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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is shown in Fig. 6. Section notch specimens which is a reproduction of real weld with local brittle zone, shown in Fig. 7 (a), and surface notch specimens which the brittle area is fully distributed along the crack tip for reference, shown in Fig. 7 (b), are prepared. The area surrounded by red colour represents the NRL-S.

Table 1. Chemical compositions of steel and weld from manufacture’s data sheet (mass %) Size C Si Mn P S Ni Cr B 0.17 0.25 1.56 0.011 0.002 0.02 0.46 0.0011

WELTEN780

32 mmt 4 mm φ

NRL-S

0.21 1.21 1.55 0.025 0.003

-

1.51

- -

MG-S80

1.2 mm φ 0.09 0.32 1.05 0.008 0.010 2.71 0.24

Fig. 6 Joint geometry of the brittle bead specimen (this figure shows section notch)

(b)

(a)

Fig. 7 Schematic image of fracture surface of (a) a section notch specimen and (b) a surface notch specimen.

2.2. Experiment In this experiment, the bending test is used as this is most common evaluation method for critical CTOD, and the tensile test is the representative of the real structures based on the similarity of the loading mode. The bending test and tensile test on both section notch and surface notch of standard specimen whose 0 /W is 0.5 are carried out. The tensile test on shallow section notch specimen whose 0 /W is 0.3 and 0.15 are also performed. The size of the specimen, notch, and the fatigue pre-crack are shown in Fig. 9, The test temperature is from 0 ℃ to -60 ℃ . The results are shown in Fig. 10. (a) compares the load drop ratio and the CTOD value of pop-ins. 100% of load drop ratio means the complete fracture, and 0% means the specimen experienced the ductile fracture. The point of CTOD is when the maximum load is observed. The data includes all temperatures, -20 ℃ , -40 ℃ , -60 ℃ . No section notch specimen fractured

30

Section Notch a/W=0.5 -40 ℃

25

20

15

10 Load [kN]

5

0

0

2

4

6

8

Clip gauge displacement [mm]

Fig. 8 Example of P - V g curve of the experiment