The prediction of vibro-acoustic behaviour of structures is of the greatest interest for the design of less noisy machines. In the low frequency (LF) range, using finite element method (FEM) and/or boundary element method (BEM) in general insure such predictions. In the case where the FEM is used, in general this corresponds to an internal vibro-acoustic coupling problem, the vibro-acoustic model is constituted of structural and acoustical models. The structural model is performed using finite element of plates and/or shells and the acoustical model is constituted of volumic finite elements. When an internal vibro-acoustic coupling problem is studied, the modal method is in general used. It consists of the computation of structural and acoustical modes, which will be used as a basis of the displacement for the structure and of the pressure for the fluid. These modes depend on mechanical properties of the structure and the cavity and on geometric dimensions. Moreover, to predict the vibro-acoustic behaviour of the coupled system, appropriate caseload and cinematic boundary conditions must be considered. Thus, the vibro-acoustic model involves in general, a big number of parameters. These parameters can be given with some uncertainties.The purpose of this paper is to measure the effect of these uncertainties on the vibro-acoustic behaviour of the whole system. With such study the reliability of the vibro-acoustic system can be evaluated. To illustrate these effects, we have considered a simple case of vibro-acoustic response of a coupled plate-cavity to a harmonic mechanical force in a LF range.Some of the design parameters are considered as uncertain. These uncertainties are represented by Gaussian distributions of the parameters.A large sample of design points is defined and the responses are evaluated in these design points. The distribution of the response is then extracted and its coefficient of variation (COV) is compared to those of the parameters. Failure criteria (pressure level on the cavity and/or cinematic energy of the structure) can be defined to estimate the failure probability of the design.
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- Effect of Parameter Uncertainties on a Vibro-Acoustic Design
S. Ben Chaabane
- Springer Netherlands
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