Papers by Author: Sung Ho Chang

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Authors: Jong Deok Kim, Heung Kyu Kim, Young Moo Heo, Sung Ho Chang
Abstract: In this paper, the effect of die chamfer shape on the die roll height was studied by fine blanking experiments for imaginary special automobile seat recliner gear. The three die inserts with different die chamfer shapes were machined, and fine blanking tool was manufactured. Using the fine blanking tool, three experiments were conducted on the 650 ton fine blanking press. Each die roll height was measured, analyzed and we found the tendency of die roll heights on imaginary special automobile seat recliner gear to increase with increasing die chamfer angle, with the horizontal distance of die chamfer being constant. This result can be used to minimize the die roll height of fine blanking gear parts when designing die chamfer of fine blanking tool.
3694
Authors: Jong Deok Kim, Heung Kyu Kim, Young Moo Heo, Sung Ho Chang
Abstract: In this paper, the relation between die roll height and die chamfer shape was studied by fine blanking experiments for imaginary special gear. The three die inserts with different die chamfer shapes were machined, and fine blanking tool was manufactured. Using the fine blanking tool, three experiments were conducted on the 650 ton fine blanking press. Each die roll height was measured, analyzed and we found the tendency of die roll heights on imaginary special gear to increase with increasing die chamfer angle, with the horizontal distance of die chamfer being constant. This result can be used to minimize the die roll height of fine blanking gear parts when designing die chamfer of fine blanking tool.
92
Authors: Sung Ho Chang, Young Moo Heo, G.H. Shin, Young Min Lee, Jeong Jin Kang, T.S. Jung
Abstract: Remarkable progress had been made in both technology and production of optical elements including aspheric lens. Especially, requirements for machining glass materials have been increasing in terms of limitation on using environment, flexibility of material selection and surface accuracy. In the past, precision optical glass lenses were produced through multiple processes such as grinding and polishing, but mass production of aspheric lenses requiring high accuracy and having complex profile was rather difficult. Against such a background, the high-precision optical GMP process was developed with an eye on mass production of precision optical glass pasts by molding press. This GMP process can produce with precision and good repeatability special form lenses such as for cameras, video cameras, aspheric lenses for laser pickup, f-θ lens for laser printer and prism, and fine glass parts including diffraction grating and V-grooved base. Generally, GMP process can be classified into batch and progressive type. In these types, because progressive type has many merits in that productivity is higher and repair/retouch of mold is easier than batch type, progressive GMP process is mainly used to produce aspheric glass lenses these days. In this paper, as a fundamental study to develop the multi-cavity mold for higher productivity of progressive GMP process used in fabrication of aspheric glass lens, compression tests for K-PBK40, which is the material of aspheric glass lens, were conducted at high temperature. As a result, flow characteristics of K-PBK40 were obtained for aspheric glass lens press simulation.
476
Authors: Hoon Cho, Jae Hong Ha, Byoung Soo Lee, Sung Ho Chang, Je Sik Shin
Abstract: Eco-friendly grain refinement of A3003 alloy was studied by addition of non-toxic Al-Ti alloy because of toxic-fluorine in Al-Ti-B alloys which used as a representative grain refiner for aluminum and its alloys. TiAl3 phase in Al-Ti alloy bring to decrease grain size of A3003 alloy. But, grain growth occurred with prolonged holding time due to the solution of Ti into aluminum matrix. In contrast, lasting grain refinement of A3003 alloy was occurred in graphite crucible. It can be mentioned that carbon comes from graphite crucible was combined with Ti solute in aluminum melt and then TiC acts as a heterogeneous nucleation for A3003 alloy.
89
Authors: Je Sik Shin, Sung Ho Chang
Abstract: In this study, it was aimed to investigate the effects of grain refining of 3003 core alloy on forming and brazing characteristics of 4343/3003/4343 aluminum clad sheet. Ti inoculation level was changed up to 0.1wt% by adding Al-10Ti master alloy into 3003 aluminum melt as grain refiner. The three-layer aluminum clad sheets of 0.7 mm thickness were fabricated by hot roll bonding process. The forming and brazing characteristics were evaluated by measuring FLD (forming limit diagram), bonding strength and sagging resistance.
457
Authors: Young Moo Heo, Sung Ho Chang, Kwang Ho Shin
Abstract: The purpose of present study was to increase productivity and to reduce the polution of dust for making of endmill by conventional method such as grinding process. The micro scale endmill manufactured by powder injection molding, the molding (green part) was debinded and sintered. After that decreasing the porosities of the parts sintered, HIP process was adapted. After HIP process the relative density was shown more than 99% of the tools sintered. Finally, the micro cutting experiment using manufactured tool by PIM and HIP were implemented for verifying the feasibility of the tool. The ware of zirconia micro tool was observed very small, but the concentricity is less than the conventional tool made by grinding process. This type of tool is adequate to use in rough milling.
131
Authors: Sung Ho Chang, Young Moo Heo
Abstract: The purpose of present study was to increase productivity and to promote the quality of the part in the forming system for hinge strap in automobile. So the roller-bending simulation was carried out to develop the forming system for the hinge strap. A square tube used in the roller-bending for the hinge strap was fabricated using process of the sheet forming and the welding. So study on the mechanical properties of the original metal sheet (SPCC 1.6t) and weld-line (including a HAZ) were performed before the roller-bending simulation. And the body forces of the roller (rigid body) in the roller-bending process simulation were calculated to make an accurate estimate the capacity of the oil pressure cylinder for a pressure device. Then the roller-bending process was divided into 5 steps for the simulation for validating the effect of the bending velocity on the springback. At the end, the shape after springback was estimated. The result was adopted in the design for the bending die.
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