Novel substructuring method towards efficient vehicle noise radiation analysis

Over the past decades, in order to keep up with both the legislations governing the noise limits and the growing customer expectations, the continuous search for noise reduction has been playing a key-role in the development process of vehicles. Since the design iterations used to improve the Noise, Vibration and Harshness (NVH) behaviour of vehicle’s components are costly and time-consuming, enhanced substructuring techniques are being developed to
quantify the contributions of separate parts of the vehicle (frame, powertrain, tires, etc.) to the overall interior and pass-by noise levels. These techniques allow an efficient collaboration across different project groups and the use of parallel computing environments, besides giving the possibility to combine parts numerically and experimentally characterised. Intensively used for subsystems connected by points, dynamic substructuring still constitutes an open
area of research for systems comprising continuous interfaces. This ongoing research in the automotive industry is driven by the significant presence of large interfaces inside a vehicle, as for instance between the floor and the upper-body structure. Within this framework, a method which allows to characterise subsystems connected along lines is presented. The approach is based on a discretisation of the continuous interfaces into a small set of points,
where the information of the subsystems is condensed. For this purpose, an inverse approach is used, which allows to characterise the dynamics of the passive subsystem using data of the assembled system. Special attention is paid to the physical consistency of the characterised subsystem, which has to possess basic physical properties as reciprocity and passivity. A new methodology to ensure such characteristics is then proposed. The method is validated on a
structure made of two plates connected along a common edge through a beam. Moreover, a description on how this method can be applied in the automotive industry is presented.
Specifically, the contribution of the car floor panel to the overall interior noise can be analysed by isolating this part from the rest of the car structure, enabling a faster design prediction and an efficient vibro-acoustic optimisation.