Gigacycle fatigue behaviour of austenitic stainless steels used for mercury target vessels

Naoe, Takashi   ; Xiong, Z.; Futakawa, Masatoshi  

Mercury enclosure vessel of the JSNS made of an austenitic stainless steel suffers radiation damage in the proton and neutron environment. In addition to the radiation damage, the vessel suffers the cyclic impact loading caused from the pressure waves. The JSNS target vessel suffers higher than 210 cyclic loading. Furthermore, strain rate of the beam window portion of the target vessel reaches to 50s at the maximum, which is much higher than the conventional fatigues. Very high cycle fatigue strengths up to 10 cycles for solution annealed (SA) and 10% cold-worked 316L (CW) were investigated through the ultrasonic fatigue test. The result showed that the fatigue strengths of SA and CW tested in high-strain rate were higher than that of the conventional fatigue. On the other hand, the fatigue failure occurred regardless of material and temperature in the very high-cycle region ( cycles) at the stress amplitude of below the conventional fatigue limit.