Vibration Attenuation in Plates with Periodic Annuli of Different Thickness

The ability of periodic structures to create stop-bands has shown great potential application in noise and vibration reduction. In mechanical and civil engineering, the studies on periodic structures typically deal with waveguides in Cartesian coordinates, while the effects of polar periodicity have been rarely analysed. However, the passive reduction of the vibrations generated from a localised excitation source on a large flexible structure can be obtained by exploiting radial periodicity effects. This paper investigates the vibration isolation properties of a plate made of a sequence of annuli with periodic alternating thickness. Two approaches are proposed and compared: the first implements a Wave Finite Element method to a small slice of the structure approximated by piecewise rectangular segments; the second deals with a standard FE model and the evaluation of the difference in the vibration before and after the insertion of n consequent periodic annuli in the finite uniform plate.