Application of mutual mean compliance to vibro-acoustic system

Abstract

The reduction of noise and vibration in the development of new automobile bodies is challenged by the directly competing requirement of lightening the body. Numerical analysis techniques such as sensitivity analysis and structural optimization are widely used to meet these requirements, as they provide optimized material thickness distributions and other parameters. Still, there have been few examples where the material thickness distributions found in numerical calculations have actually been used in designs. It is important to gain a better understanding of the material thickness distribution's effect on variations in both the stiffness and mass and the noise and vibration in order to design structures that can actually be manufactured. Currently, there is no precise understanding of the mechanisms through which material thickness affects the variations in the stiffness and mass or noise and vibration. The current results from sensitivity analysis and structural optimization cannot be considered to provide enough information to be of use in design. In this paper, mutual mean compliance was applied to a vibro-acoustic system in an attempt to gain a quantitative understanding of the variations in stiffness and mass of component structures and of the variations in noise and vibration. This paper presents a formulation for mutual mean compliance and addresses in turn the structure system, the acoustic system, and the contribution of coupling between the two. In addition, the mutual mean compliance is separated into the contributions of the component structures, and it is shown that the contributions of the stiffness mass values to the responses of interest can be identified. Mutual mean compliance is applied to a simple automobile body model and countermeasures against noise and vibration are verified to be effective.