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CNguyen, B. V. C.*; Murakami, Kenta*; Chena, L.*; Phongsakorn, P. T.*; Chen, X.*; Hashimoto, Takashi; Hwang, T.*; Furusawa, Akinori; Suzuki, Tatsuya*
Nuclear Materials and Energy (Internet), 39, p.101639_1 - 101639_9, 2024/06
Furusawa, Akinori; Takenaka, Yusuke; Nishimura, Akihiko
Applied Sciences (Internet), 9(17), p.3544_1 - 3544_12, 2019/09
Times Cited Count：9 Percentile：61.01(Chemistry, Multidisciplinary)Remote-controlled, non-destructive testing is necessary to detect corrosion of the reinforced concrete structures at the Fukushima Daiichi Nuclear Power Plant (NPP) de-commissioning site. This work aims to demonstrate that laser-induced ultrasonic guided wave technology can be applied to achieve this task. Hence, accelerated electrolytic corrosion is performed on a reinforced concrete specimen fabricated by embedding a steel rod into mortar. Waveforms of the laser-induced ultrasonic guided wave on the rod are measured with a previously employed piezoelectric transducer (PZT) probe, for each fixed corrosion time. Based on the results of Fourier and wavelet transforms of the waveforms, issues concerning the detection and extent of rebar corrosion are discussed. It is exhibited that the changes in bonding strength due to corrosion are distinguishable in the frequency domain of the ultrasonic signal.
Furusawa, Akinori; Nishimura, Akihiko; Takenaka, Yusuke; Muramatsu, Toshiharu
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 4 Pages, 2019/05
The aim of this work presented here is to demonstrate the potential of our method for remote controllable systematization, of testing reinforced concrete based on ultrasonic guided-wave on rebar. In order to investigate how the deteriorated phenomena has the effects on the ultrasonic guided-wave propagating on the rebar, following experiments are conducted. Test pieces used for the experiments are made of bare steel rod and cylindrically pored mortar to be representing the actual reinforced concrete. Irradiating the end face of the rod with nanosecond pulsed laser makes the ultrasonic guided-wave induced, at the other end face, the guided wave signal is measured with ultrasonic receiver. One test piece is with no damage and the other is deteriorated test piece. The deterioration is made by electrolytic corroded method. The guided-wave signal from the deteriorated test piece is measured with respect to each energization time, the change in the waveform is investigated. Analyzing the results from the experiments above, it is found that the deterioration of rebar has remarkable effects on the guided-wave signal. The signal from test piece with no damage has strong peak at both specific frequency and lower region, on the other hand, signals from deteriorated test piece has only at the specific frequency depending on the diameter of the steel rod. Finally, discussion concerning with the experimental results and future perspective for remote controllable systematization of our method is carried out.
Nishimura, Akihiko; Furusawa, Akinori; Takenaka, Yusuke*
AIP Conference Proceedings 2033, p.080002_1 - 080002_5, 2018/11
Times Cited Count：0 Percentile：0.06(Green & Sustainable Science & Technology)We developed a cpmpact laser maintenance device in order to access a 23 mm diameter for heat exchanger tubes of nuclear power plants. A laser instrumentation device was desighned and assembled to measure the corrosion depth at the inlet of heat exchanger tubes. This device can be applied for heat exchanger tubes in CSP where erosion or cracking might be caused by repetitive thermal induced stress.
