オーステナイト系ステンレス鋼の 二軸応力下における配管部疲労き裂進展評価
概要
Nuclear power plants (NPPs) are required to ensure safety in long term operation under aging degradation. The fatigue degradation is one of the major ageing phenomena and is evaluated to ensure safety by design fatigue curve obtained by the results of axial fatigue test. On the other hand, the stress that occurs in piping element such as elbow is not uniaxial but biaxial. For accurate evaluation of fatigue crack growth, it is required to confirm the effect of biaxial stress. In this study, membranous pressure fatigue tests were conducted to confirm biaxial stress effects. The calculation result of equivalent stress intensity factor based on test results indicates that crack growth under biaxial stress is faster than that under uniaxial stress. The relationship between crack growth rate under uniaxial stress and that under biaxial stress is clarified.
