Nonlinear vibrations of a ballistic vehicle with friction joints subjected to vibroacoustic excitation - experiments, modeling and simulations
Résumé
This study presents the experiments, modeling and numerical simulations of an industrial aeronautical structure subjected to vibroacoustic excitation. In flight, especially during atmospheric
re-entry, an aeronautical structure is exposed to major pressure fluctuations on its external
surface. These fluctuations are described as a dynamic excitation which generates structural
vibrations of the outer surface and of the components inside the aeronautical structure. Due
to some of these internal components such as joints, the assembly may exhibit a nonlinear
vibration response. The simulation of these nonlinear vibrations requires reliable modeling
of the wall pressure fluctuations and a nonlinear vibration simulation method adapted to
the nonlinear modeling of the structure. In this study, a modeling and simulation method
is developed to compute the nonlinear vibration response of an industrial assembly to such
a surface, random, correlated dynamic excitation. More specifically, numerical simulations
are performed by proposing an extension of the well-known Harmonic Balance Method for
nonlinear mechanical systems subjected to complex vibroacoustic excitation. The method is
validated using a dedicated ground experiment. A metallic industrial assembly representing a
ballistic vehicle and including friction joints is used. This structure is subjected to controlled
vibroacoustic excitation: diffuse acoustic loading in a reverberant chamber. The structure
exhibits a nonlinear vibration response due to friction. The finite element model is validated
through an experimental modal analysis with an electrodynamic shaker. The vibroacoustic
modeling of the excitation is then validated through a test-simulation comparison using diffuse
acoustic field testing at low excitation level. Then the global nonlinear simulation process is
validated using diffuse acoustic field testing at increasing excitation levels. Test and simulation
results exhibit the same nonlinear behavior: increase of dissipation and softening effect at the
main resonances. This work thus represents a new step towards the use of nonlinear vibration
simulation methods with real industrial structures and real-life loading
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