Computer simulations using the combination of finite element method and modal analysis are now useful methods for vibration prediction of machineries. Macroscopically, characteristic modes of vehicle bodies, which mainly consist of frame structures and attached panels, are regarded as combinations of global and local deformations. As these deformations differ in priorities and countermeasures in the design phase, it is essential to evaluate these deformations individually. However, when it comes to a large and complicated model, it is time consuming to analyse whole modes one by one. Therefore, an efficient analysis method to evaluate these deformations from characteristic modes is strongly desired in various industrial fields. The purpose of this study is to present an analytical method to automatically separate global and local deformations from a frame-panel structure model. The method focuses on the difference of spatial frequencies, as global deformation has lower spatial frequency than local deformation, which exists partially and thus has higher spatial frequency. Each deformation is separated from characteristic modes by means of three dimensional (3D) multiresolution analysis using 3D discrete wavelet transform (DWT). This method enables to evaluate each deformation individually and efficiently without taking a closer look at the model or considering its specification. In this study, first, a 3D finite element model is converted into voxel space in order to apply 3D-DWT. Then, mode separation method using 3D-DWT is demonstrated by a frame-panel structure model of automobile body.

Finite element method,Vibration analysis,Modal analysis,Discrete wavelet transform,Multiresolution analysis