Modeling of Notch Effects on Stress Corrosion Cracking

Abstract

The intergranular stress corrosion cracking (IGSCC) of sensitized Type 304 stainless steel (SS) has been investigated by slow strain rate tests (SSRTs) in 289°C water containing sulfate impurity. Both smooth and circumferentially notched specimens were used to assess the effects of strain concentrations on stress corrosion cracking (SCC). Experiments were conducted over a range of nominal strain rates of 10−5 to 10−7 s−1 . A comparison of the results observed for the smooth and notched specimens suggests that the estimated growth rates of small cracks in SSRT specimen geometry is influenced by the presence of strain concentrations. In particular, the average crack growth rates estimated from tests performed at the same nominal strain rate are observed to increase with the notch depth, and power-law relationships exist between strain rate and SCC parameters such as failure time and crack growth rate. The strain concentration factors at the notch roots of Type 304 specimens subjected to axial load have been estimated by finite-element elastic-plastic stress analyses, as well as by Neuber’s rule. The nominal and crack-tip strain rate effects on SCC in both smooth and notched specimens are interpreted in terms of a model based on elastic-plastic fracture mechanics and film-rupture mechanisms that invoke diffusion-controlled SCC growth kinetics.