Middle-crack Tension試験片における極低サイクル疲労下のき裂進展条件式の評価

抄録

The evaluation of life under ultra-low cycle fatigue is still under investigation. Current evaluation parameters are unsuitable due to limitations in large plastic substantial plastic deformation. In a previous study, criteria for crack propagation were suggested and assessed using equivalent plastic strain amplitude and stress triaxiality at the center of the plate thickness. However, these physical quantities cannot be directly obtained from experiments. In this study, a generation phase analysis was performed to reproduce crack growth experiments and determine difficult-to-obtain values such as stress triaxiality and equivalent compositional strain increment. The previous study focused on CT specimens made of SUS316. Therefore, this study employed specimens with a central crack made of A2024-T3 material. Crack propagation experiments were conducted using a stress ratio of -0.5 on middle-cracked tension (MT) specimens made of A2024-T3. The relevant physical quantities were measured, and these values were then used to assess the applicability of the crack propagation condition equation to MT specimens. We would like to discuss the applicability of the crack propagation conditional equation.