PSI - Issue 19

Akira Ueno et al. / Procedia Structural Integrity 19 (2019) 494–503 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

4

497

Ni eq = 12.6 C + 1.05 Mn + Ni + 0.98 Mo + 0.65 Cr + 0.35 Si

(1)

Table 1 Chemical compositions of materials used in this study.

Table 2 Ni equivalent of 3 different Lot No.

2.3. Tensile test and fatigue test

Tensile tests were carried out by means of an Instron type tensile testing machine under cross-head speed of 0.005 mm/min. Fatigue tests were carried out by means of an electro- hydraulic survo type fatigue testing machine under sinusoidal wave with stress ratio R of - 1 and test frequency f of 20 Hz. During tests up to specimen broken, H 2 gas pressure was monitored with a pressure gauge (Fig. 5). After tensile and fatigue testing, fracture surfaces were observed precisely by means of an FE-SEM.

Fig. 5 Specimen and pressure gage systems during tensile and fatigue tests