複合材料葉片振動行為之研究

Abstract

本文重點分兩部份，第一部份介紹Wilson所推導之葉片元素動量理論，引用其理論說明葉片幾合外型計算方式及演算流程，並計算風力作用於葉片上的氣動載荷，將瞬時氣動載荷施於葉片上分析葉片振動行為。 第二部份介紹複合材料三明治結構風力葉片自然頻率的實驗量測方法、葉片受瞬時激振力下的振動試驗方法，以及提供簡單的阻尼量測實驗及估算方式，並利用有限元素分析軟體ANSYS進行分析；本文先以鋁板比較振動實驗數據與有限元素分析結果，驗證有限元素分析可行性，同法分析葉片振動行為，並以實驗驗證之，最後分析葉片受瞬時陣風作用下的應力分佈情形，本研究結果將有助於葉片破壞、失效分析、及可靠度評估。

This work consists of two parts. The first part reviews the methods for determining the wind loads on wind blades, in particular, Wilson's blade element momentum theory. Based on Wilson's method, an algorithm is presented for determining a wind blade's geometry and aerodynamic load. The distribution of instantaneously applied aerodynamic load on the wind blade is analyzed and used for the wind blade's vibration analysis. Part two deals with the experimental and theoretical studies of a composite sandwich type wind blade. The wind blade's natural frequencies and its response under impulsive loads are measured. Damping of the wind blade is approximated using the measured response. A finite element model of the wind blade is constructed using the FEM package ANSYS. Validity of the FEM code for vibration analysis is first demonstrated by comparing the theoretical results with the experimental data for an aluminum plate. The finite element analysis of the composite wind blade is then analyzed. The experimental results have also validated the accuracy of the finite element model. The composite wind blade subjected to instantaneously applied wind load is analyzed to study the stress distribution in the blade. The results obtained in the study will be useful for the failure analysis of the blade.