低サイクル疲労亀裂の発生, 伝播と歪の繰り返し挙動 : 切欠付平板試験片と小型丸棒試験片の相関について

概要

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The cyclic behaviors of strain in mild steel plate specimens with a central notch were investigated in static tensile test and zero-to-tension cyclic loading test. In the cyclic test a cumulative damage law was applied to the crack initiation life by using the strain behavior at the tip of the notch, and satisfactory results were obtained. The Strain controlled fatigue test simulating the strain behavior at the tip of notch was carried out by using small bar specimens of the same material, and a good correlation u-as found between the crack initiation life of the plate specimen and that of the bar specimen. By comparing the fatigue test of a lineary increasing mean strain and that of a constant mean strain, the crack initiation life in the increasing mean strain test was shorter than that in the constant mean strain test. The fatigue crack propagation in the plate specimen was observed under the condition of a constant, stepwise increased or stepwise decreased net section stress range. The crack propagation rate was correlated to the maximum strain at the tip of a crack or the stress intensity factor range. The characteristics of the crack propagation and the strain behavior after the stepwise decrease of net setion stress range were very different from the other condition of net section stress range.
社団法人日本船舶海洋工学会の論文