In automotive acoustics, body NVH design is traditionally carried out without considering the acoustic trim parts. Nevertheless, the vibro-acoustic interaction of body structure and insulation trim cannot be neglected in the middle frequency range, where structure borne propagation might still be dominating and where classical statistical approaches are generally not able to represent the influence of local changes in stiffness and damping.
This, together with the market requirement of lightweight and more efficient sound package solutions, is leading the CAE engineers to evaluate new design approaches dedicated to vehicle components such as dash or floor systems, for which the multi-physics interaction between damping, body stiffness and trim impedance is important.
This article presents the practical application in Nastran of a new FE methodology for the simultaneous optimization of poro-elastic trim components together with body structure variable (damping and shape) with respect to the internal sound pressure level under structural borne excitation.
The method is based on genetic algorithms. All the variables of the optimization, such as damping location, material or thickness, panel shape, trim location, bill of materials and so on, have therefore to be a priori defined: the optimum design will be chosen among a set of feasible solutions, which are already implicitly including all the constraints of the design. This optimization approach is proven to be extremely versatile and can therefore be easily transposed to the FE solver solutions adopted by OEMs. This is demonstrated here by means of a comparison of the optimization results obtained with 2 different poro-elastic FE solvers.