Abstract
High cycle fatigue tests under push-pull axial loading were carried out on SNCM439 in vacuum and air environments to clarify the mechanism of sub-surface fatigue fracture. To reveal the Effect of vacuum environment on defect size dependency of fatigue limit σ_w, specimens with small artificial defects were tested. As a result, the following conclusions were obtained: (1)The vacuum environment increased the fatigue lives and lowered the fatigue limits. (2)The S-N curves in vacuum showed a gentle sweep although those in air indicated a clear knee point with a level line. (3)Defect size dependency of σ_w, is considered different in each environment. (4)Sub-surface fractures can be quantitatively simulated by vacuum fatigue tests using specimens with an artificial small defect.
