STRUCTURAL MODAL MULTIFURCATION WITH INTERNAL RESONANCE .2. STOCHASTIC APPROACH

Stochastic bifurcation in moments of a clamped-clamped beam response t o a wide band random excitation is investigated analytically, numerica lly, and experimentally. The nonlinear response is represented by the first th-e normal modes. The response statistics are examined in the n eighborhood of a critical static axial load where the normal mode freq uencies are commensurable. The analytical treatment includes Gaussian and non-Gaussian closures. The Gaussian closure fails to predict bifur cation of asymmetric modes. Both non-Gaussian closure and numerical si mulation yield bifurcation boundaries in terms of the axial load, exci tation spectral density level, and damping ratios. The results of both methods are in good agreement only for symmetric response characteris tics. In the neighborhood of the critical bifurcation parameter the Mo nte Carlo simulation yields strong nonstationary mean square response for the asymmetric mode which is not directly excited. Experimental an d Monte Carlo simulation exhibit nonlinear features including a shift of the resonance peak in the response spectra as the excitation level increases. The observed shift is associated with a widening effect in the response bandwidth.