應用光纖光柵感測器於積層製造之材料性質量測及風力發電機基座之多點動態特性量測

Abstract

基於積層製造材料具正交性的材料特性，本文首先說明正交性材料的本構方程式，推出描述積層製造材料所需的相關工程常數，接著使用熱熔沉積式的3D列印機列印出不同堆疊方式的3D列印試片，並採用不同的材料參數量測方法，包括懸臂梁動態試驗量測、拉伸試驗並搭配實驗室的光纖光柵、數位影像相關法的應變量測技術以及使用Nelder-Mead simplex反算懸臂薄板的材料參數，以量測出特定列印參數下之試片三方向相關之材料常數，並比較各量測方法量測出的材料參數結果，找出最適合量測積層製造材料參數的量測方式。接著利用光纖光柵感測器可同時量測應變與溫升的特性，將其應用於此次3D列印材料之熱學性質量測上，利用單光纖法量測該材料在不同溫度負載下的熱學特性，量測出待測物的熱應變，並使用更高階的溫度擬合模型解釋該材料非線性的變形情形並探討玻璃轉化溫度對於量測結果的影響，進行驗證實驗來驗證假設，最後把光纖光柵埋入3D列印試片當中，監測製程中所產生的殘留應變。 由於光纖光柵具備許多其他感測器沒有的優點，例如：防水、耐酸鹼、抗電磁波干擾、高靈敏度、可同時量測溫升和應變和多點長時間長距離量測，因此本文選用其作為風力發電機基座的多點動態應變訊號量測的感測器，藉由將多段光纖光柵黏貼於風力發電機基座的主要結構上，對該結構施予敲擊訊號以激發出整體結構的動態訊號，經快速傅立葉轉換，獲得整體結構振動時所產生的頻率響應，再由帶通濾波獲得該結構特定頻率下的振型，並結合有限元素的結果，還原出該結構在特定共振頻率下的振型，最後將多段光纖光柵置於水中驗證其在水下的溫度感測能力，作為日後將其應用於海水底下時溫度補償的參考。

Based on the orthotropic material properties of additive manufacturing materials, this study first explains the constitutive equations of orthotropic materials and derives the required engineering constants for characterizing these additive manufacturing materials. Subsequently, a fused deposition modeling 3D printer was used to print 3D printed specimens that have different printing orientations, and various material parameter measurement methods were employed, including dynamic testing of cantilever beams, tensile testing combined with laboratory-developed techniques, such as fiber Bragg gratings(FBG) and digital image correlation(DIC) as well as using Nelder-Mead simplex inverse algorithm to calculate the material parameters of cantilever thin plates. After that, material constants in three directions of the specimen under specific printing parameters were measured, and the results from different measurement methods were compared to find the most suitable method for measuring these additive manufacturing materials. Furthermore, taking advantages of the fiber Bragg grating’s characteristics which could simultaneously measure strain and temperature, FBG sensors were applied to measure the 3D printing specimen’s thermal properties in this study. Next, using single fiber method to measure the material’s thermal properties under different temperature, and a higher-order temperature fitting model was used to explain the nonlinear deformation of the material and discussed the influence of the glass transition temperature on the measurement results. After that, verification experiments were conducted to validate previous assumptions. At last, the FBG sensor was embed into the 3D printed specimen to monitor the generated residual strain during the manufacturing process. Due to the enormous advantages that fiber Bragg grating sensors over other types of sensors, such as waterproofing, resistance to acidic and alkaline environments, anti-electromagnetic interference, high sensitivity, and the ability to simultaneously measure strain and temperature over multiple points and long distances for a long period, this study employed FBG sensors for multi-point dynamic strain signals measurement on wind turbine generator foundations. By attaching several FBG sensors to the main structure of the wind turbine generator foundation and exerting impact to the structure, the dynamic signals of the structure would be excited and the frequency response of the overall structure could be obtained through FFT signal processing. The mode shapes of certain resonance frequencies could be acquired by using the bandpass filter method. Compared the results with the finite element analysis results, the actual mode shapes of certain resonance frequencies could be reconstructed. Finally, multiple segments of FBG were placed into water to validate the temperature sensing capability in aquatic environments, serving as a reference for temperature compensation for future applications in seawater conditions.