Abstract
To ensure safely use of hydrogen utilization machines after large earthquakes, the effects of multiple overloads and hydrogen on high-cycle fatigue strength of notched specimens were studied. The materials were SUS304 and SUS316L. For both materials, the fatigue strength was significantly reduced by multiple overloads. The cause was small cracks formed by the overloads. In SUS304, the reduction of fatigue strength was enhanced by hydrogen. The cause of the enhanced reduction was the acceleration of propagation of the small cracks. In SUS316L, there was no enhanced reduction. A prediction method of the fatigue strength under the effects of hydrogen and multiple overloads was proposed through the evaluations of the crack propagation using plastic strain range and the fatigue limit related to the crack length.
