Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Shobu, Takahisa; Shiro, Ayumi*; Kono, Fumiaki*; Muramatsu, Toshiharu; Yamada, Tomonori; Naganuma, Masayuki; Ozawa, Takayuki
Quantum Beam Science (Internet), 5(2), p.17_1 - 17_9, 2021/06
The automotive industries employ laser beam welding because it realizes a high energy density without generating irradiation marks on the opposite side of the irradiated surface. Typical measurement techniques such as strain gauges and tube X-rays cannot assess the localized strain at a joint weld. Herein high-energy synchrotron radiation X-ray diffraction was used to study the internal strain distribution of laser lap joint PNC-FMS steels (2- and 5-mm thick) under loading at a high temperature. As the tensile load increased, the local tensile and compressive strains increased near the interface. These changes agreed well with the finite element analysis results. However, it is essential to complementarily utilize internal defect observations by X-ray transmission imaging because the results depend on the defects generated by laser processing.
Wakui, Takashi; Wakai, Eiichi; Kogawa, Hiroyuki; Naoe, Takashi; Hanano, Kohei; Haga, Katsuhiro; Takada, Hiroshi; Shimada, Tsubasa*; Kanomata, Kenichi*
JPS Conference Proceedings (Internet), 28, p.081002_1 - 081002_6, 2020/02
A mercury target vessel of J-PRAC is designed with a triple-walled structure consisting of the mercury vessel and a double-walled water shroud with internal and external vessels. During the beam operation at 500 kW in 2015, small water leakages from a water shroud of the mercury target vessel occurred twice. Design, fabrication and inspection processes were improved based on the lessons learned from the target failures. The total length of welding lines at the front of the mercury target vessel decreases drastically to approximately 55% by adopting monolithic structure cut out from a block of stainless steel by the wire-electrical discharge machining. Thorough testing of welds by radiographic testing and ultrasonic testing was conducted. The fabrication of the mercury target vessel #8 was finished on September 2017 and the beam operation using it started. Stable beam operation at 500 kW has been achieved and it could experience the maximum beam power of 1 MW during a beam test.
Muramatsu, Toshiharu; Sato, Yuji; Kamei, Naomitsu; Aoyagi, Yuji*; Shobu, Takahisa
Nihon Kikai Gakkai Dai-13-Kai Seisan Kako, Kosaku Kikai Bumon Koenkai Koen Rombunshu (No.19-307) (Internet), p.157 - 160, 2019/10
no abstracts in English
Takamizawa, Hisashi; Katsuyama, Jinya; Ha, Yoosung; Tobita, Toru; Nishiyama, Yutaka; Onizawa, Kunio
Proceedings of 2019 ASME Pressure Vessels and Piping Conference (PVP 2019) (Internet), 8 Pages, 2019/07
no abstracts in English
Katsuyama, Jinya; Uno, Shumpei*; Watanabe, Tadashi*; Li, Y.
Frontiers of Mechanical Engineering, 13(4), p.563 - 570, 2018/12
Times Cited Count：2 Percentile：12.21(Engineering, Mechanical)For the structural integrity assessments on reactor pressure vessels (RPVs) under pressurized thermal shock (PTS) events, thermal hydraulic (TH) behavior of coolant water is one of the most important influence factors. Configuration of plant equipment and their dimensions, and operator action have large influences on TH behavior. In this study, to investigate the influence of operator action on TH behavior during a PTS event, we developed an analysis model for a typical Japanese plant, and performed TH and structural analyses. Two different operator action times were assumed based on the Japanese and US' rules. From the analysis results, it was clarified that differences in operator action times have a significant effect on TH behavior and loading conditions, that is, following the Japanese rule may lead to lower stresses compared to that when following the US rule because earlier operator action caused lower pressure in the RPV.
Wakui, Takashi; Wakai, Eiichi; Naoe, Takashi; Kogawa, Hiroyuki; Haga, Katsuhiro; Takada, Hiroshi; Shintaku, Yohei*; Li, T.*; Kanomata, Kenichi*
Choompa Techno, 30(5), p.16 - 20, 2018/10
A mercury target vessel has been used for the spallation neutron source at J-PARC. It has a complicated multi-layered structure composed of a mercury target and a surrounding double-walled water shroud, which is assembled with thin plates (minimum thickness of 3 mm) by welding. Thus, welding inspection during the manufacturing process is important. We investigated the applicability of new ultrasonic inspections using specimens (thickness of 3 mm) with defects to improve the accuracy of welding inspection for the mercury target vessel. Immersion ultrasonic testing using a probe (frequency of 50 MHz) could detect a spherical defect with a diameter of 0.2 mm. The size was smaller than target value of 0.4 mm. The length of unwelded region estimated using the phased array ultrasonic testing corresponded with the actual length (0.8 - 1.5 mm).
