Flexural vibration damping in beams using acoustic black hole effect

Abstract

Acoustic black hole concept states that in a beam/plate, whose thickness decreases according to power-law (to zero), any incident flexural wave propagates in it without reflections, hence damping the flexural waves. However, since zero thickness is not possible in reality, hence making this concept not very practical, at least without any supplementary method of damping. Surface damping treatments are extensively used in damping out vibrations in structures. Constrained-layered damping treatment is a type of surface damping treatment, where the surface of the structure is treated with viscoelastic layer, and this is in turn covered with an elastic layer, to provide better damping. This follows sandwich beam theory, where materials with different properties are bonded to each other, hence forming a layered structure. Application of constrained layer damping treatment to vibrating structures is a method well known for damping. In the current research, an attempt is made to improve the modal damping properties of structure. The technique of adding patches of CLDT, or partially covered shear damping treatment over the surface of structure is proposed, hence economizing damping. The method is applied on beams of dimensions which are rather novel in the research area. The studies so far in the concept of ABH dealt with plate-like structures. The beams considered in the present thesis are rather thick and short. Also, the concept of ABH was studied majorly for free-free boundary condition up until now. Uniquely, in the research, cantilever boundary condition was taken up, which has much more applications in real-world, in comparison to free-free condition.