• 한국표면공학회지
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• 제44권4호
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• pp.165-171
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• 2011

In this work, handling of sapphire substrate for LED by using an electrostatic chuck was studied. The electrostatic chuck consisted of alumina dielectric, which was doped with 1.2 wt% $TiO_2$. As the volume resistivity of alumina dielectric was decreased, the electrostatic force was increased by Johnsen-Rahbek effect. The narrower width and gap size of electrode led to the stronger electrostatic force. When alumina dielectric with $3.20{\times}10^{11}{\Omega}{\cdot}cm$ resistivity and 3 mm width/1.5 mm gap sized electrode was used, the strongest electrostatic force in this work was obtained, which value reached to ~14.46 gf/$cm^2$ at 2.5 kV for 4-inch sapphire substrate. This results show that alumina electrostatic chuck with low resistivity and fine electrode pattern is suitable for handling of sapphire substrate for LED.

• 한국산업융합학회 논문집
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• 제8권4호
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• pp.227-234
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• 2005

In this study an experimental investigation was conducted to assesment of cutting ability for CBN ball end-milling, STD11 and NAK80 materials. The cutting force and surface roughness of the work-pieces were obtained in machining center. The assessment of CBN tools were inspected through the tool dynamotor and SEM. When $30^{\circ}$ negative rake angle, the wear and cutting force were good, surface roughness was better at cutting fluid during CBN cutting.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 춘계학술대회 논문집(한국공작기계학회)
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• pp.192-196
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• 2001

This work describes the modeling of cutting process for feedback control based on signal processing in end-milling. Here, cutting force is used to design control model by a variety of schemes which are moving average, ensemble average, peak value, root mean square and analog low-pass filtering. It is expected that each model offers its own peculiar advantage in following cutting force control.

• 접착 및 계면
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• 제16권4호
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• pp.137-145
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• 2015

본 연구에서는 현재 문화재 보존 처리에 사용되고 있는 합성수지를 대체하여 금속, 목재, 도자기, 토기, 석재 유물 등 재질별 문화재 복원 작업에 활용할 수 있는 다목적용 접합, 복원재료인 에폭시 퍼티(epoxy putty)를 개발하고자 하였다. 기존에 사용되고 있는 합성수지는 높은 강도로 인한 절삭력의 문제, 긴 경화 시간으로 인한 처짐 현상, 도구나 장갑에 묻어 유물의 표면을 오염시키는 현상, 재료의 황변 현상으로 인한 재처리 등의 문제점을 보이고 있다. 이를 해결하기 위해, 1차적으로 문화재 보존 처리 현장에서 가장 많이 사용되고 있는 페이스트(paste)형태의 복원 재료를 선정하여 물성을 파악한 후 이를 비교 대상으로 선택하고, 주제 및 경화제와 충전제의 종류에 따른 에폭시 퍼티를 개발하였다. 개발된 에폭시 퍼티는 기존 재료의 문제점 해결 및 유사한 물성을 지니기 위해 성상(性狀)이 다른 주제와 경화제를 각각 선정하여 물성 실험을 실시하였다. 연구 결과 2종 모두 페이스트 형태로 경화 시간은 5~10 min 내외로 기존 재료에 비해 약 3~10배 정도 짧아 작업의 편리성과 처짐 현상을 개선하였으며, 절삭력을 높이기 위한 마모율은 약 3배 정도 향상시켜 쉽게 성형할 수 있도록 하였다. 또한 작업 중 발생하는 표면 오염 등의 단점을 보완하기 위해 충전제로 탈크(talc)와 백색의 micro-balloon을 첨가하여 사용 중 손에 묻어 나와 끈적거리는 현상을 줄여주었을 뿐만 아니라 컬러링(coloring), 경량성, 절삭력 등이 높은 저수축, 저황변, 절삭력이 우수한 다목적 복원 재료를 개발하였다.

