切欠部に発生した疲労き裂のJ積分範囲ΔJの挙動に関する数値的検討

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In previous papers, the authors discussed the J-integral range, ΔJ, evaluated by the path-integral and showed that ΔJ was a good parameter for characterizing the crack tip stress and strain fields under elastic-plastic conditions. In this study, finite-element simulations of fatigue crack growth at notches in a plate under uniaxial stress were conducted to examine the applicability of ΔJ to short fatigue cracks emanating from notches. It was found that Δl-values evaluated by the path-integral were almost path-independent when the minimum-load level or the crack-opening level was selected as a reference level for the evaluation. The value of ΔJ evaluated based on the crack-opening level correlated well with the crack-tip-opening displacement, while ΔJ based on the minimum-load level and the effective stress intensity range ΔK_<eff> did not. Crack closure was mainly responsible for the initial decrease in ΔJ-value and the deceleration of crack growth rates of short cracks emanating from notches.
1991-11-25