提升數位影像相關法全場量測表現並應用於風機系統結構量測及揚聲器減振材料分析

Abstract

數位影像相關法(Digital image correlation, DIC)為影像光學量測技術的一種，具有非接觸、非破壞、全場量測、跨尺度等特性，廣泛應用於相關工程領域及學術研究。數位影像相關法以成熟的數學理論追蹤待測物上的特徵，並計算影像序列與特徵的相關係數，取得特徵的位移、變形等資訊。 本論文以使用數位影像相關法進行實用性量測，並針對實驗中遇到的問題進行改良，以發揮數位影像相關法在全場及動態量測上的優勢，並提升現有系統的精度及便利性。在第一章中，首先針對全場量測中之自動選點方法進行優化，透過誤差點篩選濾除三維全場量測時明顯偏差的分析點，在全場變形量測及形貌重建實驗中能改善自動選點誤差造成的雜訊問題。另一方面，本文引入Distmesh演算法進行全場量測的自動選點，其中透過改變距離函數能自由調整佈點區域之形狀，並建立均勻的三角形網格做為分析點。 本文第二部分針對風力發電機系統的風機葉片及離岸風機底座兩個關鍵結構進行動態量測。其中針對風機葉片透過改變鎖固條件進行分析結構損傷對共振頻率的影響，同時由全場位移進行變形重建及模態振型分析。在離岸風機底座的實驗中，透過不同的敲擊位置及拍攝角度觀察暫態位移及頻域訊號的變化，進一步了解風機基座的動態特性，並與風機葉片之量測結合，展現數位影像相關法針對風力發電系統動態、全場的量測優勢。 本文第三部分以筆電揚聲器為研究主題，首先使用數位影像相關法配合拉伸試驗，分析不同緩衝圈材質之材料參數，並建立有限元素模型模型分析不同緩衝圈材質的減振效果。在拉伸試驗中，應用樣板更新法追蹤大變形下的軸向和橫向應變值，並對過程中的累計誤差問題進行探討及改善。得到楊氏模數與薄松比後，使用COMSOL Multiphysics分析不同緩衝圈材質的減振效果，再配合實體揚聲器的振動量測實驗驗證模擬結果。

Digital Image Correlation (DIC) is an optical imaging measurement technique characterized by its non-contact, non-destructive, fullfield measurement, and cross-scale capabilities. It is widely used in related engineering fields and academic research. DIC uses well-established mathematical theories to track features on the object under test and calculate the correlation coefficients of image sequences and features to obtain information on displacement and deformation. The thesis focuses on using digital image correlation (DIC) for practical measurements and and improving issues encountered during experiments. The goal is to maximumize the advantages of DIC in fullfield and dynamic measurements and enhance the accuracy and convenience of existing systems. The first part of the thesis improves the automatic point selection method in full-field measurements. By filtering out error points in 3D full-field measurements, the noise problem caused by automatic point selection errors in full-field deformation measurement and shape reconstruction is improved. On the other hand, the Distmesh algorithm is introduced for automatic point selection in full-field measurements. By changing the distance function, the shape of the point distribution area can be arbitrarily adjusted, and a uniform triangular mesh is established for fullfield measurement. The second part focuses on the dynamic measurement of two key structures in wind turbine systems: the turbine blades and the offshore wind turbine foundation. For turbine blades, the effect of structural damage on the resonance frequency is analyzed by changing the screw locking conditions, and deformation reconstruction and modal shape analysis are conducted based on the full-field displacement. In the experiments of offshore wind turbine foundation, transient displacement and frequency spectrum are observed through different impact locations and shooting angles to further understand the dynamic characteristics of the wind turbine base. The part demonstrates the advantages of DIC in dynamic, fullfield measurements for wind turbine systems. The third part studied on the laptop speakers. First, DIC is applied in tensile tests to analyze the material parameters of different buffer ring materials. Second, we established a finite element model to analyze the damping effects of different buffer ring materials in vibration. During the tensile test, the template update method is applied to track axial and transverse strain values under large deformation, and the cumulative error problem in the process is improved. After obtaining the Young's modulus and Poisson's ratio, COMSOL Multiphysics is used to analyze the vibration suppression of different buffer ring materials, and the simulation results are verified with vibration measurement for loudspeakers.