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Research Papers

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

[+] Author and Article Information
J. Javier Bayod

 IHI Corporation, 1 Shinnakahara-cho, Yokohama 235-8501, Japanjavier_bayod@ihi.co.jp

J. Vib. Acoust 133(6), 061003 (Sep 09, 2011) (7 pages) doi:10.1115/1.4003591 History: Received May 11, 2010; Revised December 06, 2010; Published September 09, 2011; Online September 09, 2011

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.

Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Location of accelerometers and shaker on plates

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Figure 2

Location of accelerometers and shaker on elastic wedge

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Figure 3

Left: general test setting. Right: setting of shaker (rear view)

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Figure 4

Setting with six accelerometers and damping sheet strip (front view)

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Figure 5

Plate divided in small areas

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Figure 6

P1.6 plate results by channel. Top subplot: left side: accelerometers A, C, and E. Bottom subplot: right side: accelerometers B, D, and F.

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Figure 7

P4.5 plate results by channel. Top subplot: accelerometers A, C, and E. Bottom subplot: accelerometers B, D, and F.

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Figure 8

P1.6 plate results by channel. Top subplot: accelerometers A and B. Middle subplot: accelerometers C and D. Bottom subplot: accelerometers E and F.

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Figure 9

P4.5 plate results by channel. Top subplot: accelerometers A and B. Middle subplot: accelerometers C and D. Bottom subplot: accelerometers E and F.

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Figure 10

EW plate results by channel. Top subplot: accelerometers A, C, and D. Bottom subplot: accelerometers B, D, and F.

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Figure 11

EW plate results by channel. Top subplot: accelerometers A and B. Middle subplot: accelerometers C and D. Bottom subplot: accelerometers E and F.

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Figure 12

Comparison between PL-16 test 1 (no damping), tests 2–4 (vinyl tape), and test 5 (damping sheet)

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Figure 13

Comparison between PL-4.5 test 1 (no damping), tests 2–4 (vinyl tape), and test 5 (damping sheet)

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Figure 14

Comparison between EW test 1 (no damping), tests 2–4 (vinyl tape), and test 5 (damping sheet)

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Figure 15

Comparison between EW test 1 (no damping) and test 5 (damping sheet), P1.6 test 1 (no damping) and test 5 (damping sheet), and P4.5 test 1 (no damping) and test 5 (damping sheet)

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Figure 16

Comparison between EW test 1 (no damping) and test 5 (damping sheet), P1.6 test 1 (no damping) and test 5 (damping sheet), and P4.5 test 1 (no damping) and test 5 (damping sheet) in the low frequency ranges

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Figure 17

FE model of elastic wedge plate used in the experiments. Highlighted nodes: location of measurement points for average of response. Dark color area: part with variable thickness. Light color area: extended part with constant thickness.

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Figure 18

Modal damping data extracted from experiments (cases 1 and 5)

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Figure 19

Frequency response analysis. Comparison between experimental and FEM results for top, middle, and bottom areas. Case 1: no damping applied.

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Figure 20

Frequency response analysis. Comparison between experimental and FEM results for top, middle, and bottom areas. Case 5: damping sheet applied.

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Figure 21

Nondiffused elastic wedge response (acceleration contour plot) of FEM simulation at 2858 Hz

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