A comparative study of methodologies for vibro-acoustic FE model updating of cavities using simulated data

The structural dynamic modeling errors, which at times are difficult to eliminate in a structural FE model, can affect the accuracy and reliability of the vibro-acoustic FE models for NVH design of the cavities. A large number of methods have been proposed for structural finite element model updating. However, most of the studies conducted are mainly focused on structural dynamic applications and no work is reported on vibro-acoustic systems. The objective of this paper is to compare through a simulated study two recently proposed methodologies for vibro-acoustic FE model updating of cavities with weak acoustic coupling to address structural dynamic modeling errors. These methodologies utilize a direct and an iterative method of model updating developed for purely structural systems. A simulated example of a 2D rectangular cavity with a flexible surface is presented. Cases of incomplete and noisy data are considered. The comparison is done on the basis of accuracy of prediction of vibro-acoustic natural frequencies and the responses both inside and outside the frequency range of interest. It is concluded that both the methodologies give an accurate prediction of the vibro-acoustic natural frequencies and the response inside the updating frequency range. However, beyond this range, the predictions based on the direct updated vibro-acoustic models are not accurate. It is noted that the success of updating using IESM is dependent on the correct knowledge of the modeling inaccuracies, uncertainties or approximations and also on the choice of the suitable updating parameters, which could be very challenging for complex cavities. The vibro-acoustic FE model updating using the direct method could be handy in such situations where the iterative methods are difficult to be effectively applied.