Abstract
In recent years the noise inside a vehicle is one the major criteria used to determine the comfort level within a vehicle. The noise inside the vehicle is mainly due to vibration levels from the powertrain, which are transmitted to the car body through solid connections. Thus, the reduction of the powertrain vibrations must be taken into account very early in the design process since structural design decisions will directly impact the global dynamic behaviour. When the overall sizing of a new powertrain is determined, it is necessary to use e_cient CAE tools for design guidance at this very early stage in the design process. This paper presents a new optimization approach implemented in the parametric CAE software I-DEAS Variational Analysis, co-developed by CADOE and SDRC. In a first stage, the purpose is to evaluate the variation of the eigenmodes with respect to the evolution of the global shape of the powertrain, and therefore with respect to vibration level on each powertrain bracket on the car body. For that, the di_erent components of the powertrain are represented by complete parametric reduced models (idealized models) including all the shape design parameters. Then, the software will compute the results taking into account the coupled and uncoupled influence of the shape design variables. For each new set of parameters, and then for each new configuration of the powertrain, the parametric approach gives interactively the mechanical criteria (eigenmodes in this particular case) without any new analysis. This parametric approach is completed by a topological optimization, focusing specifically on the location and on the number of attachment bolts between the engine and the gear box. With this approach, any configuration, corresponding to the number of attachment bolts, can be interactively reviewed. This optimization approach appears to be much more efficient in reducing the number of design iterations, than the traditional method. The result of this work allowed RENAULT to use CAE for design guidance and to give design recommendations to the mechanical design o_ce, for new diesel engines. This was done by taking into account, at a very preliminary stage the desired performance criteria in terms of reduction of noise in the vehicle.