Abstract:The nonlinear dynamics of a fouredge simply supported rectangular thin plate under the combination of the parametrical and external excitations were investigated. Based on the von Karman theory, the formulas of motion for the fouredge simply supported rectangular thin plate under the combination of the parametrical and external excitations were derived. The partial differential equations were discretized to the ordinary differential equations with threedegreeoffreedom using the Galerkin approach. Considering the resonant cases of 1:2:4 internal resonance and principal parametric resonance1/2 subharmonic resonance, the method of multiple scales was utilized to obtain the sixdimensional averaged equations. Furthermore, numerical method was carried out to investigate the periodic and chaotic motions of the thin plate. The results show that the chaotic responses of the thin plate are sensitive to the external excitation.