Porous materials are extensively used in the construction of automotive NVH parts. The sound package design during vehicle development requires simulation methods at vehicle level that can take into consideration the dynamical behavior of porous materials. This need has led to different numerical technologies based on Biot's equations. In particular, direct FE implementations of Biot's equations have been included into some commercial FE software programs. Such implementations, while giving good results, are time consuming and difficult to apply within the time constraints given by the timeline of vehicle development programs.
This paper presents an alternative methodology, thanks to which it is possible to build the coupled vibro-acoustic model of a trimmed vehicle without modeling physically the trim components. The trim is represented by means of transfer admittance matrices whose evaluation is based on an analytical space-domain procedure relying on a modified version of the classical transfer matrix method. A tool was developed to calculate these transfer matrices, starting from the construction and materials of the trim part. These matrices are stored and suitably included into the vibro-acoustical FE model of the vehicle body. The method allows an efficient simulation of the trim effect and as a consequence the fast prediction of sound package modifications during vehicle development. All the procedure was fully integrated within two different commercial software programs used by OEMs for virtual NVH vehicle development.
This paper presents the methodology, its validation on a test case and its application on a full-vehicle up to 500Hz, both for structure-borne and air-borne excitation.
