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겉보기 응력 개념에 기반한 공구각에 따른 비절삭저항 변화 분석
전은채(Eun-chae Jeon),최환진(Hwan-Jin Choi),이규민(Kyu-Min Lee),이윤희(Yun-Hee Lee),제태진(Tae-Jin Je),김정환(Jeong-Hwan Kim),최두선(Doo-Sun Choi) 한국기계가공학회 2014 한국기계가공학회지 Vol.13 No.2
In the past, prism patterns have been linear triangular shapes with a 90° angle; however, new micro prism patterns having acute angles or obtuse angles have recently been the subject of demand in the display, lighting and photovoltaic industries. Micro-cutting experiments for micro-prism patterns having 60°, 90°, and 120° angles on an electroplated Ni mold were performed and it was found in this study that the specific cutting resistance increased with a decrease in the tool angles (prism pattern angles). The cause of this variation had been thought to be the increase of the ploughing force due to tip rounding and the friction force due to the edge effect. However, the depth of the cut was large enough that it was possible to neglect these effects. Therefore, this study introduced the concept of representative stress of indentation. The measured stress was varied according to the indentation depth eventhoughthetestedspecimenswereidentical ; the varied stress was termed the representative stress. According to indentation theory, the strain that the Ni mold experienced increased with a decrease in the tool angle. Based on the stress-strain relationship, higher strain means higher stress and higher specific cutting resistance. Therefore, the specific cutting resistance was higher at smaller tool angles that had higher strain and stress.
Analysis of Size Effect of Nano Scale Machining Based on Normal Stress and Indentation Theories
Eun-chae Jeon(전은채),Yun-Hee Lee(이윤희),Tae-Jin Je(제태진) 한국기계가공학회 2018 한국기계가공학회지 Vol.17 No.6
Recently nano meter size pattern (sub-micro scale) can be machined mechanically using a diamond tool. Many studies have found a ‘size effect’ which referred to a specific cutting energy increase with the decrease in the uncut chip thickness at micro scale machining. A new analysis method was suggested in order to observe ‘size effect’ in nano scale machining and to verify the cause of the ‘size effect’ in this study. The diamond tool was indented to a vertical depth of 1,000nm depth in order to simplify the stress state and the normal force was measured continuously. The tip rounding was measured quantitatively by AFM. Based on the measurements and theoretical analysis, it was verified that the main cause of the ‘size effect’ in nano scale machining is geometrically necessary dislocations, one of the intrinsic material characteristics. st before tool failure.
전은채(Eun-chae Jeon),차진호(Jin-Ho Cha),이재령(Je-Ryung Lee),최환진(Hwan-Jin Choi),김창의(Chang-Eui Kim),제태진(Tae-Jin Je),김휘(Hwi Kim),최두선(Doo-Sun Choi) 한국기계가공학회 2014 한국기계가공학회지 Vol.13 No.4
The specular hologram is one type of hologram, and it consists of many arcs. They are very easy to fabricate and can even be machined by hand had a compass. In this study, we designed two squares having different depths and consisting of many arcs, after which we machined the arcs using end-mill technology. The width of the machined arcs showed high repeatability. Moving tracks were observed on the bottom surface, and top burrs were noted. In spite of them, the phenomenon of the specular hologram was observed when an observer and a light source stood on the same side. The two squares seemed to have different depths when they were observed from the left and right directions. In this study, it was verified that a specular hologram can be manufactured by end-mill technology.
패턴 주변의 소성변형현상을 제거한 고품위 불연속패턴 가공기술 개발
전은채(Eun-chae Jeon),제태진(Tae-Jin Je),장성환(Sunghwan Chang) 한국기계가공학회 2010 한국기계가공학회지 Vol.9 No.6
Patterned optical components are widely used for optical products such as LCD and lighting. Since CCFL was used as a light source in the products, prism films having linear continuous optical patterns were widely used. However, LED which is a dot light source is popular recently, therefore, the optical products need new optical components having non-continuous optical patterns. Indentation machining method is a powerful method for machining of non-continuous pattern. When a copper mold and a brass mold were machined by this method, severe plastic deformation called pile-up was observed around the patterns. Since pile-up has negative relationship to ductility, this deformation can be eliminated by annealing treatment which makes the materials ductile. No plastic deformation occurred when machined after annealing at 600℃ and 575℃ for copper and brass, respectively. Finally, non-continuous optical patterns with high quality were machined on a copper mold and a brass mold successively.
압입하중-변위곡선 분석을 통한 폴리머 소재의 절삭표면상태 예측에 관한 연구
전은채(Eun-Chae Jeon),김재현(Jae-Hyun Kim),제태진(Tae-Jin Je) 한국기계가공학회 2011 한국기계가공학회지 Vol.10 No.4
UV imprinting process can manufacture high-functional optical components with low cost. If hard polymers can be used as transparent molds at this process, the cost will be much lower. However, there are limited researches to predict the machinability and the burr of hard polymers. Therefore, a new method to predict them by analyzing load-depth curves which can be obtained by the instrumented indentation test was developed in this study. The load-depth curve contains elastic deformation and plastic deformation simultaneously. The ratio of the plastic deformation over the sum of the two deformation is proportional to the ductility of materials which is one of the parameters of the machinability and the burr. The instrumented indentation tests were performed on the transparent molds of the hard polymers and the values of ratio were calculated. The machinability and the burr of three kinds of hard polymers were predicted by the ratio, and the prediction was in agreement with the experimental results from the machined surfaces of the three kinds of hard polymers.
전은채(Jeon Eun-chae),권동일(Kwon Dongil),박주승(Park Joo-Seung) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
Ithasbeenshownthatadvancedindentationtechniquecanevaluatetensilepropertiesfromtheload-depth<br/> curveswithoutopticalobservationbymanyresearches.Whentheexperimentsareperformed,itis,however,<br/> verydifficulttodeterminethevaluesofvariousexperimentalvariations.Theireffectsontheresultswere<br/> seldomstudied.Amongthevariations,themaximumdepthratio,theindenterradius,thenumberofunloads<br/> andtheunloadingratioareveryimportant.UsingTaguchimethod,whichisoneoftheDOE(designof<br/> experiment),westudiedtheireffectsquantitatively.Theload-depthcurveswereanalyzedbythemethod<br/> toderivetensileproperties.Todeterminetheoptimumvaluesofthevariations,theSN(signal-to-noise)values<br/> werecalculated.ForeachparameterthevaluewhoseSNvalueismaximumisdeterminedastheoptimum<br/> one.Thetensilepropertiesfromtheload-depthcurveswiththeoptimumvaluesshowedbetterconsistency<br/> thanoneswithothervalues.
단결정 다이아몬드공구를 사용한 Cu 도금된 몰드의 미세 구조체 가공특성
김창의,전은채,제태진,강명창,Kim, Chang-Eui,Jeon, Eun-chae,Je, Tae-Jin,Kang, Myung Chang 한국분말야금학회 2015 한국분말재료학회지 (KPMI) Vol.22 No.3
The optical film for light luminance improvement of BLU that is used in LCD/LED and retro-reflective film is used as luminous sign consist of square and triangular pyramid structure pattern based on V-shape micro prism pattern. In this study, we analyzed machining characteristics of Cu-plated flat mold by shaping with diamond tool. First, cutting conditions were optimizing as V-groove machining for the experiment of micro prism structure mold machining with prism pattern shape, cutting force and roughness. Second, the micro prism structure such as square and triangular pyramid pattern were machined by cross machining method with optimizing cutting conditions. Burr and chip shape were discussed with material properties and machining method.