Naoe, Takashi; Wakui, Takashi; Kogawa, Hiroyuki; Wakai, Eiichi; Haga, Katsuhiro; Takada, Hiroshi
Advanced Experimental Mechanics, 3, p.123 - 128, 2018/08
A mercury target vessel, composed of SUS316L, is used for the pulsed neutron source and is assembled via TIG welding. While in operation, the target vessel suffers ca. 10
loading cycles with a high strain rate of ca. 50 s
because of the proton-beam-induced pressure waves in mercury. The gigacycle fatigue strength for solution annealed SUS316L stainless steels and its welded specimens were investigated through ultrasonic fatigue tests. The experimental results showed that an obvious fatigue limit was not observed at fewer than 10 cycles for the base metal. In the case of no weld defects observed via penetration tests, the fatigue strength of the removed-weld-bead specimen, in which the weld lines were arranged at the center of the specimen, appeared to be slightly higher than that of the base metal. By contrast, as-welded specimens with the weld bead intact showed apparent degradation of the fatigue strength owing to the stress concentration around the weld toe.
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：81.46(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.
Yamaguchi, Yoshihito; Katsuyama, Jinya; Li, Y.
Proceedings of 2018 ASME Pressure Vessels and Piping Conference (PVP 2018), 8 Pages, 2018/07
In order to assess the structure integrity of cracked pipes considering occurrence of large earthquakes, crack growth evaluation method for cracked pipes is important. In present study, evaluation method of crack growth by seismic loading was proposed for a dissimilar metal weld joint of nickel based alloy through experimental study using small specimens. Then, validation of the proposed method was performed through crack growth tests by using dissimilar metal weld pipe with circumferential through-wall crack. The predicted crack growth values were in good agreement with the experimental results and the applicability of the proposed method was confirmed.
Komatsu, Kazumi*; Seki, Takeshi*; Naganawa, Akihiro*; Oka, Kiyoshi*; Nishimura, Akihiko
Hozengaku, 16(3), p.89 - 95, 2017/10
no abstracts in English
Tsuji, Akihiro*; Zhang, S.*; Hashimoto, Tadafumi*; Okano, Shigetaka*; Shobu, Takahisa; Mochizuki, Masahito*
Zairyo, 65(9), p.665 - 671, 2016/09
It is necessary to control weld residual stress which has negative influence on fracture strengths. In structural steel welds, complex residual stress fields are formed due to phase transformation that occur according to the thermal cycles. In this study, in-situ evaluation of phase transformation and transitional stress simultaneously during welding is discussed. In the test using SM490A, after cooling process, stress evaluated by this system showed good agreement with that evaluated by lab X-ray. During austenite to ferrite transformation in weld metal, tensile stress occurred in austenite and compressive stress occurred in ferrite. Moreover, stress concentration was occurred in ferrite phase immediately after the start of phase transformation. Also, stress concentration was occurred in austenite phase just before the end of phase transformation.
Ito, Hiroto*; Onizawa, Kunio; Shibata, Katsuyuki*
JAERI-Data/Code 2005-007, 118 Pages, 2005/09
JAERI-Data-Code-2005-007.pdf:5.23MB
As a part of the aging and structual integrity research for LWR components, new PFM (Probabilistic Fracture Mechanics) codes PASCAL-SC and PASCAL-EQ have been developed. These codes evaluate the failure probability of an aged welded joint by Monte Carlo method. PASCAL-SC treats Stress Corrosion Cracking (SCC) in piping, while PASCAL-EQ takes fatigue crack growth by seismic load into account. The development of these codes has been aimed to improve the accuracy and reliability of analysis by introducing new analysis and methodologies and algorithms considering the recent development in the fracture machanics methodologies and computer performance. The crack growth by an irregular stress due to seismic load in detail is considered in these codes. They also involves recent stress intensity factors and fracture criteria. In addition, a user's friendly operation of a GUI (Graphical User Interface) which generates input data, supports calculations and plots results is introduced. This report provides the user's manual and theoretical background of these codes.
Yamada, Hirokazu*; Kawamura, Hiroshi; Tsuchiya, Kunihiko; Kalinin, G.*; Nagao, Yoshiharu; Takada, Fumiki; Nishikawa, Masahiro*
Journal of Nuclear Materials, 340(1), p.57 - 63, 2005/04
Times Cited Count：5 Percentile：35.8(Materials Science, Multidisciplinary)This study was performed to clear the effect of neutron re-irradiation on mechanical properties to welding material un-irradiated and irradiated stainless steel. The effect of re-irradiation to these weldaments were evaluated by tensile tests, metallographical observation and hardness test. The result of tensile tests shows that ultimate tensile strength of all joints specimen were almost similar, 0.2% yield strength and total elongation were depend on the irradiation damage and weldaments or not. Therefore, fracture mechanism was not change by re-irradiation. However, brittlement of material was depend on irradiation damage and the property of deformation was sensitive by the effect of irradiation damage or the effect of welding heat.
