臺灣博碩士論文加值系統

　　本文研究合成聚焦技術(Synthetic Aperture Focusing Technique，SAFT)在不同應力波波長與不同鋼筋的條件下偵測混凝土內含孔洞缺陷之檢測限制與實力。本研究首先使用有限元素數值模擬方式，來研究改變敲擊之鋼珠的大小以及混凝土內鋼筋尺寸大小與層數對檢測反應訊號之影響。檢測之結果則以合成聚焦技術處理後再以影像之方式顯現，可藉此得到各種影響參數之直接效果。本研究亦實際製作了含有單層鋼筋或雙層鋼筋之單孔洞缺陷試體，並進行了敲擊反應之實體檢測實驗，再將結果與數值模擬結果進行比較。由數值模擬與實驗結果顯示，敲擊檢測之鋼珠大小會直接影響合成聚焦影像之解析度，也發現當敲擊鋼珠所導入之應力波波長大於鋼筋半徑八、九倍時，鋼筋之影響將可被忽略，意即可將試體視為均質之材料，則檢測孔洞缺陷之結果就能較不受骨材大小之影響。藉著本研究，期望能提升合成聚焦法對於檢測掃描混凝土結構物內含缺陷之應用能力。

The testing constraints and the capability of using the Synthetic Aperture Focusing Technique (SAFT) to detect void defects embedded in concrete block subjected to different introduced stress wave lengths and rebars are studied in this paper. This study first used the numerical simulation of finite elements to study the effects of the sizes of the impacting steel balls, the rebars and the layers of rebars on the testing responses. The testing results were processed with the Synthetic Aperture Focusing Technique and presented in images so that the direct effects of various kinds of parameters can be assessed. The study also cast concrete specimen with single void and single layer and double layers of rebars. Impact-response tests were carried out and the results were compared with those from numerical simulation. The results from the numerical simulation and experiments revealed that the sizes of the impacting steel balls would directly affect the resolution of the images from the SAFT. It was also found that the effect of existing rebars on the testing signals can be neglected when the wave length of the introduced stress waves is larger than eight to ten times of the size of the rebars. In this condition, the specimen can be regarded as uniform material and thus the results of evaluating the void defects would not be affected by the size of aggregates. Through this study, it is hoped that the capability of application of the SAFT can be enhanced in scanning and detecting the defects embedded in concrete structures.

摘要.................................................................i
英文摘要.............................................................ii
誌謝...............................................................iii
目錄................................................................iv
表目錄..............................................................vi
圖目錄.............................................................vii
第一章 緒論.........................................................1
1.1前言..............................................................1
1.2研究目標...........................................................2
1.3文獻回顧...........................................................3
第二章 理論背景......................................................4
2.1基礎波傳理論........................................................4
2.2 敲擊回音法.........................................................6
2.3 合成聚焦法.........................................................8
2.4 鋼珠大小施力之模擬..................................................11
第三章 有限元素數值模擬................................................12
3.1含單孔洞與單層鋼筋之混凝土試體的數值模擬結果...............................12
3.2不同鋼珠敲擊單層鋼筋之混凝土試體的數值模擬結果.............................20
3.3不同鋼珠敲擊雙層鋼筋混凝土試體之數值模擬結果...............................26
第四章 實驗結果與分析..................................................31
4.1實驗試體之製作.......................................................31
4.2單孔洞單層鋼筋混凝土試體之檢測實驗結果....................................37
4.3單孔洞雙層鋼筋混凝土試體之檢測實驗結果....................................41
4.4實驗結果之分析與討論..................................................45
第五章 結論與建議.....................................................50
參考文獻...............................................................51

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