本研究基於利用小波轉換方法對有缺陷的長方形平板經敲擊後產生的彎曲波進行分析，進而預測平板上的破壞存在及其位置。本文是以製作的長方形鋁板利用鐵座將兩邊固定，將單軸應變規布建於板上，經敲擊後取得各應變規的應變訊號，之後利用小波進行頻域分析找出彎曲波由敲擊點至各應變規的波程時間，進而求得彎曲波在各頻率中的波群速度。當彎曲波在傳遞中遇到結構缺陷時會產生散射波，因此在量得的訊號中含有彎曲波的直接波傳與缺陷引起的散射波傳，再利用直接波傳的波程時間與散射波傳的波程時間差及所計算出的彎曲波群度，透過簡單尋優方程式得到擁有全域性及小值的等高線圖，反求破壞位置。
　　本研究方法優點可以替代超音波檢測，節省實驗儀器的成本，而缺點在於無法探求缺陷大小形狀與深度，未來可利用多點應變規量測並發展平板缺陷散射波頻譜特徵的數值方法來反求缺陷大小，達到最佳非破壞檢測效果。

　　n this investigate, a method of predicting crack existence and its location in a rectangular plate is provided by wavelet analysis of flexural waves from impact. In the experiment, the strain histories caused by impact are measured by strain gauges which are built on the rectangular simply supported plate. Then the wavelet transform will be applied to identify the group velocity of flexural wave by the arrival time of every measuring point in time-frequency analysis. The flexural waves will produce dispersive waves when propagate through the flaw of plates, so the measured signals include the direct waves propagation from impact and dispersive waves propagation from the flaw. By using the group velocity of the flexural and the time lag between the direct wave and the dispersing wave to apply the simplex algorithm method, the exact location of the flaw can be found by the contour map containing the global minimum and from the map, the flawed position can easily be detected.
　　The advantage of the method in this investigate can be instead of the ultrasonic method for structural damage detection and lessen the cost of the equipment, but it can’t detect the shape and the depth of flaws. Utilizing multiple-array measurement and to develop a numerical analysis of the dispersive waves’ spectra will get the exact result of flawed shape and depth in the future.

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