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Wakui, Takashi; Takagishi, Yoichi*; Futakawa, Masatoshi; Tanabe, Makoto*
Jikken Rikigaku, 23(2), p.168 - 174, 2023/06
Cavitation damage on the inner surface of the mercury target for the spallation neutron source occurs by proton bombarding in mercury. The prediction method of the cavitation damage using Monte Carlo simulations was suggested taking variability of the bubble core position and impact pressure distribution into account. The impact pressure distribution was estimated using the inverse analysis with Bayesian optimization was conducted with comparison between cavitation damage distribution obtained from experiment and the cumulative plastic strain distribution obtained from simulation. The average value and spread of maximum impact pressure estimated assuming the Gaussian distribution were 3.1 GPa and 1.2 
m, respectively. Simulation results reproduced experimental results and it can be said that this evaluation method is useful.
Nagata, Sho*; Miyake, Shugo*; Igarashi, Takahiro; Ota, Hiromichi*; Nishi, Tsuyoshi*
Jikken Rikigaku, 22(2), p.105 - 111, 2022/06
Thermal easy axis and thermal diffusivity of uniaxial carbon fiber-reinforced plastic sheets were determined by a offset periodic laser heating method, and investigated relationship between the thermal easy axis and fiber orientation with different thickness of CFRP sheet specimen, experimentally. It was clarified that the orientation of the thermal easy axis spreads in the in-plane direction with the sheet thickness deceases. Then, thermal diffusivity of CFRP specimens in the out-of-plane and in-plane direction were measured by two method: a variable-frequency method and a variable-displacement method, respectively. In the results of the out-of-plane directions, thermal diffusivity almost consistent with the carbon fiber direction were obtained. In contrast, the in-plane directions of those were exhibited unexpected value. Moreover, thermal diffusivity determination by offset periodic heating method was carried out. Finally, it is found that the thermal diffusivity considering the thermal easy axis with fiber angle was different characteristics from the in-plane direction measurement.
Takatsuka, Yuriko*; Matsumoto, Saori*; Nishi, Tsuyoshi*; Ota, Hiromichi*; Hori, Ayumi*; Hayashi, Kiichiro*; Yamano, Hidemasa
Jikken Rikigaku, 22(2), p.117 - 119, 2022/06
This study clarified the effect of the viscosities of molten casting steels for high temperature by measuring them using the oscillating crucible method. The casting steels for high temperature samples used for viscosity measurements contained 0, 10, 20, 30, 40, and 50 mass% Ni. Viscosities were evaluated using Roscoe's equation and measured in the temperature range of 1693-1803 K.
Wakui, Takashi; Yamasaki, Kazuhiko*; Futakawa, Masatoshi
Jikken Rikigaku, 22(2), p.96 - 104, 2022/06
Pulsed laser irradiation and indentation tests on radiation shielding glasses and a lead-free glass were carried out. The size of irradiation damage of the glass with high lead content was larger than that with low content. The micro plastic behavior of glasses was quantitatively determined using the inverse analyses based on indentation results. Flow stress decreased with an increase of lead content and that in irradiated area was lower than that in unirradiated area. On the other hand, plastic flow resistance increased with an increase of the lead content and that in irradiated area was higher than that in unirradiated area. Fracture energy and critical size of plastic zone around tip of crack in unirradiated and irradiated areas were calculated based on experimental results including constants evaluated using the inverse analysis. These values decreased with an increase of the lead content and these values in irradiated area were lower than that in unirradiated area.
Matsumoto, Saori*; Nishi, Tsuyoshi*; Ota, Hiromichi*; Hori, Ayumi*; Hayashi, Kiichiro*; Yamano, Hidemasa
Jikken Rikigaku, 22(2), p.112 - 116, 2022/06
In this study, the viscosity of the molten Ni-based superalloys were measured by the oscillating crucible method. When the logarithm of the viscosity was plotted against the inverse temperature (Arrhenius-type plot), all alloys showed a good Arrhenius-type linearity over the temperature range investigated. It was also found that the viscosities of molten Ni-based superalloys decreased with increasing the Co contents.
