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공구끝단반경이 고려된 2차원 금속절삭에 대한 열-점소성 유한요소해석
김국원,이우영,신효철,Kim, Kug-Weon,Lee, Woo-Young,Sin, Hyo-Chol 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.1
In this paper, thermo-viscoplastic finite element analysis of the effect of tool edge radius on cutting process are performed. The thermo-viscoplastic cutting model is capable of dealing with free chip geometry and chip-tool contact length. The coupling with thermal effects is also considered. Orthogonal cutting experiments are performed for 0.2% carbon steel with tools having 3 different edge radii and the tool forces are measured. The experimental results are discussed in comparison with the results of the FEM analysis. From the study, we confirm that this cutting model can well be applied to the cutting process considered the tool edge radius and that a major causes of the "size effect" is the tool edge radius. With numerical analysis, the effects of the tool edge radius on the stress distributions in workpiece, the temperature distributions in workpiece and tool, and the chip shape are investigated.estigated.
청년층 고용증진을 위한 직업능력개발 사례연구 : 청년취업아카데미사업의 성과지표 분석을 중심으로
김국원,강봉준,이우영,Kim, Kug Weon,Ghang, Bong-Jun,Lee, Woo-Young 한국실천공학교육학회 2013 실천공학교육논문지 Vol.5 No.2
청년취업아카데미 사업은 대학 졸업예정자 및 졸업생을 대상으로 산업계 주도의 맞춤형 취업역량향상 프로그램을 지원함으로써, 산업현장에 맞는 인재를 양성하고 청년실업의 구조적 수급불일치 해소를 목적으로 한다. 이 사업의 주요 특징 중의 하나는 기업맞춤식 교육에 있어서 M-to-M 모델을 적용하여 여러 기업에 공통적으로 적용될 수 있는 업종별 공통기술을 교육한다는 점이다. 청년 취업아카데미 사업의 운영기관은 사업시작 후 1년 6개월이 지난 시점에서의 최종 취업률에 의해 평가를 받으므로 중간평가의 의미를 가지는 운영기관 성과지표가 개발되어 사용되고 있다. 본 연구에서는 운영기관 성과지표의 타당성을 분석하였다. 성과지표와 성과평가 결과, 성과평가 결과와 최종 취업률 그리고 성과지표와 최종 취업률간의 상관관계를 분석하였다. Youth employment academy program focuses on resolving the job mismatch of youth unemployment through industry oriented human resource development for which company oriented capacity building program for graduate-to-be and graduate is supported. One of the major characteristics of this program is to use the M-to-M model with common skills for companies of same type of business. The operation organization in youth employment academy is supposed to be evaluated by the final employment rate after 1 year and 6 months since start of the program. So performance indicator for the operation organization was developed which means a kind of mid-term evaluation. In this research, the validity of the performance indicator is discussed. The correlations between the performance indicator and the performance evaluation, between the performance evaluation and the final employment rate, and between the performance indicator and the final employment rate are analyzed.
