Evaluation of the FRF Based Substructuring and Modal Synthesis Technique Applied to Vehicle FE Data

FRF based substructuring (FBS) predicts the dynamic behaviour of a coupled system on the basis of freeinterface FRFs of the uncoupled components. The modal synthesis technique determines the dynamic behaviour of a coupled system on the basis of a normal mode description of the uncoupled components. This paper gives a brief description of the theoretical background of these techniques. When using these techniques it is important to take into account the error due to modal truncation. This error can be significantly reduced by application of compensation methods. This paper discusses two possible methods, namely dynamic FRF compensation and compensation by residual modes. In order to evaluate the FBS and modal synthesis techniques and the compensation methods, they are applied to vehicle FE data, more specifically to the coupling of a vehicle subframe with a body-in-white. In the case of multi-component coupling with high frequency resolution and bandwidth the results are in favour of modal synthesis but in the case of frequency dependent joints and the need for easily obtainable interface forces the results are in favour of FBS.