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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3. Experimental results

3.1. Tensile tests (Slow strain rate tests)

Examples of a stress vs cross-head displacement during slow strain rate tests are shown in Fig. 6(a) and (b). Solid line and broken line indicate the relation obtained in air and in H 2 , respectively. It is obvious that strength of Lot 3 is lower than that of Lot 1, although there are almost no hydrogen embrittlement effect on the 0.2 % proof stress  0.2 and tensile strength  B of both Lot No.. Also, for case of the Lot 3, elongation is decreased in the H 2 environment. Fig. 7(a), (b) show the comparison between each reduction of area  . The relative reduction of area RRA defined as  in H2 /  in air , is a one of effective parameter to evaluate the influence of H 2 gas to tensile properties. As shown in Fig. 7, the RRA are decreased as the Ni eq decreased. An appropriate results that SUS316L with low Ni eq takes on high H 2 gas sensitivity are obtained by this experimental method.

(a) Lot 1 (Ni eq = 26.6 %)

(b) Lot 3 (Ni eq = 25.7 %)

Fig. 6 Relationship between stress  and cross-head displacement  .

(a) Lot 1 (Ni eq = 26.6 %)

(b) Lot 3 (Ni eq = 25.7 %)

Fig. 7 Effect of H 2 gas on reduction of area  .

3.2. Fatigue tests

Figure 8(a)-(c) show S-N properties of Lot 1 ( R = -1), Lot 2 ( R = -1) and Lot 2 ( R = -0.5), respectively. A solid line with open symbols and broken line with solid symbols are test results under in air and in H 2 gas, respectively. Each S-N diagram are drawn by the “ S-N diagram regression software” published by the Japan Society of Materials Science,