The Study of ODA's Formative Condition by Fatigue Test in Vacuum of High Strength Steel

摘要

A High strength steel occurred fatigue failure be called Fish-eye failure in very long life, the initiation was defect existing of material. The fatigue life of Fish eye failure dominated ODA (Optically Dark Area) around the initiation. However, ODA's formative mechanism are unknown. Therefore, to predict fatigue life of Fish-eye failure, it is important to know ODA's formative mechanism. We thought, the vacuum environment similar within the material becase of shutting off supply of air. In order to eximen ODA's crack for modifying specimen on surface, uniaxial push-pull fatigue tests were carried out in vacuum. Also, the fatigue test in vacuum use of numerical simulation carried out. The test results showed that the fatigue life property of surface failure in vacuum has corresponded to Fish-eye fatigue life. The results of fractographic observation of crack initiation showed that the rough area of surface fracture in vacuum maybe have process of ODA, and AK of the rough area were being 4 ~ 6Mpam~(1/2). Furthermore, the fatigue life of numerical simulation in vacuum, showed to have good correlation between surface failure taking account of ODA and Fish-eye failure.