PSI - Issue 54

Akihiko Fukunaga et al. / Procedia Structural Integrity 54 (2024) 115–122 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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employed to investigate strain rate dependance of SSRT tests. A286 is expected to be used in hydrogen compressor components where the temperature may increase to 200 °C. Therefore, the test environment was 70 MPa gaseous hydrogen or air at 150 °C. The RRA values were calculated from the ratio of relative reduction in area in gaseous hydrogen to air at each strain rate. The fracture surface of the specimen after tensile test was observed using a scanning electron microscope (SEM).

Photo.1. Metallurgical structure of A286.

Fig.1. Specimen configuration for SSRT test of A286.

3. Results and discussions 3.1. Strain rate dependance of SSRT tests

Fig.2 shows the nominal stress – nominal strain curves for each strain rate. Up to the yield points and maximum load points, the stress-strain curves in air (black lines) and those in 70 MPa hydrogen (red lines) are almost same. After the maximum load, the red stress-strain curves in hydrogen are shorter than those in air.

Fig.2. Nominal stress – nominal strain curves at 150 ℃ in air and 70 MPa hydrogen gas at strain rates of (a) 5 × 10 -5 , (b) 7.5 × 10 -6 and (c) 1.25 × 10 -6 s -1 .