布拉格光纖光柵於結構衝擊監測與定位之應用

Abstract

本論文提出一套改良版的三角測定法，搭配由四根布拉格光纖光柵所組成的感測器陣列及能量式調變法，成功定位了鋁板上的落鎚衝擊。實驗與數值模擬交叉比對後，證實衝擊定位誤差來自於系統雜訊和布拉格光纖光柵的角度靈敏度限制。為了改善其角度靈敏度，本文提出由黏貼位置相近但軸向垂直的兩根光纖光柵串接而成的玫瑰型布拉格光纖光柵感測器，以此感測器取代原陣列中的光柵，鋁板上能準確定位的區域被大幅擴大。 在前導實驗中，一報廢風機葉片依照剛性被劃分為三個區域，其長軸方向定義為x軸，另定義一與其垂直的y軸，原點座落於接近輪轂之處。大量布拉格光纖光柵被黏貼於原點接近且沿y方向分散至三區，透過觀察各光柵所接收之訊號，得知最節省光柵數量的佈置方式; 此外，實驗結果指出一維x座標衝擊定位的可行性。在中程實驗當中，葉片上的衝擊發生的區域可成功被定出，可定位衝擊x座標的區域也佔了整體的三分之二以上。

Experimental and numerical analyses have been carried out to demonstrate the feasibility and evaluate the limitation of using fiber Bragg gratings for impact source location on a cold rolled aluminum plate. Within the area enveloped by a four-FBG-array, source location is reasonably accurate. Beyond that area, prediction error may not be acceptable. Numerical simulations show that such error may be attributed to the limitation of equipment resolution on the one hand and angular insensitivity of the FBG on the other hand. An FBG rosette, which eliminated the limitation of angular sensitivity, was used to repeat impact source location experiment on the aluminum plate. The scope where impact events can be precisely located was expanded a lot by FBG rosettes. An impact monitoring system using an array of fibre Bragg grating (FBG) sensors has been established on a wind turbine blade. The effect of the locations and detection capability of the FBG has been investigated. One dimensional impact location along the longitudinal direction of the blade was achieved on over two-thirds of the blade. With such a system, the corresponding strain history and occurrence of local damage can be monitored, thus helping to narrow down the scope of more detailed examination during an overhaul and enabling the integrity of a wind turbine blade to be more reliably assessed and monitored.