• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.11 s.116
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• pp.1140-1148
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• 2006

In this paper, transmission loss of smart panel was investigated using piezoelectric shunt damping. Admittance of piezoelectric system was introduced to represent electro-mechanical coupling of smart panel and to predict the performance of shunt damping. Finite element method was used to obtain numerical admittance. In order to illuminate the effect of noise reduction in the shunt system, transmission loss of the smart panel was investigated. Two models were considered to show the relation between admittance and transmission loss of smart panel. It was observed that admittance of piezoelectric system could be used as a design index of smart panel.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.51-55
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• 2007

In this paper Statistical Energy Analysis has been considered to predict high frequency air borne interior noise. Dash panel Insulation is major part to reduce engine excitation noise. Transmission loss and absorption coefficient are considered to predict dash insulation performance. Transmission lose is derived from coupling loss factor and absorption coefficient is derived from internal damping loss factor. Material Biot properties were used to calculate each loss factors. Insulation geometry thickness distribution was hard to measure, so FeGate software was used to calculate thickness map from CAD drawing. Each predicted transmission losses between conventional insulation and light weight insulation were compared with SEA. Transmission loss measurement was performed to validate each prediction result, and it showed good correlation between prediction and measurement. Finally interior noise prediction was performed and result showed light weight insulation system can reduce 40% weight to keep similar performance with conventional insulation system, even though light weigh insulation system has lower sound transmission loss and higher absorption coefficient than conventional system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.1
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• pp.33-39
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• 2003

Interior parts of a vehicle are getting important to reduce interior noise. Therefore, prior analysis of cabin noise related with interior parts are necessary at first design stage. Recently, Statistical Energy Analysis(SEA) has been suggested as a possible way for high frequency range noise analysis of interior parts. The validity of noise analysis with SEA to interior parts has been preyed by comparing with experimental result, and the developed method with SEA has been applied in finding optimized interior parts package.

• Composites Research
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• v.16 no.5
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• pp.39-44
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• 2003

Embedding viscoelastic-damping materials into composites can greatly increase the damping properties of composite structures. Usually viscoelastic-damping materials behave isotropically so that their damping properties are the same in all directions. In these days, there is a desire to develop viscoelastic-damping materials that behave orthotropically so that damping properties vary with material orientation. These orthotropic damping materials can be made by embedding rows of thin wires within the viscoelastic materials. These wires add significant directional stiffness to the damping materials. where the stiffness variation with wire orientation follows classical lamination theory. In this paper, the loss factor of composite laminate was evaluated based on Ni and Adams' theory. To investigate the effect of directional damping material, the low-velociy impact response analysis was also performed. The present analysis results show that directional damping material has a great influence on vibration and damping characteristic of composite laminate.

• Composites Research
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• v.34 no.3
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• pp.192-198
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• 2021

Due to enormous market growing of electric vehicles without combustion engine, reducing unwanted BSR (buzz, squeak, and rattle) noise is highly demanded for vehicle quality and performance. Particularly, innerbelt weatherstrips which not only block wind noise, rain, and dust from outside, but also reduce noise and vibration of door glass and vehicle are required to exhibit high damping properties for improved BSR performance of the vehicle. Thermoplastic elastomers (TPEs), which can be recycled and have lighter weight than thermoset elastomers, are receiving much attention for weatherstrip material, but TPEs exhibit low material damping and compression set causing frictional noise and vibration between the door glass and the weatherstrip. In this study, high damping EPDM (ethylene-propylene-diene monomer)/PP (polypropylene) thermoplastic vulcanizates (TPV) were investigated by varying EPDM/PP ratio and ENB (ethylidene norbornene) fraction in EPDM. Viscoelastic properties of TPV materials were characterized by assuming that the material damping is directly related to the viscoelasticity. The optimum material damping factor (tanδ peak 0.611) was achieved with low PP ratio (14 wt%) and high ENB fraction (8.9 wt%), which was increased by 140% compared to the reference (tanδ 0.254). The improved damping is believed due to high fraction of flexible EPDM chains and higher interfacial slippage area of EPDM particles generated by increasing ENB fraction in EPDM. The stick-slip test was conducted to characterize frictional noise and vibration of the TPV weatherstrip. With improved TPV material damping, the acceleration peak of frictional vibration decreased by about 57.9%. This finding can not only improve BSR performance of electric vehicles by designing material damping of weatherstrips but also contribute to various structural applications such as urban air mobility or aircrafts, which require lightweight and high damping properties.

• Journal of Korea Foresty Energy
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• v.17 no.1
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• pp.47-55
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• 1998

In the search for broadband damping composites, it is desirable to have polymers with a broad and high loss region, covering the entire temperature and frequency range of interest. Interpenetrating polymer networks, IPN's, are materials composed of two or more crosslinked polymers intimately and irrevocably interwinded. The resulting distribution of microenviron-ments can result in a materials with a high mechanical loss broad end over that of either polymer component alone. In this study, several series of copolymer, crosslinked copolymer and copolymer/copolymer IPN's were synthesized for possible use as broadband damping materials. Then their dynamic tensile properties were measured and compared with the damping properties of sandwich composites. Dynamic mechanical analysis showed that the temperature of loss peak may be varied over a wide temperature range with formulation. The compatibility of IPN`s was depended on the compatibility of A and B polymers as well as crosslink density. The damping factor(tan ${\delta}_c$) of composites became greater when a polymer of approximate storage module(E`) range of 5X10$^7$ to 10$^9$ dyne/cm$^2$ and large tan ${\delta}$ at the same time was used. The damping properities of poly (2-EHA80-co-St20)/poly(2-EHA20-co-St80) IPN`s crosslinked with 3%-DEGDM were relatively better over a broad temperature range.