水素容器用アルミニウム合金の応力腐食割れおよび疲労き裂進展の評価方法に関する研究 [in Japanese] Study on Evaluation Methods for Stress Corrosion Cracking and Fatigue Crack Growth of Aluminum Alloys for Hydrogen Containers [in Japanese]
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Hydrogen gas container is one of the critical components for fuel cell electric vehicle (FCEV) , which is expected for CO<sub>2</sub>-free personal transportation. In order to choose an appropriate material for its metal boss or liner, crack growth resistance should be evaluated for various aspects such as stress corrosion cracking (SCC) and fatigue crack growth (FCG) in any environments for the purpose of commercial vehicle use. In the present study, characteristics of SCC and FCG in humid air and in NaCl solution were obtained for aluminum alloys of A6061, A6066 and A6351 with attention to the testing methods. Threshold <I>K</I> value for SCC,<I>K</I><sub>ISCC</sub> , was determined by two types of tests under <I>K</I>-increasing and <I>D</I>-constant (<I>K</I>-decreasing) conditions, where <I>K</I>and <I>D</I>are stress intensity factor and specimen displacement, respectively. In the former test, partial unloading was conducted at every 1000 s in order to monitor the crack growth by unloading compliance method. Crack growth rate of SCC, d<I>a</I>⁄d<I>t</I>, is enhanced by the partial unloading in the <I>K</I>-increasing test, while measurable d<I>a</I>⁄d<I>t</I> is much smaller in the <I>D</I>-constant test. <I>K</I><sub>ISCC</sub> of A6351 is much lower than those of A6061 and A6066 in humid air, while it was not able to determine in NaCl solution due to the anodic dissolution for all the materials. Grain size indicates minor influence on SCC tested by the <I>K</I>-increasing test. Conservative FCG characteristics are obtained by <I>K</I><sub>max</sub>-constant test, where the maximum stress intensity factor,<I>K</I><sub>max</sub> , should be less than the <I>K</I><sub>ISCC</sub> in order to avoid the SCC contribution. Crack growth rate of FCG, d<I>a</I>⁄d<I>N</I>, is similar in humid and laboratory air environments, while it is higher in NaCl solution. Larger grainsized materials show lower d<I>a</I>⁄d<I>N</I> both in humid air and in NaCl solution.
- Journal of High Pressure Institute of Japan
Journal of High Pressure Institute of Japan 54(6), 277-288, 2016
HIGH PRESSURE INSTITUTE OF JAPN(HPI)