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To create a society based on hydrogen energy in the near future, it is necessary to clarify the influence of hydrogen on the mechanical, physical and chemical properties of the materials used for hydrogen energy systems. The rubber O-rings used in the high-pressure sometimes suffer from the decrease in durability due to decompression failure, which is influenced by several factors. From this viewpoint, sensitive factors for the durability of rubber O-rings were evaluated by using a L18 orthogonal array. A high-pressure durability tester, which enables the rubber O-rings to expose repeatedly high-pressure hydrogen gas at arbitrary test conditions, was employed.

Rubber O-rings installed in hydrogen tanks for fuel cell electric vehicles are repeatedly exposed to high pressure hydrogen gas. Exposure to high pressure gas sometimes causes cracks as a result of blistering after decompression. The degree of blister damage is influenced by material, environmental conditions such as decompression rate, and sealing shape such as squeeze ratio. Focusing on environmental conditions out of these influential factors, in this study, a high pressure hydrogen durability tester which exposes rubber O-rings repeatedly to high pressure hydrogen gas at arbitrary test conditions was developed. Using this tester, the influence of hydrogen pressure and temperature on blister damage and permeability was investigated for sealing materials used conventionally for high pressure equipment.

Thermal fatigue strength has recently become the most important performance required of disc brake rotors for heavy- and medium-duty trucks. Accordingly, gray cast iron with added nickel has been used for disc brake rotors. In this study, an evaluation method for thermal fatigue strength during simulation tests has been established, and it has been found that thermal fatigue strength is improved as graphite in the microstructure gets refined. The graphite gets more refined in proportion to the added amount of nickel or as a result of cerium inoculation. Therefore, by combining cerium inoculation with nickel addition, a low-cost disc brake rotor for heavy- and medium-duty trucks with high thermal fatigue strength has been developed.