過大過小応力下の疲労き裂伝ぱと伝ぱ速度の推定

抄録

The results of a systematic investigation on the acceleration of fatigue crack propagation under periodic overstressing are summarized. The results show that a significant acceleration of fatigue crack propagation (amounting to more than one hundred times) occurs under variable stresses in which a very small number of overstress and a very large number of understress below the threshold stress intensity K_th are applied alternately. A method is proposed to predict the acceleration under complex multi-level variable stresses from test data under simpler two-level variable stresses. A reasonable agreement is obtained between the predicted acceleration and multi-level test data.