廣域應變應用於薄板結構損傷診斷之研究

Damage Detection of Thin Plate Structures Using Macro Strain Measurement

施易成(Yi-Cheng Shih)

指導教授 ： 廖文義

共同指導教授 ： 許丁友(Ting-Yu Hsu)

國立臺北科技大學/工程學院/土木與防災研究所/碩士(2014年)

摘要

基於結構動態特性進行結構健康診斷的研究在近年來相當的受重視，此類研究過去大多採用側向振動訊號之量測，而本研究更進一步改由軸向量測廣域應變之振動訊號，利用此訊號進行系統識別得到廣域應變的模態形狀並將其轉換為旋轉自由度的模態形狀。本研究將廣域應變及側向加速度兩種量測方法應用於薄板結構上，並使用模態曲率診斷方法、模態曲率平方診斷方法、基於模態應變能的損傷指數方法、應用光纖量測廣域應變模態之擬局部柔度法、應用加速度計量測側向位移模態之擬局部柔度法等的健康診斷的方法，進行數值模擬與實際試驗之驗證。其結果顯示，基於模態曲率的診斷方法中，僅基於模態應變能的損傷指數方法對於薄板結構損傷定位能有準確的結果，但該方法僅能對於損傷位置進行診斷，故本研究嘗試發表「應用加速度計量測側向位移模態」與「應用光纖量測廣域應變模態」之擬局部柔度法，期盼能進一步診斷損傷程度，但其數值模擬與實驗顯示，只有後者能夠應用於薄板結構的損傷診斷，且仍有許多誤差可能影響診斷結果。

關鍵字

擬局部柔度法 ； 廣域應變 ； 模態曲率診斷方法 ； 模態曲率平方診斷方法 ； 基於模態應變能的損傷指數法 ； 薄板結構 ； 損傷診斷

並列摘要

Vibration-based techniques become popular for structural health monitoring in last decades. In this study, several damage detection algorithms based on modal curvature were used to detect damage of a thin plate structure. Besides the existing Modal Curvature method (MC), Modal Curvature Squared method (MCS), and Damage Index based on modal strain energy (DI), the Pseudo Local Flexibility Method (PLFM) using either traditional lateral acceleration measurement or a novel macro-strain measurement was also developed to perform damage quantification of a thin plate structure. The rotary mode shapes was obtained using the macro-strain measured by long-gauge FBG sensors while the lateral mode shapes was obtained using the lateral acceleration measured by accelerometers. Both numerical and experimental studies were conducted in this study to understand the feasibility of the above methods to detect damage location and extent of a thin steel plate fixed at two edges. The results show that among all the above-mentioned methods, the DI method is the most capable one to perform damage localization. However, the results of the damage detection of the thin plate using the PLFM were not satisfactory. Nevertheless, the PLFM based on rotary mode shapes performed much better than the one based on lateral mode shapes for damage detection of the thin plate.

並列關鍵字

Pseudo Local Flexibility Method ； Macro Strain ； Modal Curvature Method ； Modal Curvature Squared Method ； Damage Index Based on Modal Strain Energy ； Thin Plate Structure ； Damage detection

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