Component Mode Synthesis methods in a body in white noise and vibration analysis

In this work the Dynamic Substructuring (DS) approach has been applied to a noise, vibration and harshness (NVH) problem within the automotive engineering field. In particular, a NVH analysis has been carried out on the body in white of a passenger car. The work focuses on the theory of Component Mode Synthesis (CMS). Two CMS reduction methods, the Craig-Bampton and the Craig-Chang, have been applied to the body in white of the Volvo V40. The influence of some different parameters has been investigated. In particular, the effect of the reduction basis on the response accuracy and on the reduction time has been studied. Moreover, the effect of the connection property between different parts of the model has been examined. The simulation times of the reduced models and of the full Finite Element (FE) model have been compared. The results show us that the Craig-Chang method performs better when the modes are retained up to one and a half time the maximum frequen-cy response studied. Additionally, the Craig-Chang method gives a very accurate representation of the system dynamics even when connections with low stiffness are used. Finally, it is possible to reduce the simulation time up to 90% if CMS methods are used instead of the full FE model.