Pitting Damage Formation up to over 10 Million Cycles Off-line Test by MIMTM

Abstract

A liquid-mercury target system for the MW-scale target is being developed in the world. The pitting damage induced by pressure wave propagation gets to be one of critical issues to estimate the life of the target structure with mercury and to evaluate its structural integrity. The off-line test on the pitting damage at high cycles over 10 millions was carried out using a novel device, the MIMTM which drives electromagnetically to impose pulse pressure into the mercury. It was found from the pitting damage data obtained by the MIMTM and comparison with classical vibratory hone tests that the pitting damage can be characterized in two steps, an incubation period that can extend to 10 6 cycles in 20% cold worked 316SS and 10 7 cycles in surface hardening treated one and steady state erosion where mass loss scales with the number of cycles to approximately the 1.27 power for mercury. The length of the incubation period is primarily a function of the material and the intensity of the pressure. This observation provides a simple model for estimating lifetime for different materials and beam power.

Study on the evaluation of erosion damage by using laser ultrasonic integrated with a wavelet analysis technique

“…If the maximum depth of damage keeps increasing, more obvious differences were shown in the relatively lower frequency range. Cavitation damage develops from isolated micro localized damage to area erosion when the maximum depth increases up to approximately 15μm [16,17]. At this stage, the number of damage changed obviously while the maximum depth of damage almost keeps a constant.…”

Cavitation Damage Evaluation Using Laser Impacts

“…The number of impacts performed at each area was 0, 10 4 , 10 5 , 10 6 and 10 7 , respectively. The peak-to-peak (P-P) roughness of the cavitation damage at each area was: (I) 45 µm, (II) 35 µm, (III) 25 µm, (IV) 15 µm.…”

Mitigation Technologies for Damage Induced by Pressure Waves in High-Power Mercury Spallation Neutron Sources (III)—Consideration of the Effect of Microbubbles on Pressure Wave Propagation through a Water Test—

“…8) As an engineering issue caused by a pressure wave, cavitation damage in liquid mercury targets raises a significant problem in the development of spallation neutron sources. [11][12][13][14][15] High-power pulsed spallation neutron sources are working in the Japan Proton Accelerator Research Complex (J-PARC) 16) and the Spallation Neutron Source (SNS) of the United States. 17) In both neutron sources, liquid mercury was selected as a target material because of its high neutron yield and high cooling performance.…”

“…The pressure waves cause a serious issue for operational stability of the neutron sources because they induce the cavitation of mercury, which results in cavitation damage on the stainless steel target vessel and degrades its structural integrity. [11][12][13][14] In order to solve this critical issue, the authors investigated a surface improvement of the target vessel walls to mitigate damage formation due to cavitation bubble collapse. 13,18) However, it was found that long-range damage mitigation by the surface improvement is very difficult and, hence, some other treatments are required.…”