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Full-Text Articles in Mechanical Engineering

Characterisation Of Porous Materials Viscoelastic Properties Involving The Vibroacoustical Behaviour Of Coated Panels, Olivier Doutres, Nicolas Dauchez Dec 2005

Characterisation Of Porous Materials Viscoelastic Properties Involving The Vibroacoustical Behaviour Of Coated Panels, Olivier Doutres, Nicolas Dauchez

Olivier Doutres Ph.D.

Porous materials are widely used as passive acoustic absorbers. For optimal design, it is often necessary to know the viscoelastic properties of these materials in the frequency range relevant to their application. The viscoelastic properties are obtained by fitting an analytical model to acoustical radiation experimental measurements carried out on a circular coated plate clamped in a rigid baffle. Compared with quasistatic method, the viscoelastic properties are here achieved at high frequency corresponding to the first resonance in the thickness of the porous layer and coupling between porous materials and external fluid is taken into account. The analytical model, developped ...


Modelling Of The Acoustic Radiation Of A Structure Covered By A Porous Layer, Olivier Doutres, Nicolas Dauchez Apr 2005

Modelling Of The Acoustic Radiation Of A Structure Covered By A Porous Layer, Olivier Doutres, Nicolas Dauchez

Olivier Doutres Ph.D.

In many applications, porous materials such as polymers foams are attached to a structure subjected to vibration. This allows to diminish vibration by increasing structural damping or to reduce noise level in cavities by sound absorption. The radiation efficiency of the coupled system is studied. An analytical model has been carried out, separating the acoustical and vibratory behaviors: - The vibratory analysis is based on a dynamic study of an equivalent plate of the coupled system. In this case the porous layer is considered as a viscoelastic layer. - In the acoustical analysis, a surface impedance is applied on this equivalent plate ...