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김병민(Kim, Byung-Min),김현기(Kim, Hyun-Gi),권순열(Kwon, Soon-Yeol),유능수(Yoo, Neung-Soo),백인수(Paek, In-Su) 강원대학교 산업기술연구소 2015 産業技術硏究 Vol.35 No.1
Two extreme wind speed prediction models, the EWM(Extreme wind speed model) in IEC61400-1 and the Gumbel method were compared in this study. The two models were used to predict extreme wind speeds of six different sites in Korea and the results were compared with long term wind data. The NCAR reanalysis data were used for inputs to two models. Various periods of input wind data were tried from 1 year to 50 years and the results were compared with the 50 year maximum wind speed of NCAR wind data. It was found that the EWM model underpredicted the extreme wind speed more than 5 % for two sites. Predictions from Gumbel method overpredicted the extreme wind speed or underpredicted it less than 5 % for all cases when the period of the input data is longer than 10 years. The period of the input wind data less than 3 years resulted in large prediction errors for Gumbel method. Predictions from the EWM model were not, however, much affected by the period of the input wind data.
금속 휴대폰 프론트 케이스 프레스성형공정에서 뒤틀림 방지를 위한 블랭크 형상설계
이인규(In-Kyu Lee),이찬주(Chan-Joo Lee),김병민(Byung-Min Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.5
This study presents a method to prevent from twisting of metal front case for mobile phone in the press forming process using a thin sheet metal. The twisting profile is evaluated by using FE analysis. And the blank shape is redesigned to increase the structural rigidity by means of making connectors. Redesigned blank reduces twisting of metal front case within tolerance in FE analysis. To verify the validity of proposed blank shape, forming experiment is performed and twisting profile is measured by 3D laser scanning method. Its dimensional accuracy is existed in tolerance and has a good agreement with FE analysis.
격자형 금형의 냉각효과를 고려한 구형 LNG 탱크용 대형 알루미늄 후판의 열간성형해석
이정민(Jung Min Lee),이인규(In Kyu Lee),김대순(Dae Soon Kim),권일근(Il Keun Kwon),이선봉(Seon Bong Lee),김병민(Byung Min Kim) Korean Society for Precision Engineering 2012 한국정밀공학회지 Vol.29 No.11
A hot forming of large thick Al plate using a grid-type hybrid die is a process to make a shell plate for the production of a spherical LNG tank. This process is characterized by using a grid-typed die with an additional air cooling system for reducing the cooling time of the heated plate after hot forming. The process consists of the plate’s feeding, heating, forming and cooling in detail and each of them is continuously performed along the rail. This paper was designed to propose the analytical and experimental methods for determining the convection and interfacial heat transfer coefficients required in hot forming analysis of Al plate. These values in the analysis are to reproduce numerically the cooling performance of grid-typed die and cooling device. Interfacial heat transfer was obtained from the heat transfer experiments for different pressures and inverse analysis method. To verify the efficiency of the coefficient values obtained from above methods, FE analysis and experiment of the hot spherical-forming process were conducted for a smallscaled model. The convection coefficient was also calculated from flow analysis of air released by cooling device within grid-typed die using ANSYS-CFX.
6단 압연롤 크라운을 고려한 동극박 냉간 압연 패스스케줄 설계
이상호(Sang Ho Lee),옥순영(Soon Young Ok),황인엽(In Youb Hwang),황원제(Won Jea Hwang),김병민(Byung Min Kim) Korean Society for Precision Engineering 2008 한국정밀공학회지 Vol.25 No.11
During the plate and foil cold rolling process, considerable values of the force of material pressure on the tool occur. These pressures cause the elastic deformation of the roll, thus changing the shape of the deformation region. Rolled copper foils should be characterized by a good quality and tight dimensional tolerances. Because of automation that is commonly implemented in flat product rolling mills, these products should meet the requirements of tightened tolerances, particularly strip thickness, and feature the greatest possible flatness. The shape of the roll gap is influenced by the elastic deformation of rolls parts of the rolling process affected by the pressure force. However, to control roll deformation should be difficult. Because the foil thickness is very thin and the permissible deviations in the thickness of foil are small. In this paper, FE-simulation of roll deformation in thin foil cold rolling process is presented.
고대철(Dae-Cheol Ko),이인수(In-Soo Lee),김병민(Byung-Min Kim),안병환(Byung-Hwan Ahn) Korean Society for Precision Engineering 2006 한국정밀공학회지 Vol.23 No.9
The lead frame manufactured by stamping process plays an important role in connecting semiconductor to PCB board. As a result of the miniaturization of semiconductor, its corresponding lead frame punch has been narrow. In case of the punch with high slenderness ratio such as lead frame punch, the punch can be broken suddenly due to buckling. To prevent the fracture of lead frame punch, some manufacturers have experientially attached stiffeners to weak parts of punch. The purpose of this study, therefore, is to suggest the guideline for design of stiffened punch. The optimal position and the number of stiffeners to be attached to punch are investigated by elastic buckling analysis. The elastic buckling analysis consists of the eigenvalue buckling analysis and nonlinear buckling analysis. The critical buckling load of elastic buckling analysis is compared with that of buckling test. Finally, the guideline for attaching stiffeners is suggested through analysis of cross section of lead frame punch such as moment of inertia and eccentricity.
崔載燦,金炳玟,金炳玟 부산대학교 공과대학 1991 工大論文集 Vol.42 No.-
This study is concerned with limit analysis of metal forming problems by finite element method. New algorithm of the limit analysis is formulated by minimizing the upper bound functional in plane strain and axisymmetric forming problems with work-hardening materials, and the finite element program is developed for the drawing and extrusion. Limit loads, velocity and flow line fields are directly obtained under various process conditions and the deformation characteristics such as grid distortion, strains, strain rates and stresses are computed from the optimum velocity components by numerical calculation. Experiments are carried out for strip drawing with the aluminum alloys and for axisymmetric extrusion with the carbon steel. For the varification of this algorithm, the computations are compared with the experiments. The good agreement between theoretical and experimental results is shown that the proposed algorithm and developed programming can be effectively applied to the numerical analysis of metal forming problems.
崔載燦,金炳玟,崔仁根 부산대학교 공과대학 1991 工大論文集 Vol.42 No.-
At hot working temperature range, it is known that the flow stresses of nearly all metals are very much strain rate dependent. In this paper, the strain rate effects are considered in the formulation and rigid-viscoplastic finite element program is developed for axisymmetric extrusion. The influence of ram speed, temperature and friction on the flow characteristics and forming pressure are investigated. The experiments are carried out for isothermal hot extrusion with hard aluminum alloy specimens(Al7075). The theoretically predicted forming pressure showed reasonably good agreement with the experimental values.