Supersonic flutter of rectangualar flat panels stiffened by flexible discrete stiffeners perpendicular to the flow direction is analytically studied without modal approximation. Numerical computation has been carried out on a panel of lengthto-width ratio 2 with a single stiffener at the mid-chord line. It is clarified that the stiffener has a destabilizing effect on panel flutter with its certain bending and torsional stiffeness. Aerodynamic and structural dampings play an important role on specifying the bending stiffeness required to prevent flutter.
A new method to determine natural frequencies and damping of structures accurately is presented in this paper. Theoretical resonance curves with unknown coefficients are fitted to experimental resonance data by the method of least squares. As a result of fitting the unknown coefficients are determined, and the natural frequencies and damping which are the functions of the coefficients can be calculated. The present method can be applied not only to linear but also to nonlinear oscillations, and can even estimate the natural frequencies using only the response data in the range below the resonance frequencies. The applications of the method are also presented and discussed in the latter part of the paper.