Papers by Author: Beom Suck Han

Abstract: The alpha-case formation mechanism was elucidated for the economic titanium casting. The α-case formation reaction between Ti and Al2O3 mold was examined in a plasma arc melting furnace. The reaction products were characterized by electron probe micro-analyzer and transmission electron microscopy. The α-case generation between Ti and Al2O3 mold was not able to be explained by the conventional α-case formation mechanism, which is known to be formed by the interstitials, especially oxygen dissolved from mold materials. However, from our experimental results and thermodynamic calculations and Calphad modeling (Thermo-calc®), it was confirmed that the α-case is formed not only by an interstitial element but also by substitutional metallic elements dissolved from mold materials. Our newly established α-case formation mechanism will surely lead to a variety of significant applications of the α-case controlled Ti casting.

Abstract: Recently the application of lever cam ass’y made of the high-functional polymer is increasing internationally to improve the productivity and weight reduction. But the application of injection molding of lever cam ass’y in our country is not reported yet because of the lack of the optimal selection technique of proper material and the optimal design of injection parameter. In order to solve the problem, the injection molding simulation is used. The modification of gate position and rib thickness was done and the parameters like injection time, injection temperature, packing pressure and cooling time were changed. As a result, the comparison between models was done and the optimal shape of lever cam ass’y was developed.

Abstract: Many researches of automotive companies have focused on reducing weight of vehicles in order to meet the needs for high fuel efficiency. Therefore, light metals such aluminum alloys have been applied on automotive body structures. Recently, roller hemming process has been introduced for hemming of aluminum automotive closing parts such as doors, roofs, and hoods. During Roller hemming, the flange of outer panels is bent and folded along the edge of inner panel by a roller attached robot. Since the stress caused by roller hemming can affect the quality of hemmed flanges, the research has focused on the stress analysis by simulation and experiment. Residual stress has been measured in the hemmed flanges and compared to the values of finite elemental analysis.