• Laser Solutions
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• v.3 no.1
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• pp.29-37
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• 2000

For a development purpose of thick metal / metal Graded-Boundary Materials(GBM), a basic research on the fabrication of Ni-Cr/steel GBM was carried out by a laser beam and its mechanical properties and thermal characteristics were investigated. In order to produce a compositionally graded boundary region between substrate steel and added Ni-Cr alloy, a series of surface alloying treatments was performed with a high power CO$_2$ laser beam. Ni-Cr sheet was placed on a low carbon steel plate(0.18%C), and then a CO$_2$ laser beam was irradiated on the surface to produce a homogeneous alloyed layer. On this first surface-alloyed layer, another Ni-Cr sheet was placed and then the CO$_2$ laser beam was irradiated again to produce second surface-alloyed layer. Sequential repetitions of laser surface alloying treatment 4 times resulted in a graded-boundary region with the thickness of about 1.4mm. Simultaneous concentration profiles of different kinds of alloying elements(Ni and Cr) showed from 42%Ni, 45%Cr and 13%Fe on surface region to 0%Ni, 0%Cr and 99%Fe in substrate region. Also a thermal conductivity gradient resulted in graded-region and its value changed from 0.03㎈/cm s$\^{C}$ in surface region to 0.1㎈/cm s$\^{C}$ in substrate region. Microstructural observation showed that any visible root porosities and solidification shrinkage cracks were not formed in graded region between alloyed layer and substrate region during rapid cooling.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.1
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• pp.18-24
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• 2010

Efforts to obtain more efficient coupling of light from a laser diode to a single mode fiber have continued for various applications such as links for optical fiber communication systems. In TO-can package, configuration of optimized aspherical lens is bi-aspheric and its diameter is 2.4mm. We designed and fabricated aspherical coupling lens by means of glass molding technique under consideration of glass shrinkage. By controlling the aspherical profile error and surface roughness which were below 90nm and 10nm, respectively, we obtained the low coupling loss, 5.40dB, which was able to use for coupling a single mode fiber to laser diode.

• Design & Manufacturing
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• v.2 no.6
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• pp.11-16
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• 2008

In order to satisfy the customer's variant needs for a product quality in recent years, a demand for developing higher precision machining technologies in a lot of application areas such as automobile, cellular phone and semiconductor has been increased more and more. Micro-magnetic induced polishing(${\mu}-MIP$) process is one of these precision technologies. In this study, to verify the parameters' effect of the ${\mu}-MIP$ process on the surface roughness improvement of the inclined workpiece, well planned experiment which was called the design of experiments was carried out. Considered parameters were spindle speed, inductor current, abrasive configuration and working gap between the workpiece and the solid tool. As a result, it was seen that the inductor current and the working gap greatly affected the surface roughness improvement. And to predict the surface roughness of the inclined workpiece, S/N ratio and first-order response surface model was developed.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.305-309
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• 2005

This paper deals with an development of screen technology for marine waste disposal. The conception of inverse inclined screen is introduced. For optimal solid-liquid separation the vibration frequency, vibration angle and vibration method are inquired. And the efficiency of proposed technology and automatic apparatus is proved through the field test.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1899-1901
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• 2001

본 논문에서는 3차원 feed horn 안테나를 볼로미터에 결합함으로써 감지도(Detectivity)를 향상시킨 비가시광 영상 감지 소자를 제안하였다. Feed horn 안테나의 우수한 지향성(Directivity)를 통해서 주위의 잡음 성분을 제거함으로써 감지도의 향상을 확인할 수 있었다. 안테나와 볼로미터와의 결합 손실을 줄이기 위해서 볼로미터의 흡수층의 모양을 원형의 형태로 하였으며 크기도 안테나 폭과 일치를 시켰다. 또한 열적 고립 구조를 만들기 위한 지지 다리의 모양도 원형의 형태로 하여서 전체 길이를 증가 시켰으며 이로 인해 열전도도(Thermal conductance)를 $4.65{\times}10^{-8}$[W/K]까지 낮출 수 있었 다. 설계된 소자의 감지도는 $2.37{\times}10^{9}$[$cm\sqrt{Hz}/W$]을 나타내었으며 안테나 결합을 통한 감지도의 향상을 확인 할 수 있었다. 볼로미터의 제작은 MEMS 기술을 이용한 표면미세가공(Surface micromachining)법으로 열적 고립 구조체를 제작할 수 있으며 3차원 feed horn안테나는 SU-8이라는 음성 감광제를 경사회전노광시켜서 제작할 수 있다.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.5
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• pp.508-513
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• 2015

In this study, the effect of the helix angle and rake angle of a flat end-mill in the milling of titanium alloy was investigated. Tool shape parameters such as helix angle and rake angle affect the cutting force, cutting zone temperature, vibration, and chip flow mechanism, which in turn determine tool life, surface integrity, and dimensional accuracy of the milling process. To investigate the effect of the helix and rake angles, a certain range of parameters was selected, and three-dimensional tool models were generated for finite element analysis (FEA) for each case. The cutting force and pressure on the tool flank face and rake face were investigated by FEA. Further, several tool models were proposed for machining tests. The cutting force characteristics were investigated by the machining tests.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.9 no.1
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• pp.1-9
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• 2015

This paper reviews trends of the rehabilitation welfare devices on the basis of products and markets. Latest assistive devices tend to have a fold function. Auxiliary power assist module has been added. The completion of products has been improved. The folding function has strong relationship with portability. Specifically, various mobility devices, including foldable devices, are associated with enhanced portability. Powered auxiliary wheels and upper extremity supporting modules have entered the market. The leading-edge technology like Segway's control technology applies to two-wheel wheelchairs. The brand- new technology, lower extremity robotic exoskeleton, applies to markets. Standing wheelchairs, ramps, stair climbing assistive devices becomes more common. In addition, a combination of a variety of smart devices is being promoted to the classical assistive devices' part. Rehabilitation welfare devices can be more valuable due to nice industrial design, improved materials, and processing technology.

