Loss factor of a beaded structure

Abstract

It is found that when beads are inserted into the interior of a pipelike structure, the damping of the beaded structure may substantially exceed that of the unbeaded structure. The beads are modeled by a ‘‘beaded fluid’’ characterized by a low density, a low sound speed, and a high loss factor. Statistical energy analysis (SEA) is developed to account for the presence of the beaded fluid within the structure. It is shown that in certain frequency regimes and certain choices of the parameters that characterize the beaded fluid, relative to those that characterize the structure, the loss factor of the beaded structure can be designed to significantly exceed that of the unbeaded structure. The mechanism for the increase lies in that the stored energy in the beaded fluid may, in the ‘‘steady state,’’ be made to substantially exceed that in the structure. The bulk of the stored energy is then decimated by the high damping capability that the beaded fluid enjoys. A selected number of computer experiments are cited to illustrate the potential effectiveness of this damping mechanism and the manner by which the parameters, that define the beads and the structure, control it.