• Analytical Science and Technology
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• v.8 no.2
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• pp.195-203
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• 1995

Carbon and small amounts of alloying elements were added in Fe-5.7% Al ferromagnetic damping alloy. The specific damping capacities(SDC) of these alloys were investigated in relation to the grain size and the magnetic hysteresis loops. The behavior of carbon was analysed by XRD and EDS. These alloys showed characteristic damping nature of ferromagnetic damping materials. The alloying elements decreased SDC and especially the carbon was remarkable. The SDC was observed to be not related with the grain size but with the magnetic hysteresis loop area. The remarkable decrease of SDC by carbon addition was attributed to the locking migration of $90^{\circ}$ magnetic domain wall by the interstitial carbon in Fe-Al solid solution. However, the carbides also seems to decrease the SDC.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.10a
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• pp.249-257
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• 1998

Vibration-resistant rubbers, whose elastic and shear behaviors are similar to viscoelastic materials, are used to make bracing dampers to reduce the building vibration. Experimental study is carried out to find the vibration characteristics of the dampers installed in the building model. The natural frequencies and modal damping ratios are obtained from the free vibration test and Fourier analysis. Shaking table test is performed to find the response behavior of the building model under earthquake loading. The present experimental study shows that the bracing dampers have the behavior of viscoelastic dampers, which increase the modal damping ratios and viscoelastic characteristics.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.10a
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• pp.367-374
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• 1999

this paper focuses on the dynamic characteristics of full-scale viscoelastic dampers through the experimental study. Viscoelastic dampers which dissipate the response energy of a building under earthquake excitation make a role of increasing damping capacity of the building. Therefore it is important to recognize the damping behavior of viscoelastic dampers. Full-scale viscoelastic dampers are made of three types of rubbers for experimental test. The hysteretic behavior is obtained through the load-deformation experiment over the various loading frequencies and damper strains The experimental results show the good performance of viscoelastic dampers under earthquake excitations,

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.784-787
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• 2003

Electrorheological(ER) and magnetorheological(MR) fluid-based dampers are typically analyzed using Bingham-plastic shear model under quasi-steady fully developed flow conditions. A Herschel-Bulkley constitutive shear flow relationship is that the linear shear stress vs. strain rate behavior of Bingham model is replaced by a shear stress that is assumed to be proportional to a power law of shear rate. This power is called the flow behavior index. Depending on the value of the flow behavior index number, varying degrees of post-yield shear thickening or thinning behavior can be analyzed. But it is not practical to analyze the damping force in a flow mode damper using Herschel-Bulkley model because it is needed to solve a polynomial equation. A useful guide is suggested to analyze the damping force in a damper using the Herschel-Bulkley model.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.1
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• pp.189-197
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• 2001

This paper presents hysteresis models of damping forces of a magneto-rheological (MR) damper which is applicable to a middle-sized passenger vehicle. After manufacturing a cylindrical type of the MR damper, its field-dependant damping force and hysteresis behavior are experimentally evaluated. Three different models ; Bingham model, Bouc-Wen model and Polynomial model are provided to predict the hysteretic damping force. The damping force characteristics predicted from three different models are compared with the measured results under various excitation conditions.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.751-756
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• 2000

The dynamic characteristics such as natural frequency, mode shape and damping ratio are most important parameters in the high-speed railway bridges rather than general roadway bridges. Also, the need to know the dynamic behavior of bridges greatly increased in recent years. In the early of 1990s, to design the high-speed railway bridges, damping ratio recommended in general code was 2.5~7.5%. However, these values were not applied in all cases. Therefore, obtaining the damping value of specific structures is important to get the correct variable for design of high-speed railway bridges. The purpose of this study is mainly to obtain the damping ratio of high-speed railway bridges. The average damping ratio of high-speed railway bridges evaluated from a field test is about 2.4%.

• Journal of Power Electronics
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• v.9 no.2
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• pp.308-319
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• 2009

An increasing number of power electronic applications require high power density. Therefore, the switching frequency and switching speed have to be raised considerably. However, the very fast switching transients induce a strong voltage and current ringing. In this work, a novel damping concept is introduced where the parasitic wiring inductances are advantageously magnetically coupled with a damping layer for attenuating these unwanted oscillations. The proposed damping layer can be implemented using standard materials and printed circuit board manufacturing processes. The system behavior is analyzed in detail and design guidelines for a damping layer with optimized RC termination network are given. The effectiveness of the introduced layer is determined by layout parasitics which are calculated by application of the Partial Element Equivalent Circuit (PEEC) simulation method. Finally, simulations and measurements on a laboratory prototype demonstrate the good performance of the proposed damping approach.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.345-348
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• 2004

In this paper it is to establish a comprehensive model for predicting damping in sandwich Laminated composites on the basis of strain energy method. In this model, the effect of transverse shear on the material damping has been considered with in-plane stresses. Results showed that the viscoelastic core thickness in the sandwich beam and the Length of a beam have a high impact on the material damping. The transverse shear appears to be highly influenced by the damping behavior in $0^0$ laminated sandwiched composites. However, it is Little influenced by that in $90^0$ laminated sandwiched composites.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.3
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• pp.1-6
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• 2008

The performance of shock absorber is directly related to the car behavior and performance, both for handling and comfort. Most of compact car are assembled the passive shock absorber for cost effect but some of compact driver want better performance of shock absorber than standard parts. Therefore, they want the semi-active suspension control system instead of standard damper system. But they only can change the mechanical damping control shock absorber at A/S market. The mechanical damping control shack absorber can not vary the damping force in driving condition so they do not satisfy the mechanical damping control shock absorber system. In this study, electrically damping force controlled shock absorber system is developed based on the mechanical damping force control damper system. This system can vary damping force by switch on dashboard in driving condition. And, this system can satisfy the requirement of tuning market. Therefore, it is expected the system to show the engineering capability of korean damper company and to increase export market share to oversea damper market.

• Polymer(Korea)
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• v.31 no.4
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• pp.289-296
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• 2007

The material factors influencing the sound absorption of the polyurethane foam were investigated with FT-IR, small-angle X-ray scattering (SAXS), and dynamic mechanical thermal analyzer (DMTA). The measurements were performed using the samples which had a similar cell structure but different absorption coefficients. It was found that the ability of the sound absorption of the polyurethane foams was closely related to the damping behavior over the transition range. In order to confirm the use of the low monol polyol (LMP) in high-performance applications, the polyurethanes based on LMP and polypropylene oxide polyol (PPG) were prepared by the solution polymerization method. The microstructure and the physical properties of these polyurethanes were compared. The PPG-based polyurethane showed a higher level of the phase-separated structure because the considerable amount of monol presented in PPG made a contribution to the increased chain mobility. However the short chains formed due to the monol species deteriorated the damping property. As a result, the LMP-based polyurethane showed the superior damping behavior as compared with the PPG-based one.