Prediction of the Coupled Impedance from Frequency Response Data

This work deals with the common case of large mechanical systems which can be modelled considering two main sub-structures: a source structure, corresponding for example to the engine, and a receiving structure, as the accommodation area/cabin in these machines. Numerical models are highly desired for predicting the vibroacoustic behaviour of the receiver at a design stage and for design optimisation. In many cases the mechanical systems must be studied using sub-structuring techniques. Here a standard frequency response coupling technique (or impedance coupling technique) is applied for the prediction of the complex power transmitted between a source structure and a receiving structure in a multi-point-connection case. The data required in this case are the frequency response functions (FRFs) of both the source and the receiver and the velocity at the connecting points under operating conditions. Experimental aspects and issues associated with this technique are investigated considering a simplified mechanical model. This consists of a driven beam connected in two or more points to a source. Results are discussed and compared with those obtained from a numerical model.