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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Table 2. Configurational conditions of the test specimens. Mark B [mm] W [mm] L [mm] S [mm]

a 0 [mm]

a 0 /W

(1) (2) (3) (4) (5) (6) (7) (8)

40 20 10 40 20 10 40 20

80 40 20 80 40 20 80 40

340 180 100 340 180 100 340 180

320 160

40 20 10

0.5 0.5 0.5 0.1 0.1 0.1

80

320 160

8 4 2

80

320 160

10 10

0.125

0.25

Fig. 2. Specimen configuration and its design concept.

A diagram of each of the eight types of specimens and an enlarged view of the notch are shown in Fig. 2. W , B , S , and L of the specimen are defined in accordance with the CTOD test standard on ISO (2016) and are illustrated in Fig. 2. R was set to 0.25 mm for all eight specimens to introduce the sharpest possible radius. (1), (2), and (3) are the sizes 1, 1/2, and 1/4 with a notch length ratio of 0.5; (4), (5), and (6) are the sizes 1, 1/2, and 1/4 with a notch length ratio of 0.5; and (7), (8), and (3) are the sizes 1, 1/2, and 1/4 with the notch length fixed at 10 mm. All specimens were subjected to a three-point bending test at -60°C. The test temperature was selected to prevent ductile cracking from the notch tip in all specimens. The test temperature was selected as the temperature at which ductile cracks did not appear from the notch tip in all specimens. The temperature was controlled by gently adding liquid nitrogen and dry ice to alcohol in a cooling tank made of stainless steel, and the temperature was always controlled within ±3°C during the test. A 500 kN hydraulic universal testing machine was used to apply bending load to the specimens via a jig. The test results were recorded as the load cell load and the notch opening displacement, which were constantly measured using a clip gauge. The test results are shown in Fig. 3. The vertical axis of the figure shows the load P [kN], and the horizontal axis shows the clip gauge opening displacement V g [mm]. Under all conditions, almost all of the load was released in a single brittle fracture of the specimen.