Tremendous interest to the study of guided waves in pipe inspection in the oil, chemical, and power generating industries has peaked during the last decade. Since the advantages are inspecting long lengths of pipe quickly and without removing insulation. Recent researches in defects inspection are determined by reflection coefficients from the cracks. However, the purpose of this thesis is to excite at a single probe position and to receive the signals of guided waves with the form of loops. For the variations of wave profiles of guided wave, this thesis aimed at the largest energy distribution of wave profiles to proceed with the researches of mode conversion phenomena caused by defects.
This thesis utilizes the partial loading source, and excites the non-axisymmetric and axisymmetric guided waves individually along the carbon steel pipes with circumferential defects and without defects to contrast and analyze. According to the change of wave profiles, we can find the variables that change wave profiles for different guided waves modes include propagating distance and frequency, and these cause that the circumferential energy distribution will change. For the non-axisymmetric guided waves in this thesis are non-dispersive, and its variations of phase velocity and group velocity are small, so the variations of wave profiles are also small. Moreover we study the mode conversion phenomena caused by defects from its position which the circumferential energy is largest. It also investigates new modes from mode conversion phenomena produced by defects more completely.
Finally, we can predict the types and the number of new modes from mode conversion phenomena by phase velocity dispersion curve, and compare with the experiments well.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0830105-135234 |
| Date | 30 August 2005 |
| Creators | Huang, Ji-mo |
| Contributors | Shao-yi Hsia, Bor-tsuen Wang, Shiuh-kuang Yang, Ruey-chang Wei |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0830105-135234 |
| Rights | not_available, Copyright information available at source archive |
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