基于模态综合和移频方法的中频段模态计算

采用基于特征约束模态降阶的模态综合方法计算结构中频段振动特性时，针对低阶特征约束模态不能截断的问题，引入了移频方法对子结构动力学方程进行变换，并推导了移频后低阶特征约束模态与系统中频段模态的关系，结果表明：采用移频方法后，低阶特征约束模态可以截断。采用该方法计算了某白车身有限元模型160~190Hz频段内的振动特性，结果表明：采用移频方法后，保留的特征约束模态阶数较少，系统振动特性的计算时间较短，说明该方法有助于提高复杂结构中频段振动特性的计算效率。

Middle Frequency modes computation Based on Component Mode Synthesis and frequency shifting

when the component mode synthesis method based on characteristic constraint modes reduce order been used to compute the structure mid-frequency modes, all of the low frequency characteristic constraint modes can’t been cut off. The frequency shifting method been introduced to transform for the substructures dynamic functions, and the relationship between the low frequency characteristic constraint modes and the mid-frequency system modes been deducted. the results show that the low frequency modes play a little part after using the frequency shifting method. This method been used to compute the vibration response of a body-in-white vehicle mode in the frequency band of 160~190Hz. The results show that this method retains fewer characteristic constraints modes, and reduces the computation time. It means this technique can improve the computational efficiency for middle frequency band modes of complex structure.