Vibration damping analysis for panels with beads including edges followed by acoustic black hole's function

Abstract

There exist important problems in strength or durability to adopt structures having conventional acoustic black holes to utilize as actual products like cars, trains and airplanes and so on. This is because the acoustic black hole includes extraordinary thin thickness in panels. For the acoustic black holes, specific power functions are used to decrease thickness sharply. In this study, we proposed structures including new acoustic black holes to have high damping, high rigidity and light weight. In these new propositions, height of bead decreases around its edge according to the black hole function. There are no regions in panels having extraordinary thin thickness, then this leads to apply real products. To investigate performances of the new acoustic black holes, numerical analysis are carried out to compute their damping effects using modal strain energy method with finite element method in consideration of coupling in damping. We set our target to reduce the structure borne sound in road noise for body panels in cars. New acoustic black holes called as twin edges type are proposed. In this new black holes, height of the bead diminishes around both their edges in panels. When the appropriate residual thickness is added around the edges and viscoelastic damping materials are laminated around the edges, we can obtain not only high damping but also high rigidity. Further, we show that higher damping can be obtained in the lower frequency range including the first eigenmode of panels when the edges around the acoustic black holes are constrained because the strain energy can be concentrated around the edges having the black holes.