• 대한기계학회논문집A
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• 제28권10호
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• pp.1566-1573
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• 2004

When a projectile travels at high speed underwater, supercavitating flow arises, in which a huge cavity is generated behind the projectile so that only the nose, i.e., the cavitator, of the projectile is wetted, while the rest of it should be surrounded by the cavity. In that case, the projectile can achieve very high speed due to the reduced drag. Furthermore if the nose of the body is shaped properly, the attendant pressure drag can be maintained at a very low value, so that the overall drag is also reduced dramatically. In this study, shape optimization technique is employed to determine the optimum cavitator shape for minimum drag, given certain operating conditions. Shape optimization technique is also used to solve the potential flow problem fur any given cavitator, which is a free boundary value problem having the cavity shape as unknown a priori. Analytical sensitivities are derived for various shape parameters in order to implement a gradient-based optimization algorithm. Simultaneous optimization technique is proposed for efficient cavitator shape optimization, in which the cavity and cavitator shape are determined in a single optimization routine.

• 한국컴퓨터그래픽스학회논문지
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• 제17권1호
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• pp.1-7
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• 2011

본 논문에서는 2-변수 모션 (two-parameter motion)을 이용한 새로운 스윕곡면의 생성 및 편집기법을 제시한다. 먼저, 하나의 변수로 매개화되는 기존의 모션에서 방향곡선 (orientation curve)과 크기 변환곡선 (scaling curve)을 곡면의 형태로 확장한 2-변수 모션의 개념을 소개하고, 이를 이용한 새로운 스윕곡면을 제안한다. 제안된 스윕곡면은 하나의 정점이 2-변수 모션에 적용된 결과이며, u-방향의 등위곡선 (iso-curve)이 매개변수 ${\upsilon}$에 따라 다른 형상을 갖게된다. 또한 이에 대한 효율적인 모델링 및 편집기법은 2-변수모션의 직관적인 제어를 통해서 이루이진다. 본 논문에서는 복잡한 형상에 대한 모델링 및 편집 실험을 통해서 제안된 기법의 효율성 및 편리성을 입증한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.15-18
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• 2005

As consumer in optics, electronics, aerospace and electronics industry grow, the demand for ultra-precision aspheric surface lens increases higher. To enhance the precision and productivity of ultra precision aspheric surface micro lens, The development of ultra-precision grinding system and manufacturing properties for the aspheric surface micro lens are described. In the work reported in this paper, and ultra-precision grinding system for manufacturing the aspheric surface micro lens was developed by considering the factors affecting the surface roughness and profiles accuracy. And this paper deals with mirror grinding of an aspheric surface micro lens by resin bonded diamond wheel and spherical lens of BK7. It results was that a form accuracy of $3\;{\mu}m$ P-V and a surface roughness of $0.1\;{\mu}m\;R_{max}$.

• 한국정밀공학회지
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• 제16권1호통권94호
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• pp.68-74
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• 1999

One of the recent changes in machining technology is rapid application of micro- and high precision grinding processes. A fine groove generation is necessary for the fabrication of optic, electronic and semiconductor parts, and achieved by chemical or mechanical processes. Slot grinding is very efficient for the generation of micro ordered groove with hard and brittle materials. As slot grinding is continuous, the ground depth become gradually shallow because of wheel wear. The form accuracy become worse from the increase of ground slot width by the loading phenomena at wheel side, results on chipping damage of the workpiece. The experiments achieve to the enhancement of the form accuracy and chipping free of the brittle materials using V shaped cast iron bonded diamond wheels. In this study we focused on the investigation of the effect of the high pressure air jet on the grinding characteristics. As a results, we found that the high pressure air jet is very effective on the reductions of the wheel wear, enhancement of the form accuracy.

• 대한조선학회논문집
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• 제51권3호
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• pp.203-211
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• 2014

To raise the industrial competitiveness in the field of ship-building, it is crucially important that the yard should use production facilities and working space effectively. Among the related works, the management of tremendous blocks' number, the limited area of assembly shops and inefficient personnel and facility management still need to be improved in terms of being exposed to a lot of problems. To settle down these conundrums, the various strategies of block arrangement on the assembly floors have been recently presented and in the results, have increasingly began to be utilized in practice. However, it is a wonder that the sampled or approximated block shapes which usually are standardized projections or the geometrically convex contour only have been prevailed until now. In this study, all parts including the panel, stiffeners, outer shells, and all kinds of outfitting equipment are first extracted using the Volume Primitive plug-in module from the ship customized CAD system and then, the presented system constructs a simpler and more compact ship data structure and finally generates the novel projected contours for the block arrangement system using the adaptive concave hull algorithm.

