• Journal of the Korean Society for Heat Treatment
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• v.13 no.4
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• pp.231-238
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• 2000

Flake graphite cast irons with the high damping capacity have been used for the control of vibration and noise occurring in the members of various mechanical structures under vibrating conditions. However, the damping capacity which is morphological characteristics of graphite is one of the important factors in reducing the vibration and noise, but hardly any work has deal with this problem. Therefore, the authors have examined the damping capacity of various cast irons with alloying elements and studied the influences of the matrix structures, mechanical properties and morphological characteristics of graphite. The main results obtained are as follows: Effects of pouring temperature on the damping capacities and mechanical properties were investigated in 3.6%C cast iron. At $1400^{\circ}C$, specific damping capacity showed the maximum value, and decreased with increase pouring temperature. Mechanical properties showed opposite trend with the damping capacity. And then, effects of Ni on the damping capacities and mechanical properties have been investigated in 3.6%C gray cast iron. At 0.2%Ni content, specific damping capacity showed the maximum value, and decreased with further increase in Ni content. Graphite length also showed same behavior. This indicates that the specific damping capacity has a close relation with graphite length. In case of Mo addition in 3.6%C-0.2%Ni cast iron, specific damping capacity and tensile strength was 27% and $20kgf/mm^2$ at 3.6%C-0.2%Ni-0.3%Mo cast iron respectively.

• Journal of Adhesion and Interface
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• v.11 no.1
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• pp.3-8
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• 2010

Thermal properties, flame retardant property, and sound-damping properties of polyurethane (PU) nanocomposite foams prepared with oligomeric 1,2-propanediol isobutyl polyhedral silsesquioxane (POSS) were investigated. It was found that the PU nanocomposite foams showed good sound-damping performances comparing to the PU foams without POSS.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.464-467
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• 2002

This paper presents investigation of damping characteristics of squeeze mode type MR (magneto-Rheological) mount experimentally. Since damping property of the MR fluid is changed by variation of the applied magnetic field strength, squeeze mode type MR mount proposed in the study has variable damping characteristics according to the applied magnetic field strength. Impact and excitation tests were performed to investigate the dynamic properties of squeeze mode type MR mount. Responses of the mount were compared in proportion to the applied magnetic field strength. The experimental results show that the mount can effectively reduce vibration amplitude in a wide frequency range by changing the applied magnetic field strength.

• KIEE International Transactions on Power Engineering
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• v.4A no.3
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• pp.134-140
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• 2004

This paper presents an improved group of energy functions reflecting generator damping effects for multi-machine power systems by using Center of Inertia (COI) formulation as an extension of the previous work. Since rotor angles at the Stable Equilibrium Point (SEP) of post-fault systems are generally calculated in COI, system transient energy can be found without assumption of infinite or slack bus, which is a crucial drawback of the absolute rotor angle frame approach. The developed energy functions have a structure preserving property with which it is very flexible to incorporate various models of power system components, especially various load and generator models. The proposed damping-reflected energy functions are applied to the Potential Energy Boundary Surface (PEBS) method, one of the direct methods. Numerical simulation of WSCC 9-bus shows that conservativeness of the PEBS method can be considerably reduced.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.10a
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• pp.228-235
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• 1999

As a seismic damper the viscoelastic damper is known the effective method to control the drift of the flexible building. As the viscoelastic damper has the characteristics of both damping and stiffness specially when the rubber material used hysteretic damping. The behavior of the hysteretic damping is quite different from that of the viscous damping. For the evaluation of the viscoelastic damper for the seismic purpose the nonlinear response spectrum was generated based on the dynamic test of the viscoelastic damper and the results is compared to that of the typical linear response spectrum,

• Korean Journal of Materials Research
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• v.4 no.5
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• pp.502-509
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• 1994

New damping measurement equipment was designed using the dynamic strain gage and high speed analog to digital signal 12 bit converter and compared it with existing equipment. The damping properties of general material and high damping material were also studied by this machine. The SDC (specific damping capacity) was measured with various heat treatment condition, initial vibration amplitude and internal stress. The vibration amplitude of high damping material is decreased within nearly less than 0.4 second after applying the initial forced vibration. But that of general material is still vibrating at the same time. After furnace-cooling heat treatment, SDCmax of Fe-lGwt.%Cr system was more than 40% and that of Fe-5.5wt.%Al alloy was more than 30% after air-cooling heat treatment. Upon increasing of initial vibration amplitude, it is detected the migration of SDCmax into the region of small vibraton amplitude. Damping capacity is decreased rapidly as the internal stress Increases. Damping measurement equipment in the present study was ahln to give the more accurate results of damping properties in the small vibration amplitude region.

