A study on construction of evaluation method for defect sizing utilizing numerical simulation

Takao Yoshikawa, Masahiro Maeda, Hideyuki Hirasawa

研究成果: 書籍/レポート タイプへの寄稿会議への寄与

1 被引用数 (Scopus)

抄録

To prevent the brittle fracture of the extremely thick plate which is used in the deck plate and the hatch side coaming of the large container ships, it is important to detect surely and repair the inner defects, which are possible to lead the brittle fracture at an early stage. Now Ultrasonic Testing is used in order to inspect the inner defect in a thick plate, and it is necessary to select adequately the probe size and oscillating frequency to evaluate the defect size accurately. The estimation of the defect size in vertical direction to plate surface is important from the viewpoint of fatigue strength. But the vertical flaw length and also the inclined flaw length are hardly to be estimated accurately. In this study, to clarify the characteristics of reflected ultrasonic wave from the defect, the wave propagation behavior is simulated with the numerical simulation program by FEM which is developed by the authors. In this program, the governing equation of elastic wave propagation is calculated in time domain with explicit method utilizing the central-difference scheme. First, the effect of the probe size and oscillating frequency on the accuracy of defect sizing are investigated utilizing the developed program. The numerical simulation is performed for imaging to examine the length of flaw which is parallel to plate surface by normal beam technique. And, the applicability of 6dB method, which is one of the methods for estimating flaw length, is examined. Moreover, a new method for estimating flaw length which cannot be estimated by 6dB method is proposed. Secondly, in order to examine the inclined flaw length, the angel beam test is performed. The accuracy of numerical simulation for angle beam technique is confirmed by comparing experimental result. And, it is examined how the inclined angle of flaw affects the echo height, and it is shown that 6dB method and L level method are useful for the defect which is perpendicular to wave beam and the tip echo method is useful for the defect which is inclined to wave beam. The actual structure usually has a paint film. Therefore, the echo height level will be affected by paint thickness, and the paint film effects on the accuracy of defect sizing. Thirdly, the effects on echo height by film thickness are clarified by experiments and numerical simulations.

本文言語英語
ホスト出版物のタイトルASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering, OMAE2011
ページ247-256
ページ数10
2
DOI
出版ステータス出版済み - 12月 1 2011
イベントASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering, OMAE2011 - Rotterdam, オランダ
継続期間: 6月 19 20116月 24 2011

その他

その他ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering, OMAE2011
国/地域オランダ
CityRotterdam
Period6/19/116/24/11

!!!All Science Journal Classification (ASJC) codes

  • 海洋工学
  • エネルギー工学および電力技術
  • 機械工学

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