疲労き裂進展下限界条件試験法に対する検討 : き裂開閉口挙動に及ぼす荷重履歴の影響

概要

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The effect of loading history on the crack closure behavior was investigated during K-increasing and K-decreasing processes in fatigue crack propagation tests. It was found that the crack opening point, K_<op>, which had been once raised by the prior loading did not easily decrease in the following K-decreasing process, so K_<op> in the K-decreasing process was higher than that in the K-increasing or K-constant process, which resulted in to give the low crack propagation rate and the high threshold condition for crack propagation in the K-decreasing test. This is the reason for the fact that the K_<th> determined by the conventional K-decreasing test is usually higher than that calculated from the fatigue strength of a cracked specimen. From the above mentioned testing results and discussion, it may be concluded that it is dangerous to estimate the criterion whether a flaw will grow or not based on the K_<th> determined by the K-decreasing test and it should be determined by the K-increasing method using an ideally pre-cracked specimen.
社団法人日本材料学会の論文
1981-03-15