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AuGe ( = Y, Gd-Tm, and Lu)Kurumaji, Takashi*; Gen, Masaki*; Kito, Shunsuke*; Ikeuchi, Kazuhiko*; Nakamura, Mitsutaka; Ikeda, Akihiko*; Arima, Takahisa*
Journal of Alloys and Compounds, 947, p.169475_1 - 169475_8, 2023/06
Times Cited Count：1 Percentile：48.82(Chemistry, Physical)Yoshida, Masayuki*; Nishihata, Itsuki*; Matsuda, Tomoki*; Ito, Yusuke*; Sugita, Naohiko*; Shiro, Ayumi*; Shobu, Takahisa; Arakawa, Kazuto*; Hirose, Akio*; Sano, Tomokazu*
Journal of Applied Physics, 132(7), p.075101_1 - 075101_9, 2022/08
Times Cited Count：5 Percentile：64.66(Physics, Applied)Takagi, Rina*; Matsuyama, Naofumi*; Ukleev, V.*; Yu, L.*; White, J. S.*; Francoual, S.*; Mardegan, J. R. L.*; Hayami, Satoru*; Saito, Hiraku*; Kaneko, Koji; et al.
Nature Communications (Internet), 13, p.1472_1 - 1472_7, 2022/03
Times Cited Count：58 Percentile：99.59(Multidisciplinary Sciences)Nishimura, Hayato*; Hojo, Tomohiko*; Ajita, Saya*; Shibayama, Yuki*; Koyama, Motomichi*; Saito, Hiroyuki*; Shiro, Ayumi*; Yasuda, Ryo*; Shobu, Takahisa; Akiyama, Eiji*
Tetsu To Hagane, 107(9), p.760 - 768, 2021/09
Times Cited Count：0 Percentile：0(Metallurgy & Metallurgical Engineering)no abstracts in English
Shibayama, Yuki; Hojo, Tomohiko*; Koyama, Motomichi*; Saito, Hiroyuki*; Shiro, Ayumi*; Yasuda, Ryo*; Shobu, Takahisa; Matsuno, Takashi*; Akiyama, Eiji*
ISIJ International, 61(4), p.1322 - 1329, 2021/04
Times Cited Count：3 Percentile：24.75(Metallurgy & Metallurgical Engineering)Nishimura, Hayato*; Hojo, Tomohiko*; Ajita, Saya*; Shibayama, Yuki*; Koyama, Motomichi*; Saito, Hiroyuki*; Shiro, Ayumi*; Yasuda, Ryo*; Shobu, Takahisa; Akiyama, Eiji*
ISIJ International, 61(4), p.1170 - 1178, 2021/04
Times Cited Count：3 Percentile：24.75(Metallurgy & Metallurgical Engineering)Yamanaka, Kenta*; Kuroda, Asumi*; Ito, Miyu*; Mori, Manami*; Bian, H.*; Shobu, Takahisa; Sato, Shigeo*; Chiba, Akihiko*
Additive Manufacturing, 37, p.101678_1 - 101678_12, 2021/01
Times Cited Count：24 Percentile：86.75(Engineering, Manufacturing)Hojo, Tomohiko*; Akiyama, Eiji*; Saito, Hiroyuki*; Shiro, Ayumi*; Yasuda, Ryo*; Shobu, Takahisa; Kinugasa, Junichiro*; Yuse, Fumio*
Corrosion Science, 177, p.108957_1 - 108957_9, 2020/12
Times Cited Count：18 Percentile：75.61(Materials Science, Multidisciplinary)Hydrogen assisted cracking on hemispherically-stretch-formed specimens of transformation induced plasticity-aided martensitic steel was investigated. Hydrogen charging induced cracking around the foot of the impression formed on the steel sheet, and the cracks propagated along the radial direction toward the hillside and the plains. Distributions of stress, plastic strain and volume fraction of retained austenite were analyzed employing the energy-dispersive X-ray diffraction method utilizing the synchrotron X-ray radiation at SPring-8. It was notable that the crack initiation took place in the region where the measured tensile stress was the highest. Influences of plastic strain and resulted martensitic transformation were also suggested.
