陳國在臺灣大學：工程科學及海洋工程學研究所葉育超Yeh, Yu-ChaoYu-ChaoYeh2007-11-262018-06-282007-11-262018-06-282004http://ntur.lib.ntu.edu.tw//handle/246246/51018本文旨在四邊固定矩形均勻平板進行內支承及附加質量的改裝，探討其聲輻射改善之情形。其係利用輻射模態的概念找出聲輻射效率較高的基本振態，並利用內支承破壞之，再利用附加集中質量輔助改善。因此對於支承位置以及附加質量加載大小與位置，均屬研究的內容。 結構振態數值模擬的部份，係採用半解析分析的方法(Semi-Analytical Method)，其概念為利用均勻平板之基本振態函數及共振頻率已可得到閉式解析解(Close Form)的特性，配合結構動力學的概念，以結構矩陣的方法來推導出修正後的基本振態及共振頻率，將可大幅降低電腦運算時間，並於文中利用簡單的實驗佐證之。 研究結果顯示，利用內支承及附加質量的改裝技術，對單頻噪音源而言，只要利用改裝使其新的共振頻率偏離原來共振頻率5 Hz以上，則能立即且有效的改善平板振動問題。然而對無特定頻率的噪音源，也可利用此方式，經模擬後找出最佳的改裝位置，經實際平板振動聲輻射試驗後，確實有不錯的效果，雖然由於共振頻率已改變，噪音尖峰頻率處不同，但對平板整體聲輻射已有效降低，達到改裝的目的。The purpose of this study was focused on using the inner support and the additional centralization mass to refashion the fixed end sequare homogenous plate , and the subsequent improvement of the sound radiaton . We uses the radiation mode to find out the fundamental modes of more effective sound radiation . Then , the modes was broken by inner support with subsequently improved by additional centralization mass . All the supporting postion , the loading size and position of the additional mass are the topic of our study . The mathematical model was analyzed by semi-analytical method . We use the characteristics that the close form derived from the fundamental function and resonance frequency of homogenous plate , combining with structural dynamic and matrix , to deduce the result that the modified fundamental function and resonance frequency will save the CPU time effectively . We had proven it by simple experiment . The results revealed that , for single frequency noise , the plate vibration can be improved immediately and effectively if we used the refashion technology to change the resonance frequency for more than 5 Hz . Besides , it also can be applied to noise with arbitrary frequency to find out the best refashion position . We had proven that , even though with the different resonance frequency and noise peak frequency , the refashioned plate did reduce the general sound radiation effectively .目 錄 頁次 誌謝.............................................Ⅰ 摘要.............................................Ⅱ 目錄.............................................Ⅳ 圖目錄...........................................Ⅶ 表目錄........................................... X 符號說明.........................................XI 第一章 緒 論............................1 1.1 研究動機及方法................................1 1.2 文獻回顧 .....................................3 第二章 理 論 分 析..........................6 2.1 均勻矩形未改裝平板振動分析....................6 2.2 改裝後平板振動分析............................9 2.3 平板內部支承之模擬...........................14 2.4 改裝後平板振動造成之聲必v計算...............15 第三章 實驗方法與量測..............19 3.1 實驗佈置.....................................19 3.2 受陶瓷壓電片(PZT)激振所造成之動態反應........20 3.3 聲必v量測...................................22 3.4 實驗方法及儀器配置...........................23 第四章 數值模擬與實驗之比較........27 4.1 未改裝固定邊界矩形平板運動分析...............27 4.2 中點處內支承對平板動態特性之影響.............31 4.3 中點處附帶集中質量對平板動態特性之影響.......40 4.4 數值模擬與實驗之比較.........................48 第五章 平板改裝後對聲輻射之影響....49 5.1 輻射模態.....................................49 5.2 改裝前均勻平板聲輻射特性.....................52 5.3 內支承位置對平板動態特性之影響...............57 5.4 附帶單一集中質量對平板動態特性之影響.........69 5.5 內支承配合附帶集中質量對平板聲輻射之改善.....73 第六章 結論與未來展望 ..............79 6.1結論..........................................79 6.2未來展望......................................80 參考文獻...........................81en-US平板聲輻射Sound Radiation from a Platethesis