PSI - Issue 19

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

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JSMS (JSMS Standard (JSMS-SD-11-07)). In case of high Ni eq materials(Fig. 8(a)), it is clear that fatigue strength are scarcely affected H 2 gas. This tendency coincide with fatigue tests results obtained a full-scale fatigue tests conducted in a ultra-high pressure H 2 gas vessel (NEDO Report 2014). In cases of low Ni eq materials(Fig. 8(b), (c)), it is obvious that fatigue strength decreased significantly by the H 2 gas effect.

(a) Lot 2 (Ni eq = 27.0 %), R = -1.0.

(b) Lot 3 (Ni eq = 25.7 %), R = -1.0.

(c) Lot 3 (Ni eq = 25.7 %), R = -0.5.

Fig. 8 Results of fatigue tests.

4. Discussion

4.1. Effect of Ni eq on tensile test properties

As mentioned above, Ni equivalent is a profitable parameter to measure a stability of the austenite phase. The relative reduction of area RRA of SUS316L in high pressure H 2 gas have been studied as a function of Ni eq as shown in Fig. 9 (Yamada, T. et. al.(2012)). Two red lines in Fig. 9 show the RRA of Lot 1 and Lot 3 materials indicated in Fig. 7(a) and (b). Although the RRA values of in Fig.7(a)&(b) are slight higher than depicted in Fig. 9, a relative tendency that lower Ni eq content show lower RRA value are same.