探討質量效應對於樑結構頻率域之影響以及移動質量的動態特性分析

近年來以布拉格光纖光柵（Fiber Bragg Grating, FBG）作為感測器的研究領域之發展十分迅速，因其量測應用範圍相當廣泛，例如搭配波長解調器可作靜態的監測、結合能量調變法之動態量測系統以及利用分波多工器可實現多點同時量測的技術等。而數位影像相關法（Digital Image Correlation, DIC）的非接觸式全域性量測技術為其重要優勢，近十年來學者積極投入相關技術的研發，在量測的範疇中亦佔有一席之地，這些量測技術都已由本實驗室自行研發創立並將應用於本論文中。本文針對質量效應造成樑結構之頻率域影響作深入探討，其中質量效應又分為靜態與動態兩種情況，主要藉由實驗量測的方式，利用布拉格光纖光柵搭配能量調變法來擷取系統的時域動態訊號，並從頻率域的角度分析質量效應對於系統彎曲模態之共振頻率的影響，先從靜態的質量效應結果，探究質量大小及擺放位置與共振頻率變化之關聯，再進一步採用曲線擬合的方式，將質量效應的影響趨勢以函數之形式表示，便可推廣至應用層面，若測得系統共振頻的變化資訊，即可反算系統中質量效應之現況。此外，更探討不同邊界條件之樑結構，其質量效應所導致的頻率變化特性，並於特殊的量測需求中適當引入數位影像相關法，可提供微米尺度的動態精密量測。最後研究動態質量效應即移動質量對於樑結構系統之特性分析，以FBG及光纖位移計作為主要感測器並相互印證量測結果之正確性，且利用DIC同時追蹤移動質量的軌跡，目的是期望將動態的質量效應與靜態之間的關係建立關聯性，並針對動態質量效應所呈現頻率的特性提出解釋。

關鍵字

布拉格光纖光柵；數位影像相關法；質量效應；移動載荷；頻率飄移；能量調變法；多點量測；分波多工

並列摘要

Recently, Fiber Bragg Grating (FBG) sensors have been developed rapidly. Its application has covered a wild range for measuring technique. For instance, static analysis by peak wavelength shifting, dynamic analysis by power modulated system and multi-point measurement by wavelength division multiplexer. On the other hand, Digital Image Correlation (DIC) is a non-contact and full field measurement technique. Both of them are developed in our laboratory and are used in this dissertation. The main object of this research is focused on the mass effect for beam structures. Mass effect will induce the shifting of resonant frequency and will be discussed based on the experimental measurement. Transient responses are measured by FBG with high resolution in time domain. The responses are then transformed to frequency domain by fast Fourier transformation. The resonant frequency shifting caused by mass effect is represented as a function by fitting process. Therefore, by measuring the quantity of frequency shifting, the mass effect on beam structure can be determined. Moreover, mass effect is also investigated for different boundary condition of beam structure. In order to measure the vibration of beam structure induced by the moving mass, DIC with high resolution is used. Another main topic of the thesis is about the dynamic characteristic for moving mass. From the result of the experimental measurement, the effect of moving mass can be regarded as a superposition of mass in different location. The dynamic characteristic of the system disturbed by moving mass is related to the static mass effect.

並列關鍵字

Fiber Bragg Grating ； Digital Image Correlation ； mass effect ； moving mass ； frequency shifting ； power modulated method ； multi-point measurement ； wavelength division multiplexer

參考文獻

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探討質量效應對於樑結構頻率域之影響以及移動質量的動態特性分析

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