過大な圧縮荷重がき裂進展挙動に及ぼす影響

Effect of excessive compressive loading on crack growth behavior

山口 義仁 ; Li, Y.* ; 杉野 英治*; 勝山 仁哉  ; 鬼沢 邦雄 

Yamaguchi, Yoshihito; Li, Y.*; Sugino, Hideharu*; Katsuyama, Jinya; Onizawa, Kunio

国内の原子力発電所は非常に大きな地震動を経験しており、き裂等の経年劣化を考慮した配管等の健全性評価法の高度化が重要な課題となっている。本研究では、過大圧縮荷重を含む地震動を模擬した繰返し荷重によるき裂進展試験を行い、圧縮荷重がき裂進展挙動に及ぼす影響を調べた。その結果、過大圧縮荷重によるき裂進展の加速及びき裂開口荷重の低下を確認し、これらはき裂先端に引張応力が生じるためであることを応力解析から明らかにした。これらの結果を踏まえ、き裂進展速度に及ぼす過大な圧縮荷重の影響の評価手法を提案した。

In recent years, Japanese nuclear power plants experienced multiple large earthquakes, such as Niigata-ken Chuetsu-Oki Earthquake in 2007 and the Tohoku District - off the Pacific Ocean Earthquake in 2011. Therefore, it is very important to assess the structural integrity of reactor piping under such a large earthquake when a crack exists in the piping. In this study, an effect of excessive compressive loading on the crack growth behavior of piping materials has been evaluated through cracked plate testing. It was observed that excessive compressive loading had an acceleration effect on crack growth rate. The evaluation method using J-integral to evaluate the crack growth behavior under the condition beyond small-scale yielding has been proposed for the acceleration effect of excessive compressive loading on crack growth rate. It was indicated that the acceleration effect by excessive compressive loading simulating a large earthquake could be evaluated using the proposed method.