Morisaki, Norihiro; Hayashi, Koji; Inagaki, Yoshiyuki; Kato, Michio; Fujisaki, Katsuo*; Maeda, Yukimasa; Mizuno, Sadao*
JAERI-Tech 2005-009, 37 Pages, 2005/03
JAERI-Tech-2005-009.pdf:14.33MB
The breakage of the catalyst dust filter was found at the nozzle flange, which was welded onto the end plate of the filter, by the bubbling test using nitrogen gas of the mock-up model test facility. We investigated the cause of breakage and devised a repairing method. The cause of the breakage was the stress corrosion cracking (SCC) generated from the inside of the filter. The filter was repaired based on the following countermeasures such as reduction of condensed water in the filter, tensile stress and sensitization at welding joints. Furthermore, the inspection was carried out to investigate the structural integrity of the welding joints in the test facility of which structure, material and operating condition were similar to the filter. As the results, it was confirmed that the structural integrity was maintained.
Sn superconducting conductorKudo, Yusuke; Sakasai, Akira; Hamada, Kazuya; Takano, Katsutoshi*; Nakajima, Hideo; Okuno, Kiyoshi; Matsukawa, Makoto; Tamai, Hiroshi; Ishida, Shinichi
Journal of Nuclear Materials, 329-333(Part1), p.634 - 638, 2004/08
Times Cited Count：3 Percentile：23.52(Materials Science, Multidisciplinary)Japan Atomic Energy Research Institute (JAERI) has a plan to construct a tokamak fusion device called JT-60SC in which superconducting magnet system will be used. The objectives of this study are to clarify applicability of conventional austenitic stainless steel wire for the SS316LN to the conduit material of the Nb3Sn cable-in-conduit conductor for the central solenoid (CS) of JT-60SC. Tensile properties, fracture toughness and fatigue crack growth rate of both as-weld and aged (923 K 
240 hours) weld metals were evaluated at 4 K. The measured tensile properties of aged weld metal satisfied the requirement of JT-60SC. Fatigue crack growth property was enough to ensure the required operation cycles of 9.0 10e4. However, fracture toughness of aged weld metal could not be validated due to unstable crack extension. It was concluded that improvement of fracture toughness after aging was required to ensure the structural integrity of the CS conduit.
The Working Team for Examination Operation of Samples from Primary Loop Recirculation Piping at Onag
JAERI-Tech 2004-003, 74 Pages, 2004/02
JAERI-Tech-2004-003.pdf:30.08MB
The present examination has been performed with the objective to provide technical basis for identifying causes of cracking through the examination of the samples, which was conducted at the post irradiation examinations facilities of JAERI, taken from the cracked region of the recirculation pipe at the Onagawa Nuclear Power Station Unit-1. The following findings were obtained from this examination result. (1) Cracks were observed near the weld region of inner surface of the pipe and depth of the crack was about 5 to 7mm. (2) Intergranular crackings were observed in the almost whole fracture surface. Partially transgranular cracking was observed at the surface layer with the depth of about 100
m. Microstructure formed by cold work and increase of hardness were observed in these surface layers. Cracks initiated near the region where hardness value was the highest. Based on the examination results described above concerning presence of tensile residual stress by welding and relatively high dissolved oxygen contents in core coolant and so on, it is concluded that these cracks were initiated in the cold work layer of inner surface by stress corrosion cracking (SCC) and propagated along the grain boundaries.
Al superconducting conductor jacketed with a round-in-square type stainless steel conduit for the toroidal field coils in JT-60SCTsuchiya, Katsuhiko; Kizu, Kaname; Miura, Yushi; Ando, Toshinari*; Nakajima, Hideo; Matsukawa, Makoto; Sakasai, Akira; Ishida, Shinichi
Fusion Engineering and Design, 70(2), p.131 - 140, 2004/02
Times Cited Count：3 Percentile：23.52(Nuclear Science & Technology)no abstracts in English
cycling techniques for thermo chemical hydrogen production process; R&D on refractory and corrosion resistant pressure sensor for hydrogen iodide cycling test loopIshiyama, Shintaro
Nihon Kikai Gakkai Rombunshu, A, 69(686), p.102 - 107, 2003/10
no abstracts in English
Sato, Satoshi; Maki, Koichi*
Fusion Engineering and Design, 65(4), p.501 - 524, 2003/07
Times Cited Count：8 Percentile：49.89(Nuclear Science & Technology)no abstracts in English
Kogawa, Hiroyuki; Ishikura, Shuichi*; Hino, Ryutaro; Kato, Takashi; Aso, Tomokazu; Sato, Hiroshi; Harada, Masahide; Kai, Tetsuya; Teshigawara, Makoto; Maekawa, Fujio; et al.
Proceedings of ICANS-XVI, Volume 2, p.635 - 644, 2003/07
no abstracts in English
