The Effect of Off-Neutral Axis Excitation on the Vibration Response of Finite Ribbed-Plates

In this paper, an analytical solution is derived and used for studying the effect of off-neutral axis loading (point force excitation applied off the neutral axis of a rib) on ribbed-plate responses. Effects of off-neutral axis loading on ribbed-plate responses, in terms of input power and kinetic energy distribution in the component plates, are found to be significant except at frequencies where the beam flexural impedance is small (near the natural frequencies of the uncoupled beam). The negative input power component due to the point force or moment excitation is observed and explained in this analysis. Energy flow from the beam to the plates is dominated by the shear force coupling at the beam/plate interface if the force excitation is applied on the neutral axis of the beam. As the point force excitation location shifts away from the neutral axis, the beam is excited by a force and a moment. These dual excitations involve both shear force and moment couplings at the interface. Thus, changes in the energy flow into the component plates are dependent on the relative phase between the individual induced responses by the point force and moment excitations. This paper also discusses changes in the kinetic energy of the component plates due to changes in the energy flow.