• 한국정밀공학회지
• /
• 제29권12호
• /
• pp.1285-1289
• /
• 2012

This study has been focused on application of ELID lapping process for mirror-surface machining of sapphire wafer. Sapphire wafer is a superior material with optic properties of high performance as light transmission, thermal conductivity, hardness and so on. High effective surface machining technology is necessary to use sapphire as various usages. The interval ELID lapping process has been set up for lapping of the sapphire material. According to the ELID lapping experimental results, it shows that 12.5 kg of load for lapping is most pertinent to ELID lapping. the surface of sapphire can be eliminated by metal bonded wheel with micron abrasives and the surface roughness of 60 nmRa can be gotten using grinding wheel of 2,000 mesh in 4.5 um, depth of cut. In this study, the chemical experiments after ELID grinding also has been conducted to check chemical reaction between workpiece and grinding wheel on ELID grinding process. It shows that the chemical reaction has not happened as the results of the chemical experiments.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1997년도 춘계학술대회 논문집
• /
• pp.970-976
• /
• 1997

The ultra-precision machining is widely used for final machining process of precision parts, so in this study, mirror surface finishing systems using the micro abrasive film, one of ultra-precision machining method, have to examine mirror surface characteristics of the cylindrical workpiece(SM45) such as surface roughness, workpiece removal and evaluated under the condition varing film feed rate, applied pressure, grinding speed after fixing other condition. It was found that varrious machining condition have significant influences on workpiece removal, surface roughness.

• 한국생산제조학회지
• /
• 제18권5호
• /
• pp.469-476
• /
• 2009

Hard facing overlay welding in high chromium carbide is a representative way of extending the fatigue life or recompensing damage, because workpiece surface is uniformly overlay-welded by alloy material. In general, grinding process is currently used for finish due to hardness of weld material. The development of tool material, such as PCBN, has made it possible to use turning instead of grinding. There are many advantages of hard Owning, as lower equipment costs, shorter setup time, fewer process steps, higher material removal rate, better surface integrity and the elimination of cutting fluid. In this paper, machining characteristics and cutting performance are examined to investigate turning possibility of overly welding in high chromium carbide.

• 대한자원환경지질학회:학술대회논문집
• /
• 대한자원환경지질학회 1999년도 춘계 공동학술발표회
• /
• pp.288-290
• /
• 1999

• 한국소음진동공학회논문집
• /
• 제19권4호
• /
• pp.386-392
• /
• 2009

This paper reports on the research which investigates acoustic signals acquired in progressive compressing, hole blanking, shearing and burr compacting process. The work piece is the head pin of the electric connector, whose raw material is the preformed steel bar. An acoustic sensor was set on the bed of hydraulic press. Because the acquired signals include the dynamic characteristics generated for all the processes, it is required to investigate signal characteristics corresponding to unit process. The corresponding dynamic characteristics to the respective process were first studied by analyzing the signals respectively acquired from compressing, blanking and compacting process. The combined signals were then periodically analyzed from the grinding to the grinding in the sound frequency domain and in the ultrasonic wave. The frequency of around 9 kHz in the sound frequency domain was much correlated to the tool wear. The characteristic frequency in the acoustic emission domain between 100 kHz and 500 kHz was not only clearly observed right after tool grinding but its amplitude was also related to the wear. The frequency amplitudes of 160 kHz and 320 kHz were big enough to be classified by the noise. The noise amplitudes are getting bigger, and their energy was much bigger as coming to the next regrinding. The signal analysis was based on the real time data and its frequency spectrum by Fourier Transform. As a result, the acousto-ultrasonic signals were much related to the tool wear progression.

• 한국철도학회논문집
• /
• 제20권2호
• /
• pp.234-240
• /
• 2017

레일표면 품질지수(QI: Quality Index)가 동적 궤도작용력에 미치는 영향을 알아보기 위하여 현장측정을 통해 레일연마횟수(Pass)에 따른 레일표면 품질지수의 변화를 분석하였다. 이론식에 근거하여 레일표면 품질지수에 영향을 미치는 매개변수인 열차속도에 따른 상관관계를 분석하였다. 레일연마횟수에 따른 레일표면 품질지수가 동적 궤도작용력에 미치는 영향을 분석한 결과, 레일표면 품질지수는 레일연마가 진행됨에 따라 감소하고 동적 궤도작용력 역시 일정 비율로 감소하는 것으로 분석되었으며, 고속주행 시 레일표면 품질지수에 따라 동적 궤도작용력은 크게 증가하는 것으로 분석되었다. 즉, 레일연마는 레일표면 품질지수를 일정비율로 감소시킬 수 있고, 궤도시스템 전반에 영향을 미치는 동적 궤도상호작용력을 저감 시킬 수 있는 것으로 분석되어 효율적인 레일표면관리를 위해서는 운행 노선의 열차속도를 감안한 레일표면 품질지수의 관리가 필요한 것으로 분석되었다.

