• Journal of Welding and Joining
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• 제5권1호
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• pp.23-33
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• 1987

플라즈마 절단은 산업계에서 널리 사용되고 있으나 공정의 해석에 대한 연구는 매우 부족하다. 본 연구에서는 알미늄판재에 나타나는 온도분포를 해석함으로써 절달폭을 이론적으로 예측하고 자 하였다. 열유동을 해석하는데 있어서, 플라즈마 아아크의 강도가 폭방향으로는 정상분포 (Gaussian distribution)을 갖고 두께방향으로는 지수함수적으로 감소한다고 가정하였다. 측정된 아아크효율을 이용한 계산결과 이론적으로 예측된 절단부의 크기 및 형상이 실험치와 매우 잘 일치하였으며, 따라서 제안된 해석방법은 플라즈마 절달공정의 해석에 유용하게 적용될 수 있 었다.

• 한국표면공학회지
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• 제43권1호
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• pp.41-45
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• 2010

The effect of $MoS_2$ and graphite content on wear resistance and mechanical properties of Cu/Sn bonded diamond micro blades was comparatively investigated in terms of volume and weight fraction. For the evaluation of endurance and cutting performance, instantaneous electric power consumption and cumulative wear loss during cutting glass work piece at constant velocity were measured with the micro blades of the wide range of lubricant content. The energy consumption of blades for glass cutting decreased with the content of lubricants. Wear amount of blade in volume increased with the amount of lubricant addition. It was found to be relevant to the decrease in flexural strength and hardness with the amount of lubricants. With the same amount of lubricant content in volume fraction $MoS_2$ showed superiority in mechanical properties and cutting performance than graphite while graphite could result in stronger effect on lowering electric consumption during cutting work piece for the same weight percent fraction than $MoS_2$ because of lower density.

• 터널과지하공간
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• 제30권6호
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• pp.591-602
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• 2020

기존의 전통적인 암석절삭방식의 한계점을 극복하고자 다양한 신개념의 암석절삭메커니즘이 연구되고 있으며, 그 중 언더커팅은 최근 연구가 수행되고 있는 기술이다. 본 논문에서는 언더커팅에 대한 기초연구로서 구동형 언더커팅에 의한 암석절삭메커니즘과 절삭에 관여하는 중요핵심변수들에 대하여 소개하였다. 구동형 언더커팅에 의한 절삭성능을 평가하기 위한 시험시스템을 구축하고 이를 활용하여 주요 핵심변수들을 변화시켜가며 구동형 언더커팅 디스크를 활용한 절삭시험을 수행하였다. 구동형 언더커팅 절삭시험으로부터 획득되는 3방향 커터작용력의 특성을 분석하였으며, ADC의 주요 절삭변수인 선형 이동속도, 법선압입깊이, 편심의 증가에 따라 3방향 커터작용력의 평균값과 최댓값은 모두 선형적으로 증가하는 결과를 나타내었다.

• Tribology and Lubricants
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• 제32권2호
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• pp.44-49
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• 2016

Diamond mechanical polishing (DMP) is a crucial process in a sapphire wafering process to improve flatness and achieve the target thickness by using free abrasives. In a DMP process, material removal rate (MRR) is a key factor to reduce process time and cost. Controlling mechanical parameters, such as velocity and pressure, can increase the MRR in a DMP process. However, there are limitations of using high velocities and pressures for achieving a high MRR owing to their side effects. In this paper, we present the lapping characteristics and improvement of MRR by using a fixed abrasive plate through an experimental study. The change in MRR as a function of velocity and pressure follows Preston's equation. The surface roughness of a wafer decreases as the plate velocity and pressure increases. We observe a sharp decrease in MRR over the lapping time at a high velocity and pressure in the velocity and pressure test. An analysis of surface roughness (Rq and Rpk) indicates that wear of abrasives decreases the MRR sharply. In order to investigate the effect of abrasive wear on the MRR, we utilize a cutting fluid and a rough wafer. The cutting fluid delays the wear of abrasives resulting in improvement of MRR drop. The rough wafer maintains the MRR at a stable rate by self-dressing.

• 한국기계가공학회지
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• 제16권1호
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• pp.118-123
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• 2017

It is well known that water jetting is now widely used in the advanced cutting processes of polymers, metals, glass, ceramics, and composite materials because of some advantages, such as heatless and non-contacting cutting different from the laser beam machining. In this paper, we proposed the simulation model of waterjet by lengths and the inner spiral structure of the nozzle. The simulation results show that the outlet velocity of the nozzle is faster than the inlet. Furthermore, we found rapid velocity reduction after passing through the outlet. The nozzle of diameter ${\phi}500$ and length 70mm, shows the optimal fluid width and velocity distribution. Also, the nozzle with inner spiral structure shows a Gaussian distribution of velocity and this model is almost twice as fast as the model without spiral structure, within the effective standoff distance (2.5 mm). In the future, when inserting abrasive material into the waterjet, we plan to analyze the fluid flow and the particle behavior through a simulation model.

