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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.
깊이 측정이 가능한 마이크로 압입 시험기 개발 및 성능평가
정진성,김호경 한국트라이볼로지학회 2009 한국윤활학회지(윤활학회지) Vol.25 No.3
We developed a compact micro indentation testing device (designated SNUT) which is capable to measure Young’s modulus of a sample using depth and applied load data during indentation. Performance of this device was evaluated using pure Ti, pure Ni, and die steel (SKD11). As a result of analysing the indentation test data, the frame compliance Cf was found to influence mainly the modulus by 80% among several factors affecting accuracy of Young’s modulus. Project area, which was determined by indirect indentation method, was modified using direct SEM observation. Finally, Young’s modulus error was reduced to 5% after taking into consideration the frame compliance and modified projected area from 80% error without any these two correction factors. The performance of SNUT and MTS instruments was compared using same specimen (pure Ti).
Manufacture of microscale random pattern using indentation machining technology
Je-Ryung Lee,Seung Hwan Moon,Tae-Jin Je,Doo-Sun Choi,Hwi Kim,Eun-chae Jeon 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.7 No.6
The display industries recently demand new microscale dot-type patterns for thinner and brighter displays with high energy efficiency, which are randomly distributed with irregular separation distances and have uniform optical characteristics. We developed a new program to generate the coordinates of the controlled microscale random patterns considering their diameter and the distance to the nearest pattern for preventing overlap of each pattern. Then the microscale random patterns were machined on a metal mold using the indentation machining which is a simple and low-cost machining method. We decreased the total machining time by the optimization of machining order of the random patterns. The coordinates, the diameter and the fi ll-factor of the machined patterns by the indentation machining were much consistent to the designed values. The controlled microscale random patterns had uniform optical characteristics over all areas of the manufactured optical fi lm. Moreover, if optical films have the same diameters and fi ll-factor, they showed the same optical characteristics even they have totally different coordinates of random microscale patterns. This technology is expected to reduce the number of the optical films and the light sources in the display, which can save much energies.
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.
솔레노이드 전압변화에 따른 사각뿔 구조체의 크기변화 경향 분석에 관한 연구
문승환,정지영,한준세,최두선,최성대,전은채,제태진 한국금형공학회 2019 한국금형공학회지 Vol.13 No.4
The light diffusion component spreads the light from one point evenly over a large area. Various types of light diffusion parts such as films and lenses are applied in the high-tech industries such as LCD display devices, lighting devices, and solar energy generation. Among these, a diffuser sheet (Diffuser Sheet) has a function to uniformly distribute the light, and various studies have been conducted to improve its function. The shape of the conventional light diffusion pattern is mainly made of a dot or hemispherical shape. In this study, a rectangular cone-shaped structure having a light diffusion function and an advantage of controlling the angle of refraction of light was fabricated by using a solenoid indentation process. The change in shape of the indentation structure was analyzed.