Experimental verification of structural-acoustic modelling and design optimization

A number of papers have been published on the simulation of structural-acoustic design optimization. However, extensive work is required to verify these results in practical applications. Herein, a steel box of 1.0 x 1.1 x 1.5 in with an external beam structure welded on three surface plates was investigated. This investigation included experimental modal analysis and experimental measurements of certain noise transfer functions (sound pressure at points inside the box due to force excitation at beam structure). Using these experimental data, the finite element model of the structure was tuned to provide similar results. With a first structural mode at less than 20 Hz, the reliable frequency range was identified up to about 60 Hz. Obviously, the finite element model could not be further improved only by mesh refinement. The tuning process will be explained in detail since there was a number of changes that helped to improve the structure. Other changes did not improve the structure. Although this model of the box could be expected as a rather simple structure, it can be considered to be a complex structure for simulation purposes. A defined modification of the physical model verified the simulation model. In a final step, the optimal location of stiffening beam structures was predicted by simulation. Their effect on the noise transfer function was experimentally verified. This paper critically discusses modelling techniques that are applied for structural-acoustic simulation of sedan bodies. (C) 2002 Elsevier Science Ltd. All rights reserved.