New Results on the Identification of Normal Modes from Experimental Complex Modes
New Results on the Identification of Normal Modes from Experimental Complex Modes
复制标题
从实验复杂模态识别正态模态的新结果
DOI：
10.1006/mssp.1996.0058
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发表时间：
1994
影响因子：
8.4
通讯作者：
É. Balmès
中科院分区：
文献类型：
--
作者：
É. Balmès
摘要复模态与结构动力学的一阶表示有关，而正常（真实的）模态与无阻尼的二阶模型有关。由于与无阻尼有限元模型进行比较需要正常模式，因此确定正常模式是一个关键问题。阻尼引入了简正模式之间的耦合，因此，通常简正模式和复模式之间没有简单的关系。二阶模型的复模态称为完备模态。它表明，一组复杂的模式是完整的，如果它验证了一个定义的适当性条件，这是用来找到完整的近似确定复杂的模式。找到一组复杂模式的完全近似的可能性与阻尼特性有关。结果表明，传统的比例阻尼假设可以推广到矢量组，相应的分离准则可以选择一组完全近似的复模态，并讨论了用于表示质量、阻尼和刚度特性的坐标系。所提出的方法的实验应用是使用六个独立的测试MIT/SERC干涉仪测试台。结果清楚地表明适用于真实的结构具有高模态密度和显着的非比例阻尼。
Abstract Complex modes are associated to first-order representations of structural dynamics and normal (real) modes to undamped second-order models. As normal modes are needed for comparison with undamped finite element models, their determination is a key issue. Damping introduces coupling between the normal modes so that, in general there is no simple relation between normal and complex modes. The complex modes of a second-order model are said to be complete. It is shown that a set of complex modes is complete if it verifies a defined properness condition which is used to find complete approximations of identified complex modes. The possibility of finding a complete approximation of a set of complex modes is linked to damping properties. It is shown that the traditional assumption of proportional damping can be extended to groups of vectors and that the associated separation criterion enables the selection of groups of complex modes for which a complete approximation can be found. Co-ordinate systems used to represent the mass, damping and stiffness properties determined by the proposed approach are also discussed. An experimental application of the proposed methodology is made using six independent tests of the MIT/SERC interferometer testbed. The results clearly demonstrate applicability to real structures with high modal densities and significant non-proportional damping.