布拉格光纖光柵於固體結構多點動態應變及熱學量測之技術開發及資料解析

近年來以布拉格光纖光柵(Fiber Bragg Grating, FBG)作為感測器的相關研究發展相當迅速，因其具有優異的傳輸特性和幾何形狀特質、高靈敏度及不受電磁波干擾等優點，可搭配波長解調器進行準靜態的定量量測或利用能量調變型系統作動態訊號擷取，亦能同時利用多光柵光纖來達成多點的同時監測，而上述方法本實驗室過去已投入許多的精力於相關研究，並已經擁有相當成熟之技術。本文主要利用光纖光柵感測器作為固體結構多點的量測系統，並將其應用於暫態波傳及熱學特性等相關量測，首先利用萬能試驗機對光纖進行拉伸實驗，探討光纖光柵的應變量測之線性度以及機械性質；接著藉由結構物受到動態外力加載所激發出的動態訊號，透過快速傅立葉轉換及時頻譜分析方法，探討固體結構的頻率響應的共振頻率和阻尼比特性，並結合有限元素法模擬加以驗證；再者針對複雜幾何結構的溫度負載問題，透過共振波長飄移理論將多點的溫度及熱應變訊號解耦合，討論待測物的幾何結構及邊界條件對於其熱行為影響，並提出改良後的溫度擬合模型來解釋非線性變形現象，再經由結構物於升溫過程的多點動態特性分析，探討材料常數與溫度的關係。續而利用光纖光柵製作高靈敏度的壓力感測器，並進行水下靜態及動態壓力感測實驗，最後針對鋼板於不同電化學反應階段的訊號進行監測，並建構光纖光柵的水下感測系統。

關鍵字

布拉格光纖光柵；能量調變法；暫態波傳；應變；溫度；熱變形；熱膨脹係數；壓力感測器

並列摘要

Fiber Bragg grating (FBG) sensors have recently undergone a rapid development due to its excellent transmission capability, thin geometries, high sensitivity and electromagnetics immunity. FBG can be integrated with the I-MON system to monitor quasi-static situation. It may also be utilized to measure the transient response of solid structures by applying the power modulating method. Furthermore, the use of multi-grating fiber could accomplish the purpose of simultaneously measuring multiple points. All of the aforementioned techniques were successfully developed in our lab and will be implemented in this thesis. In this study, the FBG sensor is mainly used to measure transient response and thermal characteristics for solid structures with a multi-point measuring system. The linearity of strain and material properties of FBG are first measured with a universal testing machine for a tensile test. Then, using FBG to acquire the multi-point transient strain wave propagation and analyze the frequency response behavior to obtain the dynamic characteristics of the structure, and comparing the results with the finite element method simulation. In addition, the influence of the geometric structure and boundary conditions on its thermal behavior is discussed and quantified using the Bragg wavelength shift theory in order to address the nonlinear thermal deformation problem of a complex geometric structure under temperature loading. Furthermore, the relationship between the material constant and temperature is constructed using the resonant frequency analysis of the solid structure at various temperatures. At the end of this paper, a high-accuracy pressure sensor based on FBG is made. The sensitivity and capacity of this sensor are verified by measuring static and transient fluid pressure changes. Finally, the FBG underwater measurement is performed and used to monitor the steel specimen signal at different stages of the electrochemical reaction.

並列關鍵字

Fiber Bragg Grating ； power modulated method ； transient response ； strain ； temperature ； thermal deformation ； coefficient of thermal expansion ； pressure sensor

參考文獻

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