Analysis of Crack Growth Kinetics and Crack Tip Strain Rates of Sensitized Type 304 Stainless Steel in Simulated Boiling Water Reactor Environment : Experiments and Theory(EAC2)

Abstract

Three slow strain rate tests (SSRT) on one-inch thick-compact tension (1T-CT) specimens, which were fabricated from sensitized 304L stainless steel, were performed with different extension rates in a simulated boiling water reactor (BWR) environment, to derive the environmentally assisted cracking (EAC) growth kinetics. The crack growth kinetics, depending on the testing conditions, were also described theoretically by Shoji's model. Inverse analysis was performed by fitting the experimental data to the theoretical data, to determine the model parameters r_0, which represents a characteristic distance to define crack tip strain rate (CTSR), and m, which is a slope of the current decay curve and a function of crack tip water chemistry. Both r_0 and m can be determined using experimental crack growth data in the analysis. Theoretical CTSR of sensitized 304 stainless steel during constant load line displacement rate tests was calculated using Shoji's model and experimental data of P. Aaltonen et al. The calculation shows that dependences of experimental crack growth rate (CGR) on theoretical CTSR for tests under different loading conditions are quite consistent. The theoretical CTSR was also compared to that evaluated using Rice's model under the same experimental conditions. Differences between the two theoretical CTSRs were found and the causes are discussed.