• 한국정밀공학회지
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• 제13권7호
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• pp.167-175
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• 1996

Work roll wear in the cold rolling of steel strip is strongly affected by rolling materials, rolling conditions and lubrication. Tests were performed to find the effects of rolling materials under the same lubricating conditions. Surface roughness of cold rolled steel strip as well as the coating technique itself is quite improtant in obtaining high image clarity of electronic products and car outer panels. Therefore this paper reviews for improvement of roughness and peak count about the surface of Cr coated work roll is investigated from the actual temper mill. The conclusions were obtained as follows; 1) Work roll wear in the cold rolling of steel strip is strongly affected by carbon contents of rolling materials, but there is not a separating force and total reduction ratio. 2) The roughness of strip surface is larger in the direction of width than in roll direction. 3) The electro-discharge textured roll has more uniform roughness distribu- tion than shot blasted roll and it's life time is two times longer than shot blasted because it has more harmonic wave roughness, and the higher peak count of surface roughness. 4) The life time of Cr coated work roll is 2 times longer than that of shot blasted work roll and variation of peak count, roughness and life time of Cr coated work roll is similar to electro-discharge texturing work roll. 5) The proper Cr coating thickness is 10 .mu. m at the work roll of temper mill.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 D
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• pp.2155-2156
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• 2006

The purpose of this work is to investigate the fundamental properties of the gradual muscle force potentiation for the prediction of muscle force and body movement from the stimulation input with musculo-skeletal model. We investigated the dependence of force potentiation on both the pulse-amplitude and the pulse-duration. The experimental result showed that the force increment ratio during electrical stimulation decreased with pulse-amplitude. The force increment ratio decreased with short pulse-duration and was maintained to be constant with pulse-duration longer than $500{\mu}s$. A new model of the muscle potentiation based on these results is desired in the future.

• 한국공작기계학회논문집
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• 제10권1호
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• pp.94-100
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• 2001

Distortion is a potential problem with all welded fabrication and should be caused dimensional changes and mismatch of joints during welding fabrication. Correction unacceptable weld distortion is extremely costly and in some case impossible. The aim of the present work is to verify the variation of the compressive force, tensile force and distortion during plastic deformation under Tungsten-inert-gas(TIG) welding, on type 304 stainless steel. Experimental results show that possibili-ty if measuring deformation during welding and good correlation was found between analytical and experimental result ad finite element methods have been used to model temperature analysis.

• 한국소음진동공학회논문집
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• 제25권6호
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• pp.426-431
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• 2015

In this work, a new type of MR damper with additional flow path in piston is proposed and damping force characteristics are numerically evaluated. Flow-mode type MR damper is considered and mathematical model is established based on Bingham rheological model of MR fluid to obtain accurate prediction of damping force characteristics. Damping force of the proposed MR damper are calculated with respect to piston velocity and input current. In addition, investigation on damping force characteristics is carried out according to number of additional flow path and excellence of the proposed MR damper is demonstrated.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.130-134
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• 1992

The ability of a robot system to comply to an environment via the control of tool-environment interaction force is of vital for the successful task accomplishment in many robot application. This paper presents the implementation of external force control for two dimensional contour following task using a commercial robot system. Force accommodation is used since a constraint imposed in our work is not to modify the commercial robot system. A linear, decoupled model of two dimensional contour following system in the discrete time domain is derived first. Then the experimental verification of linear control is obtained using a PUMA 560 manipulator with standard Unimation controller, Astek FS6-120A six axis wrist force sensor attached externally to the arm and LSI-11173 microcomputer. Experimentally obtained data shows that the RMS contact force error is 0.8246 N when following the straight edge and 2.3768 N when following 40 mm radius curved contour.

• Journal of Mechanical Science and Technology
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• 제18권5호
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• pp.789-797
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• 2004

The nanoscale sensing and manipulation have become a challenging issue in micro/nano-robotic applications. In particular, a feedback sensor-based manipulation is necessary for realizing an efficient and reliable handling of particles under uncertain environment in a micro/nano scale. This paper presents a piezoresistive MEMS cantilever for nanoscale force measurement in micro robotics. A piezoresistive MEMS cantilever enables sensing of gripping and contact forces in nanonewton resolution by measuring changes in the stress-induced electrical resistances. The calibration of a piezoresistive MEMS cantilever is experimentally carried out. In addition, as part of the work on nanomanipulation with a piezoresistive MEMS cantilever, the analysis on the interaction forces between a tip and a material, and the associated manipulation strategies are investigated. Experiments and simulations show that a piezoresistive MEMS cantilever integrated into a micro robotic system can be effectively used in nanoscale force measurements and a sensor-based manipulation.