本論文利用有限元素法的模擬實現了脈衝式渦電流和掃頻式渦電流檢測的數值分析。我們也討論到利用有限元素法去完成並且分析二層導磁性金屬材料在磁場中的互相影響。脈衝式渦電流和掃頻式渦電流檢測的解析解已經很成功地適用於判定許多非破壞性檢測的現象，但是解析解只適用於簡單的幾何結構，為了預測更複雜結構材料的渦電流信號，必須使用到一些數值分析的方法，例如邊界元素法、有限元素法。以非破壞性檢測為目的的單一頻率渦電流數值分析的研究已經很成功地應用在許多解析解很難解甚至無法解的一些重要的檢測上。因為鍍層厚度檢測和材料參數的影響是非破壞性檢測的主要考量，所以我們利用有限元素法來分析脈衝式渦電流和掃頻式渦電流檢測的結果。並將數值分析計算出來的結果和理論值、實驗值做比較。

In this study, the numerical simulations of swept-frequency eddy current and pulsed eddy current by means of the finite element method (FEM) are demonstrated. Finite element simulations carried out to analyze the interactions of magnetic field with two-layer magnetic metal structure (i.e. a bulk metal with coating) are also discussed. The closed-form analytical solutions of swept-frequency eddy current and pulsed eddy current techniques have successfully been applied to the predications of many NDT phenomena. But the analytical solutions are only for simple geometry situations. To predict the EC signals of more complex material structure, numerical methods like boundary element method (BEM) or finite element method are used. The numerical study of single-frequency eddy-current phenomena for NDT purposes has successfully been applied to many practical inspection situations for which analytical solutions are either difficult or impossible to obtain. Since coating inspection and the influence of materials parameters (electrical conductivity, magnetic permeability) are the main concern of NDT applications, we take it as an example to show the prediction results of the frequency-domain swept-frequency eddy current and the time-domain pulsed eddy current by the finite element method. Results from the numerical calculations, practical measurements, and analytical solutions will be compared and demonstrated.

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