Creep-fatigue crack growth in austenitic stainless steel centre cracked plates at 650°C. Part II: Defect assessment according to the A16 document

In this paper, a defect assessment according to the simplified methods proposed in the French A16 document is presented. These methods allow one to estimate fracture mechanic parameters such as δK or C* based on a reference stress approach. The overall objective of the study is to evaluate the ability of such methods to predict creep-fatigue crack growth obtained in a large component containing a semi- elliptical surface notch. The experiment consists of a wide austenitic stainless steel centre cracked plate heated up to a temperature of 650°C and subjected to more than 3000 bending cycles with a one hour holdtime at the maximum load of the cycle. The analysis according to the A16 document together with the material properties necessary for the analysis are detailed in the paper. The experimental crack growth rates are modelled both on the surface and through the thickness of the plate using a linear summation of cyclic and creep contributions. The applicability of two models, consisting for the first one in re-initialising the creep law at the beginning of the holdtime and for the second one in accounting for creep history is investigated. The results predicted with the first model are found to be very conservative whilst those obtained using the second model are found to be in good agreement with the experimental measurements.