SAE International An Efficient Input Mobility Mapping Computational Method 2017-01-1806

The input mobility is a crucial structural parameter regarding vibro-acoustic design of industrial objects. Whatever the frequency range, the vibrational power input into a structure -and consequently the average structural-acoustic response- is governed by the input mobility. When packaging structure-borne noise sources, the knowledge of the input mobility at the source connection points is mandatory for noise control. The input mobility is classically computed at the required points as a specific Frequency Response Function (FRF). During an industrial design process, the choice of connection points requires an a priori knowledge of the input mobility at every possible location of the studied structure-borne source, i.e. a mapping of the input mobility. The classical FRF computation at every Degree Of Freedom (DOF) of the considered structure would lead to consider millions of load cases which is beyond current computational limits. This paper presents how to efficiently compute the full map of band-averaged input mobility over a Finite Elements mesh. The proposed method is based upon a modal decomposition of the structural response and analytical frequency integration; consequently, it only requires the modal basis as it is currently computed. The frequency band average allows optimizing the storage size. Since the input mobility is a real quantity, associated to each DOF of a structure, modal display tools can be used without modification. Thus, a meaningful map is provided, allowing efficient structural dynamics analysis over a broad frequency range.