Using ultrasonic guided waves improve a problem of time-consuming and laborious with conventional ultrasonic method involving point¡Vby-point inspection. In order to measure of hundreds meters of pipeline in oil and chemical industries, guided waves inspection technique is used and developed widely. For fast and long range inspection, a pulse-echo system is used to excite Lamb waves propagating along the pipe. The collection and analysis of the returning echoes indicate the present of corrosion. But if the pipe features, like bends or supports, are corrosive, the signal of corrosions is often covered with echoes of pipe features. Then it causes the inspection more difficult. In this study, the pipe feature which discussed is the welded support. The focus of the advanced analysis, Discrete Wavelet Transform, of the echoes reflected from the welded support on a 3 inch pipe by experimental and finite element method, so as to improve the ability of corrosion inspection on pipe features. To study the feasibility of the improvement in the effect of coherent noise for guided wave inspection by Wavelet analysis. Results show that original signals can not be differentiated by comparing with signals of normal support, general corrosive support, and support with notch. But after processing these three signals by Wavelet analysis, the situation of the 3 type supports from the signals can be differentiated. The simulated results of two different models and five exciting frequencies show the similar trend to the experimental results after Wavelet transform processing. It is success on separating the signals of normal support and corrosive support with Wavelet Analysis, and this method of this study is useful to improve the effect of coherency noise for guided wave inspection.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0209109-114037 |
| Date | 09 February 2009 |
| Creators | Liou, Tz-yu |
| Contributors | SYUE-JIAN WU, Shiuh-Kuang Yang, Chung-yung Wu, Shao-Yi Hsia |
| 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-0209109-114037 |
| Rights | not_available, Copyright information available at source archive |
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