Yamasaki, Kazuhiko*; Kato, Hironori*; Futakawa, Masatoshi; Teshigawara, Makoto
Jikken Rikigaku, 21(4), p.308 - 313, 2021/12
In this study, coloration and damage of radiation-resistant lead glasses by nanosecond pulse laser with visible wavelength are evaluated. Three kinds of radiation resistance glasses with different lead content: PbO-55 wt%, 71 wt% and PbO free glass are used. As a result, the transitional coloration and damage formation with phase differences had observed by nanosecond pulsed laser irradiation at peak power of 1 kW. Although high-lead concentration glass has lower thresholds for coloration in laser intensity, damage-formation thresholds for both PbO glasses were almost the same. On the other hand, no change was observed after laser-irradiation to PbO-free glass. In addition, photochemical and thermal reaction of PbO by nanosecond pulsed laser irradiation is considered from the result of intensity change at wave numbers 200-500
and 1000 cm in Raman spectrums.
Wan, T.; Wakui, Takashi; Naoe, Takashi; Futakawa, Masatoshi; Maekawa, Katsuhiro*; Wan, T.*
Jikken Rikigaku, 13(4), p.387 - 394, 2013/12
The mercury target system is used for MW-scale neutron sources in the Japan Spallation Neutron Source. During this operation, cavitation damage is imposed on the mercury target vessel. It is very important to nondestructively evaluate the cavitation damage from the viewpoints of the structural integrity evaluation and lifetime estimation of the mercury target vessel. In this study, the cavitation damage was evaluated using a nonlinear ultrasonic method. First, the cavitation damage was imposed on plate specimens using an electro-Magnetic IMpact Testing Machine with 108 impact cycles. Nonlinear ultrasonic imaging was used to evaluate the damage. We found that the damping factor and higher harmonics of reflected waveforms from the damaged area can be used to evaluate the damage. An effective cavitation damage evaluation process has been developed based on our results. The evaluation process successfully detected minimal cavitation damage with peak-to-peak roughness of about 25 m.
Hirabayashi, Masaru; Monji, Hideaki*; Sagawa, Hiroshi*
Jikken Rikigaku, 12(4), p.391 - 397, 2012/12
Tanaka, Masaaki
Jikken Rikigaku Handobukku, p.417 - 428, 2008/01
I had written a part of the Handbook of Experimental Dynamics published by the Asakura-shoten. Contents were related to the visualization techniques of thermal-hydraulics in a porous blockage in fuel subassembly and also the visualization technique of temperature fluctuation on the inner surface of main pipe in T-junction piping system.
Bucheeri, A.; Kogawa, Hiroyuki; Naoe, Takashi; Futakawa, Masatoshi; Maekawa, Katsuhiro*
Jikken Rikigaku, 7(4), p.331 - 336, 2007/12
A mercury target system will be installed in Japan Proton Accelerator Complex (J-PARC). High intense proton beams injected into the target will induce cavitation by pressure waves. Injection of microbubbles with 50 to 200 m in diameter into mercury may be effective to reduce cavitation damage. Bubble generation in mercury is difficult because of its poor wettability. Therefore, we artificially change wetting condition in water to simulate bubble formation in poor wetting conditions. Experimentally, visualization of bubble growth at an orifice type nozzle of 100 m in diameter was done by a high-speed CCD camera. Wetting condition on the orifice surface was worsen by coating it with a water-repellent. Computational Fluid Dynamics simulation was carried out under stagnant water to understand the effect of wettability on bubble formation from the orifice nozzle. It was found that the bubble diameter depends on contact angle and it increases as wetting become worse.
