基于Zernike矩的网壳结构的振型表征及损伤识别
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摘要
在结构模态识别中常用的模态保证准则(MAC)仅能显示结构不同振型的相关性,并不能反映模态的细节,对于模态复杂的网壳结构则更是如此。因此,提出利用Zernike矩表征网壳结构的振型,即将振型数据视为图像函数,通过离散Zernike矩变换,得到表征各阶模态的Zernike矩值(包括幅值和相位角)。对一个单层球面网壳结构的有限元模型进行数值模拟,结果表明,此矩可有效地反映模态的振型特性并能识别结构的重频模态,较传统的MAC具有明显的优越性。在此基础上,初步提出将Zernike矩的幅值及相位角作为结构损伤识别的新指标。构造了网壳结构杆件物理参数改变的几种损伤工况,通过分析,发现了不同的损伤形式导致的Zernike矩的不同变化规律,验证了Zernike矩用于损伤识别的可行性。
In the structural mode recognition,the most widely used method is the modal assurance criterion(MAC),which simply shows the correlation of different modes but can not represent the details on mode shape features,especially for modal complex latticed shell structures.Mode shape characterization using Zernike moments is studied for latticed shell structures,and the mode shapes are regarded as image functions in this paper,and then transformed into Zernike moments(including amplitudes and phase angles).A finite element model of a single-layer spherical latticed shell structure is established and the numerical simulation is performed,while the results shows that the Zernike moments can reflect the features of mode shapes and recognize overlap modes,which is superior to the traditional MAC.On this basis,a new index of damage detection based on the amplitudes and phase angles of the Zernike moments is presented.Through several damage cases by changing the structural physical parameters in the latticed shell structure,different changes of the Zernike moments caused by different damage cases are detected and the Zernike moments are verified to be feasible for damage detection.
引文
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