• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.162-162
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• 2016

We present multifunctional indium tin oxide (ITO) thin films formed at room temperature by a normal sputtering system equipped with a plasma limiter which effectively blocks the bombardment of energetic negative oxygen ions (NOIs). The ITO thin film possesses not only low resistivity but also high gas diffusion barrier properties even though it is deposited on a plastic substrate at room temperature without post annealing. Argon neutrals incident to substrates in the sputtering have an optimal energy window from 20 to 30 eV under the condition of blocking energetic NOIs to form ITO nano-crystalline structure. The effect of blocking energetic NOIs and argon neutrals with optimal energy make the resistivity decrease to $3.61{\times}10-4{\Omega}cm$ and the water vapor transmission rate (WVTR) of 100 nm thick ITO film drop to $3.9{\times}10-3g/(m2day)$ under environmental conditions of 90% relative humidity and 50oC, which corresponds to a value of ~ 10-5 g/(m2day) at room temperature and air conditions. The multifunctional ITO thin films with low resistivity and low gas permeability will be highly valuable for plastic electronics applications.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.2
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• pp.1-6
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• 2011

PHE(Process Heat Exchanger) is a key component required to transfer heat energy of $950^{\circ}C$ generated in a VHTR(Very High Temperature Reactor) to the chemical reaction that yields a large quantity of hydrogen. Korea Atomic Energy Research Institute established a small-scale gas loop for the performance test of components, which are used in the VHTR, and they manufactured a PHE prototype made of Hastelloy-X to be tested in the small-scale gas loop. Results from the elastic structural analysis on the PHE prototype were reported in the previous article. In order to investigate the macroscopic structural characteristics and behavior of the PHE prototype under the test condition of the small-scale gas loop far more in detail, elastic-plastic high-temperature structural-analysis of the PHE prototype was carried out in this study.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.6 s.177
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• pp.1456-1469
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• 2000

Mechanical behaviors of uniaxially fiber-reinforced metal matrix composites under transverse loading conditions were studied at room and elevated temperatures. A mono-filament composite was selecte d as a representative analysis model with perfectly bonded fiber/matrix interface assumption. The elastic-plastic and visco-plastic models were investigated by both theoretical and numerical methods. The product of triaxiality factor and effective strain as well as stress components and strain energy was obtained as a function of location to estimate the failure sites in fiber-reinforced metal matrix composite. Results showed that fiber/ matrix interfacial debond plays a key role for local failure at the room temperature, while void creation and growth in addition to the interfacial debond are major concerns at the elevated temperature. It was also shown that there would be an optimal diameter of fiber for the strong fiber-reinforced metal matrix composite.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1690-1695
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• 2007

Lightweight metallic truss structures with open, periodic cell are currently being investigated because of their multi-functionality such as thermal management and load bearing. The Kagome truss PCM has been proved that it has higher resistance to plastic buckling, more plastic deformation energy and lower anisotropy than other truss PCMs. The subject of this paper is an examination of the failure mechanism of Wire woven Bulk Kagome(WBK). To address this issue, the out-of-plane compressive responses of the WBK has been measured and compared with theoretical and finite element (FE) predictions. For the experiment, 2 multi-layered WBK are fabricated and 3 specimens are prepared. For the theoretical analysis, the brazed joints of each wire in WBK are modeled as the pin-joint. Then, the peak stress of compressive behavior and elastic modulus are calculated based on the equilibrium equation and energy method. The mechanical structure with five by five cells on the plane are constructed is modeled using the commercial code, PATRAN 2005. and the analysis is achieved by the commercial FE code ABAQUS version 6.5 under the incremental theory of plasticity.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.3
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• pp.206-214
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• 2015

In this study, low-velocity impact damage (LVID) in glass fiber reinforced plastic (GFRP) was investigated using pulse thermography (PT) and lock-in thermography (LIT) techniques. The main objective of this study was to evaluate the detection performance of each technique for LVID in GFRP. Unidirectional and cross-ply GFRPs were prepared with four energy levels using a drop weight impact machine and they were inspected from the impact side, which may be common in actual service conditions. When the impacted side was used for both inspection and thermal loading, results showed that the suggested techniques were able to identify the LVID which is barely visible to the naked eye. However, they also include limitations that depend on the GFRP thickness at the location of the delamination produced by the lowest impact energy of five joule.