Nishimura, Akihiko; Takenaka, Yusuke*; Furusawa, Akinori; Torimoto, Kazuhiro; Ueda, Masashi; Fukuda, Naoaki*; Hirao, Kazuyuki*
E-Journal of Advanced Maintenance (Internet), 9(2), p.52 - 59, 2017/08
no abstracts in English
Furusawa, Akinori; Nishimura, Akihiko; Takebe, Toshihiko*; Nakamura, Masaki*; Takenaka, Yusuke*; Saijo, Shingo*; Nakamoto, Hiroyuki*
E-Journal of Advanced Maintenance (Internet), 9(2), p.44 - 51, 2017/08
The aim of this work is to investigate the applicability of ultrasonic guided wave for evaluation of laser beam butt-welding quality. Ten in total test pipes having welding seam is prepared. Two piece of pipe are jointed and continuous laser beam is irradiated on the edges, varying laser irradiation power, welding side and surface profile of the adjacent edges of the pipe. Ultrasonic guided wave testing experiment is performed on the pipes. Torsional mode guided wave is excited by EMAT. The experimental results are analyzed and issues are discussed. The reflection wave bullet from the poor interface of the welding seam is clearly observed, whereas no reflection from fine welded line. From the aspect of laser irradiation power, welding side and surface profile of the adjacent edges, the relation between the interface condition and detection wave bullet are analyzed. It is found that the ultrasonic guided wave technologies have the potential for evaluating laser beam butt-welding seam.
Furusawa, Akinori; Takenaka, Yusuke*; Nishimura, Akihiko; Mizutani, Haruki; Muramatsu, Toshiharu
Nihon Hozen Gakkai Dai-14-Kai Gakujutsu Koenkai Yoshishu, p.479 - 480, 2017/08
Industry development activities on applied laser research held at Fukui branch of Japan Atomic Energy Agency are reported. Industry development is inevitable in long-term vision and strategy for developing maintenance technology and establishing decommissioning technology. Fukui branch of JAEA has organized public seminar offering businesses to promote these activities and technology exchange for years. Here some examples offered in the current seminar are introduced concerning with laser technology. Finally, our goal and important point of view are discussed.
Furusawa, Akinori; Nishimura, Akihiko; Takenaka, Yusuke*; Nakamura, Kaori*
Proceedings of 54th Annual Meeting of Hot Laboratories and Remote Handling (HOTLAB 2017) (Internet), 6 Pages, 2017/00
Testing of concrete structures in NPPs is needed to guarantee hereafter workability. Recent work says Core Concrete Reaction advances erosion of the concrete structures of Fukushima NPPs and it's difficult to estimate the correct depth of CCR. In addition, it is clear that seawater intrusion makes the rebar in the concrete structures corroded, thus, advanced remote testing methods for the deterioration should be considered. Gap or decrease of the adhesiveness between rebar and outer concrete appears in its deterioration process. We had a sense of possibility introducing a new testing method based on that. The concept is to propagate laser-excited ultrasonic gathering the information about the deterioration inside and received at distance with LDV. In this work, we investigate and report how it has the effect on propagating ultrasonic along the rebar to decrease adhesiveness between the rebar and the concrete experimentally.
Furusawa, Akinori; Nishimura, Akihiko; Torimoto, Kazuhiro; Takenaka, Yusuke*; Saijo, Shingo*; Toyama, Ryoji*
no journal, ,
The aim of this work presented here is to investigate the applicability of the guided wave testing to detect and evaluate the quality of laser beam butt welding line. First, four test pipes were prepared. All of the pipes were laser beam butt welded from inside of the pipe using laser torch. Two pipes of them were high-quality welded, the others were low-quality. Two different pipe-wall-thicknesses were in each quality. Secondly, Laser beam butt welding line detection and the quality evaluation experiments were performed. T(0,1) mode guided wave was excited and received by electromagnetic acoustic transducer array. Finally, the experimental results were analyzed and issues concerning with the applicability of the guided wave testing to detection and quality evaluation of the laser butt welding line were discussed.
Furusawa, Akinori; Nishimura, Akihiko; Torimoto, Kazuhiro; Takenaka, Yusuke*
no journal, ,
This paper is concerning with non-destructive evaluation of the concrete construct using laser excited ultrasonic. Laser ultrasonic excitation and receiving experiments are performed and the resulting ultrasonic wave forms are analyzed as compared with simulation ones. Issues concerning with the applicability are discussed.
