The reference Fatigue Crack Growth (FCG) rate behaviour for austenitic stainless steel in a deaerated Pressurised Water Reactor (PWR) environment is provided in ASME Section XI Code Case N-809. This FCG law is dependent on load ratio and environmental factors in terms of a defined temperature and rise time.

Previous papers by Emslie et al (PVP2016-63497 and PVP2017-65645) demonstrate that environmental FCG rate enhancement is significantly better characterised by Stress Intensity Factor (K) rate than by rise time. It also demonstrates that K rate effects are increasingly important towards the top of the load cycle (ie. closer to the maximum K) and provides the Weighted Stress Intensity Factor Rate (WKR) method to account for both effects under isothermal loading conditions.

This paper extends the WKR method to include varying temperature during the loading waveform, so that both complex K and varying temperature waveform FCG rates can be predicted. A substantial body of validation test data of standard compact tension specimens under such loading is provided in support of the presented method. Further testing is proposed to enable validation suitable for future inclusion of the proposed method within Code Case N-809.

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