An application of two experimental modal analysis methods for the determination of operational deflection shapes

Two methods are presented for the determination of operational deflection shapes (ODSs). The first method allows one to determine the ODSs by measuring mechanical vibrations at test points of the operating machine (created by the forces occurring in the actual work cycle). The second method is based on the modal model of the machine, including the forces which occur in the operation process, and yields the operational modes of vibration. The forces introduced into the model are determined by methods of pseudo-inversion of the matrix of the spectral transmissibility functions of the mechanical system and the vector of operating vibrations. The determination of the forces involved is necessary for the definition of the paths of energy transfer and the analysis of the noise emitted by the mechanical system (machine). (C) 1996 Academic Press Limited.