• Journal of Sensor Science and Technology
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• v.17 no.2
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• pp.100-105
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• 2008

The objectives of this study are to measure and to remove Cerenkov lights generated in a fiber-optic radiation sensor by a charge-coupled device. we have fabricated a fiber-optic radiation sensor which comprises an organic scintillator, a plastic optical fiber and a charge-coupled device. Charge-coupled device as a light measuring tool has many advantages which are easy in multi-dimensional measurements, high spatial resolution and relatively low cost.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.6 s.249
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• pp.653-661
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• 2006

Metallic sandwich plates with various inner cores have important new features with not only ultra-light material characteristics and load bearing function but also multifunctional characteristics. Because of production possibility on the large scale and a good geometric precision, sandwich plates with inner dimpled shell structure from a single material have advantages as compared with other solid sandwich plates. Inner dimpled shell structures can be fabricated with press or roll forming process, and then bonded with two face sheets by multi-point resistance welding or adhesive bonding. Elasto-plastic bending behavior of sandwich plates have been predicted analytically and measured. The measurements have shown that elastic perfectly plastic approximation can be conveniently employed with less than 10% error in elastic stiffness, collapse load, and energy absorption. The dominant collapse modes are face buckling and bonding failure after yielding. Sandwich plates with inner dimpled shell structure can absorb more energy than other types of sandwich plates during the bending behavior.

• Structural Engineering and Mechanics
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• v.44 no.1
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• pp.61-72
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• 2012

The paper is on contact analysis of a spherical ball with a deformable flat, considering the effect of tangent modulus on the contact parameters of a non-adhesive frictionless elastic-plastic contact. The contact analysis of this model has been carried out using analysis software Ansys and Abaqus. The contact parameters such as area of contact between two consecutive steps, volume of bulged material are evaluated from the formulated equations. The effect of the tangent modulus is considered for determining these parameters. The tangent modulus are accounted between 0.1E and 0.5E of materials E/Y value greater than 500 and less than 1750. Result shows that upto an optimal tangent modulus values the elastic core push up to the free surface in the flat. The simulation is also carried out in Abaqus and result provide evidence for the volume of bulged material in the contact region move up and flow into the free surface of the flat from the contact edge between the ball and flat. The strain energy of the whole model is varied between 20 to 40 percentage of the stipulated time for analysis.

• Steel and Composite Structures
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• v.37 no.5
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• pp.571-587
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• 2020

In this article the seismic demand and performance of two recent braced steel frames named steel moment frames with the elliptic bracing (ELBRFs) are assessed through a laboratory program and numerical analyses of FEM. Here, one of the specimens is without connecting bracket from the corner of the frame to the elliptic brace (ELBRF-E), while the other is with the connecting brackets (ELBRF-B). In both the elliptic braced moment resisting frames (ELBRFs), in addition to not having any opening space problem in the bracing systems when installed in the surrounding frames, they improve structure's behavior. The experimental test is run on ½ scale single-story single-bay ELBRF specimens under cyclic quasi-static loading and compared with X-bracing and SMRF systems in one story base model. This system is of appropriate stiffness and a high ductility, with an increased response modification factor. Moreover, its energy dissipation is high. In the ELBRF bracing systems, there exists a great interval between relative deformation at the yield point and maximum relative deformation after entering the plastic region. In other words, the distance from the first plastic hinge to the collapse of the structure is fairly large. The experimental outcomes here, are in good agreement with the theoretical predictions.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.2
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• pp.212-219
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• 2002

In the frontal collision of cars, front parts of cars such as engine rail and side members that are composed of hatted section tubes should absorb most of the collision energy far the passenger compartment not to be deformed. For these reasons the study on the collapse characteristics, maximum crushing load and energy absorption capacity of hatted section tubes are needed. In this study, top hatted section tubes and double hatted section tubes are investigated. The maximum crushing load of hatted section tubes is induced from plastic buckling stress of plates by considering that the hatted section tubes are composed of plates with each different boundary conditions and that its material has a strain hardening effect. On this concept maximum crushing load equations of hatted section tubes are derived and verified by experiments. from the results of experiment, the differences of collapse characteristics between top hatted section tube and double hatted section tube are analysed. And mean crushing loads of hatted section tubes from experiments are compared with other theory.