PSI - Issue 33

Toru Yagi et al. / Procedia Structural Integrity 33 (2021) 1225–1234 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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completely. There are some section notch specimens whose load drop ratio of a pop-in is more than 10%. Some surface notch specimen fractured completely in brittle manner. From the results of the section notch specimens, it is suggested that when the specimen experiences a pop-in with around 10% of load drop ratio, the crack would arrest itself in the real structures. (b) compares the standard three-point bending test whose 0 /W is 0.5 and the three-point bending test of shallow notch specimens whose 0 /W is 0.15 and 0.3. The vertical axis and the horizontal axis are the same as the previous comparison. The figure shows the results of the temperature of 0 ℃ and -20 ℃ . Some shallow specimens at lower than -20 ℃ fractures completely in brittle manner. The maximum load drop ratio of CTOD test at -20 ℃ is 21.4%. Shallow specimens at 0 ℃ experiences pop-ins. The maximum load drop ratio at 0 ℃ is 16.6%. Therefore, pop-ins with 16.6% of the load drop ratio or below could be judged as insignificant. Based on the results of the experiments, it would be safe to change the critical load drop ratio for the pop-in judgement from the current 5% to 10%.

Fig. 9 Specimen configuration

Fig. 10 Results comparison of (a) section notch vs. surface notch and (b) standard specimen vs. shallow specimen