The effects of uncertainties on the nonlinear dynamics of complex structures remain poorly mastered and most methods deal with the linear case. This article deals with a model of a large and complex structure with uncertain parameters for the nonlinear dynamic case, and the reduction in the model discretized by the finite element method is obtained by reducing the degrees of freedom in the numerical model. This is achieved by the development of the unknown displacement vector on the basis of the eigenmodes; a particular attention is paid to the calculation of the nonlinear stiffness coefficients of the model. The method combines the stochastic finite element methods with a modal reduction class based on sub-structuring the component mode synthesis method. The reference method is the Monte Carlo simulation which consists in making several simulations for different values of the uncertain parameters. The simulation of complex and nonlinear structures is costly in terms of memory and computation time. To solve this problem, the perturbation method combined with the component mode synthesis reduction method significantly reduces the computational cost by preserving the physical content of the original structure. The numerical integration by the Newmark schema is used; the first statistical moments (mean and variance) of the nonlinear dynamic response are computed. Numerical simulations illustrate the accuracy and effectiveness of the proposed methodology.

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This paper describes a stochastic approach to the vibration behavior of a nonlinear damping structure. The deterministic approach is based on motion equations including the non-linearity of damping. For the stochastic calculation, the deviations were assigned to the input parameters of the mathematical model. The probabilistic distribution of these parameters must reflect real operational situations. Numerical simulations were performed with MATLAB using the Monte Carlo and perturbation method. The resulting curves for the parameters studied can find a practical application in the optimization of rotating machines (washing machine), where the parameters of mass, position of the center of gravity, etc. change during operation.