き裂開閉口挙動に基づく疲労き裂伝播特性の検討 : 第1報

概要

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A fatigue crack propagation model with consideration of crack opening/closure phenomenon and the inferior limit stress for hysteresis loop generated at a crack tip during part of stress cycle was already reported in the previous paper^<3)>. In order to study the effectiveness, fatigue crack propagation tests are carried out by using center notched tension test specimens under various stress ratios and constant loading with over/under-spike loads. These test results are in good agreement with the simulated calculation. In addition, the following phenomenon become clear from both the experimental results and the predicted results. l) As a stress ratio increases, fatigue growth rates and m-value of Paris's equation slightly increase. 2) Spike overloading leads to acceleration and delayed retardation of crack growth rates. On the other hand, spike underloading leads to small delayed acceleration after acceleration and delayed retardation. An underload applied after an overload causes the crack to grow faster than when the underload occurs before the overload.
社団法人日本船舶海洋工学会の論文