Development of Scanning Damage Index Method for Nondestructive Damage Detection of Plate Structures (Ⅰ)-Isotropic Plate

發展掃描破壞指標於平板結構之非破壞性檢測(Ⅰ)－等向性平板

胡惠文(Hui-Wen Hu) ； 吳承柏(Cheng-Bo Wu) ； 王桀民(Jie-Ming Wang)

《中華民國振動與噪音工程學會論文集》 2008 (2008/05) Pp. 19-25

https://doi.org/10.30028/CSSVANNUAL.200805.0019

摘要

本論文應用實驗模態分析(EMA)與模態應變能法於鋁合金6061平板結構表面裂縫之非破壞性檢測上提出新的方法。實驗模態分析的執行是為了獲得平板破壞前後的模態振型位移來計算模態應變能，應變能計算採用微分值積法(DQM)，應用平板破壞前後的模態應變能的比值定義破壞指標同時檢測整個平板結構以辨認出表面裂縫的位置。掃描破壞指標則是將模態振型重疊分割成多個振型位移區塊，應用區塊內的振型位移計算結構破壞前後之區塊應變能。同樣地將結構破壞前後之區塊應變能差異以能量指標法定義一區塊破壞指標，應用區塊破壞指標對結構做重疊掃描並疊加破壞指標來檢測結構破壞的位置。掃描破壞指標可以增強破壞位置的破壞指標訊號，獲得更好的檢測效果。結果顯示，掃描破壞指標可成功檢測出鋁合金平板的表面裂縫位置。本研究方法對局部或整個結構的非破壞檢測提供了有彈性與較好破壞檢測效果。

關鍵字

掃描破壞指標 ； 表面裂縫 ； 模態應變能、實驗模態分析

並列摘要

This work presents a novel approach of nondestructive detection of damage in isotropic plate by using conventional experimental modal analysis (EMA). An aluminum alloy 6061 thin plate with a surface crack is investigated in this study. EMA is conducted on the plate to obtain the mode shapes of the plate before and after damage. The modal displacements of each mode shape are then used to compute the modal strain energy. For all measured mode shapes, a damage index is defined by using the ratio of modal strain energies of the plate before and after damage. This approach has been adopted to detect the damage location in plate structures. In this study, a scanning damage index is developed by moving damage indices obtained from the local area throughout the structure as if a scanning sensor is used to inspect the structure. The damage indices in overlap areas are added up and the summation may intensify the signals of damage in the plate. Different sizes of scanning area are investigated in terms of the numbers of measured point. Limited by the numbers of measured point, a differential quadrature method (DQM) is employed to calculate the partial differential terms in strain energy formula. Experimental results show that scanning damage index successfully detect the location of surface crack in aluminum plate. The advantage of this method is to provide a flexible and relatively good nondestructive damage evaluation in either local or global structure.

並列關鍵字

Scanning damage index ； surface crack ； experimental modal analysis ； modal strain energy