Gyeongbuk Hybrid Technology Institute

South Korea

Gyeongbuk Hybrid Technology Institute

South Korea

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Lee H.-Y.,Keimyung University | Kim T.-J.,Keimyung University | Kim T.-J.,Gyeongbuk Hybrid Technology Institute | Cho Y.-J.,Keimyung University | Cho Y.-J.,Korea Institute of Industrial Technology
Metals and Materials International | Year: 2013

The application of ball-milling for reactant powders to improve the intermetallic coating reaction was examined. Ni-50 at.% Al powder compacts milled at three different ball-to-powder weight ratios in a planetary mill were analyzed by differential scanning calorimetry (DSC) and coated onto mild steel through the reaction synthesis in a hot press. The effects of ball-milling on the coating reaction in the hot press were compared with those in the reaction synthesis in DSC. The experimental results show that the particle size of the elemental powders was decreased by ball-milling, and that the coating reaction in the hot press was enhanced by ball-milling for the reactant powders, unlike the reaction synthesis in DSC. This improvement was attributed to the increase in the density of the reactant compact by the load applied during the reaction. © 2013 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht. © KIM and Springer.


Chung B.-M.,Yeungnam University | So B.-S.,Gyeongbuk Hybrid Technology Institute | Lee S.-H.,Gumchang Co.
International Journal of Precision Engineering and Manufacturing | Year: 2011

Today's world automobile market is highly competitive. Quality of automobile is considered even more important and thus efforts are being made to improve the quality of automobile parts in order to survive in such competitive market. Despite rapid development of inspection devices using the vision system, there are few inspection systems for automobile parts. The reason is because the inspection with only one camera is nearly impossible, since automobile parts are three-dimensional and large. The seat frame, one of the typical automobile parts, has various models and is assembled using more than 20 subparts. This paper suggests a flexible assembly inspection system of seat frame through the following procedures: first, the inspection method is standardized so that the system can cope with not only some currently existing models but also latent models in the future. Second, 6 cameras are used for inspecting seat frame assembly; 4 cameras are for measuring accuracy, and 2 for right and left-hand sides. Third, a simple pattern matching method is proposed for checking the position of assembly parts. Finally, slit beam method is proposed for checking the existence of assembly parts. Especially, it is very effective to inspect assembly of automobile parts with 3D shape and complex background image. © KSPE and Springer 2011.


Lee H.-Y.,Keimyung University | Cho Y.-J.,Korea Institute of Industrial Technology | Kim T.-J.,Keimyung University | Kim T.-J.,Gyeongbuk Hybrid Technology Institute | Bang H.-J.,Korea Institute of Industrial Technology
Journal of Korean Institute of Metals and Materials | Year: 2012

Bali-milled Ni-Al powder compacts have been synthesized by the heat of molten cast iron and have been coated on cast iron. The effects of the ball-milling time on the microstructure of the intermetallic coatings have been investigated. The experimental results showed that the ball-milled Ni-Al powder compacts were completely reacted and were successfully coated on the cast iron without re-melting the substrate. Densification of the coating layers was enhanced by increasing the ball-milling time. This might be attributed to the fact that the heat released during the intermetallic reaction was dispersed over a prolonged reaction time by the ball-milling of the elemental powders.


Mun J.H.,Gyeongbuk Hybrid Technology Institute | Jouini A.,CNRS Laboratory of Physical Chemistry of Luminescent Materials | Novoselov A.,Tohoku University | Yoshikawa A.,Tohoku University | Fukuda T.,Tohoku University
Journal of Ceramic Processing Research | Year: 2011

Refractory undoped and Tm3+-doped (0.15, 1, 3 and 5 mol.%) Y2O3 single crystals were grown by the micro-pulling-down method. Chemical analysis showed a homogeneous distribution of Tm3+ dopant along the crystal rod. The dependence of thermal conductivity on Tm3+ concentration in Tm3+: Y2O3 was characterized. The value decreases when the Tm3+ concentration increases in the host but still stays high enough (7.46 Wm-1K-1) when doped with Tm3+ (5 mol.%), which represents a promising material for an infrared eye-safe laser application.


Chang W.S.,Korea Institute of Machinery and Materials | Kim J.W.,Gyeongbuk Hybrid Technology Institute | Choi D.G.,Korea Institute of Machinery and Materials | Han C.S.,Gyeongbuk Hybrid Technology Institute
Applied Surface Science | Year: 2011

The synthesis of isolated carbon nanotubes with uniform outer diameters and ordered spacing over wafer-scale areas was investigated for fabrication of nano-electrode arrays on silicon wafers for field emission and sensor devices. Multi-walled carbon nanotubes (MWCNTs) were grown on TiN electrode layer with iron catalyst patterned by nano-imprint lithography (NIL), which allows the precise placement of individual CNTs on a substrate. The proposed techniques, including plasma-enhanced chemical vapor deposition (PECVD) and NIL, are simple, inexpensive, and reproducible methods for fabrication of nano-scale devices in large areas. The catalyst patterns were defined by an array of circles with 200 nm in diameter, and variable lengths of pitch. The nano-patterned master and Fe catalyst were observed with good pattern fidelity over a large area by atomic force microscope (AFM) and scanning electron microscopy (SEM). Nano-electrodes of MWCNTs had diameters ranging from 50 nm to 100 nm and lengths of about 300 nm. Field emission tests showed the reducing ignition voltage as the geometry of nanotube arrays was controlled by catalyst patterning. These results showed a wafer-scale approach to the control of the size, pitch, and position of nano-electrodes of nanotubes for various applications including electron field-emission sources, electrochemical probes, functionalized sensor elements, and so on. © 2010 Elsevier B.V. All rights reserved.


