Experimental Study of Vibration Damping in a Modified Elastic Wedge of Power-Law Profile

Abstract

The objective of this research is to evaluate and propose a modified elastic wedge as passive damping system for structural damping. An elastic wedge is a plate whose thickness decreases smoothly toward zero. It has been proposed as an effective passive damping system to reduce structural vibration, especially in the high frequency range. Several authors have researched elastic wedge theory and showed that if the thickness of a plate decreases toward zero following a power law function, the flexural waves traveling in that plate do not suffer reflection along their path. That energy accumulates at the zero thickness edge, which results in a very efficient damping. In practice, manufacturing a zero thickness edge is not possible and a large amount of the wave energy is reflected at the thinner edge. However, when a small quantity of damping material is added on that edge, a very effective damping can be achieved. The damping effectiveness of the elastic wedge increases proportionally to the thinness of the edge for a given quantity of the added damping material. However, manufacturing of an elastic wedge with a very thin edge is economically costly since high precision machining is required. This presents a problem for practical implementation into the manufacturing line. In this paper, a modified elastic wedge is proposed to facilitate manufacturing and to reduce cost so that practical implementation is possible. In the proposed modified elastic wedge, the thin edge has a thickness achievable with conventional tools. Then, to increase its damping effectiveness, the thin edge is extended for some length with constant thickness. Finally, damping material is added on the extended part. Experimental and finite element method (FEM) frequency response analyses were carried out with a modified elastic wedge. The results show that the proposed modified elastic wedge can also achieve very effective vibration damping, especially in the high frequency range, while being manufactured with conventional tools. This method is currently under evaluation for noise reduction in structures of large dimensions, like platelike components of ship structures, or other machinery to reduce vibration and noise emission, and where cost and manufacturing accuracy limit the application of the conventional elastic wedge.