高強度鋼平滑材の遅れ破壊寿命に及ぼす試験片薄肉化の影響

概要

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To examine an influence of the reduction in specimen thickness on hydrogen induced cracking in high strength bolts steels, ASTM A 490 and S 35 C, delayed fracture tests were carried out under hydrogen environment using solid bar, thin plate and thin walled hollow specimens. Cathodic hydrogen charging was used for introducing hydrogen in the specimen under sustained load conditions. The lifetime under delayed fracture depends on the plate or wall thickness. A brittle fracture due to hydrogen still occurs in extremely thin, t=0.3 mm, plate and thin walled hollow specimen. The QC cracks in thin walled hollow specimen, still develops at the subsurface of the specimen and the origin of cracks is shifted to the center of the specimen as the specimen thickness becomes thinner. The condition for brittle fracture in delayed fracture can be evaluated by the classical Griffith criterion employing fracture stresses and QC crack lenghs. Difference of hydrogen damages caused by the difference of mechanistic conditions, would make difference of fracture lives between thick and thin specimens.
社団法人日本機械学会の論文
2003-12-25