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Triggered by the need for a reduction of CO2-emissions a variety of new powertrain-concepts had been brought up in the latest years. These concepts are ranging from “Micro-Hybrid” over “Full-Hybrid” up to cars powered by an electric machine. Integration of those new powertrain-concepts into passenger vehicles leads to new demands on the acoustic development. The acoustic development process as many other processes in vehicle engineering follows the so called “V-Model”. Coming from overall subjective and objective N&V-targets, which have to be defined at the very beginning of a vehicle development project, it is essential to break down these targets to system (and even component) level in order to be able to handle the work split between complete vehicle responsibility and suppliers. In the development process these defined targets have to be reached and validated coming from system level to full vehicle level.

This paper deals with the analysis of a complete axle of a passenger car, which shows brake squeal in test runs. The complete brake system including the parts of the corner is studied with two different Finite Element Analysis programs and their brake squeal calculation algorithms. Thereby significant differences between the results of the two simulations and also the experiments are observed. The used element type and the chosen discretisation level influence largely the simulated contact and thereby the overall results. In order to explain these outcomes, the force distribution and the force vectors between disc and pad are analysed. On the one hand tetrahedral elements cause stiffening of the parts and hence of the contact. On the other hand the effort to create hexahedral elements in daily meshing practice is often omitted due to cost reasons. This trend is enforced by the statement of software vendors.

Lightweight vehicle design causes special demands for functional NVH design. The reduction of weight by reducing material thickness, enabled by new alloys, the combination of materials and new materials increases the sensitivity of a vehicle body to the vibrational and acoustical response of external forces like powertrain or road and wind excitation. To be able to fully raise lightweight potentials design has to be driven closer to functional boundaries, putting higher demands on the accuracy of the prediction by simulation. For a robust design a very broad view on several loadcases is needed to make sure that by optimization on one target no other target is violated. In this paper, optimization strategies for complex NVH load-cases should be investigated in detail. In reality, load-cases, excitations as well as boundary conditions are very often complex and complicated.