FREE WAVE-PROPAGATION IN PERIODICALLY RING-STIFFENED CYLINDRICAL-SHELLS

The free wave propagation characteristics of several periodically ring stiffened cylindrical shells have been investigated using a previously developed finite element based methodology. Results indicate that predicted stop bands that are associated primarily with shell flexure can be classified into three types. The most important stop band type for structurally efficient cylinders is one in which the structural half-wavelength (or integer multiples there of) approaches the stiffener spacing. For the cylinders investigated, these stop bands are broadband and can be easily tuned to a particular frequency band. Cylinder designs utilizing double curvature are shown to have significantly more coupling between flexural and longitudinal wave modes. This conclusion is reinforced by results from an analytical investigation of a curved beam. An axisymmetric formulation for the prediction of propagation constants is also identified.