Hojo, Tomohiko*; Kumai, B.*; Koyama, Motomichi*; Akiyama, Eiji*; Waki, Hiroyuki*; Saito, Hiroyuki*; Shiro, Ayumi*; Yasuda, Ryo*; Shobu, Takahisa; Nagasawa, Akihiko*
International Journal of Fracture, 224(2), p.253 - 260, 2020/08
Times Cited Count：14 Percentile：66.22(Materials Science, Multidisciplinary)In the study, the pre-strain effect on hydrogen embrittlement property of the ultra-high-strength transformation-induced plasticity -aided bainitic ferrite steel was investigated towards application for automobile frame parts. 3-10% tensile pre-strain suppressed hydrogen-induced mechanical degradation relative to total elongation while 12-15% pre-strained specimen did not exhibit elongation after hydrogen charging. The advantageous effect of the 3-10% pre-strain was attributed to the suppression of crack initiation related to retained austenite. The TRIP by pre-straining decreased the volume fraction of retained austenite before hydrogen charging, thereby reducing existing probabilities of preferential crack initiation sites and propagation paths. Conversely, high pre-strain such as 12-15% does not effectively work due to work hardening resulting in increases in hydrogen embrittlement susceptibility and a significant increase in hydrogen content due to the multiplication of dislocations.
Miyakawa, Susumu*; Ito, Toshimasa*; Iwahori, Keisuke*; Aoyama, Yoshihiko*; Kubo, Ryosuke*; Murata, Shinji*; Shobu, Takahisa; Shiro, Ayumi*; Kajiwara, Kentaro*
Zairyo, 69(4), p.308 - 314, 2020/04
White etching area which looks white with nital corrosive liquid may be recognized at the flaking part of a rolling bearing on which high contact stress of several GPa is applied repeatedly. Up to now, studies of white etching area of a ball have been less than studies of white etching area of inner and outer rings. In this study, as part of the flaking mechanism explication with white etching area of a ball, internal residual stress distributions of ball by using high energy white X-ray of SPring-8 (A method) and laboratorial X-ray measurement equipment (B method) were investigated. The former was modified by surface residual stress according to B method. The latter was modified by releasing stress in the form of electrolytic polishing. The results showed modified residual stress distributions almost agree qualitatively.
Sano, Tomokazu*; Eimura, Takayuki*; Hirose, Akio*; Kawahito, Yosuke*; Katayama, Seiji*; Arakawa, Kazuto*; Masaki, Kiyotaka*; Shiro, Ayumi*; Shobu, Takahisa; Sano, Yuji*
Metals, 9(11), p.1192_1 - 1192_13, 2019/11
Times Cited Count：15 Percentile：64.79(Materials Science, Multidisciplinary)The purpose of the present study was to verify the effectiveness of dry laser peening (DryLP), which is the peening technique without a sacrificial overlay under atmospheric conditions using femtosecond laser pulses on the mechanical properties such as hardness, residual stress, and fatigue performance. After DryLP treatment of the laser-welded 2024 aluminum alloy, the softened weld metal recovered to the original hardness of base metal, while residual tensile stress in the weld metal and heat-affected zone changed to compressive stresses. The fatigue life almost doubled at a stress amplitude of 180 MPa and increased by a factor of more than 50 at 120 MPa. As a result, DryLP was found to be more effective for improving the fatigue performance of laser-welded aluminum specimens with welding defects at lower stress amplitudes.
Miyagi, Masanori*; Hongze, W.*; Yoshida, Ryohei*; Kawahito, Yosuke*; Kawakami, Hiroshi*; Shobu, Takahisa
Scientific Reports (Internet), 8(1), p.12944_1 - 12944_10, 2018/08
Times Cited Count：42 Percentile：81.64(Multidisciplinary Sciences)The behavior inside the metal during laser welding is very important because it greatly affects the material strength, defect generation, and so on. In this study, weld pool dynamics in laser welding of various series of aluminum alloys were investigated by the 
synchrotron radiation X-ray phase contrast imaging system. The experimental results showed that metal irradiated by laser was evaporated immediately, which generated the keyhole. Then metal surrounding the keyhole was melted gradually with the heat from keyhole. The growth rate of keyhole depth had a positive linear correlation with the total content of low boiling temperature elements (TCE), so did the keyhole depth and diameter at the stable stage. Then, by repeating the experiment, we succeeded in quantifying the effect of alloying elements on the dynamics of the weld pool in laser welding of aluminum alloys.
