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研究生:張佳家
研究生(外文):Chia-Chia Chang
論文名稱:時頻譜法應用於混凝土內部鋼筋與瑕疵之偵測辨識
論文名稱(外文):Recognition of detected reinforcing bars and cracks in concrete based on time-frequency spectral analysis
指導教授:林宜清林宜清引用關係
口試委員:朱聖浩劉佩玲宋裕祺余志鵬
口試日期:2016-07-20
學位類別:碩士
校院名稱:國立中興大學
系所名稱:土木工程學系所
學門:工程學門
學類:土木工程學類
論文種類:學術論文
論文出版年:2016
畢業學年度:104
語文別:中文
論文頁數:86
中文關鍵詞:非破壞檢測敲擊回音法時頻譜法
外文關鍵詞:Nondestructive TestingImpact-echotime-frequency spectral analysis
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以敲擊回音法量測表面位移波形,在經由傅立葉轉換可得到頻率尖峰判讀試體內是否有瑕疵缺陷,因瑕疵與鋼筋皆會反映出頻率尖峰,因此尖峰並無法顯示內部反應界面究竟是鋼筋或裂縫所造成。
本文以時頻譜法做試驗,由小波轉換得之時頻圖可清楚的表現出頻率與振幅大小的關係曲線,相較於只有頻率域資訊的傅立葉轉換,時頻圖多了時間域的資訊,也能讓訊號更容易分析。並由時頻圖裡觀察主頻率的振幅大小,找出鋼筋與瑕疵的辨別方法。從兩者聲阻係數不同由時頻圖可觀察出能量消散的快慢,由結果可得知瑕疵聲阻係數遠小於混凝土,所以幾乎會有100%的反射行為,使得來回重複反射能量消散時間延長;反觀鋼筋聲阻係數約為混凝土的5~6倍,應力波入射鋼筋時會產生部分折射與部分反射現象,使得應力波的反射能量變弱或消散時間變短。
時頻圖確實可以清楚分析出鋼筋與瑕疵上的差異,並透過能量振幅圖,可讓試驗結果更明顯,也讓混凝土板內的瑕疵與鋼筋訊號分辨更容易。


In an impact-echo (IE) test, the Fast Fourier transform (FFT) of the impacted surface responses reveals frequency peaks of major periodical events and can be used to determine depth information, such as the thickness of a target specimen and the depth of a delaminated crack. Since rebar interfaces also result in comparable spectral frequencies but with different depth characteristics, IE testers might sometimes have difficulty to determine whether a certain peak frequency is associated with a crack or a rebar. The objective of the thesis is to illustrate the use of the time-frequency spectral analysis technique with wavelet transform to discriminate the crack response from the rebar response. When comparing with the traditional frequency domain amplitude spectrum, the time-frequency spectrum provides more useful information for the analyzed signals. The proposed method for recognizing crack and rebar can be carried out first by observing the peak frequencies in the FFT spectrum. Then, through the time axis of the time-frequency spectrum, we can examine the decay pattern of the amplitude curve with respect to the selected peak frequency and “the duration of amplitude-decay” is defined. Based on the comparison between results of the two studied interfaces where the associated acoustic impedance are highly different, it is preliminarily summarized that the acoustic impedance of crack is far less than the acoustic impedance of concrete, the stress wave would retain nearly 100% reflection and thus exhibit further extension for the duration of amplitude-decay. On the other hand, the acoustic impedance of steel is 5~6 times of the acoustic impedance of concrete so the stress wave would be partially reflected and refracted. This leads to weaker reflective energy and thus shortens duration of amplitude-decay.
It is concluded that the proposed methodology can be practically applied to distinguish the difference between signals caused by crack and rebar reflections via the use of the time-frequency spectrum. As a result, this innovated technique provides IE testers for a simple yet reliable tool in the recognition between signals due to cracks and rebars in concrete plates.


摘要 i
Abstract ii
目錄 iii
圖目錄 vi
表目錄 ix
第一章 緒論 1
1-1前言 1
1-2研究動機與目的 1
第二章 文獻回顧 3
2-1敲擊回音法 3
2-1-1時間領域分析法 4
2-1-2頻率領域分析法 4
2-1-3接觸時間與主能量頻率分布之關係 7
2-2經驗模態分解法 8
2-2-1瞬時頻率(Instantaneous Frequency,IF) 8
2-2-2內建模態函數(Intrinsic Mode Function,IMF) [10] 9
2-2-3經驗模態分解法(Empirical Mode Decomposition,EMD) 10
2-3相位法 14
2-3-1傅立葉頻譜相位[14] 14
2-3-2一維波傳在不同邊界條件下之相位 15
第三章 試驗原理與試體規劃 18
3-1 量測方法與原理 18
3-1-1應力波動行為 18
3-1-2時頻譜法(Time-frequency Spectral Analysis) 23
3-2試體規劃與儀器設備 25
3-2-1試體規劃 25
3-2-2試驗儀器配備 29
3-2-3試驗過程 31
第四章 數值分析與討論 32
4-1數值分析模型 32
4-1-1建立模型尺寸 32
4-1-2模型參數設定 33
4-2經驗模態分解法 35
4-2-1數值模擬流程 35
4-2-2 深度4公分鋼筋與深度8公分瑕疵之訊號分析 39
4-3相位法 42
4-3-1 sin波分析 42
4-3-2純混凝土與上層混凝土下層鋼板之訊號分析 44
4-4時頻譜法 47
4-4-1主頻率之能量振幅圖繪製程序 47
4-4-2純混凝土與上層混凝土下層鋼板之訊號分析 47
4-4-3不同深度的瑕疵與鋼筋之訊號分析 49
4-4-4不同深度的鋼筋與瑕疵同時存在混凝土板內之訊號分析 55
4-4-5能量振幅圖 57
4-4-6訊號衰減處理 61
第五章 試驗結果分析與討論 66
5-1時頻譜法 66
5-1-1無裂縫之混凝土版波速量測 66
5-1-2不同深度的瑕疵與鋼筋之訊號分析 66
5-1-3不同深度的鋼筋與瑕疵同時存在混凝土板內之訊號分析 70
5-1-4能量振幅圖 72
5-1-5訊號衰減處理 75
第六章 結論與建議 79
6-1結論 79
6-2建議 80
參考文獻 81


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