Title page for etd-0617118-140108


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URN etd-0617118-140108
Author Chun-Hsiang Tseng
Author's Email Address No Public.
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Department Mechanical and Electro-Mechanical Engineering
Year 2017
Semester 2
Degree Master
Type of Document
Language zh-TW.Big5 Chinese
Title The Characteristic and Application of SH Guided Wave on Plate Weld
Date of Defense 2018-06-25
Page Count 129
Keyword
  • Magnetostrictive EMAT
  • Guided wave method
  • Finite element method
  • Weld
  • Plate inspection
  • SH0 mode
  • Abstract The applications of guided wave are important in industry. The advantage of this method is that it can quickly inspect the whole pipeline system and can excite waves from a certain distance to exclude surroundings restrictions. The SH wave propagating with simple wave structure is suitable for plate inspection. However, when using the SH guided wave for plate inspection with weld: since the obvious weld signal covers the defect signal around the weld, it generates inspection blind zone; the energy of transmission wave through weld would reduce, so it is difficult to find the defect signal behind the weld.
    In this study, the common plate welds types like butt, T-type and lap weld would be investigated. The purpose of this study is to investigate the interaction properties of incident SH0 waves on each weld joint. The SH0 waves inspection application for the defect behind the weld is also assessed. The weld structures have been modeled using numerical simulation by finite element method, and guided waves of SH0 mode can be generated by using a customized magnetostrictive EMAT (Electromagnetic Acoustic Transducer) for experimental verification. By the comparison result, the generating mechanism and the amplitude of each weld signal are found. With reference to the number of cycles from the measured signal, the simulation signal range can be obtained within 3.5 % error. The blind zone range produced by obvious weld signal is defined by the signal range and width of each weld.
    Defect with at least 18 mm2 cross-section area can be detected by experiment equipment. In terms of energy reduction and inspection ability, artificial holes with 30~120 mm2 cross-section area losses as defect is used. Defect detection capability is estimated by ratio of defect to weld signal amplitude. The measurement results show that most of the defects behind weld can be detected. Defect under 60 mm2 cross-section area and behind lap weld cannot be detected. The above research results will make the SH guided wave detection system using magnetostrictive EMAT more applicable for defect detection practices, improve its detection capability and accuracy, and reduce the risk of public/labor safety.
    Advisory Committee
  • Wang,Bor-Tsuen - chair
  • Hsia,Shao-Yi - co-chair
  • Lee,Ping-Hung - co-chair
  • Cheng,Jyin-Wen - co-chair
  • Yang,Shiuh-Kuang - advisor
  • Files
  • etd-0617118-140108.pdf
  • Indicate in-campus at 5 year and off-campus access at 5 year.
    Date of Submission 2018-07-17

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