Nakajima, Taro*; Inamura, Yasuhiro; Ito, Takayoshi*; Oishi, Kazuki*; Oike, Hiroshi*; Kagawa, Fumitaka*; Kikkawa, Akiko*; Taguchi, Yasujiro*; Kakurai, Kazuhisa*; Tokura, Yoshinori*; et al.
Physical Review B, 98(1), p.014424_1 - 014424_5, 2018/07
Times Cited Count：7 Percentile：34.24(Materials Science, Multidisciplinary)We investigated the phase-transition kinetics of magnetic skyrmion lattice (SkL) in MnSi by means of stroboscopic small-angle neutron scattering (SANS). Temporal evolutions of SANS patterns were measured with time resolution of 13 ms while sweeping temperature as fast as 50 Ks
. It turned out that the paramagnetic-to-SkL transition immediately occurs upon traversing the equilibrium phase boundary on the rapid cooling, whereas the SkL-to-conical transition can be kinetically avoided to realize the low-temperature metastable SkL with a long-range magnetic order. The formation of the metastable SkL was found to be strongly dependent not only on cooling rate, but also on magnetic eld and trajectory in the H-T phase diagram.
Akita, Koichi; Miyashita, Daisuke*; Takeda, Kazuya*; Oya, Shinichi*; Shobu, Takahisa; Sano, Kenji*; Saito, Toshiyuki*
Nihon Zairyo Gakkai Dai-44-Kai X Sen Zairyo Kyodo Ni Kansuru Shimpojiumu Koen Rombunshu, p.46 - 50, 2010/07
Relaxation process of surface compressive residual stress during tensile or compressive loading on a laser peened aluminum alloy was investigated. The residual stress was measured by X-ray, synchrotron and neutron diffractions and analyzed by a finite element method. The relaxation process clarified in this study was described as follows. When the tensile loading was increased, plastic deformation was occurred at the tensile residual stress region that existed inside of the material to be balanced with the surface compressive residual stress. On the other hand, when the compressive loading was applied, the plastic deformation was started at the maximum compressive residual stress region located just beneath the surface. Because the plastic deformation of the inside of the material induced the redistribution of the residual stress in the sample, the surface compressive residual stress was relaxed prior to the surface yielding.
Tobita, Kenji; Nishio, Satoshi; Enoeda, Mikio; Kawashima, Hisato; Kurita, Genichi; Tanigawa, Hiroyasu; Nakamura, Hirofumi; Honda, Mitsuru; Saito, Ai*; Sato, Satoshi; et al.
Nuclear Fusion, 49(7), p.075029_1 - 075029_10, 2009/07
Times Cited Count：139 Percentile：97.7(Physics, Fluids & Plasmas)Recent design study on SlimCS focused mainly on the torus configuration including blanket, divertor, materials and maintenance scheme. For vertical stability of elongated plasma and high beta access, a sector-wide conducting shell is arranged in between replaceable and permanent blanket. The reactor adopts pressurized-water-cooled solid breeding blanket. Compared with the previous advanced concept with supercritical water, the design options satisfying tritium self-sufficiency are relatively scarce. Considered divertor technology and materials, an allowable heat load to the divertor plate should be 8 MW/m
or lower, which can be a critical constraint for determining a handling power of DEMO (a combination of alpha heating power and external input power for current drive).
