超音波檢測法主要是利用超音波探頭對待測物進行聲波的激發與接收，藉由量測待測物之穿透與反射聲波，來對其內部缺陷、材料性質及外形尺寸做定性與定量的評估。一般超音波法是以所接收訊號之振幅能量、頻率與延遲時間做為評估的依據；本文則是針對訊號的相位進行分析，藉以評估薄層材料的厚度。
水中表面波特徵模態於傳遞時的洩漏現象，是固-液界面上波傳遞現象的重點研究，此洩漏現象的主要特性在於其波傳相位與反射波之相位相反，意即呈180度之相位差。此特性在以有限聲束入射激振表面波時，會因反射波與洩漏波以180度相位差疊加的緣故，於反射聲束中出現振幅零點。而在眾多研究中亦指出，此相位差關係容易受表面狀態的影響而改變，包括粗糙表面、鑲嵌物件與層狀結構均會使相位差改變。故可利用此一現象進行薄層厚度的檢測。
本文是以層狀結構之暫態波傳理論為主，並利用常模理論解波傳特徵值的方式，建立薄層結構的表面波洩漏聲場理論。而於實驗量測上，將掃描量測所擷取聲場之時域訊號，經由相位分析得到反射聲場與洩漏聲場之相位差，再以量測之相位差計算薄層厚度。
實驗結果顯示，以低頻在薄層結構中激振的表面波傳，其洩漏現象較高頻激振明顯，故檢測時應以低頻訊號為起始頻率進行檢測，以利相位差的觀察。而於銅薄層量測的結果，顯示檢測面的表面粗糙情形，對於此檢測方法有相當大的影響，因此也限制了此檢測法的適用性。

The ultrasonic nondestructive technique is mainly used to evaluate interior defect, material properties and outside dimensions by measuring the transmitting and reflecting sound waves. Generally, the evaluation of the ultrasonic testing depends on the amplitudes and delay time of the received signals; however, this research is focused on the analysis of the phase differences of the received signals.
The leakage phenomenon of surface waves propagating at the liquid-solid interface has been studied for more than fifty years. The main characteristic of this phenomenon is the 180-degree phase difference between the reflected and leaky ultrasound when a bounded ultrasonic beam is incidented. And the null zone caused by the interference of these two waves is appearing in the reflected field. The phase difference is changed as the surface condition altered, including surface roughness and layered structures.
The normal-mode theory is used at this research to analyze the analytical model of the leaky surface wave in thin layered structures. In experiments, the measurements of the reflected field are proceeded by the scanning system, so as to analyze the phase difference between the reflected and leaky ultrasound and calculate the layer thickness by the phase difference.
As a result of the surface roughness of the thin layers, the leakage is more serious when the ultrasound propagates with lower frequency. For the consideration of locating the null-zone in the reflected field, this research prefers using lower frequency as an initial frequency at the beginning of the testing, then increasing the frequency to achieve a better sensitive of the thickness.

摘要
Abstract
謝誌
目錄
表目錄
圖目錄
第一章 緒論
1-1 前言
1-2 文獻回顧
1-3 研究目的
第二章 理論分析
2-1 表面波洩漏理論
2-2 薄層結構之波傳遞理論
2-3 表面波傳遞模態理論
2-4 水-鋼界面傳遞之表面波特徵模態數值分析
第三章 實驗方法及儀器
3-1 實驗儀器
3-2 探頭聲束寬量測實驗
3-3 反射聲場量測實驗
3-4 試片製作
3-5 實驗數據分析方法
第四章 結果與討論
4-1 實驗設定討論
4-2 探頭高斯分佈量測實驗結果
4-3 水-鋼界面反射聲場之理論模擬
4-4 水-鋼界面反射聲場量測實驗結果
4-5 薄層結構之反射聲場理論模擬
4-6 薄層結構之反射聲場量測實驗結果
第五章 結論與建議
參考文獻
附錄1
附錄2

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