• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.7
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• pp.261-266
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• 2001

The flexural vibration of laminated composite beams with active and passive constrained layer damping has been investigated to design a structure with maximum possible damping capacity. The equations of motion are derived fro flexural vibrations of symmetrical,. multi-layer laminated beams. The damping ratio and model damping of the first bending mode are calculated by means of iterative complex eigensolution method. The direct negative velocity feedback control is used for the active constrained layer damping. It is shown that the flexible laminated beam is more effective in the vibration control for both active and passive constrained layer damping. and this paper addresses a design strategy of laminated composite under flexural vibrations with constrained layer damping.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.1072-1076
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• 2004

In automotive industry, all passenger vehicles are treated with damping materials to reduce structure borne noise. The effectiveness of damping treatments depends upon design parameters such as choice of damping materials. locations and size of the treatment. Generally, the CAE method uses modal strain-energy information of the bare structural panels to identify flexible regions, which in turn facilitates optimization of damping treatments with respect to location and size. This paper proposes a design of the damping material with a CAE(Computer Aided Engineering) methodology based on finite element analysis and DOE(Design Of Experiments) to optimize damping treatments.

• Journal of the Korean Society for Heat Treatment
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• v.4 no.4
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• pp.15-23
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• 1991

The damping capacities of the nonthermoelastic bcc type lath martensite and of the nonthermoelastic hcp type thin plate martensite in Fe-Mn alloys were studied. Fe-17%Mn alloy showing the hcp type thin plate martensite was superior to Fe-4%Mn alloy having the bcc type lath martensite in damping capacity. The damping capacity of the Fe-17%Mn alloy became greater with increasing the hcp martensite volume fraction. The damping mechanism of the Fe-4%Mn alloy was well explained by the dislocation model. However, the damping mechanism of the Fe-17%Mn alloy was explained on the basis of austenite/martensite interface moving model. The two alloys showed almost same levels of tensile strength. However, the elongation was greater in the Fe-17%Mn alloy than in the Fe-4%Mn alloy, showing lower yield strength in the former than in the latter. This result was considered to be attributed to formation of stress-induced martensite during tension test.

• Journal of Power System Engineering
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• v.16 no.4
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• pp.60-65
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• 2012

This study was carried out to investigate the effect of reverse transformation on the damping capacity in high manganese austenitic stainless steel. ${\alpha}^{\prime}$-martensite was formed with the specific direction and surface relief by deformation. Over 95% of the austenite phase was transformed to deformation-induced ${\alpha}^{\prime}$-martensite by 70% cold rolling. Reverse transformation became rapid above an annealing temperature of $550^{\circ}C$, but there was no significant transformation above $700^{\circ}C$. In addition, with increasing annealing time at $700^{\circ}C$, reverse transformation was induced rapidly, but the transformation was almost completed at 10 min. Damping capacity was increased up to $700^{\circ}C$, and than unchanged with the increasing annealing temperature. Damping capacity increased steeply with an increasing reverse treatment time up to 10min, whereas there were no significant change with a treatment time of more than 10 min. Damping capacity increased with an increasing the reversed austenite and was strongly affected by reversed austenite.

• Journal of the Korean Society for Heat Treatment
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• v.9 no.1
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• pp.53-61
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• 1996

Effects of carbon and Ti on damping capacity are investigated in an Fe-17%Mn alloy. The suppressive force of carbon against ${\gamma}{\rightarrow}{\varepsilon}$ transformation increases linearly with an increase in its content, lowering Ms temperature and volume fraction of ${\varepsilon}$ martensite. Carbon deteriorates damping capacity by reducing the interfacial area of damping sources and mobility of the boundaries contributing to anelastic deformation. The reduction in damping capacity is accelerated when carbon-containing alloy is aged at higher temperatures above room temperature. The effect of Ti on damping capacity is found to be benificial in carbon-containing alloy, which is attributed to the depletion of carbon solute due to the formation of TiC.

• Journal of the Korean Society for Heat Treatment
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• v.27 no.6
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• pp.295-301
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• 2014

In this study, the relationship between strength and damping capacity of annealed magnesium alloys after hot rolling was investigated. The microstructure of hot rolled magnesium consisted of dendrite structure and $Mg_{17}Al_{12}$ compounds precipitated along the grain boundary. The dendrite structure was dissipated, $Mg_{17}Al_{12}$ compounds was decomposed by annealing, and then its dissolved in ${\alpha}$-Mg. With an increasing the annealing temperature and time, strength was slowly decreased and damping capacity was slowly increased by the growth of grain size and decreasing of defects induced by hot rolling. In annealing treatmented magnesium alloys after hot rolling, damping capacity was decreased rapidly with an increase of strength. There was on proportional relationship between tensile strength, and damping capacity.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.362.1-362
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• 2002

Eigenvalues are taken as performance criteria for structural damping design using viscoelastic material. Given material properties, optimal distribution of damping material is sought based on eigenvalue sensitivity. For eigenanalysis of frequency dependent viscoelastic material rented structures, Golla-Hughes-McTavish(GHM) model is used and some dominant modes are chosen for consideration. (omitted)

• Journal of Power System Engineering
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• v.22 no.1
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• pp.87-93
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• 2018

Specimens were machined out from hot-rolled AZ31 magnesium alloy, and deformed at 623K with rolling reduction of 30%. After hot rolling, specimens were annealed at various range of temperature and time. In this study, static recrystallization was occurred during heat treatment, however, variation of main component and intensity of texture was not revealed. The results of microstructure observation, damping capacity test and dislocation mechanism indicated that increasing of damping capacity was caused by grain growth. It means that grain size is effective factor to damping capacity.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.6
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• pp.31-37
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• 2005

This paper presents an experimental study on vibration characteristics of an automotive roof with damping material. The goal of the study is to extract modal parameters(natural frequency, loss factor, and mode shape) of automotive roof with damping materials treatment. To determine the effective positions and thickness of the damping material on a roof, vibration tests have been carried out for six cases; an aluminum plate with damping material on maximum strain energy positions, and an aluminum plate with damping material on nodal lines. From the result of aluminum plate, it is found that the damping material should be placed on the location with maximum strain energy part. For the automotive roof, patches of constrained damping material, which has two different density, have been attached to the positions of the maximum strain energy with four kinds of thicknesses. This paper shows that the proper positioning of the damping material is very important and the effective thickness is about twice that of the roof panel.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.5
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• pp.138-146
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• 2002

The new type of vibration reduction material far an automotive interior, which is spray-type liquid material, is developed in this study The new material has better damping property and lower mass density than other damping materials, for example asphalt sheet. It can be sprayed by an automatic robot, so it is expected to improve productivity and cut down manpower. And it solves a poor adhesion problem and makes an automotive to be lightweight by optimizing spray process. So, It is a next generation automotive vibration reduction material. In this paper, the chemical process for making the new damping materials is described. And then, the damping properties of the vibration reduction materials are analyzed by modal testing of damping treatment specimens. The new vibration reduction materials have good damping properties than asphalt sheet in the experimental results.