Search Results

Layered structures made from elastic and porous materials are widely used as insulation systems in the automotive industry. They have a dynamic behavior which is strongly influenced by the various interaction mechanisms within the porous material. The paper concentrates on modeling such materials using a 3-D finite element (FE) approach. This model can be combined with a boundary element (BE) procedure in order to assess the radiated acoustic field. The key part of FE representation is a Biot's model for the two phase porous material. A mixed displacement formulation is selected. The model can be used for predicting the surface impedance and/or the acoustic transmission characteristics of layered materials. The combined use of this mixed FE/BE model enables also the evaluation of the acoustic response (radiated power, field pressure).

The effect of different types of control force actuator models and geometries on the intensity flow between a cylindrical shell and the contained acoustic space has been analytically investigated. The primary source was an external monopole located adjacent to the exterior surface of the cylinder midpoint. Actuator models of normal point forces and in-plane piezoelectric patches were assumed attached to the wall of a simply-supported, elastic cylinder closed with rigid end caps. Control inputs to the actuators were determined such that the integrated square of the pressure over the interior of the vibrating cylinder was a minimum. Test cases involving a resonant acoustic response and a resonant structural response were investigated. Significant interior noise reductions were achieved for all actuator configurations. Intensity distributions for the test cases show the circuitous path of structural acoustic power flow.