き裂先端近傍のひずみ計測に基づく単一過大荷重による疲労き裂進展の遅延現象の検討

概要

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Load-controlled fatigue crack extension tests with a single peakoverload were carried out in copper. The localized strains in the vicinity of a crack tip were measured under cyclic loadings by means of the grid method, where special attention was given to the strain behavior during one load cycle before and after a single peakoverload. The application of a single peakoverload greatly opened the crack and intensely developed both the longitudinal and shear strains in the direction of θ≃±60℃ ahead of the crack tip, where θ is the angle inclined with respect to the general direction of crack extension. Such strains were virtually retained and the crack did not grow during some loading cycles subsequent to the peakoverload application. The variation of the two strains and the crack tip opening displacement during half a load cycle were fairly small at the retardation period of crack extension, compared with those in the stable crack growth stage. When the crack extends beyond the region strained intensely by the peakoverload, the crack began growing again in a stable manner. At that time, the amounts of the strains around the crack tip and crack tip opening displacement returned to almost the same as those in the crack extension process before overload application.
一般社団法人日本機械学会の論文
1993-11-25