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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.

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.

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.

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.

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.

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