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成果報告書詳細
管理番号20190000000149
タイトル*平成30年度中間年報 次世代火力発電等技術開発 次世代火力発電基盤技術開発 石炭火力の競争力強化技術開発/石炭火力の保全手法の確立に向けたType4クリープボイド初期検出システムの開発
公開日2019/4/10
報告書年度2018 - 2018
委託先名国立大学法人東北大学 東北発電工業株式会社
プロジェクト番号P16002
部署名環境部
和文要約
英文要約In the high chromium steel weld parts of main pipe for coal-fired thermal power plant, Type IV creep voids are apt to be occurred and grow into micro cracks rapidly and finally lead to accidents. To avoid the accidents, the development of the quantitative nondestructive monitoring techniques for creep voids has been required. However, all the conventional ultrasonic inspection methods can detect only mm order defects and inner creep voids of μm order in diameter can’t be measured. In this project, we plan to develop the accurate ultrasonic Type IV creep void imaging system for aged structures of coal-fire thermal power generator.
First, we prepared a cylindrical damaged test specimen with circumferential welding, which has actual creep voids cut out from used coal-fired thermal power plant pipe. In addition, we reconfirmed sound field analysis of angled focus transducer with experimental 10MHz, focus 30mm in depth and confirmed the effectiveness of the design technique using this software 2MHz, focus 30mm in depth transducer model. We developed the systems which work a common rail, for phased array device and comprehensive evaluation of developed acoustic imaging system have the common location system. With a cylindrical damaged test specimen, we pinpointed the position by the phased array method at an upswing in heat affected zone (Type IV creep void area). Furthermore, we acquired acoustic imaging by a developed system and it was highly precise and linked the position. We plan to compare the density of actual creep voids and sensitivity condition of acoustic imaging, using the small damaged specimen and improve this device and measurement precision in future. We made efforts in convergence-related fixed-quantity evaluation method establishment of angled focus transducer. A low frequency becomes the noise and is hard to measure by the photoelastic ultrasonic visualization method. We cannot measure the size less than the laser irradiation size, because that of the laser displacement meter is 600μm. In addition, to improve the SN ratio of the received waveform in the measurement system, we examined three points of improvement and produced an experimental unit.
Finally, since we develop the ultrasonic highly focusing technique to obtain high resolution imaging instead of high frequency ultrasound with small wavelength, the acoustic detection mechanism of micro voids by focused sound field should be investigated. We made a scattering ultrasonic wave FEM model and confirmed the effectiveness of the large-scale analysis models.
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