• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.1
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• pp.31-40
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• 1992

This paper presents an automatic feature recognition system for recognizing and extracting feature information needed for the process planning input from a 3D CAD system. A given part is modeled by using the AutoCAD and feature information is automatically extracted from the AutoCAD database. The type of parts considered in this study is prismatic parts composed of faces perpendicular to the X, Y, Z axes and the types of features recognized by the proposed system are through steps, blind steps, through slots, blind slots, and pockets. Features are recognized by using the concept of convex points and concave points. Case studies are implemented to evaluate feasibilities of the function of the proposed system. The developed system is programmed by using Turbo Pascal on the IBM PC/AT on which the AutoCAD and the proposed system are implemented.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.04a
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• pp.79-80
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• 2006

새로운 급속소결방법인 고주파유도가열 소결법과 펄스전류활성 소결법을 이용하여 습식 볼밀링으로 혼합한 WC-8wt.%Co분말에 60MPa의 압력과 90%의 고주파출력 또는 2800A의 필스전류를 가하여 상대밀도가 98.6% 이상인 초경재료를 2분이내의 짧은 시간에 제조하였다. 초기의 WC분말의 입도가 미세해짐에 따라 고주파유도가열 소결법과 펄스전류활성 소결법 모두 소결시간이 단축되는 경향을 보였으며 그 소결체의 결정립 크기도 감소하였다. 고주파유도가열 소결법으로 제조된 초경합금의 WC 결정립 크기는 초기입도가 증가함에 따라 가각 410, 540, 600, 700 및 850nm으로 측정되었으며. 그 결과를 Fig. 1.에 나타내었다. WC의 초기입도가 $0.5{\mu}m$일 경우 고주파유도가열 소결법과 펄스전류활성 소결법으로 제조된 WC-8wt.%Co 소결체의 경도와 파괴인성은 각각 $1923kg/mm^2$과 $10.5MPa{\cdot}m^{1/2}$ 및 $1947kg/mm^2$과 $10.8MPa{\cdot}m^{1/2}$ 이었다.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.10
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• pp.34-41
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• 2004

A new method to fabricate the fine magnetic abrasives by using mechanical alloying is proposed. The mechanical alloying process is a solid powder process where the powder particles are subjected to high energetic impact by the balls in a vial. As the powder particles in the vial are continuously impacted by the balls, cold welding between particles and fracturing of the particles take place repeatedly during the ball milling process using a planetary mill. After the manufacturing process, fine magnetic abrasives which the guest abrasive particles c lung to the base metal matrix without bonding material can be obtained. The shape of the newly fabricated fine magnetic abrasives was investigated using SEM and its polishing performance was verified by experiment. It is very helpful to finishing the injection mold steel in final polishing stage. The areal ms surface roughness of the workpiece after several polishing processes has decreased to a few nanometer scales.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.5
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• pp.1-7
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• 2016

In the present study, a plastic surface end-milling was implemented to investigate the effects of processing parameters on surface quality. The end milling can be considered an efficient method for rapid prototyping of thermoplastic bio-systems since it exhibits several beneficial functions including short fabrication time and high dimensional accuracy. In this regard, putative biocompatible thermoplastic materials, such as PMMA, PET, and PC, were chosen as workpiece materials. Among the relevant processing parameters influencing the surface quality of the final product, depth of cut, feed rate, and spindle speed were considered in the present study. The roughness of surfaces machined under various conditions was measured to elucidate the effect of each parameter. We found that the cut depth was the most significant factor. Heat generation during machining also had a remarkable effect. From these investigations, an appropriate combination of processing conditions specific to each type of use and end-product could be found. This optimization can be useful in end-milling of thermoplastic bio-systems.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.94.2-94.2
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• 2012

에너지 하베스터에 적용 가능한 $0.72Pb(Zr_{0.47}Ti_{0.53})O_3-0.28Pb((Ni_{0.55}Zn_{0.45})_{1/3}Nb_{2/3})O_3$ (PPZNN) 후막세라믹의 구조적 압전 특성을 조사하였다. $850^{\circ}C$에서 하소를 마친 파우더를 72시간 볼 밀링 처리한 후, 테잎 캐스팅 공정을 이용하여 0.3mm의 두께로 PPZNN 압전 세라믹을 제조하였다. $900^{\circ}C$에서 $1200^{\circ}C$까지 다양한 온도에 소결하여 온도가 증가될수록 정방형 구조로 상전이 거동하는 모습을 보였으며, 특히 $1050^{\circ}C$에서 소결된 PPZNN후막 세라믹은 이차상이 없는 고밀도의 미세구조가 관찰되었다. $d_{33}$=440 pC/N 그리고 kp = 0.46의 우수한 압전 특성을 보였으며, 에너지 변환 성능을 나타내는 $d33{\cdot}g33$ 값은 약 $20439{\times}10^{-15}\;m^2/N$ 로 매우 우수하였다. PPZNN후막 세라믹을 유니몰프 켄틸레버 형태로 제작하여 발전 평가하였을 때 저항이 470 $k{\Omega}$에서 969 ${\mu}W$ (4930 ${\mu}W/cm^3$)로 관찰되었다. PPZNN 후막 압전 세라믹은 향후 압전에너지 하베스터 소재로 다양한 응용분야에 사용될 것으로 예상된다.

