平板裂縫散射係數之數值計算與分析

Numerical Calculation and Analysis of a Plate Crack Scattering Coefficient

楊澤民(J. M. Yang) ； 涂季平(G. P. Too) ； 劉家綸(C. L. Liu) ； 謝羽豪(Y. H. Hsieh) ； 林楷霖(K. L. Lin)

《中國造船暨輪機工程學刊》 32卷4期 (2013/11) Pp. 147-154

摘要

時間反轉法理論現已廣泛應用於水下探測、醫學檢測上以及結構非破壞檢測。理論發展隨著疊代式時間反轉法與時間反轉因子分解的出現，解決了許多不利於單純使用時間反轉處理的因素，進一步的拓展了時間反轉理論的應用範圍；而此運用時間反轉因子分解的方式，可去除繁複的疊代實驗流程，直接由數學推導得到疊代後之結果。本研究應用時間反轉因子理論探討平板製縫之散射係數，以及不同入射方向之訊號對於含裂縫平板散射特性的影響。於模擬方面，本研究運用ANSYS有限元素軟體進行模擬平板結構與訊號發射擷取；於訊號分析方面，撰寫MATLAB程式處理以及輸出散射幅射圖。透過半圓形及圓形陣列元件將各個角度之散射係數計算出來，畫出散射幅射圖，再藉由不同裂縫之形狀和尺寸建立其特性表格來探討不同裂縫之散射特性。藉由此方法建立一套計算裂縫各方向之散射係數流程，期望未來能應用於實務上之裂縫偵測，對於非破壞檢測能有進一步的貢獻。

關鍵字

平板裂縫 ； 訊號散射 ； 非破壞檢測 ； 時間反轉因子分解

並列摘要

Time Reversal Method (TRM) is now widely used in under water exploration, medical testing and on the structure of non-destructive testing. In theory, Iterative Time Reversal Process and Decomposition of Time Reversal Operator (D.O.R.T.) appear to solve many issues, simply are not only resolved by utilizing the time reversal method but also further expand the time reversal theory application scope. While using this process for time reversal, the cumbersome process of iterative experiments can be eliminated directly by the mathematical derivation obtained from the iteration results. This research will explore the application of the D.O.R.T. theory in analyzing the scattering coefficient related to the signal refracting off the cracked plate, along with the affect of repositioning the signal at different angle in retrospect to the crack on the plate.As one component of this simulation, the ANSYS finite element software is implemented to stimulate the plate structure and retrieve the signal transmitter. Writing MATLAB programs, processing applications along with outputting scattered patterns are inclusive with the signal analysis. Circular-shaped array transducers are used to calculate the various angles of the scattering coefficient, which we used to draw the scattered patterns. A characteristic chart is developed to differentiate the scattering characteristics of different size and shaped cracks. Based on this method a calculation of the scattering coefficient procedure in each direction can be established. Furthermore, the method may have a further contribution for non-destructive testing.

並列關鍵字

Plate crack ； Signals Scattering ； Non-Destructive Testing ； D.O.R.T.