Abstract
Computer simulations using the combination of finite element method and modal analysis are now useful methods for vibration prediction of machineries such as vehicles. 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 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 analyze whole modes one by one. Therefore, it is essential to analyze these deformations respectively and efficiently from characteristic modes. In this study, an analytical method to automatically extract global and local deformations from a frame-panel structure model is presented. This method focuses on the difference of spatial frequencies, as global deformation has lower spatial frequency and local deformation has higher spatial frequency. Each deformation is extracted from characteristic modes by means of three dimensional discrete wavelet transform (3D-DWT) and multiresolution analysis. This method enables to evaluate each deformation individually without considering its specification. In this study, a 3D finite element model is converted into voxel space in order to apply 3D-DWT. Then, proposed mode extraction method using 3D-DWT is demonstrated by a frame-panel structure model of automobile body.
