PSI - Issue 33

Naoya Oie et al. / Procedia Structural Integrity 33 (2021) 586–597 Oie, N. / Structural Integrity Procedia 00 (2019) 000–000

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2.3. Critical quasi-CTOD (Crack Tip Opening Displacement) The results of the tests in the previous section are organized using one of the classical fracture mechanics parameters, CTOD. The CTOD calculation equations formulated by Kawabata et al. (2016) are shown in equations (1)-(6). In this study, sharp notches are used instead of fatigue precracks, so CTOD loses its physical meaning and is referred to as quasi-CTOD to show the clear difference in this study. �������� � �� � �1 � � � � �� � � ∙ � � ∙ 0.43� � � � � 0.43� � � � � � �1� � �� ∙ �⁄� �2� � 3� � 1.�� � � � ⁄ ��1 � � � ⁄ ���2.15 � 3.�3� � ⁄ � � 2.�� � ⁄ � � � 2�1 � 2� � ⁄ ���1 � � � ⁄ �� �⁄� �3� � 4.� � 3.5 � �� �� � �4� � � ��1.4 � �� �� � � � 2.� � �� �� � � 0.35� �0.� � 0.2�����0.01�� � 25��� �5� � � � �1.�4 �� � � � 0.45� � � 1 �6�

Fig. 3. Load–clip gauge displacement curves of three-point bending tests at -60°C. �� = 420 MPa and �� = 746 MPa were obtained by conducting a low-temperature tensile test at -60°C. ν and E were set to ν = 0.3 and E = 2.06 × 10 5 MPa in this three-point bending test. The results of �������� at the initiation of brittle fracture calculated by equations (1)-(6) are shown in Fig. 4 in relation to B . For each of the 8 specimens, 5 specimens were subjected to three-point bending tests for each of the eight specimens, and the range of variation is shown as an error bar and the average value as a plot. Comparing the �������� of specimens with the same value of