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유중학,정현석 한국정밀공학회 2015 한국정밀공학회지 Vol.32 No.12
In this paper, it is analyzed the characteristics of plastic lens dimensional deviation according to injection mold clamping force. The influences of fill time, mold clamping force, injection pressure, shear rate, etc., are examined. It was found that mold clamping forces which increased 100, 200, 300, 400, 500 kN can affect the thickness deviation of the lens. Dimensional deviation of the lens derived by injection molding was found to be 2.9% at 100 kN and 0.7% at 500 kN, the smallest observed deviation throughout the study. This indicates that mold clamping force and dimensional deviation of lens thickness were inversely proportional to each other. A prediction of filling time was 1.87 sec performed by injection molding analysis, however, filling time was observed at 1.72 sec in the actual experiment, which is 8.0% shorter than expected. This can be attributed to packing pressure.
폴리프로필렌의 사출성형조건이 성형품의 선형수축률과 중량에 미치는 영향
유중학,김희송 대한기계학회 1995 대한기계학회논문집 Vol.19 No.2
Series of experimental work was performed to mold tensile specimens by using the injection molding machine Mold temperature, melt temperature and packing time were chosen as processing parameters for studying the effects of those conditions on the linear shrinkage of final product. Here, each processing variable was decided from the numerical simulation and resin manufacturer's suggested value. The effects of molding conditions on the linear shrinkage in flow direction of the resin were analyzed by measuring the parts 2, 10, 30 and 60 days after molding. As a result, the linear shrinkage increased with the higher mold and melt temperature, and the change of mold temperature has shown more influence. The linear shrinkage of polypropylene has been found to progress up to 30 day with the lapse of the time, and the amount of the linear shrinkage has shown to be between 2.14% and 2.75%. In addition, the effects of packing pressure on the weight has shown to be extremely significant up to freezing time, and proper packing time of the tensile specimen has been found to be 2.0 seconds.
TiAIN 코팅 평 엔드밀의 성능평가에 관한 기초 연구
유중학,국정한,김문기 한국공작기계학회 2001 한국생산제조학회지 Vol.10 No.5
The purpose of this study is an evaluation of flat end mills to develop appropriate tools for the high speed machining. First of all, several flat end mills which are produced by different markers are selected to analyze the performances of the tools. Experimental works are also executed to measure cutting force, tool wear and surface roughness for different cutting conditions. And then the results are compared and analyzed for developing optimal cutting tool in the high speed condition.
최만성,유중학 한국기술교육대학교 1994 論文集 Vol.1 No.1
The mechanism of the cutting process in drilling with twist drill is not well-Known yet because a drill with a complex geometry of two cutting lips is used and it causes the dynamical interaction with some parts of machine. Chip forms in drilling are affected by three factors being flow angle, side and up curl of the chip. This paper describes the relation between the chip forms and cutting conditions. Drilling tests are carried out for SM45C by using the conventioanl HSS drills. The torque and thrust forces are measured for different drill diameter and compared with those chip forms. It is found that the feedrate and drill diameter are more affected than cutting speed on the chip form and cutting forces.
임경화,유중학,이우영,장헌탁 한국공작기계학회 2004 한국공작기계학회 춘계학술대회논문집 Vol.2004 No.-
Performance Evaluation of end mills for high speed cutting has been performed in a view of dynamic characteristics and noise-vibration under operation. The tools tested in this research consist of three foreign country made and one korean made. In addition, numerical models using finite element method are established, which are confirmed by experimental results. The evaluation results has been feedback for developing high performance end mills for high speed cutting tools.
장헌탁,유중학,이우영,임경화 한국공작기계학회 2003 한국공작기계학회 춘계학술대회논문집 Vol.2003 No.-
Performance Evaluation of end mills for high speed cutting has been performed in a view of dynamic characteristics and noise-vibration under operation. The tools tested in this research consist of three foreign country made and one korean made. In addition, numerical models using finite element method are established, which are confirmed by experimental results. The evaluation results has been feedback for developing high performance end mills for high speed cutting tools.