抄録
Sub-surface fatigue fractures in titanium alloys are frequently observed in very high cycle region. However, the mechanism of sub-surface fractures has many unclear points. This study focused on an idea that the environment around sub-surface cracks resembles vacuum environment. To reveal the effects of vacuum environment on small fatigue crack propagation, uni-axial fatigue tests were conducted in air and vacuum environments using specimens with an artificial small defect. Crack propagation rates were measured by observation of crack propagation behaviors. As a result, fatigue crack propagation rates in vacuum were much lower than those in air. And the distinctive characteristics of small fatigue crack growth behaviors were more remarkable in vacuum than in air.
