Abstract
Fish eye failure that is unique fatigue fracture occurs in very long life region of high strength steel. The fatigue life of Fish eye failure dominated ODA (Optically Dark Area) around the fracture origin. A granular looking area of ODA is visible close to the crack initiation, Fatigue life of Fish eye failure is almost exclusively spent propagating the fatigue clack in ODA. Therefore, to predict fatigue life of Fish-eye failure is important to know ODA of formative mechanism. In this study, fatigue and tensile test was performed in vacuum that simulated environment of subsurface failure and compared the result by the test condition. The observation of Process when ODA is formed on the precrack tip was examined in order to make clear a mechanism of ODA formation. Crack growth rate has depended on maximum stress by range of ΔK ≤ 4MPa√<m>. Under the fixed maximum stress of value, initiated fatigue cracks became non-propagating cracks. When the tensile stress of 800MPa or less was given, the remarkable growth of the ODA crack was not seen.
