Finite element analysis on the application of Mini-C(T) test specimens for fracture toughness evaluation

Takamizawa, Hisashi ; Tobita, Toru; Otsu, Takuyo; Katsuyama, Jinya  ; Nishiyama, Yutaka ; Onizawa, Kunio 

Fracture toughness evaluation by the Master Curve method using miniature compact tension (Mini-C(T)) specimens taken from the broken halves of surveillance Charpy specimens has been proposed. We performed finite element analysis (FEA) to examine the difference in constraint effect of the crack tip for the different size C(T) and precracked Charpy v-notch specimens. The constraint effect for Mini-C(T) specimens in terms of the T-stress and Q-parameter was similar to the larger C(T) specimens. To optimize the fatigue precracking conditions for the Mini-C(T) specimen fabrication, plastic zone distribution analysis was performed. We confirmed the fatigue precrack length and the availability of the mitigated crack shape for Mini-C(T). We also obtained the fracture toughness data for different sizes specimen. It was shown that To obtained from the Mini-C(T) specimens is in reasonably good agreement with that from others. We compared the fracture toughness data with T41J based fracture toughness curves proposed in recent study. All of the data were well enveloped by the proposed lower bound curve.