• 터널과지하공간
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• 제30권3호
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• pp.181-192
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• 2020

Pin-on-disk 시험방법은 ASTM에서 제안한 마모시험방법 중 하나이다. 이 시험법에서는 Pin-on-disk 시험에서 나타나는 핀의 나선운동을 간략히 설명하고 있다. 이 방법을 암석공구의 마모성능을 평가하는데 적용하기 위해서는 핀의 등속도 운동을 수학적으로 구현하여야 한다. 먼저 합산속도에 관여하는 2가지 속도성분(핀의 선형이동속도, 디스크의 회전운동)을 정의하였다. 각각의 성분에 대해 아르키메데스 나선방정식의 등속도 조건을 만족하는 미분방정식을 전개하여 수학 해를 도출하여, 풀이의 난해함을 설명하였다. 이를 해결하기 위한 기존 문헌의 근사해를 조사하고, 정확도와 한계점을 분석하였다.

• 한국기계가공학회지
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• 제3권2호
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• pp.25-31
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• 2004

Machinability in metal cutting processes depends on cutting input conditions such as cutting velocity, feed rate, depth of cut, types of work material and tool shape factors. In this study, to assess chip breaking characteristics of a turning process, an equivalent oblique cutting system to this has been established. And the equivalent effective rake angle was determined using side rake angle, back rake angle and side cutting edge angle of the tool. A non-dimensional parameter, Chip breaking index(CB), was used to assess Chip breaking characteristics of chip in conjunction with the equivalent effective rake angle. In case of positive rake angles of the equivalent effective rake, the back rake angle has little effect on the chip breaking characteristics however, in case of negative ones, the side rake angle has some effect on Chip breaking characteristics.

• 한국정밀공학회지
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• 제11권6호
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• pp.42-49
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• 1994

One of the parameters that influence the productivity of every industry, involved in metal cutting, is the chip from ; continuous or broken chip. Chip form varies according to machining conditions, material used, tool geometry and chip breaker geometry. Therefore, in this study we carried out the experiment on the chip control in machining STS304 using an attached obstruction type chip breaker. Namely, with the change of a chip breaker distance, chip breaker angle, cutting characteristics in machining STS304 which is well-known as a machining difficult material and produces a saw-toothed chip. The results of the experiment are as follows : 1. The chip breaker distance and angle under which the preferred chip is produced, show 1.5mm and 60 .deg. , while chip breaker angle in machining an ordinary steel was well-known 45 .deg. . 2. During the cutting process, the change of feed than the change of velocity was applied as cutting conditions, effects more clearly on the chip breaking. 3. Considering a whole surface roughness, it is not advisable to apply chip breaker mentioned above for precision cutting.

• 한국공작기계학회논문집
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• 제17권1호
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• pp.59-64
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• 2008

Micro machining can manufacture complex shapes with high accuracy. Especially, this enables wide application of micro technology in various fields. For example, micro channels allow fluid transfer, which is a widely used technology. Therefore, liquidity research of flow in micro channels and micro channel manufacturing with use of various materials and cutting conditions has very important meaning. In this study, to find out correlation between fluid velocity in micro channels and surface roughness, we manufactured micro channels using micro end-mill and dropped ethanol into micro channels. We compared several surface roughness and fluid velocity in micro channels that were created by various processing conditions. Finally, we found out relationship between fluid velocity and surface roughness in micro channels of different materials.

• Journal of Biosystems Engineering
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• 제36권4호
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• pp.257-266
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• 2011

Consumption of chicken feet has been increasing recently, thus it was necessary to produce good quality of bone less chicken feet. In the process of bone removal during chicken feet production, feeding, conveying, cutting and bone removing process takes about 90% of overall labor. Therefore, the development of a chicken feet-bone remover was necessary to reduce the cost of labor. The main objective of this study was to make and test of chicken feet-bone remover. The optimum vibration level of feeder wes 8, and the optimum conveyor speed was 3.6 m/min. The feeding speed of feeder were 0.18 m/s, 0.13 m/s and 0.19 m/s for the weight ranges of chicken feet of >20 g, 20~30 g and 30 g< respectively. The sensing success rates of chicken feet were 100%, 98% and 96% for the conveyor speeds of 3.0, 3.6 and 4.2 m/min respectively. The slips of chicken feet were 1.0 mm, 1.9 mm and 3.2 mm for conveyor speed of 0.8, 1.9 and 4.2 m/min respectively, with the average moisture content of 65% (w.b). The incision accuracy rates of the chicken leg were 46%, 95%, 97% for the size ranges of >15 mm, 15~18 mm, 18 mm< respectively with the velocity of cutting blade 3.9 m/s. The removal rates of the chicken feet bone were 98%, 96%, 88% for toes diameter >10 mm, 10~15 mm, 15 mm> respectively with the velocity of cutting blade 11.8 m/s.