Determination of system vibratory response characteristics applying a spectral-based inverse sub-structuring approach. Part I: analytical formulation

The frequency response functions of discretely connected structures, such as a vehicle system, are determined by inverting the spectral-based sub-structuring equation in dynamic compliance form, which is classically used to compute coupled system response in terms of the characteristics of the free sub-structures. The resulting formulation backs out the response spectra of the free sub-structures including the dynamic stiffness terms of the coupling elements. When analysing the vibration response of one sub-structure due to an externally applied harmonic excitation on an adjacent sub-structure, the proposed theory can express the force transmissibility and structural path contribution functions directly in terms of the coupled system response. This provides a convenient way to identify the critical elements of a physical structure containing multiple coupling points without having to disconnect the individual sub-structures. The salient features of this approach are demonstrated using an idealized lumped parameter dynamic system.