Park D.-H.,Gyeongbuk Hybrid Technology Institute | Kwon H.-H.,Daejin University
International Journal of Precision Engineering and Manufacturing | Year: 2015

According to current development trends for automotive parts, light-weight is a key issue in improving fuel efficiency and CO2 reduction. Compared to steel and aluminum, magnesium has a relatively low specific gravity. However, it is challenging to use magnesium to produce a product at room temperature because magnesium has a hexagonal close-packed crystal structure. Therefore, the structure is not suitable for plastic deformation without using a heating system. As a result, a magnesium alloy sheet and die need to be heated from 250 to 300ºC. This paper presents the development of warm forming technology for automotive dash panel using magnesium alloy sheet. © 2015, Korean Society for Precision Engineering and Springer-Verlag Berlin Heidelberg.


Park D.-H.,Gyeongbuk Hybrid Technology Institute | Kwon H.-H.,Daejin University
International Journal of Precision Engineering and Manufacturing - Green Technology | Year: 2016

Main advantages of cold forging are improvement of mechanical properties, excellent dimensional accuracy, and surface quality. Hot forging is a processing of plastic deformation for the metal at recrystallization temperature or higher. It is possible to decrease the flow stress and energy required to form the material at elevated temperature. Complex forging for combining cold forging and hot forging was applied in this study to ensure the shape accuracy of engine mounting parts. The complex forging technology of engine mounting parts would be very useful to improve dimension accuracy, reduce manufacturing cost, and increase die life. © 2016 Korean Society for Precision Engineering.


Park D.H.,Gyeongbuk Hybrid Technology Institute | Sreejith P.S.,UC College
World Academy of Science, Engineering and Technology | Year: 2010

Geometrical surface defects such as wrinkles, surface deflection and spring back are most serious problems in the press forming of high strength steel sheets into autobody outer panels. It is shown that surface deflection is classified into two types, plastic and elastic. Stretching is effective for the removal of surface deflection during the forming. Particularly, the effects which elastic recovery exerts on the mechanism and on the extent of the occurrence of surface deflection in actual panels are clarified.


Chang W.S.,Korea Institute of Machinery and Materials | Kim J.W.,Gyeongbuk Hybrid Technology Institute | Choi D.G.,Korea Institute of Machinery and Materials | Han C.S.,Gyeongbuk Hybrid Technology Institute
Thin Solid Films | Year: 2010

For this paper, the fabrication of nano-electrodes by the synthesis of multi-wall carbon nanotubes (MWCNTs) has been investigated. MWCNTs were grown on a TiN coated quartz plate with Fe catalysts patterned by UV nano-imprint lithography (NIL). The proposed study is the realization of a simple, inexpensive and reproducible method to produce nano-scale electrode arrays in large areas. The patterns were defined by an array of circles 200 nm in diameter, and 500 nm in pitch. The nano-patterned master and Fe catalyst are observed with good pattern fidelity over a large area by atomic force microscope (AFM) and scanning electron microscopy (SEM). Among various synthesis methods for carbon nanotube growth, plasma-enhanced chemical-vapor deposition (PECVD) was used for the growth of vertically aligned multi-wall carbon nanotube arrays. Ammonia (NH3) and acetylene (C2H2) were used as the etchant gases and the carbon source, respectively. The carbon nanotubes were vertically aligned in high density on a large area of the plain quartz substrates. High-resolution transmission electron microscopy analysis reveals that the synthesized CNTs are multi-walled with a bamboo-like structure. Patterned catalysts made it possible to allow the precise placement of individual CNT electrodes on the substrate. These electrodes have diameters ranging from 50 nm to 100 nm and lengths of about 300 nm. A field emission test using isolated CNTs on quartz plates showed the ability of CNTs as nano-electrodes. Bio-compatibility was also investigated by cell culturing on the fabricated CNTs/quartz template for potential bio-applications. © 2010 Elsevier B.V. All rights reserved.


Doh J.,Yonsei University | Lee S.U.,Gyeongbuk Hybrid Technology Institute | Lee J.,Yonsei University
Journal of Mechanical Science and Technology | Year: 2016

In this study, a Back-propagation neural network (BPN) is employed to conduct an approximation of a true stress-strain curve using the load-displacement experimental data of DP590, a high-strength material used in automobile bodies and chassis. The optimized interconnection weights are obtained with hidden layers and output layers of the BPN through intelligent learning and training of the experimental data; by using these weights, a mathematical model of the material’s behavior is suggested through this feed-forward neural network. Generally, the material properties from the tensile test cannot be acquired until the fracture regions, since it is difficult to measure the cross-section area of a specimen after diffusion necking. For this reason, the plastic properties of the true stress-strain are extrapolated using the weighted-average method after diffusion necking. The accuracies of BPN-based meta-models for predicting material properties are validated in terms of the Root mean square error (RMSE). By applying the approximate material properties, the reliable finite element solution can be obtained to realize the different shapes of the finite element models. Furthermore, the sensitivity analysis of the approximate meta-model is performed using the first-order approximate derivatives of the BPN and is compared with the results of the finite difference method. In addition, we predict the tension velocity’s effect on the material property through a first-order sensitivity analysis. © 2016, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.

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