| In this paper, the nondimensional amplitude in the centre of the elastic circular cone flat shell and the inclination of the generatrix of flat shell are used as the parameters to expand the derivatives of the stress and deflection functions with respect to the radiusand the frequency of the free vibration into dual parameter power series. Direct perturbation method is used to get every orders of recursive linear partial differential equations, and the variational method to get approximate solutions of these equations. Thus the fundamental formula of the nonlinear vibration frequency about elastic circular cone flat shell is obtained. |