김국원(Kim Kug Weon),이기연(Lee, Ki-Yeon),김남웅(Kim, Nam-Woong) 한국산학기술학회 2014 한국산학기술학회논문지 Vol.15 No.4
나노 임프린트 리소그래피는 수십 나노미터에서 수십 마이크론에 이르는 패턴을 간단하고 저비용으로 대면적 기판에 제작할 수 있어 차세대 패터닝 기술로 주목 받고 있다.특히,발광소자,태양전지,디스플레이 등의 분야에서는 저반사 나노패 턴,광결정 패턴 등 기능성 패턴을 제작하고 이를 적용하는 연구가 활발히 진행 중에 있다.NIL공정을 통해 성공적으로 패턴을 전사시키기 위해서는 적절한 공정조건의 선택이 필요하다.이에 본 연구에서는 열 나노임프린트를 이용하여 모스아 이 패턴을 전사할 때,충전과정 및 잔류층 형성을 수치 해석하여 폴리머 레지스트의 점탄성 거동을 살펴 보았고,레지스트 초기 코팅 두께의 변화 및 가압력의 변화가 충전과정 및 잔류층에 미치는 영향을 조사하였다.해석결과 본 논문에서 고려된 PMMA의 경우,4MPa이상의 압력에서 100초 내로 충전공정이 완료되는 것으로 나타났다. Nanoimprint lithography (NIL) fabrication process is regarded as the main alternative to existing expensive photo-lithography in areas such as micro- and nano-electronics including optical components and sensors, as well as the solar cell and display device industries. Functional patterns, including anti-reflective moth-eye pattern, photonic crystal pattern, fabricated by NIL can improve the overall efficiency of such devices. To successfully imprint a nano-sized pattern, the process conditions such as temperature, pressure, and time should be appropriately selected. In this paper, a cavity-filling process of the moth-eye pattern during the thermal-NIL within the temperature range, where the polymer resist shows the viscoelastic behaviors with consideration of stress relaxation effect of the polymer, were investigated with three-dimensional finite element analysis. The effects of initial thickness of polymer resist and imprinting pressure on cavity-filling process has been discussed. From the analysis results it was found that the cavity filling can be completed within 100 s, under the pressure of more than 4 MPa.
김국원(Kug-Weon Kim),이우영(Woo-Young Lee),최성주(Sung-Joo Choi) 한국기계가공학회 2008 한국기계가공학회지 Vol.7 No.3
In order to design establish automation or optimization of the machining process, predictions of the forces in machining are often needed. In this paper, a theoretical model in face milling is presented based on Oxley's predictive machining theory, where the cutting forces are predicted from input data of fundamental work material properties, tool geometry and cutting conditions without any preliminary cutting experiment. A simulation system for the cutting forces in face milling is developed using the model. Milling experimental tests are conducted to verify the model and the predictive results are compared and discussed with the experimental results.
김국원(Kim Kug Weon),안태길(Ahn, Tae-Kil) 한국산학기술학회 2006 한국산학기술학회논문지 Vol.7 No.2
본 연구에서는 설계단계에서 소형 직류 모터의 동특성을 파악할 수 있는 유한요소 해석모텔을 개발하였다. 유한요소해석 결과의 검증을 위하여 충격실험을 실시하였으며 모터의 고유진통수와 모드형상을 추출하여 비교하였다. 개발된 유한요소 해석모델을 이용하여 모터의 형상변화가 동특성에 미치는 영향을 분석할 수 있었으며 이는 향후 고품위 저진동 직류모터를 개발하는 데 효과적으로 이용될 수 있다. In this paper, described is a research on the modal analysis of small DC motor by finite element method for the vibration reduction. An impact test is performed to obtain the natural frequencies and modal shapes of DC motor, which valuate the usefulness of the finite element analysis model. From the study, we show that this finite element analysis model can be applicable for designing a new motor with improvement in vibration characteristics. As an example, a shape modification of DC motor is performed and its vibration characteristics is discussed in comparison with those of original shape.
정면 밀링 가공에서의 비절삭 저항 모델링 및 절삭력 예측
김국원(Kug Weon Kim),주정훈(Jung Hoon Joo),이우영(Woo Young Lee),최성주(Sung Joo Choi) 한국생산제조학회 2008 한국생산제조학회지 Vol.17 No.5
In order to establish automation or optimization of the machining process, predictions of the forces in machining are often needed. A new model for forces in milling with the experimental model based on the specific cutting pressure and the Oxley’s predictive machining theory has been developed and is presented in this paper. The specific cutting pressure is calculated according to the definition of the 3 dimensional cutting forces suggested by Oxley and some preliminary milling experiments. Using the model, the average cutting forces and force variation against cutter rotation in milling can be predicted. Milling experimental tests are conducted to verify the model and the predictive results agree well with the experimental results.