Vibration damping characteristics of laminated steel sheet
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I.
INTRODUCTION
LAMINATED steel sheets are widely used in the industrial world for noise reduction purposes. Examples include the applications in automotive body panels, tlj housings of appliances and business machines, and in the building industry. The basic structure of the laminate consists of a viscoelastic layer which is sandwiched between two steel sheets. The vibration damping is effective because the laminate can convert the mechanical vibrational energy due to vibration into thermal energy, thus reducing the noise. The damping mechanism for general laminated composite sheets can be found in the literature, t2-Tj Most of the studies consist of theoretical analyses. According to the model proposed by Ungar, t2] the damping of the laminated steel sheet used in this study is caused by a shear deformation. Useful data of laminated steel sheet for practical applications were published by steel companies. ts,9] In general, the damping of laminates is affected by the following parameters: (1) material parameters such as the stiffness of the steel sheet and the glass transition temperature of the polymer, (2) operating parameters such as frequency and temperature, and (3) design parameters such as the thickness of steel sheets and that of the constrained polymer, t~~ In this paper, results on the vi-
Y.S. CHEN, 2nd Lieutenant (Army Service), and T.J. HSU, Associate Professor, are with the Institute of Materials Science and Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan, Republic of China. S.I. CHEN, Associate Scientist, is with the New Materials Research & Development Department, China Steel Corporation, Kaohsiung, Taiwan, Republic of China. This paper is based on a presentation made in the symposium "Acoustic/Vibration Damping Materials" presented during the TMS Fall Meeting, Indianapolis, IN, October 1-5, 1989, under the auspices of the TMS Physical Metallurgy Committee. METALLURGICAL TRANSACTIONS A
bration damping efficiency of laminated steel sheet, both experimentally and theoretically, are reported. II.
EXPERIMENTAL
A. Materials The materials used in this study include two steel sheets with a single polymeric viscoelastic layer. The steel sheet was of SPCC grade from China Steel Corporation, and no surface treatment was applied. Two polymeric materials, a copolymer based on ethylene and acrylic acid (PEAA) and polyvinyl butyral (PVB) were used. The PEAA was purchased from Dow Chemical USA (PRIMACOR* 3440). The PVB was purchased from *PRIMACOR is a trademark of Dow Chemical USA, Midland, MI.
Eternal Chemical Company Taiwan (PVB B-08M).
B. Sample Preparation The basic structure of the laminated steel sheet is shown schematically in Figure 1. It consisted of a basic substrate layer, a viscoelastic layer, and a consWaining layer. Each steel sheet had a thickness of 0.5 mm, and the thickness of the viscoelastic layer varied from 0.05 to 0.35 mm. The lamination was done in a thermal press. The press temperature was controlled at 125 ~ for PEAA and 190 ~ for PVB, respectively. Varied press p
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