Naoe, Takashi; Futakawa, Masatoshi; Koyama, Tomofumi*; Kogawa, Hiroyuki
Jikken Rikigaku, 6(3), p.301 - 307, 2006/09
A mercury target for spallation neutron source is subject to pressure waves caused by proton bombarding mercury. The pressure wave propagation induces the cavitation in mercury that imposes pitting damage on the target vessel. In this paper, single micro-bubble behavior in mercury was evaluated using numerical calculation on the basis of bubble dynamics given by Rayleigh-Plesset. Impact pressure loading tests using an electro-Magnetic IMpact Testing Machine (MIMTM) were performed to measure the impact pressure and acoustic vibration. Additionally, in order to visualize micro-bubble behavior in mercury, high-speed video camera observation was carried out. As the result, we confirmed that the maximum bubble radius and lifetime of micro-bubble are dependent on the imposed pressure and the pressure saturate time and that the acoustic vibration with high frequency components above 15 kHz is exited by the micro-bubble collapse.
Naoe, Takashi*; Futakawa, Masatoshi; Koyama, Tomofumi*; Kogawa, Hiroyuki; Ikeda, Yujiro
Jikken Rikigaku, 5(3), p.280 - 285, 2005/09
no abstracts in English
Naoe, Takashi*; Futakawa, Masatoshi; Naito, Akira*; Ioka, Ikuo; Kogawa, Hiroyuki
Jikken Rikigaku, 5(1), p.15 - 21, 2005/03
no abstracts in English
Kogawa, Hiroyuki
Jikken Rikigaku, 5(1), P. 64, 2005/03
no abstracts in English
Futakawa, Masatoshi; Wakui, Takashi*; Naoe, Takashi*; Ioka, Ikuo
Jikken Rikigaku, 4(3), p.222 - 227, 2004/09
no abstracts in English
Futakawa, Masatoshi; Kubo, Shinji; Wakui, Takashi*; Onuki, Kaoru; Shimizu, Saburo; Yamaguchi, Akihisa*
Jikken Rikigaku, 3(2), p.109 - 114, 2003/06
Micro-indentation technique was applied to evaluate the mechanical properties of corroded surface layers of Ni-alloy, 316SS, Ti and Ta, which were exposed into the corrosive gaseous environment consisting of HI+I
+HO+H. The corrosion condition was chosen so as to simulate one of the environments in the thermochemical hydrogen production, IS process, where the degradation due to the corrosion attack by HI and the hydrogen embrittlement is a key issue from the viewpoint of material integrity. The micro-indentation tests using a spherical indenter and the inverse analysis with Kalman filter were performed to quantitatively estimate material constants of corroded surface layer. Ni-alloy exhibited good corrosion resistance and Ta was remarkably influenced by the hydrogen embrittlement.
Kogawa, Hiroyuki; Ishikura, Shuichi*; Futakawa, Masatoshi; Hino, Ryutaro
Jikken Rikigaku, 2(2), p.122 - 127, 2002/06
no abstracts in English
Date, Hidefumi*; Futakawa, Masatoshi; Ishikura, Shuichi*
Jikken Rikigaku, 2(2), p.103 - 108, 2002/06
In order to examine the impact behavior of mercury, which is one of important key-issues in a facility for high intensity neutron sources, the falling and colliding profiles of mercury droplets were recorded by high-speed video recorder. The impact force was also measured using the strain gage glued on an elastic bar. The falling mercury droplet oscillated between a prolate spheroid and an oblate one, repeatedly. The regathering and jumping of mercury at the collision point on the impact face of the target were observed after impact because of the strong surface tension of mercury. The impact force of mercury droplet was in proportion to the impact velocities and the square root of the potential energy. Scince the non-dimensional duration time K that obtained experimentally is independent of the impact velocity and the size of the droplet, the mean applied stress due to the mercury droplet against the target is easily predictable by the equatiion using K value and the impact velocity is known.
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Dai-8-Kai Jikken Rikigaku Kokusai Kaigi, 0 Pages, 1996/06
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