小波理論應用於樑的破損偵測之研究

A Study of Structural Damage Detection in Beams by Wavelet Transform

本文利用小波轉換方法偵測結構破壞時所造成之模態不連續性，進而預測缺陷存在以及其位置。文中以一具缺陷懸臂樑為例，利用有限元素分析方法，進行模態振型分析，再以小波轉換偵測破損；在實驗模態分析方面，主要是量測振動訊號，利用振動訊號之小波結點範數產生一種新的振型預估方法，依此獲得模態振型參數，再以小波轉換分析。以本文所提之缺陷預測方法，可偵測懸臂樑破損，並對於不同破壞程度的缺陷、位置，都來有良好的檢測能力。經由軟體擬驗證出實驗量測之分析方法具可行性，所提出的缺陷位置預測模式將可應用於其他形式的結構。 This paper utilizes wavelet transform technique to detect the location and the approximate size of the flaw in a damaged structure based on the model analysis. At first, the finite element method was used to analyze the vibration modes of a damaged cantilever beam and then the wavelet transform was used to identify the flawed location of the beam. By using experimental modal analysis, the vibration signals were first recorded and then evaluated by the norm defined in the wavelet transform to obtain the parameters of newly re-constructed vibration modes. Finally, the wavelet transform method was applied to the re-constructed vibration modes to observe the flaw of the cantilever beam. The results obtained from the finite element method (FEM) were compared with those attained from the experimental analysis. It is found that with the proposed method the location and the approximate size of the flaw of a cantilever beam can be detected. The FEM computer simulation results support the feasibility of the proposed method and this defect-detecting technique may be applied to other types of structures.