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MEASUREMENTS OF NONLINEAR VIBRATIONS OF A BEAM SUBJECTED TO TWO BROADBAND CORRELATED RANDOM EXCITATIONS

Abstract. This paper presents experiments of a nonlinear system subjected to two broadband correlated random excitations. The system studied is a steel beam bonded on both sides to a heavy steel block. First of all, correlation between two broadband random excitations is studied. This study analyses and compares the effects of the correlation choice into the apparition and/or attenuation of some symmetric or anti-symmetric modes of the beam. Two different types of correlation are experimentally introduced: in phase and opposite phase. Secondly, nonlinear effects are identified according to the presence of secondary peaks corresponding to the appearance of harmonic components of the first three natural modes (i.e. two symmetric and one anti-symmetric) of the clamped-clamped beam. Then, from experimental output data, the correlation effects added to the nonlinear effects open the discussion about the observation of some combinations of different harmonics from different modes of the nonlinear system under study. Finally, an extension of the classical Harmonic Balance Method (HBM) is proposed for the numerical prediction of the nonlinear dynamic behavior of a mechanical system subjected to two broadband correlated random excitations. Comparison between experiments and numerical simulations validate the numerical strategy for the prediction of the global nonlinear response as well as the contribution of harmonics for a mechanical system subjected to multipoints correlated random excitations.