• 동아시아식생활학회지
• /
• 제23권3호
• /
• pp.382-390
• /
• 2013

The purpose of this study is to provide the basic findings concerning a quality evaluation. The first conclusion is the coffee's $CO_2$ gas production between a roast brewed at 0 hour and 72 hours after grinding. The espresso, 48 hours after its grind, emits a small amount of $CO_2$ gas, whereas 72 hours after being grinded there is no discharge. In the sensory evaluation, the overall preference is the 72 hours later grind, in accordance to the decrease of the bitter, acid, and sour taste with the increase of the sweet, nutty, and chocolaty flavors. The foam index indicates a significant reduction between the roasts brewed at 0 hour and 72 hours after grinding. A persistence of crema in the Colombian Colombia and Ethiopian Yirgacheffe decline for the 72 hours after its grind coffee. The Tanzanian Kilimanjaro and Brazilian Cerrado roasts show no difference. The pH is decreased in the 72 hours after its grind roast. Moreover, sugar contents in the Colombian Excelso and Brazilian Cerrado are increased, whereas the Tanzanian Kilimanjaro sugar contents are decreased, along with its density.

• 한국분말재료학회지
• /
• 제13권4호
• /
• pp.243-249
• /
• 2006

Yttrium aluminum garnet (YAG) powders were synthesized via mechanochemical solid reaction using $Y_2O_3$ with three types of aluminum compounds. $Y_2O_3$ reacted mechanochemically with all A1 compounds and formed YAM (yttrium aluminum monoclinic), YAG and YAP (yttrium aluminum perovskite) phases depending on the starting materials. The ground samples containing ${\gamma}-A1_2O_3$ showed the best reactivity, whereas the ground sample containing A100H, which had the largest surface area, exhibited pure YAG after calcination at $1200^{\circ}C$. The sample containing Al had the least reactivity, producing YAP along with YAG at $1200^{\circ}C$. The types and grinding characteristics of the starting materials and grinding time are believed to be important factors in the mechanochemical synthesis of YAG.

• 한국생산제조학회지
• /
• 제20권1호
• /
• pp.96-100
• /
• 2011

The hydrostatic bearings have a relatively small run-out comparing to its shape error by fluid film effect in hydrostatic state as like pneumatic bearing and have a high stiffness, load capacity and damping characteristics. As there is no maintenance and semipermanent in these bearing type, it has been usually adopted as main spindle bearing for grinding machine. In this thesis, to develop hydrostatic bearing for high speed spindle, the cooler setting temperature, bearing clearance and nozzle pressure of belt-driven hydrostatic bearing are investigated. The bearing temperature is decreased, as the cooler setting temperature is lower, nozzle pressure is higher and bearing clearance is wider. The front temperature of bearing is nearly $8^{\circ}C$ higher than the rear one up to 13,000 rpm of spindle revolution. The thermal deflection of X-axis is ${\pm}16\;{\mu}m$ in range of 12,000 rpm-13,000 rpm. Therefore, it is conformed that the built-in motor hydrostatic bearing can be used to high speed spindle.

• 청정기술
• /
• 제10권3호
• /
• pp.139-148
• /
• 2004

스와프는 철강 제조 공정 중에 발생되는 금속 부산물로서 연마유의 함량이 10%이상 되므로 국내에서 지정폐기물로 분류된다. 연마유가 함유된 스와프를 재활용하기 위하여 초임계 이산화탄소를 이용하여 재생하였고, 온도(313.15K-323.15K), 압력(10MPa-30MPa)의 실험 조건이 연마유 추출 효율에 미치는 영향을 살펴보았다. 초임계 이산화탄소의 압력이 높을수록 높은 추출 효율을 보였고, 같은 압력을 기준으로 하였을 때는 온도가 높을수록 빠른 시간 내에 추출 공정이 완료됨을 확인하였다. 본 실험에서는 선형 탈착 kinetics가정의 단일 매개 변수 모델을 사용하여 재생 효율을 예측하였고, 이는 실험 결과와 비교적 잘 일치하였다.