• Journal of the Korean Society of Safety
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• v.24 no.2
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• pp.7-12
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• 2009

The machining process of ceramics can be characterized by cracking and brittle fracture. In the machining of ceramics, edge chipping and crack propagation are the principal reasons to cause surface integrity deterioration. Such phenomenon can cause not only poor dimensional and geometric accuracy, but also possible failure of the ceramic parts. Thus, traditional ceramics are very difficult-to-cut materials. Generally, ceramics are machined using conventional method such as grinding and polishing. However these processes are generally costly and have low MRR(material removal rate). To overcome such problems, in this paper, h-BN powder, which gives good cutting property, is added for the fabrication of machinable ceramics by volume of 10 and 15%. The purpose of this study is an analysis of endmill's rake angle for appropriate tools design and manufacturing for the machinable ceramics. In this study, Experimental works are executed to measure cutting force, surface roughness, tool fracture, on different axial rake angle of endmills. Cutting parameters, namely, feed, cutting speed and depth of cut are used to accomplish purpose of this paper. Required experiments are performed, and the results are investigated.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.76-76
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• 2017

Ni-Ti 파일은 근관치료 시 근관형성에 사용되며 근관계 내 조직 잔사와 세균 을 포함한 모든 내용물을 제거하고 미세누출이 생기지 않도록 성공적으로 근관충전을 할 수 있는 근관의 형태를 만드는데 사용된다. Ni-Ti 파일은 수동형 파일처럼 날이 풀어지거나 예각으로 꺾이는 등 시각적으로 나타나는 파일의 피로도나 손상정도를 인지하기 어려워 파일이 근관 내에서 부러지는 것을 막기가 어렵다. Ni-Ti 파일은 육안으로 관찰 할 수 있는 구부러짐이나 풀림 등의 소성변형 없이 기구의 탄성한계 내에서 갑작스럽게 파절되는 경우가 있는데, 이는 만곡 근관 내에서 기구가 회전하는 동안 만곡의 안쪽에는 압축응력이, 만곡의 바깥쪽에는 인장응력이 반복적으로 가해짐으로써 파절의 표면에 미세 파절과 균열이 발생하고 전파되어 결국 피로파절(fatigue fracture)을 야기하게 된다. 또한 Ni-Ti파일이 반복응력을 받으면 균열이 형성되면서 파절이 야기되며 연성파절(ductile fracture) 양상을 나타낸다고 보고하였다. Ni-Ti 파일을 이용한 피로파절에 대한 이전의 연구에서는 파일의 직경이나 경사도 (taper), 단면 형태 및 회전속도, 표면결함 등이 파절에 영향을 미친다고 보고되고 있다. 사용하지 않은 Ni-Ti파일을 구부려 응력을 가 한 상태에서 주사전자현미경으로 관찰한 결과 기계 가공 과정에서 발생한 균열, 미세 결함, 긁힌 자국 및 불균질성 등이 원인으로 알려져 있다. 따라서 본 연구발표에서는 표면결함을 최소화하고 기구의 회전응력 하에서 피로파절저항성을 향상시키기 위한 방법에 대하여 알아보고자 한다.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2009.05a
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• pp.223-226
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• 2009

최근 의생활에 있어서 가장 큰 변화는 쾌적성의 추구와 건강을 중심으로 한 기능성 소재에 대한 소비자들의 욕구가 증대된다는 것이다. 천연 섬유 중 모시는 통기성이 우수하고 감촉이 깔깔하여 고온 다습한 우리나라의 여름철 옷감으로 좋으므로 현대 의생활로의 도입이 요구되고 있다. 그동안 모시직물은 심미적인 욕구에도 잘 맞아 한국인의 정서에 좋은 이미지로 자리 잡고 있지만 수공예적 생산방식을 그대로 답습하고 있어 전통모시직물로는 많이 이용이 되어왔으나 현대 방적모시직물을 이용한 새로운 직물디자인 개발은 이루어지기 어려운 실정이었다. 그러나 최근 방적모시섬유에 대한 연구가 활발하게 진행되기 시작하면서 현대 방적모시직물의 생산이 가능하게 되었다. 따라서 본 연구에서는 원사의 특성과 제조공정 특성에 의해 미세한 감성촉감의 차이를 유발하기 좋은 폴리에스터를 경사로하고 방적모시와 라이오셀을 위사로 하여 현대 모시직물의 개발을 시도하였다. 모시의 소비를 증가시키고 현대인의 감성에 맞게 심미성을 향상시킬 수 있도록 직물문양을 디자인하였다. 직물의 복잡한 문양을 컴퓨터로 디자인하고 자동으로 제직이 가능하게 하는 시스템인 EAT 프로그램을 이용하여 자카드 직물 특유의 고급스러움을 살리며 공정과정에서의 실의 밀림 등을 고려하며 조직을 설계하였다. 설계된 직물은 제직 후 염색 가공하여 쿠션, 방석, 테이블 러너 등의 시제품으로 제작하여 고부가가치 모시제품의 개발가능성을 살펴보았다.