非破壞檢測技術中之導波法具有檢測長距離管線的能力，並且經由判斷其反射波以及波式轉換現象便可以指出其管線特徵或缺陷所在；而為了能提供現場檢測人員較為直觀的訊息，往往將導波檢測所得回波訊號予以B掃描或C掃描成像來呈現缺陷外觀。而由於圓管導波多模態與頻散特性，其缺陷C掃描成像結果在軸向與周向解析度上並不理想，無法呈現其缺陷在管線上分佈情形；有鑑於此，本研究藉由合成孔徑聚焦技術(Synthetic Aperture Focusing Technique, SAFT)來提升成像解析度。本文藉由有限元素法暫態應力分析模擬圓管導波基礎扭矩T(0,1)模態於管線之波傳與散射現象，配合數值分析軟體進行SAFT之訊號後處理，結果發現激振波於高頻率與多週期數時有著較為良好的成像結果。本文使用了周向裂縫、軸向裂縫與孔蝕三種不同類型之缺陷進行SAFT成像比較，結果顯示周向裂縫於SAFT成像修正後有著優於軸向裂縫與孔蝕的效果；而在管線軸向方向上同時具有兩周向裂縫之情形下，SAFT修正亦呈現了良好的成像結果。實驗方面本研究亦藉由實際檢測周向與軸向裂縫兩缺陷管線，將檢測所得訊號進行SAFT修正於周向裂縫有著不錯的成像結果，而在焊道成像也有著很好的結果。SAFT應用於圓管導波成像得到了不錯的成果，克服了導波多模態與頻散特性在成像上的困難，提供了檢測者一項缺陷辨識的新方法。

The guided wave method is one of the non-destructive testing methods with the ability to inspect long length of pipeline. The presence of defects and pipe features can be indicated by analyzing the reflected echoes and the mode conversion phenomena of guided waves. To provide the profile of defects, the signals of guided wave are usually processed to form a B-scan or C-scan image. As for the characteristics of multimodes and dispersion, the C-scan image of defect shows a poor resolution both in the axial and cricumferential directions. Therefore, this study uses the synthetic aperture focusing technique (SAFT) to improve the resolution of the C-scan image. The propagation and scattering of the fundamental torsional mode T(0,1) in pipes are analyzed by the transient analysis of finite element method. Furthermore, the reflected signals are processed by SAFT to form a C-scan image with better resolution. Three types of defects including circumferential crack, axial crack and pitting were discussed in this study both by finite element method and experimental method. In the numerical study, the modification of the C-scan image of the circumferential crack showed a better consequent than the axial crack and pitting. The SAFT was also used to separate the images of two circumferential cracks with different axial location on the pipe succesfully. In the experimental study, the signals of the axisymmetric weld and non-axisymmetric defects were processed by SAFT to form the C-scan image. The results showed a nice resolution of circumferential cracks and the circumferential distribution of the weld in the modified C-scan image at the same time. The application of SAFT to guided wave on a pipe is valid to overcome the effects of guide wave multimode and dispersion characteristics, it provides a new way to defects identification.

中文摘要 …………………………………………………………i
英文摘要 …………………………………………………………iii
目錄 ………………………………………………………………v
表目錄 ……………………………………………………………vii
圖目錄 ……………………………………………………………viii
第一章、緒論 ……………………………………………………1
1.1 前言 ……………………………………………………1
1.2 文獻回顧 ………………………………………………3
1.3 本文架構 ………………………………………………6
第二章、研究基本理論 …………………………………………9
2.1 圓管型蘭姆波 …………………………………………10
2.1.1 縱向模態 ……………………………………………11
2.1.2 扭矩模態 ……………………………………………12
2.1.3 撓曲模態 ……………………………………………12
2.2 頻散曲線 ………………………………………………13
2.3 波形結構 ………………………………………………15
2.4 合成孔徑聚焦技術基本理論 …………………………15
2.4.1 時域SAFT成像修正-體波 …………………………16
2.4.2 頻域SAFT成像修正-蘭姆波………………………18
2.4.3 二維傅立葉轉換法 …………………………………20
2.4.4頻域SAFT成像修正-圓管導波 ……………………21
2.5 有限元素法 ……………………………………………24
第三章、圓管導波波傳行為模擬與SAFT成像 ………………40
3.1有限元素暫態模擬 ……………………………………40
3.1.1 網格劃分 …………………………………………41
3.1.2 圓管導波激振 ……………………………………43
3.1.3 求解與分析結果 …………………………………43
3.2 SAFT成像 …………………………………………44
3.2.1 不同尺寸缺陷成像比較 …………………………45
3.2.2 頻率於成像之影響 ………………………………47
3.2.3 激振週期數於成像之影響 ………………………48
3.3 不同缺陷類型 ………………………………………49
3.3.1 軸向型裂縫 ………………………………………49
3.3.2 孔蝕 ………………………………………………49
3.3.3 多缺陷成像 ………………………………………50
3.3.4 軸對稱型缺陷……………………………………50
3.4 本章結論 ……………………………………………51
第四章、圓管導波實驗與SAFT成像 …………………………81
4.1 導波檢測儀器 ………………………………………81
4.2 實驗管線規格 ………………………………………82
4.3 實驗步驟 ……………………………………………82
4.3.1 實驗準備 …………………………………………82
4.3.2 實驗管線NO.1之SAFT成像結果 ………………84
4.3.3 實驗管線NO.2之SAFT成像結果 ………………84
第五章、結論與未來展望……………………………………96
5.1 結論 ………………………………………………96
5.2 未來展望 ……………………………………………97
參考文獻 ………………………………………………………99

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