複数表面欠陥からの疲労亀裂伝播寿命評価(第1報) : 直列配置複数亀裂問題

概要

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A project of three years experimental researches on fatigue crack growth from multiple planar surface flaws has been made since 1976. On the basis of these data, we proposed an estimation procedure for fatigue life of multiple series surface cracks at one sided surface of a plate under axial and out-of-plate bending loads. Dividing fatigue crack propagation process into two parfs, i.e., process before coalescence and process after coalescence, we assumed that there is no mutual influence between multiple series surface cracks before coalescence and that these cracks unite at touching and become one semi-elliptical crack immediately. Paris's law and experimentally-modified Kobayashi's solution of K-value were used for calculation of crack depth. On the other hand. Iida and Kho's empirical expression of surface fatigue crack shape was used for calculation of surface crack length. In addition, effect of finite specimen width was taken into consideration. As a result of case studies, it was found that the present method can give us more reasonable fatigue life to coalescence and penetration in comparison with ASME Code Section XI. The accuracy of the present method was proved to be good by statistical analysis.
社団法人日本船舶海洋工学会の論文