• Title/Summary/Keyword: structural materials

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Structural Performance Enhancement of Seismic Retrofitted Column Using New Reinforcing Materials (신보강재로 보수 보강한 기둥의 구조 성능 개선)

  • Oh, Chang-Hak;Han, Sang-Whan;Lee, Li-Hyung
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.5 no.2
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    • pp.121-128
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    • 2001
  • Reinforced concrete frame buildings in regions of low to moderate seismicity are typically designed only for gravity loads with non-seismic detailing provisions of the code. These buildings possess strong beam-weak column, which brings about the brittle structural performance like the column sidesway failure mechanism during the strong lateral load. The objective of this paper is to enhance the column strength and deformation capacity for reconfiguring the structural failure mode by averting a column soft-story collapse and moving to a more ductile beam-sides way mechanism suing new reinforcing materials. Aramid fiber sheet and reinforcing rod-composite materials was used for this purpose. The column was modeled by the 2/3 scale experimental specimen retested. According to the concept of the capacity design, the damaged column was strengthened by the column jacketing using new reinfocing materials such as rod-composite materials. In conclusion, the improvement of the flexural strength is observed and the capacity of the energy dissipation and the ductility is enhanced, too.

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Characteristics of Friction Behavior of Ceramic Friction Materials according to Surface Materials

  • Ji-Hun Park;Jung-Woo Lee;Jong-Won Kwark;Woo-Jin Han;Oneil Han
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.11 no.4
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    • pp.535-541
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    • 2023
  • Friction material, an integral constituent of bearing supports, facilitates frictional interactions between two components. Polytetrafluoroethylene (PTFE), a commonly employed friction material in bearing supports, has assessed resultant friction equilibrium. Nonetheless, protracted utilization diminishes frictional performance as the lubricating agent is progressively depleted. Friction materials can affect the entire structural system. Hence, this study applied ceramic material as a friction material due to its high strength, low friction, and low deformation. The frictional behavior was investigated using a cyclic friction test, considering various friction materials as the primary design variables and examining their covariance in cyclic frictional movements. The results substantiated that the ceramic friction material yielded a low variance and friction coefficients in cyclic frictional movements.

Energy Absorption Capability of Amorphous Alloys During Homogeneous Deformation (균일변형시 비정질 합금의 에너지 흡수력 평가)

  • Park, Kyoung-Won;Lee, Chang-Myeon;Lee, Hong-Gi;Lee, Jae-Hoon;Lee, Jae-Chul
    • Korean Journal of Metals and Materials
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    • v.46 no.9
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    • pp.572-576
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    • 2008
  • Elastostatic compression tests were carried out on amorphous alloys to evaluate their energy absorption capability during homogeneous deformation at room temperature. Experiments demonstrated that a compressive stress below the global yield imposed on amorphous alloys for extended periods causes homogeneous plastic strain associated with the irreversible structural disordering. During the disordering process, free volume was created, dissipating the externally applied strain energy and the rate of creation was found to converge to a saturated value. We evaluated the capability of energy absorption of amorphous alloys during homogeneous deformation using recent theories on the evolution of the structural state.

Shear Flow Analysis of Aircraft Composite Wing Structure (항공기 복합재 날개구조 전단흐름 해석)

  • Choi Ik-Hyeon;Kim Seong-Chan;Kim Seong-Jun
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2004.04a
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    • pp.75-78
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    • 2004
  • Traditionally aluminum alloy have been used in manufacturing of aircraft structures, and semi-monocoque structural concept have been mainly applied in structural design of fuselage and wing. However, recently monocoque structural concept is applied in many small-size aircraft structures manufactured with composite materials. In such case appling monocoque structural concept, in initial conceptual design stage on wing, it is not easy to analyze shear flow using classical shear flow analytical method because composite skin structure can support span-wise tension/compression stress as well as sectional shear stress. In this study, an extended shear-flow analytical method to apply to composite monocoque structural concept was developed through extending the classical shear-flow analytical method.

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Thermal Emissivity of Nuclear Graphite as a Function of its Oxidation Degree (3): Structural Study using Scanning Electron Microscope and X-Ray Diffraction

  • Seo, Seung-Kuk;Roh, Jae-Seung;Kim, Suk-Hwan;Chi, Se-Hwan;Kim, Eung-Seon
    • Carbon letters
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    • v.12 no.1
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    • pp.8-15
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    • 2011
  • We study the relationships between the thermal emissivity of nuclear graphites (IG-110, PCEA, IG-430 and NBG-18) and their surface structural change by oxidation using scanning electron microscope and X-ray diffraction (XRD). The nonoxidized (0% weight loss) specimen had the surface covered with glassy materials and the 5% and 10% oxidized specimens, however, showed high roughness of the surface without glassy materials. During oxidation the binder materials were oxidized first and then graphitic filler particles were subsequently oxidized. The 002 interlayer spacings of the non-oxidized and the oxidized specimens were about $3.38{\sim}3.39{\AA}$. There was a slight change in crystallite size after oxidation compared to the nonoxidized specimens. It was difficult to find a relationship between the thermal emissivity and the structural parameters obtained from the XRD analysis.

