Sensitivity of Creep Crack Initiation and Growth in Plates to Material Properties Variations

摘要

In this paper, creep crack initiation and growth data are reported on type 316L(N) stainless steel at 650°C on compact tension (CT) specimens and on plates containing a semi-elliptical surface defect. The compact tension tests were carried out according to standard ASTM E 1457 procedures, and the results are plotted against experimental determinations of the creep fracture mechanics parameter C~* derived from load-line displacement rate. Generally, satisfactory agreement is found between the CT specimen and plate results, although longer initiation times and slower cracking rates were observed in the plates consistent with the lower constraint anticipated in this specimen geometry. Also, predictions of the cracking behavior of the plates have been made using deterministic and probabilistic methods. In the former case, combinations of upper and lower bound material properties were used, which were based on the ± 2 standard deviation (± 2SD) limits obtained from the measured scatter in the data. In the latter, a Monte Carlo simulation was adopted. It is found that the combination of bounds (± 2SD) giving the shortest failure time corresponds with a failure probability of about 0.05 % from the probabilistic calculations.