Nonlinear dynamics of spacecraft with nonlinear joints

Most spacecraft are usually assembled from some simple substructures by various joints. These joints are generally nonlinear and it can strongly affect the dynamics of spacecraft. Finite Element(FE) models of spacecraft usually have many degrees of freedom(DOFs), and the nonlinear joints are generally spatially localized. It is difficult to calculate the forced harmonic response of spacecraft by using current methods. In the present paper, a new approach is proposed to overcome the difficulties. The approach can greatly reduce the computational efforts by only keeping DOFs associated with nonlinear elements, DOFs on which external forces act and DOFs that are of interest. Hence it can be applied to large-scale FE models with local nonlinearities. A FE model of a satellite with some nonlinear joints is used to demonstrate the concept and show the effectiveness of the proposed procedure. The effects of the joints on the acceleration response of payloads in the frequency domain are also discussed.