Modal Identification of Multi-Degree-of-Freedom Mechanical Systems Endowed With Geometric Nonlinearities

An identification procedure for a sample class of mechanical system exhibiting non-linear behavior is presented and validated experimentally. The proposed procedure operates on the free-vibration response of the system and is able not only to extract the time-depended modal parameters, but also to identify the functional relationships between modal frequencies and modal amplitudes of oscillation. These relationships depend just on the mechanical characteristics of the system and thus, they characterize entirely the dynamic behavior. An experimental validation of the procedure performed on a physical laboratory system is presented and discussed. The experimental set-up was designed in order to allow for different configurations and hence for different levels of nonlinearity. The comparison between the identified results and the results of a proper analytical model of the system allows for highlighting the sensibility and effectiveness of the proposed procedure.