从自由模态试验提取约束结构模态参数的方法研究

摘要

Based on synthesis modal technique, a method of extracting modal parameters of constrained structure from free modal test data is researched on. A steel plate experiment is conducted in ordor to prove the extracting method. The normal mode spectrum matrix constituted of low order frequencies of the structure can be derived from the free test data, while the normal mode shapes and the extra high order modes can be obtained through FEM analysis. The boundary constrains are equivalent as a kind of sub-structure, and the modal synthesis is used to extract the constrained modal parameters. Experiment results are consistent with numeric calculation results, so the extracting method is feasible.%研究了如何基于模态综合法实现自由试验边界与约束边界的转化.以矩形钢板为例进行理论研究,分别在自由与一端固定两种状态下进行模态试验,提取模态参数,并将自由试验获得的低阶模态频率构成主模态谱矩阵,而主模态振型和高阶剩余模态则由矩形板有限元模型提供,同时将约束条件等效为一种子结构,共同参与模态综合,完成自由试验结果到约束模态参数的转化.数值计算结果与试验结果一致,证明了基于模态综合理论并将试验模型和解析模型相结合的提取方法是可行的.