Vol.8 No.2 2015

Research paper : Development of material testing equipment in high pressure gaseous hydrogen and international collaborative work of a testing method for a hydrogen society (T. IIJIMA et al.)−64−Synthesiology - English edition Vol.8 No.2 (2015) laboratory space will be much lower than the explosion limit.The shapes of the main testing devices are shown in Fig. 4. The fatigue testing device of Fig. 4(a) has the signal output port and internal load cell using strain gauge that functions stably in hydrogen. It is capable of conducting fatigue tests at load cycle 1 Hz, crack growth tests, and fracture toughness tests by a rising displacement method, in gaseous hydrogen atmosphere at normal operation pressure of 115 MPa and room temperature. The slow strain rate tensile testing device shown in Fig. 4(b) is capable of tensile tests at a rate of 1 × 10−5S−1 in gaseous hydrogen atmosphere at normal operation pressure of 70 MPa and room temperature. The exposure chamber of Fig. 4(c) has a signal output port, and is capable of hydrogen charging materials at operation pressure of 115 MPa and temperatures from room to 350 ºC, as well as fracture toughness tests (delayed fracture tests) by a constant displacement method.4 International comparison of fracture toughness testing methods4.1 Consideration of fracture toughness evaluation method for finite life designIn the vessels and pipes to which stress is repeatedly applied due to the cycle of filling and releasing of gaseous hydrogen, in order to attempt finite life design based on the leak-before-break (LBB) thinking and supposition of fracture critical crack length, it is important to calculate the fracture toughness value of the materials in high-pressure gaseous hydrogen environment. As mentioned earlier, in the ASME Article KD-10 in Division 3, which is one of the testing standards for high-pressure gas vessel materials, the execution of fracture toughness tests by the constant displacement method or constant load method in gaseous hydrogen are required.[11]However, the Sandia National Laboratories recently conducted research on ferrite steel with relatively low Fig. 3 (a) Fireproof wall and control panel installed in non-explosion-proof area and (b) protective wall isolating the individual testing devicesFig. 4 (a) Fatigue testing device: normal operation pressure of 115 MPa, room temperature. (b) Slow strain rate tensile testing device: normal operation pressure of 70 MPa, room temperature. (c) Exposure testing chamber: normal operation pressure of 115 MPa, room temperature ~ 350 ºCFig. 2 PC control system installed in the control room(a)(b)(c)(a)(b)


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