奈米材料披覆層之特性識別研究

Abstract

本計畫研究建立一套評估奈米鍍層品質的非破壞檢測方法，此法利用量測鍍膜板的自然頻率來識別奈米鍍層的材料常數及厚度分布，從而判斷奈米鍍層的品質。本研究將建立一分析奈米材料鍍膜平板自然振動頻率的方法，其中將平板分成若干區域，每一區域的鍍膜具有不同的材料常數及厚度，然後利用Rayleigh-Ritz方法建立鍍膜板的振動控制方程式，藉求解特徵值問題來得到鍍膜板的自然振頻。若量測的自然振頻與分析得到的自然振頻有異，則鍍膜的參數(材料常數及厚度)顯然與假設值不同。本研究利用最佳化方法來找尋鍍膜的真實參數，藉使理論與實驗自然振頻間的誤差最小化而找到正確的鍍膜參數。本研究將探討如何選取最佳化中合適的係數，使尋找的過程更快速及有效。本研究將進行奈米材料試片的系列實驗，先決定奈米材料在不同混合比例下的材料常數。然後進行奈米材料的鍍膜製作，預先設計不同鍍膜厚度及材料常數，然後製作鍍膜板供驗證本非破壞檢測方法之正確性。鍍膜板的自然振頻可藉敲擊法的振動試驗或用掃頻振動方法來求得，這些方法都非常方便及有效。量測到的自然頻率以取最低的5-7個頻率來進行鍍膜參數的識別，本研究將探討本方法在不同鍍膜材料及分布狀況的識別能力，結果可供產業界及學術界參考。

In this project, a technique is proposed for nondestructive evaluation of the quality of nanocomposites coating. Due to uncertain factors a film of nanocomposites coated on a substrate may have different properties and thicknesses on the substrate surface. The variations of the material properties and thickness of the nanocomposites film which may affect the performance of the coated substrate need to be detected in an efficient and effective way. The proposed technique uses the measured natural frequencies of the coated substrate to identify the distributions of the material constants and thickness of the nanocomposites film. In this technique, a method via the Rayleigh-Ritz approach is developed to predict the natural frequencies of the coated substrate which has been divided into several regions. It is assumed that the films in different regions have different material constants and thicknesses. An optimization method is then used to search for the true material constants and thicknesses of the films in the regions by minimizing the differences between the measured and predicted natural frequencies. In the experimental study, the material constants of different nanocomposites are determined by testing. A number of substrates coated with different nanocomposites are fabricated. Their natural frequencies are determined by impulse testing or sweep sine vibration testing. The measured natural frequencies are first used to validate the proposed method for vibration analysis. Finally, the measured natural frequencies are used in the proposed nondestructive evaluation method to identify the material constants and thickness of the nanocomposites films.