表面き裂の疲労き裂進展クライテリオンの検討（第1報，モードⅠ負荷を受ける表面き裂のパリス則）

摘要

構造物の破壊の多くは疲労破壊によることはよく知られている．そのため，構造物を健全に保守管理するために疲労破壊への対策が必要である．特にき裂検出後の余寿命を正しく評価する為には，疲労き裂の進展解析が不可欠となる．二次元問題においては，貫通き裂を対象として混合モード(Ⅰ+ Ⅱ)の数値解析と実験の比較が多く行われてきた．%Change of C value in Paris' law along crack front of surface crack is measured experimentally. It is necessary to predict the growth of surface crack by fatigue. It is shown that C value decreases near specimen surface. It coincides with previous literature. Crack closure effect is studied numerically for a surface crack by elastic-plastic cyclic analyses. It is found that closure effect appears more strongly near specimen surface than the maximum-depth point. By determining effective stress intensity factor including closure effect, it is shown that change of C value is equal to the change of closure effect along crack front. Using new C value considering closure effect, fatigue crack growth is predicted using S-FEM. It is shown that fatigue life and crack configuration agree well with experimental ones.