Fatigue Strength Degradation by Pitting Damage
Takashi NAOE, Masatoshi FUTAKAWA, Toshiyuki Oi, Takashi WAKUI and Yoshinobu MOTOHASHI
Abstract:High power spallation targets for neutron sources are being developed in the world. Mercury target will be installed at the material and life facility in J-PARC, which will promote innovative science. Pressure waves will be generated in mercury by thermally shocked heat deposition when the high intense proton beams bombard the mercury target. Cavitation will be induced through the pressure wave propagation in the mercury and eroded the vessel inner surface contacting with the mercury. The eroded vessel wall is damaged by cyclic fatigue because pulsed proton beams strike the target repeatedly. It is, therefore, important to investigate the fatigue strength of the eroded vessel wall. Actually, the erosion and fatigue damages will be imposed on the vessel wall at the same time. In order to precisely investigate the effects of damages, at the first, the pitting damage by erosion was evaluated against the number of pulses, and then the fatigue test was carried out using the specimen with a certain pitting damage. Key Words:Spallation target, Mercury, Cavitation erosion, Pitting damage, Fatigue strength, Degradation