Kim, S.-W.; Shobu, Takahisa; Otsuka, Satoshi; Kaito, Takeji; Inoue, Masaki; Onuma, Masato*
Materials Transactions, 50(4), p.917 - 921, 2009/04
The size and density distribution of dispersed oxide particles is recognized as one of the main issues for ensuring good microstructural stability and high temperature strength in a high temperature (
700 
C) and neutron irradiation (250 dpa) environment. However, the behavior of oxide particles in the hot-solidification process has not been determined yet. This study evaluated the correlation between nano-size oxide particles and the heat treatment temperature and time in order to characterize the mechanism of formation and the behavior during growth and coalescence for these particles in 9Cr-ODS steel raw powder. XRD and SAXS measurements were made using high-energy synchrotron radiation X-rays in SPring-8. This is the first report of the oxide complex particles (Y
TiO
and YTiO
) being formed from 800 C to 960 C, and they were observed to grow and coalesce on increasing both heat-treatment temperature and time.
Kim, S.-W.; Shobu, Takahisa; Otsuka, Satoshi; Kaito, Takeji; Inoue, Masaki; Onuma, Masato*
Materials Transactions, 50(4), p.917 - 921, 2009/04
Times Cited Count：26 Percentile：74.82(Materials Science, Multidisciplinary)Abe, Hiroyoshi; Haga, Takahisa; Fukaya, Hiroyuki; Sonoda, Takashi; Sakazume, Yoshinori; Ito, Mitsuo; Shirahashi, Koichi
JAEA-Technology 2009-008, 24 Pages, 2009/03
JAEA-Technology-2009-008.pdf:5.62MB
Analysis of the uranyl nitrate solution fuel is carried out at the analytical laboratory of NUCEF (Nuclear Fuel Cycle Engineering Research Facility), which provides essential data for operation of STACY (Static Experiment Critical Facility), TRACY (Transient Experiment Critical Facility) and the fuel treatment system. Analyzed in FY 2007 were uranyl nitrate solution fuel samples taken before and after experiments of STACY and TRACY, samples for the preparation and pulification of uranyl nitrate solution fuel in the fuel treatment system and samples for nuclear material accountancy purpose. The total number of the samples analyzed in FY 2007 was 143. This report summarizes work related to the analysis and management of the analytical laboratory in the FY 2007.
Kawamata, Yoichi; Naito, Osamu; Kiyono, Kimihiro; Itami, Kiyoshi; Totsuka, Toshiyuki; Akasaka, Hiromi; Sueoka, Michiharu; Sato, Tomoki; Oshima, Takayuki; Sakata, Shinya; et al.
Fusion Engineering and Design, 83(2-3), p.198 - 201, 2008/04
Times Cited Count：3 Percentile：23.51(Nuclear Science & Technology)The design activity of JT-60SA (JT-60 Super Advanced) which is remodeled to a superconducting tokamak device has been starting under the JA-EU collaborative ITER-BA project. For the JT-60SA control system, the existing system should be reused as much as possible from the viewpoint of cost-effectiveness. We have just begun to discuss the configuration of the advanced Supervisory Control System (SVCS) including the following systems: (1) ultimately flexible real-time control system, (2) precise timing system enough to clarify cause and effect, and (3) safety shutdown control system. In this report, we present the design study of the JT-60SA SVCS with focusing on these systems.
Sakazume, Yoshinori; Aoki, Hiromichi; Haga, Takahisa; Fukaya, Hiroyuki; Sonoda, Takashi; Shimizu, Kaori; Niitsuma, Yasushi*; Ito, Mitsuo; Inoue, Takeshi
JAEA-Technology 2007-069, 44 Pages, 2008/02
JAEA-Technology-2007-069.pdf:4.55MB
Analysis of the uranyl nitrate solution fuel is carried out at the analytical laboratory of NUCEF (Nuclear Fuel Cycle Engineering Research Facility), which provides essential data for operation of STACY (Static Experiment Critical Facility), TRACY (Transient Experiment Critical Facility) and the fuel treatment system. Analyzed in FY 2006 were uranyl nitrate solution fuel samples taken before and after experiments of STACY and TRACY, samples for the preparation of uranyl nitrate solution fuel, and samples for nuclear material accountancy purpose. The total number of the samples analyzed in FY 2006 was 254. This report summarizes work related to the analysis and management of the analytical laboratory in the FY 2006.
