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Naoe, Takashi; McClintock, D.*
JPS Conference Proceedings (Internet), 45, p.011169_1 - 011169_7, 2026/06
Mercury target vessel for the pulsed spallation neutron source suffers two kinds of cyclic stress during operation. One is the thermal stress due to the internal heating and swings by proton beam trip. The other is the impulsive stress by the pressure waves generated by the proton beam injection. The total number of loading cycles for the former is 
, and the later is 
for 2 years operation in the J-PARC mercury target vessel. The target vessel is made of 316L stainless steels and assembled by electron beam welding (EBW) and gas tungsten arc welding (GTAW). However, fatigue data of welded 316L stainless steels up to gigacycle is insufficient. Ultrasonic fatigue test, applying load cycle by utilizing ultrasonic resonance, for the welded metals were performed to investigate the effect of welding on gigacycle fatigue behavior. Fatigue strength of EBW and EB+GTAW specimens including weld bead effect will be discussed.
Naoe, Takashi; Harjo, S.; Kawasaki, Takuro; Xiong, Z.*; Futakawa, Masatoshi
JPS Conference Proceedings (Internet), 28, p.061009_1 - 061009_6, 2020/02
At the J-PARC, a mercury target vessel made of 316L SS suffers proton and neutron radiation environment. The target vessel also suffers cyclic impact stress caused by the proton beam-induced pressure waves. The vessel suffers higher than 4.5
10
cyclic loading during the expected service life of 5000 h. We have investigated fatigue strength 316L SS up to gigacycle in the previous studies. The cyclic hardening and softening behavior were observed. In this study, to evaluate the cyclic hardening/softening behavior, the dislocation densities of specimens were measured using the neutron diffraction method at the MLF BL-19. The result showed that the dislocation density of a 316L SS was increased with increasing the number of loading cycles. By contrast, in the case of cold-rolled 316L SS, annihilation and re-accumulation of dislocation by cyclic loading were observed. In the workshop, result of neutron diffraction measurement will be introduced with the progress of fatigue test.
