多数切欠き付試験片を用いた微小疲労き裂の発生および成長観察

概要

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This paper presents a fatigue testing method using a multi-notched fatigue specimen for the purpose of estimating the statistical properties of micro-crack initiation and propagation processes. A plate specimen which has fifty-five V-notches on both surfaces is applied for the fatigue test. Notch arrangement on the specimen is determined based on FEM analysis such that the stress condition on notch root becomes uniform for all the notches. When some micro-cracks are initiated in the specimen, the stresses on uncracked notch surfaces may be influenced by the micro-cracks. This stress change effect is also examined by the FEM analysis and fatigue tests are carried out within the range that the stress change can be negligible. In order to execute reliable observation of micro-cracks, a static tensile load just exceeding general yielding is applied to each specimen to open the closed micro-cracks after fatigue test is terminated. Microscope video camera system is employed for the crack observation, and the distributions of micro-crack density and crack length are measured for each specimen. From the test results, it is found that the application of multi-notched specimen is useful to illuminate the mechanism of early stage of fatigue process, because enough data to perform the statistical analysis can be obtained by the fatigue test using a single specimen.
社団法人日本船舶海洋工学会の論文
1991-12-00