• Analytical Science and Technology
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• v.9 no.3
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• pp.302-309
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• 1996

Fe-5.7%AI-1.1%Cr-0.5%Si damping alloys containing 0%C and 0.12%C were heat-treated at $800^{\circ}C$ for an hour and then cooled by using some different methods. The damping behaviors of these alloys were observed by optical microscopy, X-ray diffraction and a specific damping capacity(SDC) test. Effect of cooling method on microstructures and the internal stresses of these alloys were negligible while the damping capacity of these alloys was considerably deteriorated by water quenching. The (200) texture was mainly developed by water quenching while the (110) texture by furnace cooling. These results were interpreted by the magnetization behaviors of the ferromagnetic $\alpha$ ferrite. The easy axis of magnetization in <100> direction means that <100> axis has more $180^{\circ}$ magnetic domain walls than $90^{\circ}$ ones. Thus. $180^{\circ}$ magnetic domain walls were more formed by water quenching, which deteriorated the damping capacity of these alloys. Consequently, the amount of magnetic domain walls giving good damping capacity became less so that the damping capacity was poor in water quenching.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1019-1023
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• 2006

Conventional methods for reducing vibration in engineering designs may be undesirable in conditions where size or weight must be minimized, or where complex vibration spectra exist. Fe-Mn Damping alloy with a combination of high damping capacity and good mechanical properties can provide attractive technical and economical solutions to problems involving seismic, shock and vibration isolation. We have studied the noise and vibration characteristic of Dampalloy and checked Dampalloy reduced noise about 3.9dB and vibration about 15.9 times as compared conventional material through laboratory research. With this result, we obtained a good possibility of material substitution about the bridge expansion joint

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.04b
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• pp.108-113
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• 1993

The material for the machine tool structure should have high static stiffiness and damping in its property to improve both the static and dynamic performances. The static stiffness of a machine tool can be inceased by using either higher modulus material in the structure of a machine tool. However, the machine tool structrue with high stiffness but low damping is vulnerable to vibration at the resonance frequencies of the structure . For the high precision and highsped machine tool structure, therefore, the high damping capacity is most important in order to suppress vibration. The damping of a machine tool can not be increased by increasing the static stiffness. The best way to increase the damping capacity of the machine tool structure is to use a composite material which is composed of on material with high stiffness with low damping and another material with low stiffness with high damping. Therefore, in this paper, the bed of the ultra high precision grinding machine for mirror surface machining of brittle materials such as ceramics and composite materials was designed and manufactured with the epoxy concrete material. The epoxy concrete material was prepared by mixing epoxy resin with different size sands and gravels. The modulus, compressive strength, coefficient of thermal expansion, specific heat, and damping factor were measured by varying the compaction ratio, sizes and contents of the ingredients to assess the effect of the processing parameters on the mechanical properties of the material. Based of the measured properties, the prototype epoxy resin concrete bed for the mirror surface CNC grinding machine was designed and manufactured.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.189-196
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• 2001

Machine tools of high-speed and high-precision are required for various fields of industry such as semiconductor, automobile, mold fabrication and so on. Light-weight machine tool structure is essential for reduction of production time through rapid transportation. Also, high damping capacity of the structure is required to obtain precise products without vibration during manufacturing. Composite materials have high potential for machine tool structures due to its high specific stiffness and good damping characteristics. In this study, the design and the manufacture of a hybrid machine tool structure using composite materials was attempted and the damping capacity was investigated experimentally.

• Journal of KSNVE
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• v.2 no.4
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• pp.305-315
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• 1992

In order to investigate the effects of layer-wise in-plane displacements on vibration and damping characteristics of composite laminated plates, the finite element method based on the generalized laminated plate theory(GLPT) has been formulated. Specific damping capacity of each mode was obtained by modal strain energy method. To see the effect of transverse shear on deformation, the strain energy of stress components was computed. The accuracy of this study was examined for the cylindrical bending vibration of cross-ply plate strip. The results were very accurate compared with 3-D solutions. The numerical results show that through-thickness variation of in-plane displacements has not so much influence on the natural frequency, but has a great influence on the damping of composite plates, especially on the damping of thick composite plates since the damping is affected by local behavior while the natural frequency is affected by global behavior.

