応力集中部から発生・伝播する表面き裂の成長過程とその寿命予測について

概要

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Surface cracks emanated from stress concentration field occur at a lot of points and grow while repeating coalescence. However, it is difficult to find a regularity in the growth process for each surface crack. Therefore, in the previous paper, a supposed representative surface crack of which K value at the deepest point is the same as the increased K value due to the interference effect was introduced, which has the same depth of the largest surface crack. It became clear that the change of aspect ratio of a supposed representive surface crack decreases linearly as the surface crack grows. In this paper, it becomes clear that the change of aspect ratio of a supposed representive surface crack emanated from a notch or a toe of weld is estimated appoximately by the balanced growth curve of a semi-circular surface crack with the same size as grain size. And then, we carried out fatigue crack propagation analyses for fatigue tests with a gusset weld specimen by using an alogorithm of fatigue life assessment by ΔK_<RP> approach without distinguishing between the crack initiation and the crack propagation. As a result, it is confirmed that the estimated S-N curve is in good agreement with the experimental one.
社団法人日本船舶海洋工学会の論文