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Vibroacoustics of Vehicles and Machines
Acoustic mode in an unbounded computational air-filled domain around a
car model
Decoupling Coupled Structural-Acoustic Systems:
Investigation of Structural Acoustic Damping
Mechanisms (DFG)
In the framework of a project within the DFG priority
program 1897 ‘Calm, Smooth and Smart’, dissipation of
kinetic energy of vibrating structures into the acoustic far
field is studied. It can be understood as radiation damping
and is particularly relevant for weakly damped structures,
such as sandwich panels and musical instruments. The
mathematical access to radiation damping involves the
coupled equations of time-harmonic elastodynamics and
acoustics, which are addressed respectively by means of
finite and boundary element methods and solved mono
lithically. The main work packages include systematic
investigation of radiation damping and the derivation of
numerical formulation, which enable an efficient consider-
ation of the phenomenon in decoupled structural simula-
tions. Overall, the project aims for a better understanding
of the effect of acoustic radiation damping and to estimate
its relevance in future research.
Modal quantities and their usage for evaluation
of radiated sound power (DFG)
In order to describe acoustic sources, the sound power
is often used as a variable, since it is independent of the
position of the viewer. The sound power can only be ade-
quately determined if the sound source is examined under
free-field conditions, i.e. the source is in a reflection-free
environment, so the influence of the surrounding room
does not influence the results. If one wants to produce
this condition in a computer-aided simulation, then special
methods are required, such as the so-called infinite
element method (IFEM), which can map the properties of
an infinitely large surrounding area with a finite number of
discrete degrees of freedom and for a physically correct
decay of the sound pressure with increasing distance.
Subject of the research of this project is the decomposi-
tion of the vibrations in the acoustic exterior domain into
orthogonal eigenvectors or modes, whose superimposi-
tion again results in the real vibration behavior. In order to
be able to reduce the computational effort, those modes
are to be identified by means of mathematical criteria,
which already provide a sufficiently accurate result for
the sound pressure or the radiated sound power when
superimposed, so that the complete basis of modes need
not be considered and calculated.
Sound emission of multi-layer composites with non-
linear and locally varying damping properties (DFG)
The project goal is focused on the simulation of sound
radiation caused by the vibroacoustic behavior of thin-
walled structures. Lightweight structures of multi-layer
fiber reinforced composites and hybrid metal-plastic
composites offer high damping capabilities and a high
stiffness-weight ratio. The mechanical properties of
such components are influenced by interfaces and local
inhomogeneities resulting in uncertainties and non-linear-
ities of the characterizing parameters. The investigations
are focused on the simulation of amplitude depending
damping by finite-element procedures.