of a short hold time. It was shown that the crack initiation and propagation were dominated by a creep.