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Xiong, Z.; Naoe, Takashi; Wan, T.; Futakawa, Masatoshi; Maekawa, Katsuhiro*
Procedia Engineering, 101, p.552 - 560, 2015/03
Times Cited Count：1 Percentile：62.19(Engineering, Multidisciplinary)Very high-cycle fatigue behaviour of SUS316L, which is used as the structural material of the spallation neutron sources, was investigated through the ultrasonic fatigue test with the strain rate of 10
s
. Cross-sectional hardness distributions of the fatigue-failed specimens for solution annealed (SA) and cold worked (CW) 316L were measured to understand the cyclic hardening or softening. In addition, the tensile tests of the fatigue-failed specimens were performed at room temperature. Furthermore, the nonlinear ultrasonic system was used for evaluating the dislocation density variation. The results showed the cyclic hardening in the region of very high-cycle fatigue in the case of SA. In contrast, in the case of 10%CW, cyclic softening occurred when the number of cycles below 10
and followed by cyclic hardening. In the case of 20%CW, cyclic softening was observed when the number of cycles below 10
, while cyclic hardening occurred subsequently.
Xiong, Z.; Naoe, Takashi; Futakawa, Masatoshi; Wakui, Takashi; Kogawa, Hiroyuki; Haga, Katsuhiro; Maekawa, Katsuhiro*
no journal, ,
An enclosure vessel of liquid mercury spallation target, which is made of 316L stainless steel, is suffered from the cyclic loading due to the proton beam-induced pressure waves. The number of loading cycles will be beyond 10
to giga-cycle region throughout the expected service life. In and around giga-cycle region, the fatigue failure occurs under the conventionally defined fatigue limit. In addition to the cyclic loading, the strain rate at the beam window of the target vessel reaches to 50 1/s at the maximum, which is much higher than the conventional fatigues. In this work, ultrasonic fatigue tests were conducted with controlling specimen surface temperature to investigate effects of the temperature and the work hardening that simulates the irradiation embrittlement on very high-cycle fatigue strength of 316L SS. The experimental result showed that the obvious fatigue limit was not observed up to 10
cycles, and the fatigue strength was reduced about 75% of R.T. around 250 
C regardless of the work hardening, which was the conceivable maximum temperature of the beam window at the 1 MW operation.
