應用超音波量測壓電材料彈性常數及薄層動態液體黏度

Abstract

超音波檢測不僅在工業界應用廣泛，於醫療體系、日常生活中亦普遍存在。工業中尤以非破壞檢測領域最常使用，因為其具有幾乎能穿透各種試件並對人體無害的優點，也可同時作缺陷檢測、材料常數量測與即時監控樣品品質，並因操作簡易所以被廣泛接受。 傳統超音波量測是直接由示波器上時域訊號的回波間距配合已知試片厚度，計算波行進的時間藉以求得波速值(脈衝回波法)，然而主要待測材質為等向性材料因此超音波的入射方向並不會影響波速值，本文將嘗試先以脈衝回波法測量異向性(壓電)塊狀材料的波速，評估量測的準確度與可行性。 完成較厚的壓電塊狀材料測試之後，再進一步利用超音波搭配振幅頻譜法對於一般無法由拉伸試驗求得的薄層固體材料與陶瓷材料作非破壞性檢測，本文主要討論的內容是目前被廣為應用的壓電材料(PZT、半導體晶圓)之彈性性質，包含縱波波速、橫波波速與彈性常數測定，以作為相關元件設計之參考數據。 文中也探討改用液體延遲層代替固體延遲層對實驗結果所產生的影響。分析液體黏度與厚度等變因對量測訊號與計算結果影響的程度，可以歸納液體延遲層的優缺點作為實驗架設的考量。論文中也利用振幅頻譜法配合流體力學公式推算液體黏度，並實際針對高黏度液體(甘油、果糖)與低黏度液體(液晶)進行靜態黏度測定，同時探討一般環境中的壓力與溫度對液體黏度的影響。另一部份的實驗則是分析動態流體的黏度，其中包含牛頓流體的定量檢測與非牛頓流體的定性觀察。

Ultrasonic inspection, a technique of non-destructive test (NDT), is widely applied in material properties testing because of its low cost and high accuracy. Elastic constants of materials play an important role in many engineering applications and designs. In general, the piezoelectric material properties are not easily obtained from tensile test. Therefore, the non-destructive ultrasonic technique is used in this study to evaluate phase velocities by pulse-echo and amplitude-spectrum methods, and then determine the elastic constants of materials by using phase velocities. In this regard, the experimental results of phase velocities did an excellent work in correlating the standard values calculated from the wave propagation theory. The influence of buffer layer on the experimental measurement for the thin layer system has also been investigated in this study. We replaced solid buffer layer with liquid ones which has different viscosity and layer thickness to analyze the differences of longitudinal wave velocity between different test conditions. The accuracy of experimental measurement on longitudinal wave velocity will be increased with the increasing liquid viscosity. In addition, the viscosity of thin liquid layer in static equilibrium and the environmental influence on the liquid viscosity are also discussed. The viscosity of liquids are obtained by inverting the wave velocities and attenuation coefficients with amplitude-spectrum method. The viscosities of liquid obtained in this study agree with the results presented in the literature. Furthermore, the viscosity of flowing fluid is measured by a self-designed liquid circular system.