在石化煉油廠中常常看見許多管線分布在各個主要區域，隨著工廠長時間運作，廠內運輸管線難免會產生鏽蝕、腐蝕…等缺陷，尤其在管線彎曲處更容易發現因這些缺陷而產生管線破損或管內流體外洩的問題。導波法能對長距離且大範圍的管線進行快速、有效的檢測，所以常被視為對管線檢測的利器。本研究中使用全頻非頻散的T(0,1)扭矩模態作為選用之檢測模態，以電腦模擬及實際實驗解析T(0,1)模態經過彎管後波式轉換出來的模態，並將不同厚度深、周向分布及軸向長度之缺陷加工在彎管上，討論比較其訊號的差異。
由於沖蝕缺陷常發生在彎管部分且隨著管內流體流速不同、腐蝕性強弱和流動方向，沖蝕造成的缺陷也會跟著改變。所以本研究使用有限元素法軟體模擬設計出與沖蝕缺陷相近的幾何模型，並模擬T(0,1)模態在模型中傳遞的物理特性，再對沖蝕缺陷位置、沖蝕缺陷厚度深作變化，擷取出不同變化缺陷的反射回波訊號加以分析。本導波實驗則在無缺陷的彎管上加工缺陷，缺陷位置設在沖蝕最為嚴重的彎管外壁中央部分，並探討不同幾何變化之彎管缺陷對導波訊號的影響。
綜合以上模擬與實驗結果，可知在彎管上仍可辨識出不同厚度深、不同周向分布之缺陷回波訊號。而彎管上不同軸向分布之缺陷回波訊號則與直管上不同軸向分布缺陷回波訊號相近似，皆受到建設性、破壞性干涉交互影響，使得在缺陷軸向長度為四分之一波長長度及二分之一波長長度，分別得到缺陷回波訊號振幅最大及最小值。由此結果即可利用不同軸向長度變化之缺陷訊號估算彎管缺陷之軸向分布情形，幫助現場對彎管受損程度之判斷。從模擬中亦可得知T(0,1)模態對管線外部缺陷較管線內部缺陷敏感許多，故同樣幾何形狀之凹槽缺陷在管壁外側會有較大之缺陷訊號振幅。由模擬的過程中亦可知波傳遞經過彎管時，有波形疊加與波式轉換之情形發生，故造成彎管上的缺陷訊號振幅放大。此一結果可提供實際檢測時之參考，以避免缺陷訊號被放大而造成誤判之情形發生。

It is usually to see a large number of pipelines separating around the refineries, chemical and petro-chemical plants. The corrosion and erosion defects are unavoidable to occur in transporting pipe line. Especially, the maintain stuff usually find out breakage pipe or leaking liquid at elbowing pipe line because of the corrosion and erosion defects. So it is essential to examine these pipelines with an efficient method. The use of guided waves method is very attractive to solve this problem since guided wave could be excited at one circle on the pipeline and propagate over considerable distance. To choose guided wave torsion mode T (0, 1) as excitation mode because its group velocity doesn’t change with frequencies. And the research analyzes the mode conversion that occurred when T (0, 1) mode propagated after the elbow pipe. The research also discusses the signal difference in different depth, circumferential distribution and axial length defects on the elbow pipe.
The erosion defect usually occurs in the elbow pipe line and it would change with fluid velocity, causticity of fluid and flow direction. Therefore, the research designs the defects according to the character of erosion defect by finite element method software and simulates T (0, 1) mode propagating in the pipe line. Then this research extracts and analyzes the reflection signals from defects. In this guided wave experiment, the research manufactures the defect on elbow pipe. Because the erosion defect could be usually found at outer side of elbow pipe, artificial defect would be set there. And the elbow pipe is manufactured with different depth, circumferential distribution and axial length defect.
The research would discuss the relationship between change of defect and reflection signal. By elbow pipe defect signals of simulation and experiment consequence, the different depth, circumferential distribution and axial length defect signals could be still distinguished. The signals with different axial length defect that received from straight pipe and elbow pipe are similar and are affected by signal constructive and destructive interference. So the research could get maximum and minimum defect signal amplitudes from one-fourth wavelength axial defect and half wavelength axial defect. Therefore, the axial length defect of elbow pipe could be estimated from defect signals and this consequence could help judge the level of damaged elbow pipe. T (0, 1) mode has better sensitivity to outside of the pipe than inside of the pipe. So the bigger signal amplitude could be received from the notch at outside of the pipe. In the process of wave propagation simulation, there are overlapping waveforms and mode conversions occur at elbow pipe. This situation causes the defect signals were amplified at elbow pipe. In practical detection, the misjudgments of amplified defect signals should be attended to.

中文摘要 .................................................................................... i
英文摘要 .................................................................................... ii
目錄 ............................................................................................ iv
表目錄 ........................................................................................ vi
圖目錄 ........................................................................................ vii
第一章 緒論 ................................................................................ 1
1.1 前言 ...................................................................................... 1
1.2 研究動機與目的 ................................................................... 2
1.3 文獻回顧 .............................................................................. 3
1.4 研究方法 .............................................................................. 6
1.5 論文結構 .............................................................................. 8
第二章 基本理論 ....................................................................... 10
2.1 導波於圓管傳遞之波動方程式 ............................................ 10
2.1.1 縱向模態 ........................................................................... 11
2.1.2 扭矩模態 ........................................................................... 11
2.1.3 撓曲模態 ........................................................................... 11
2.2 頻散曲線 .............................................................................. 12
2.3 波形結構 .............................................................................. 14
2.4 波式轉換 .............................................................................. 15
2.5 有限元素法 .......................................................................... 16
第三章 實驗架構與模擬設定 ..................................................... 23
3.1 導波管線檢測系統 ............................................................... 23
3.2 實驗管線之設置及沖蝕缺陷之設計加工 ............................. 27
3.3 有限元素法模擬分析 ........................................................... 29
第四章 實驗與模擬結果 ............................................................ 48
4.1 無缺陷彎管之實驗訊號 ....................................................... 48
4.2 彎管上不同厚度深缺陷之實驗訊號 .................................... 51
4.3 彎管上不同周向分布缺陷之實驗訊號 ................................ 52
4.4 彎管上不同軸向分布缺陷之實驗訊號 ................................ 53
4.4.1 彎管上不同軸向分布缺陷之訊號分析 ............................. 53
4.4.2 彎管上全穿透缺陷之訊號分析 ........................................ 54
4.5 直管上不同軸向分布缺陷之實驗訊號 ................................ 55
4.6 無缺陷彎管模擬之訊號 ....................................................... 57
4.7 含缺陷彎管模擬之訊號 ....................................................... 58
4.7.1 彎管上不同位置沖蝕缺陷訊號模擬 ................................. 58
4.7.2 直管及彎管上沖蝕缺陷訊號模擬 ..................................... 59
4.7.3 彎管內壁及外壁缺陷訊號模擬 ......................................... 59
4.7.4 直管管壁內、外側及彎管管壁內、外側缺陷訊號模擬 ... 60
第五章 結論與未來展望 ............................................................ 95
5.1 結論 ..................................................................................... 95
5.2 未來展望 .............................................................................. 97
參考文獻 .................................................................................... 98

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