埋管導波波傳行為之模擬及探討

工業所使用之物料傳輸管線，如運輸油管、化工原料運輸管線等，因管線數量多、距離甚長，經年累月後，其運輸管受到土壤環境的影響，使得管壁產生腐蝕現象，隨後將導致管壁變薄承受不住土壤重力而導致破裂，相對於傳統的超音波檢測技術，導波檢測以其長距離傳播、高效率、高靈敏度等優點，具有全域性的檢測範圍優勢，但由於圓管導波的頻散和多模態的特性，模態和檢測頻率的選擇成為導波檢測的關鍵，而導波在埋管的檢測中，訊號從管壁進入土壤層時，受到土壤層含水量與土壤顆粒大小的影響，使得導波反射訊號判斷為之困難。有鑑於此，本研究使用有限元素方法模擬導波T(0,1)模態檢測埋管缺陷之波傳行為。研究結果顯示，缺陷長度在0.25倍的T(0,1)模態波長時，有最大反射訊號；在0.5倍的T(0,1)模態波長時，有最小反射訊號；從反射係數觀察缺陷長度時，缺陷長度與T(0,1)模態波長有著M字形的趨勢，缺陷減薄率越大時，反射係數越大；土壤密度增加時，導波在埋管的反射係數會變小，在檢測缺陷距離中，T(0,1)模態能有效檢測出7 m內的缺陷反射訊號。藉由本研究對圓管缺陷形式與土壤參數的反射訊號分析，不僅能提高導波技術在埋管檢測的應用，還能得到導波對於埋管缺陷靈敏度的分析，有利於檢測實務上的幫助。

關鍵字

導波檢測；埋管；缺陷；有限元素分析

並列摘要

The wall of pipeline leak of defects because the millions and miles of pipeline exist in all kings of pipeline such as power generation, petrochemical, manufacturing industry in recent years.The guided wave can inspect for more than ten meters of propagation and less few attenuation,but it’s importmant problem for distance that less than few meters of energy leakage of soil properies. In order to reduce cost times for inspection charge.The 3-D model is created on finite element method based on T(0,1) mode of guided wave propagation in soil layer of boundary condition. The Hamming windowed tone burst signal excite to characterize the propagation behaviors of T(0,1) mode along buried pipe. The resulting of T(0,1) wave propagation on the point of reflection signals compares accuracy with theory of group velocity. Next step, The effects of defect’s geometric parameters are investigated from T(0,1) mode. On soil of boundary condition, It’s good to use for reflection signal and attenuation for soil layer.

並列關鍵字

Guided Wave ； Buried Pipe ； defect ； FEM

參考文獻

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[3] M. Ratassepp, S. Fletcher and A. Klauson, "Axial defect imaging in a pipe using synthetically focused guided waves, "Estonian Journal of Engineering, vol. 17, no. 1, 2011, pp. 66-75.

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埋管導波波傳行為之模擬及探討

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