In order to perform design code (ASME III, RCC-M, JSME) compatible direct strain-controlled tests in simulated PWR water, a unique environmental fatigue testing facility was previously developed. Pneumatic bellows are used to generate strain in the stainless steel specimen mid-section, while eddy current based measurement is used as a feedback signal.
The NUREG/CR-6909 report gathered a large database of test results and proposed environmental reduction factors (Fen) to account for a reduction in fatigue life in simulated LWR environment when comparing to a reference value in air. The database was composed of non-stabilized stainless steels tested using methods which are not directly comparable to those used in air to define the reference curves. Applicability of the stainless steel Fen factors has already been challenged in previous PVP papers (PVP2013-97500, PVP2014-28465, PVP2016-63294).
Results in this paper continue to show this trend of lower experimental Fen factors compared to predictions made by the NUREG report. Dual strain rate tests were performed, specifically focusing on the effect of strain waveform shape on fatigue life. Similarly to last year’s results (PVP2016-63294) a distinct effect of strain waveform, presently inadequately accounted for in Fen predictions, was observed.