Main difficulties in the midfrequency range and reduced matrix models for structural-acoustic problems

Abstract

In the MF range, the modal density of 3-D structures increases with respect to the LF range, but is not yet high enough to be able to apply SEA, which is adapted to the HF range. This means that finite-element models have to be used to model the master system constituted of the master structure coupled with the internal and external acoustic fluids. The main difficulties in the MF range are due to the mechanical model and the solving methods. Concerning the mechanical model, the difficulties are induced by the structural complexity for which the fuzzy structure theory can be used; we present recent results concerning the validation of the fuzzy structure theory for continuous junctions between the master structure and the fuzzy substructures whose structural complexity is due to local modes of continuous structures on which are attached many discrete dynamical subsystems. Concerning analysis and solving methods in the MF range, finite-element models of master systems have a large number of DOF and modal analysis is not efficient for constructing a reduced model. We then present recent developments and applications concerning a reduced model adapted to structural-acoustic systems in the MF range.