Papers by Author: Young Min Lee

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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.
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Authors: Sung Keun Cho, Jung Hun Choi, Young Min Lee, Chang Sung Seok
Abstract: In this study, we performed thermal stress analyses on a ventilated disk brake with a 3D model for two cases (whether the pressure distribution on a contact surface is uniform or not). A pressure distribution analysis was performed to determine the pressure distribution on the contact surface. Then, by using the results that were obtained from the pressure distribution analyses, we performed thermal stress analyses. Finally, we have found the spots where the maximum thermal stresses occur. Also, for the life evaluation of a disk brake, we have conducted the fatigue test and obtained the S-N curve. From those results, we evaluated the life of a disk brake.
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