Effect of the Compositional Modulation on the Plasticity of Amorphous Alloys: Shear Localization Viewpoint Interpretation (비정질 합금의 조성분리가 소성에 미치는 영향: 변형국부화 관점에서의 해석)

  • Lee, Mi-Rim;Park, Kyoung-Won;Sa, Hyun-Je;Lee, Jae-Chul
    • Korean Journal of Metals and Materials
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    • v.47 no.11
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    • pp.687-693
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    • 2009
  • Experiments have demonstrated that a moderate amount of Be added to $Zr_{57.5}Cu_{38.3}Al_{4.2}$ amorphous alloy enhances the plasticity of the alloy. In particular, $Zr_{54}Cu_{36}Al_{4}Be_{6}$ alloy exhibited 19% of strain to fracture along with a strength exceeding 2 GPa. Energy dispersive x-ray spectroscopy conducted on the $Zr_{54}Cu_{36}Al_{4}Be_{6}$ alloy exhibited the presence of compositional modulation, indicating that nm-scale phase separation had occurred at local regions. In this study, the role played by the nm-scale phase separation on the plasticity was investigated in terms of structural disordering, structural softening and shear localization in order to better understand the structural origin of the enhanced plasticity shown by the developed alloy.

Review of seismic vibration control using 'smart materials'

  • Valliappan, S.;Qi, K.
    • Structural Engineering and Mechanics
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    • v.11 no.6
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    • pp.617-636
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    • 2001
  • For the potential application of smart materials to seismic structural control, this paper reviews seismic control techniques for civil engineering structures, and developments of smart materials for vibration and noise control. Analytical and finite element methods adopted for the design of distributed sensors/actuators using piezoelectric materials are discussed. Investigation of optimum position of sensors/actuators and damping are also outlined.

Structural test of KSLV-I Payload fairing (KSLV-I 페이로드 페어링 구조시험)

  • Lee, Jong-Woong;Kong, Cheol-Won;Eun, Se-Won;Nam, Gi-Won;Jang, Young-Soon;Shim, Jae-Yeul;Lee, Young-Shin
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.41 no.11
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    • pp.900-907
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    • 2013
  • Payload fairing(PLF) protects satellites and related equipment from the external environment. They are separated before the satellite separation. Payload fairing made of composite sandwich materials due to their considerable bending stiffness and strength-to-weight ratio. Payload fairing have compression, shear and bending load during the flight. In this study, To check the strength of PLF and connected part, structural test of PLF accomplished using an actuator and a fixture. Purpose of structural test is to verify the strength of PLF in force of separation spring and combination structural load applied. Test result shows that the PLF have an acceptable margin of safety for the combination structural load and force of separation spring.

Thermal and structural analysis of a cryogenic conduction cooling system for a HTS NMR magnet

  • In, Sehwan;Hong, Yong-Ju;Yeom, Hankil;Ko, Junseok;Kim, Hyobong;Park, Seong-Je
    • Progress in Superconductivity and Cryogenics
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    • v.18 no.1
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    • pp.59-63
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    • 2016
  • The superconducting NMR magnets have used cryogen such as liquid helium for their cooling. The conduction cooling method using cryocoolers, however, makes the cryogenic cooling system for NMR magnets more compact and user-friendly than the cryogen cooling method. This paper describes the thermal and structural analysis of a cryogenic conduction cooling system for a 400 MHz HTS NMR magnet, focusing on the magnet assembly. The highly thermo-conductive cooling plates between HTS double pancake coils are used to transfer the heat generated in coils, namely Joule heating at lap splice joints, to thermal link blocks and finally the cryocooler. The conduction cooling structure of the HTS magnet assembly preliminarily designed is verified by thermal and structural analysis. The orthotropic thermal properties of the HTS coil, thermal contact resistance and radiation heat load are considered in the thermal analysis. The thermal analysis confirms the uniform temperature distribution for the present thermal design of the NMR magnet within 0.2 K. The mechanical stress and the displacement by the electromagnetic force and the thermal contraction are checked to verify structural stability. The structural analysis indicates that the mechanical stress on each component of the magnet is less than its material yield strength and the displacement is acceptable in comparison with the magnet dimension.