• Journal of the Korean Society for Heat Treatment
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• v.14 no.6
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• pp.330-335
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• 2001

Flake graphite cast irons with the high damping capacity have been used for the control of vibration and noise occurring in the members of various mechanical structures under vibrating conditions. However, the damping capacity which Is morphological characteristics of graphite is one of the important factors in reducing the vibration and noise, but hardly any work has deal with this problem. Therefore, the authors have examined the damping capacity of various cast irons with alloying elements and studied the influences of the matrix structures, mechanical properties and morphological characteristics of graphite. The main results obtained are as follows: Effects of Sb on the damping capacities and mechanical properties have been investigated in 3.6%C-0.2%Ni gray cast iron. At 0.02%Sb, specific damping capacity showed the maximum value, and decreased with further increase in Sb content. Mechanical properties showed opposite trend with the damping capacity. And then, effects of Ti on the damping capacities and mechanical properties have been investigated in 3.6%C-0.2%Ni-0.02%Sb gray cast iron. Specific damping capacity increased with increase in Ti content. Graphite length also showed same behavior. Tensile strength increased with Ti content due to refinement of pearlite. In the case of 0.14%Ti addition in 3.6%C-0.2%Ni-0.02%Sb cast iron, specific damping capacity and tensile strength was 36% and 25 $kgf/mm^2$ which are higher than 32% and 15 $kgf/mm^2$ at 3.6%C-0.2%Ni cast iron respectively.

• Elastomers and Composites
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• v.20 no.3
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• pp.189-204
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• 1985

The purpose of this study is to examine the dynamic properties, especially the damping and fatigue properites, of NR vulcanizates and to find out the vulcanizate which can be used as damping materials in industry. The results of this study can be summarized as follows: 1. In the ODR test, the S-2 vulcanizate was the fastest one in terms of having reached to optimum cure times($t_{90}$) and, with the same formula, when 50phr of HAF carbon black loaded, the shortest optimum cure times has shown. 2. The S - 2 vulcanizate was the best than the others in the physical properties. In aging properties, however, the E - 1 vulcanizate appeared to be better than the other vulcanizates. 3. The results of the RDS test for the NR vulcanization system under the condition of 0.1% strain amplitude and 1 Hz frequency showed no connection between Tg and the the nature of the crosslinking system, but 50phr loading of HAF carbon black increased Tg. The damping values of vulcanizates in the elastic region showed a strong relations the damping values and the crosslinking system. The S - 2 vulcanizate with higher crosslink density had lower damping values than other vulcanizates, and furthermore, the SH - 2 vulcanizates with 50phr loading of HAF carbon black increased the damping values. 4. The Goodrich Flexometer test showed that the heat buildup for the gum NR vulcanizates was less than for those which contained 50phr of HAF carbon black. In particular, the fatigue life of the vulcanizate with lower damping values appeared to be longer than that of the vulcanizates with higher damping values. In the fatigue test, the increasment of the loading or the temperature, applied to the vulcanizates, appeared to be shorten their fatigue life.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.7
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• pp.517-523
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• 2003

This paper presents response property of the squeeze mode type mount using Magneto-Rheological fluid (MR fluid) . The MR mount for the isolation of multi-directional vibrations was constructed in this study. Both the mechanism and shape of the mount are the same as squeeze film dampers for a rotor system. In the present work, the performance of the mount was experimentally Investigated according to the magnetic field strength. The experimental results present that the MR mount can effectively reduce the vibration in a wide range of frequency by controlling the applied electromagnetic filed strength. Viscous damping and stiffness coefficients of the MR mount tend to be changed according to the variation of the applied currents In this study.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.510-513
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• 2003

The paper represents the stability of a rotor system with the squeeze film damper (SFD) using an electromagnet. The electromagnet is installed in the inner damper of the SFD. The proposed SFD has basically property of a conventional SFD and variable damping property according to variation of the applied electric current. Therefore, when the applied current controlled, the whirling vibration of the rotor system can be effectively reduced in a wide operational speed range. In the present work, the performance of the SFD was experimentally investigated according to changing the magnetic field strength. When the applied current increased, the whirling amplitude greatly reduced and the damping ratio also increased.