• Journal of Powder Materials
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• v.17 no.2
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• pp.130-135
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• 2010

Sm-16.7wt%Co alloy powders were prepared by high energy ball milling under the conditions of various milling time and the content of process control agent (PCA), and their microstructure and magnetic properties were investigated to establish optimum processing conditions. The initial powders employed showed irregular shape and had a size ranging from 5 to $110\;{\mu}m$. After milling for 5 h, the shape of powders changed to round shape and their mean powder size was approximately $5\;{\mu}m$, which consisted of the agglomerated nano-sized particles with 15 nm in diameter. The coercivity was reduced with increasing the milling time, whereas the saturation magnetization increased. As the content of PCA increased, the powder size minutely decreased to approximately $7\;{\mu}m$ at the PCA content of 10 wt%. The XRD patterns showed that the main diffraction peaks disappeared apparently after milling, indicating the formation of amorphous structure. The measured values of coercivity were almost unchanged with increasing the content of PCA.

• Journal of Powder Materials
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• v.14 no.2 s.61
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• pp.101-107
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• 2007

Ultrasonic-milling of metal oxide nanopowders for the preparation of tungsten heavy alloys was investigated. Milling time was selected as a major process variable. XRD results of metal oxide nanopowders ultrasonic-milled for 50 h and 100 h showed that agglomerate size reduced with increasing milling time and there was no evidence of contamination or change of composition by impurities. It was found that nanocomposite powders reduced at $800^{\circ}C$ in a hydrogen atmosphere showed a chemical composition of 93.1W-4.9Ni-2.0Fe from EDS analysis. Hardness of sintered part using 50 h and 100 h powder samples was 399 Hv and 463 Hv, respectively, which is higher than the that of commercial products (330-340 Hv).

• Journal of Powder Materials
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• v.25 no.2
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• pp.126-131
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• 2018

In the present study, we investigate the effects of milling time and the addition of a process control agent (PCA) on the austenite stability of a nanocrystalline Fe-7%Mn alloy by XRD analysis and micrograph observation. Nanocrystalline Fe-7%Mn alloys samples are successfully fabricated by spark plasma sintering. The crystallite size of ball-milled powder and the volume fraction of austenite in the sintered sample are calculated using XRD analysis. Changes in the shape and structure of alloyed powder according to milling conditions are observed through FE-SEM. It is found that the crystallite size is reduced with increasing milling time and amount of PCA addition due to the variation in the balance between the cold-welding and fracturing processes. As a result, the austenite stability increased, resulting in an exceptionally high volume fraction of austenite retained at room temperature.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.3
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• pp.135-142
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• 2017

In this study, we prepared the board of vermiculite materials utilizing coal bottom ash from the Western thermal power stations in Korea and obtained experimental data in applications for building interior materials with the characteristics of sound absorption. To produce the mixture materials of vermiculite and coal bottom ash, we used a microwave drying process. In addition, a ball milling process was used to produce particles of coal bottom ash with a uniform size of $65{\mu}m$. When the board made from mixture materials of vermiculite and coal bottom ash were produced with bottom ash sulfur concentrations of 5, 10 wt%, maximum bending loads were analyzed. These experimental results would contribute much to fundamental data essential to the recycling technology of coal bottom ash.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.6
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• pp.30-36
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• 2013

An FFD(flexible fine die) is an embossed mold that consists of a thin plate ranging from 0.6 to 3 mm in thickness. FFDs are primarily used for cutting LCD films and F-PCB sheets. In the high-speed micro-milling process of flexible fine dies, the lubrication and cooling of the cutting edges is very important from the aspect of eco machining and cutting performance. In this paper, a comparative study of tool wear and surface roughness between cutting fluid and hybrid lubrication for eco-machining of FFD was conducted for processes of high-speed machining of highly hardened material (STC5, HRC52). Especially, the incorporated fluid method for eco machining, in which the cutting performances can be simultaneously measured, was introduced. The machining results show that hybrid lubrication, instead of conventional cutting fluid, leads to excellent tool wear and surface roughness and represents the proper conditions for eco micro-machining of flexible fine dies.