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열응력 해석을 이용한 순차이송 GMP 방식용 유리 렌즈 금형의 열변형에 관한 연구
이영민(Y.M. Lee),장성호(S.H. Chang),허영무(Y.M. Heo),신광호(G.H. Shin),정태성(T.S. Jung),김동식(D.S. Kim) 한국생산제조학회 2007 한국생산제조시스템학회 학술발표대회 논문집 Vol.2007 No.10
Generally, a thermal deformation is generated in the structure used at high temperature and this thermal deformation causes trouble such as the strength decline or the breakage of the structure. Especially, in the case of the precision mold such as a press type glass lens mold, the thermal deformation of a mold affects in the quality of products. In the present study, to obtain the thermal deformation at forming step and calculate the modified height of a glass lens mold at a design step, thermal stress analysis was carried out for a glass lens mold.
이영민(Y. M. Lee),박재실(J. S. Park),석창성(C. S. Seok),이찬우(C. W. Lee),김재훈(J. H. Kim) 한국정밀공학회 2005 한국정밀공학회 학술발표대회 논문집 Vol.2005 No.10월
A brake disk and a pad are important parts that affect the braking stability of a railway vehicle. Especially, because a brake disk stops the vehicle using conversion of the kinetic energy to frictional energy, thermal fatigue cracks are generated by the cyclic thermal load, as frictional heat, on a frictional surface and these cracks cause the fracture of a brake disk. Therefore, many researches for the thermal stress must be performed to improve the efficiency of brake disk and ensure the braking stability. In this study, we performed the thermal stress analysis for a ventilated brake disk with 3-D analysis model. For that, we simplified the shape of a ventilated hole to minimize problems that could be occurred in analysis process . Thermal stress analysis was performed in case that pressure distributions on a frictional surface is constant and is not. To determine pressure distributions of irregular case, pressure distribution analysis for a frictional surface was carried out. Finally using the results that were obtained through pressure distribution analysis, we carried out thermal stress analysis of each case and investigated the results of thermal stress analysis.
RGB 레이저 가시화를 위한 축대칭 구면 f-θ 렌즈 설계 및 프로젝션응용
이영민(Y. M. Lee),최해운(H. W. Choi) 한국레이저가공학회 2011 한국레이저가공학회지 Vol.14 No.2
The design of a telecentric f-θ lens with a field of view (FOV) 30° and an effective focal length of 1000㎜ is presented. The optical stop is placed at the front plane and the design is based on a geometric ray tracing technique, and the designed system consists of a series of convex and concave lenses. The designed f-θ lens showed a considerable reduction in weight with a simplified structure and resulted in a good performance in the designated FOV. Detail analysis of rays is also presented. 653㎚ (red laser), 586㎚ (green laser), and 468㎚ (blue laser) were simulated as a light source and image illuminating source. The developed optical design requires 7 pieces of lenses made of SF1, N-FK56, N-LAK33, and BK7 glass materials. With optimal parametric design, the effective focal length was calculated to be 974.839㎜ which is very close to the initial design target. For the manufacturing purpose, the dimensions of lens curvature and thickness were truncated with error ranging 0.1% to 3.2%. As a result, the overall error was calculated to be 3.2% which can be still tolerable for display, laser material, and machining processing.
이영민(Y. M. Lee),최정훈(J. H. Choi),허용(Y Huh),박재실(J. S. Park),석창성(C. S. Seok),최경진(K. J. Choi) 한국철도학회 2004 한국철도학회 학술발표대회논문집 Vol.- No.-
In this study, we compared the strength of a material used in the A-type disk brake with that in the B-type. From tensile test results, it has been found that the strength of the B-type disk brake is higherthan that of the A-type. The microstructure observation and chemical analysis were conducted to determine the cause of the difference between the strength of A and B types of disk brake materials. From the experimental results, it has been confirmed that the difference in the strength between the two types of disk brake is due to the difference in the shape of graphite.