A Wave Based Transfer Matrix Method for accurate simulation of acoustic problems with multilayered damping treatment

Invited paper

Stijn Jonckheere

KU Leuven - BE0419.052.173

Tuesday 2 june, 2015, 14:00 - 14:20

0.7 Lisbon (47)

Abstract:
Nowadays, engineers strongly rely on damping treatments to improve the NVH properties of their product. These materials are often a complex, multilayered combination of elastic, viscoelastic and poroelastic layers. In order to come to an optimised design, efficient CAE-models are indispensable. Currently, most tools for 3D vibro-acoustic simulation are based on the Finite Element Method (FEM) or the Boundary Element Method (BEM). However, as these methods are in practice limited to low-frequency simulations due to the strongly increasing computational cost with frequency to control the innate approximation errors which originate from the use of polynomial approximation functions. The damping materialís complex parameters and high number of local degrees of freedom even require additional mesh refinement. Therefore, techniques are developed to replace the expensive element based techniques, with no or a limited cost in accuracy. Through its innate modelling procedure, the Wave Based Method (WBM) has an increased efficiency. Also, in many cases, at higher frequencies, Transfer Matrix models can be used to replace the detailed models of the multilayer. When incorporating these TM models into a classical FEM vibro-acoustic model, however, one should live with two approximation types; (i) the innate approximations of the TMM and (ii) the fact that the angle of incidence is not known a priori, such that often values for normal incidence or averaged values are used. Whereas the first class of approximations are innate to the TMM, the second class can be overcome by using the WBM since it incorporates a priori known information in the approximation function set. This way, the TMM can be nested into the WBM.

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