• Journal of the Korean Society for Heat Treatment
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• v.18 no.2
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• pp.99-104
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• 2005

In this study, the effects of C and Si on damping capacity and mechanical properties of as-cast and as-rolled Fe-17%Mn alloys were investigated as a basic study for the purpose of the commercialization of the alloy. The $M_s$ temperature of ${\gamma}{\rightarrow}{\varepsilon}$ martensitic transformation in Fe-17%Mn alloy was decreased with increasing C and Si contents, resulting in the less volume fraction of ${\varepsilon}$ martensite. The damping capacity was also decreased with increasing alloying content because of less ${\varepsilon}$ amount and the reduction in mobility of the damping sources such as the stacking fault boundaries and ${\gamma}/{\varepsilon}$ interfaces due to the pinning effect by alloying elements. The mechanical properties of as-rolled alloys were superior to those of as-cast alloys probably because of finer ${\gamma}$ grains, larger amount of ${\varepsilon}$ martensite, and chemical homogeneity.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1391-1407
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• 1990

In this paper, optimization procedures are presented considering the static and dynamic constraints for laminated composite plate and hybrid laminated composite plate subject to concentrated load on center of the plates. Design variables for this problem are ply angle or ply thickness. Deflection, natural frequency and specific damping capacity are considered as constraints. Using a recursive linear programming method, the nonlinear optimization problems are solved. By introducing the design scaling factor, the number of iterations is reduced significantly. Composite plates could be designed optimally combined with FEM analysis under various conditions. In the optimization procedure, verification for both analysis and design of the laminated composite plates are compared with the results of the others. Various design results are presented for the laminated composite plates and hybrid laminated composite plates.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.275-285
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• 2003

Pinching is an important property of reinforced concrete member which characterizes its cyclic behavior. In the present study, numerical studies were performed to investigate the characteristics and mechanisms of pinching behavior and the energy dissipation capacity of flexure-dominated reinforced concrete members. By analyzing existing experimental studies and numerical results, it was found that energy dissipation capacity of a member is directly related to energy dissipated by re-bars rather than concrete that is a brittle material, and that it is not related to magnitude of axial compressive force applied to the member. Therefore, for a member with specific arrangement and amount of re-bars, the energy dissipation capacity remains uniform regardless of the flexural strength that is changed by the magnitude of axial force applied. Due to the uniformness of energy dissipation capacity pinching appears in axial compression member. The flexural pinching that is not related to shear force becomes conspicuous as the flexural strength increases relatively to the uniform energy dissipation capacity. Based on the findings, a practical method for estimating energy dissipation capacity and damping modification factor was developed and verified with existing experiments.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.2 s.95
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• pp.161-168
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• 2005

The absorbing material is mostly used to changing the acoustic energy to the heat energy in the passive control, and that consists of the porous media. That controls an air borne noise while the stiffened plates, damping material and additional mass control a structure borne noise. The additional mass can decrease the sound by mass effect and shift of natural frequency, and damping material can decrease the sound by damping effect. The passive acoustic control using these kinds of control materials has an advantage that is possible to control the acoustic in the wide frequency band and the whole space at a price as compared with the active control using the various electronic circuit and actuator. But the space efficiency decreased and the control ability isn't up to the active control. So it is necessary to maximize the control ability in the specific frequency to raise the capacity of passive control minimizing the diminution of space efficiency such an active control. Therefore, the characteristics of control materials and the optimum layout of control materials that attached to the boundary of structure-acoustic coupled cavity were studied using sequential optimization on this study.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.831-836
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• 2000

During machining, since more than 50% compliance of the cutting point in machine tool structures comes from headstocks, with the remainder coming from beds, slides and structural joints, the structural analysis of the headstock is very important to improve the static and dynamic performances. Especially, in case of machining hard and brittle materials such as glasses and ceramics with the grinding machine, the reinforced headstock with the high damping material is demanded. Since the fiber reinforced composite materials have excellent properties for structures, owing to its high specific modulus, high damping and low thermal expansion, it is expected that the dynamic and thermal characteristics of the headstock will be improved if they are employed as the materials fur headstock. In this paper, the design and the manufacturing methods as well as the static and dynamic characteristics of a steel-composite hybrid headstock were investigated analytically and experimentally to improve the performance of the grinding machine system.