力學與電學耦合問題之含裂縫壓電陶瓷板動態特性研究與實驗量測

Abstract

由於壓電陶瓷材料是屬於脆性材料，且在動態的週期性高頻電壓驅動下壓電陶瓷材料的溫度會急速升高，在這種高溫且高頻率的動態負載環境下，脆性壓電陶瓷材料極易由於疲勞的累加而產生微裂紋，並逐漸擴展成巨觀形式的裂紋，不但對於壓電材料會衍生應力集中甚至裂紋快速擴展的破壞問題而影響壓電陶瓷材料的安全及穩定性，進而由於裂紋的產生也會影響壓電陶瓷材料的動態特性，並對於壓電陶瓷平板表面的電極也會形成部分的短路而影響壓電材料內部電場的分布，因而對於壓電陶瓷平板的動態加載衍生額外的問題進而改變壓電陶瓷平板的動態特性。 本論文主要應用光學全域式的振幅變動電子斑點干涉術並配合逐點式的雷射都卜勒振動儀和阻抗分析儀等三種實驗量測技術，並配合有限元素分析和理論解析針對無裂縫、含單一對稱裂縫及非對稱裂縫壓電陶瓷平板在自由邊界及單邊固定的邊界條件下，以兩種不同厚度的試片，對於其振動特性加以分析，文中亦將探討特殊電極分布對振動特性的影響，以及溫度與振動特性的關係，以期能對於壓電元件日漸廣泛之應用與研究分析能有所助益；並對於工業上不同需求的壓電元件，提供設計上的參考與依據

Because piezoelectric material is a brittle material and usually be driven by high frequency and voltage, cracks are easily found in piezoceramic material. These cracks will result in stress concentration and the safety and reliability of the materials will become a problem. Moreover, the existence of cracks will change the shape of electrodes and the dynamic characteristics of the piezoceramic plates will be influenced. Hence the problem of piezoceramic plates with cracks is complicated because it combines the fields of vibration analysis, electricity and fracture mechanics. In this thesis, three experimental techniques, AF-ESPI, LDV and impedance analyzer are used to obtain the vibration characteristics of piezoceramic plates and the experimental results are verified by FEM simulation. The dynamic characteristics of piezoceramic plates without crack, with one center crack and two cracks are investigated in detail. It is shown that the theoretical predictions by the finite element method and the experimental results agree fairly well for the resonant frequencies and mode shapes. Besides, in order to understand the influence of electrode on the vibration properties, we also analyze dynamic characteristics of the piezoceramic plates with special design of electrodes. Finally, the relationship between temperature and vibration characteristics of piezoceramic plates is established base on experimental measurement.