• 한국소음진동공학회논문집
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• 제19권11호
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• pp.1151-1157
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• 2009

Ensuring both product quality and reducing material cost are important issue for the design of the piping system of an air conditioner outdoor unit. This paper describes a shape optimization that achieves mass reduction of an air conditioner piping system while satisfying two design constraints on resonance avoidance and the maximum stress in the pipes. In order to obtain optimized design results with various analysis fields considered simultaneously, an automated multidisciplinary analysis system was constructed using PIAnO v.2.4, a commercial process integration and design optimization(PIDO) tool. As the first step of the automated analysis system, a finite element model is automatically generated corresponding to the specified shape of the pipes using a morphing technique included in HyperMesh. Then, the performance indices representing various design requirements (e.g. natural frequency, maximum stress and pipe mass) are obtained from the finite element analyses using appropriate computer-aided engineering(CAE) tools. A sequential approximate optimization(SAO) method was employed to effectively obtain the optimum design. As a result, the pipe mass was reduced by 18 % compared with that of an initial design while all the constraints were satisfied.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1876-1881
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• 2003

When a projectile travels at high speed underwater, supercavitating flow arises, in which a huge cavity is generated behind the projectile so that only the nose, i.e., the cavitator, of the projectile is wetted, while the rest of it should be surrounded by the cavity. In that case, the projectile can achieve very high speed due to the reduced drag. Furthermore if the nose of the body is shaped properly, the attendant pressure drag can be maintained at a very low value, so that the overall drag is also reduced dramatically. In this study, shape optimization technique is employed to determine the optimum cavitator shape for minimum drag, given certain operating conditions. Shape optimization technique is also used to solve the potential flow problem for any given cavitator, which is a free boundary value problem having the cavity shape as unknown a priori. Analytical sensitivities are derived for various shape parameters in order to implement a gradient-based optimization algorithm. Simultaneous optimization technique is proposed for efficient cavitator shape optimization, in which the cavity and cavitator shape are determined in a single optimization routine.

• 한국생산제조학회지
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• 제21권3호
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• pp.425-432
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• 2012

This paper investigates shape design processes of two implant systems for bone fracture treatment ; Bone plate and Interlocking nail system. These systems can directly fix fractured human bones by surgical operations. The bone plates consist of various shaped plates and implant screws for fixation of fractured human bones with various manual instruments allowing to handle them. The material corresponds to titanium alloy Ti6Al4V because it is harmless material for human body as well as significantly rigid. This system has to be suitably rigid as well as manually bended in orthopedic surgery operations. The Interlocking nail system is a kind of nail implanted inside fractured human bones. The shapes of these systems have to be suitably designed in order to endure various loads as well as avoid any damages. If various shaped prototypes would be fabricated and tested to design the optimal shapes, optimal shapes could be obtained but very long time and expensive costs must be required. In this paper finite element method was applied into these systems. Under various boundary conditions a series of structural analysis was conducted by using ANSYS. Finally important shape factors could be determined on the basis of the analysis results.

• 한국해양환경ㆍ에너지학회지
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• 제5권4호
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• pp.57-62
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• 2002

본 연구는 크기와 형상이 동일한 2차원 모래언덕이 계속해서 이어지는 2차원 난류유동장의 해석에 관한 연구이다. 실험은 완전발달 유동장이 형성된 Flume에서 PIV를 사용하여 진행되었다. 모래언덕의 모형은 강화유리로 제작되었으므로 그 형상은 흐름에 의하여 변하지 않는 경우이다. 연구를 통하여 모래언덕을 지나는 유동의 일반적인 특성들을 재확인할 수 있었는데, 여기에는 재순환영역의 크기, 유통박리 영역과 재부착영역 등이 포함된다. 언덕의 정상 (y/h=1) 부근을 따라 유동방향으로 난류와 와도가 매우 크게 얻어졌으며, 뚜렷이 구별되지는 않지만 y/h=2 부근에는 그 전 언덕들로부터 전달되어진 난류유동특성을 확인할 수 있었다.

• 한국정밀공학회지
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• 제31권3호
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• pp.207-213
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• 2014

A study was carried out to fabricate the cutting tool geometry with micro/nanoscale on the single crystal diamond tool by using the FIB. The FIB technique is an ideal tool for TEM sample preparation that allows for the fabrication of electron-transparent foils. The FIB is appropriate techniques to sample and subsequently define the chemical composition and the structural state of mineral inclusion on the micro/nanoscale. The combination of FIB with a SEM allows for 3D information to be obtained from samples including 3D imaging. Cutting strategies were demonstrated to improve the performance of cutting tool geometry and to generate high aspect ratio micro cutting tool. A finely focused beam of 30keV Ga+ ions was used to mill cutting tool shapes for various micro patterns. Therefore FIB sputtering is used to shape a variety of cutting tools with dimensions in the $1-5{\mu}m$ range and cutting edge radii of curvature of under 50nm.