Furusawa, Akinori; Nishimura, Akihiko; Torimoto, Kazuhiro; Takenaka, Yusuke*; Toyama, Ryoji*; Nakamoto, Hiroyuki*
no journal, ,
The aim of this work presented here is to investigate the applicability of ultrasonic guided wave for evaluation of laser beam butt welding quality. First, laser beam butt welded pipes are prepared. Two pipes are jointed and continuous wave laser beam is irradiated on the line. The test pipes are divided into two groups according to the difference in laser welding quality. One group is fine quality welded, another group is poor. Second, ultrasonic guided wave testing experiment is performed on the pipes. Torsional mode guided wave is excited by Electromagnetic Acoustic Transducers. Finally, the experimental results are analyzed and issues are discussed. The reflection wave bullet from the poor welded line is clearly observed, whereas no reflection from fine welded line. It is found that the ultrasonic guided wave technologies have the potential for laser beam butt welding line evaluation.
Furusawa, Akinori; Nishimura, Akihiko; Takenaka, Yusuke*
no journal, ,
Large number of concrete structures built in the era of rapid economic growth will exceed fifteen years old in next 10 to 20 years. Developing maintenance and health monitoring techniques for these existing concrete structures is inevitable problem to be resolved. JAEA have tackled to that problem on collaborative research, having achieved to crack detection technique for surface on the concrete of railroad tunnel (1). The technique reported in ref. (1), however, is focusing on the surface cracks, not taking into account the condition of the deep region, including a steel reinforcing bar (rebar) in a reinforced concrete structure. This work supposes a new approach for detecting deteriorated rebar in concrete structure based on laser-ultrasonic. Irradiating the one end of a rebar by nanosecond laser pulses repetitively generates ultrasonic wave propagating along it. The waveform of the ultrasonic received the other end is analyzed to extract the information about its condition.
Furusawa, Akinori
no journal, ,
In this work, it is reported that pipe work repairing system and evaluation method of the repairing quality. The repairing system, which is composed of the insertion laser-torch, rotating mechanism, hybrid optical fiber and CW laser source, enable us to repair and reprocess inner surface of the pipework. Operators are able to manipulate the system while monitoring the laser irradiation point through the hybrid optical fiber. On the other hand, the repairing quality is confirmed by visual images, it is natural of developing remote evaluation method for the repairing quality to enhance the value of the repairing system. One of the most promising techniques for remote repairing quality evaluation is ultrasonic guided wave. In this work, we focus on the evaluating butt-welding quality with guided wave, investigating its applicability experimentally. Guided wave is generated and measured on butt-welded pipes that are butt-welded in different conditions. Through the experiments and investigation of the wave profiles, it is found that welding condition effects on the strength of the guided wave detecting signal, revealing its applicability and obtaining some knowledge to establish remote repairing quality evaluation method.
Furusawa, Akinori; Nishimura, Akihiko; Takenaka, Yusuke*
no journal, ,
The purpose of this work is to develop ultrasonic methodology of detecting corrosion of the steel bar embedded in concrete. Irradiating pulse-laser beam at the bottom of the corroded steel bar embedded in concrete generates ultrasonic propagating the bar to be measured at another bottom. The corroded steel bar embedded in concrete is made by electrical corrosion method. Comparing waveforms of the corroded steel bar and of the sound one, issues concerning with the different waveforms are reported.
Nishimura, Akihiko; Yamada, Tomonori; Shibata, Takuya; Furusawa, Akinori; Takenaka, Yusuke*
no journal, ,
no abstracts in English
Nishimura, Akihiko; Yamada, Tomonori; Furusawa, Akinori; Takenaka, Yusuke*
no journal, ,
no abstracts in English
Furusawa, Akinori
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no abstracts in English
Furusawa, Akinori
no journal, ,
no abstracts in English
Furusawa, Akinori
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no abstracts in English
