The effects of LWR water environments on fatigue life reduction of LWR component materials have been evaluated quantitatively. The environmental correction factor Fen, which is determined by strain rate, temperature and dissolved oxygen content has been proposed for assessing this reduction in the case of carbon, low alloy and austenitic stainless steels. Equations to calculate Fen have been established based on fatigue data derived under constant test conditions but strain rate and temperature in actual transients are usually not constant. A method for calculating Fen under conditions of continuously changing strain rate and temperature was established in this study for use in assessing fatigue damage on actual transients, with due consideration to the effects of LWR water environments. The method should be found applicable to Class 1 vessels. It should be possible to determine the stress cycle and fatigue usage factor in air in accordance with the ASME B&PV Code Section III NB-3200. Fatigue damage in LWR water may be found by linear summation of the products of Fen and partial fatigue usage factor in stress cycles. The method is consisted of simple and detailed methods. The evaluation of Fen must be applied for the strain range in which the strain increases continuously. In the simple method, the entire range of stain increasing is used as one segment and the average strain rate and the highest temperature in it are used for computing Fen. In the detailed method, the strain increasing range should be divided into small segments and average strain rate and highest temperature in it are used for finding Fen and Fens in all segments are subsequently averaged by weighting with strain increment in it. The Fen by this latter procedure was found much less than with the former under a condition of considerable temperature change.
Plate-impact-driven ring expansion test (PIDRET) for dynamic fragmentation
