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

Invited paper

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 material’s 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.