Effect of tensile stress on cavitation damage formation in mercury

Naoe, Takashi   ; Kogawa, Hiroyuki  ; Yamaguchi, Yoshihito ; Futakawa, Masatoshi  

Pressure wave induced cavitation is a critical issue to realize a MW-class mercury target because structural integrity of the target vessel is remarkably degraded by the pitting damage. The target vessel suffers tensile stress by welding residual stress and/or thermal stress due to proton beam injection. In this study, in order to examine the effect of tensile stress on pitting damage formation, cavitation erosion test was performed using an ultrasonic homogenizer in mercury. The result showed that the damaged area was increased with increasing in tensile stress. The depth and diameter of pits were larger than that of no-stressed specimen, and the eroded area was increased. Indentation tests under tensile stress were carried out to quasi-statically simulate impact load. Vickers hardness was slightly decreased. Threshold stress of the deformation, i.e. pitting damage formation, was decreased by tensile stress.