微小欠陥を有する高強度鋼の疲労特性に及ぼす真空環境の影響

概要

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High cycle fatigue tests under push-pull axial loading were carried out on SNCM439 in high vacuum and air environments to clarify the mechanism of sub-surface fatigue fractures. To reveal the effects of vacuum environment on defect size dependency of fatigue limit σw, specimens with different sizes of small artificial defects were tested followed by fracture surface observations. The main results obtained in this study are summarized as follows: (1)High vacuum environment increased the fatigue lives and lowered the fatigue limits compared with air environment. (2)Regardless of defect sizes, S-N curves in high vacuum did not show clear endurance limit although those in air indicated a clear knee point with a level line. (3)Defect size dependency of σw is considered different between high vacuum and air environments. (4)Sub-surface fractures initiating from Al2O3 can be simulated by vacuum fatigue tests using specimens with an artificial small defect.
一般社団法人日本機械学会の論文