• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.192-197
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• 1995

소재의 손실을 최소한 줄이면서 원하는 형상의 제품을 가공하는 가장 기본적인 금속 가공 방법은 금형을 이용하는 금속 성형(metal forming)이다. 본 논문에서는 준정적 금속 성형 문제 해석 에대한 외연적 시간 적분 유한 요소법의 적용성을 평가 하기 위하여 변형모드가 복잡한 박판튜브 (thin-walled tube)의 좌굴문제를 해석하여 변형과정이 이론 및 실험결과와 비교적 잘 일치하는지 살펴보기로 한다. 또한 준정적 금속 성형 문제 해석에 외연적 시간 적분 유한 요소법을 사용할 때 계산 시간을 줄이기 위하여 많이 사용되는 가압속도 조절법(loading velocity control technique) 의 타당성을 평가하기 위하여 박판 튜브와 중실 실린더(solid cylinder)의 변형 속도에 따른 변형 모드의 변화를 비교 관찰하여 기하학적 형상에따른 가압속도 조절법의 적용 가능 여부를 분석하여 보겠다.

• The Transactions of the Korea Information Processing Society
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• v.6 no.7
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• pp.1817-1824
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• 1999

How to efficiently and optimally schedule iterative is one of the critical issues in FMC(Flexible Manufacturing Cell). In this paper, we apply transformation rules to find the solution of the scheduling problem in FMC. These kinds of rules have already been applied for the analysis of autonomous Petri nets. Here in, transformation is intended to preserve the existence of at least one optimal solution for the scheduling problem. Some transformations rules to reduced TPN's size without changed the initial characteristics are proposed and applied to analyze the scheduling problem of FMC.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.42 no.3 s.303
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• pp.63-72
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• 2005

In this paper, we propose a deformation technique based on Radial Basis Function (RBF) and a blending technique combining the deformed facial component with the original face for a Virtual Aesthetic Surgery (VAS) system. The deformation technique needs the smoothness and the accuracy to deform the fluid facial components and also needs the locality not to affect or distort the rest of the facial components besides the deformation region. To satisfy these deformation characteristics, The VAS System computes the degree of deformation of lattice cells using RBF based on a Free-Form Deformation (FFD) model. The deformation error is compensated by the coefficients of mapping function, which is recursively solved by the Singular Value Decomposition (SVD) technique using SSE (Sum of Squared Error) between the deformed control points and target control points on base curves. The deformed facial component is blended with an original face using a blending ratio that is computed by the Euclidean distance transform. An experimental result shows that the proposed deformation and blending techniques are very efficient in terms of accuracy and distortion.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.1
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• pp.9-15
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• 2011

The influence of the strain-rate on the superelastic behaviors of shape memory alloys (SMAs) wires is experimentally and numerically investigated. The one-dimensional SMA constitutive equations considering strain-rate effect is developed. The evolution of stress-strain curves of SMA wires is examined with various strain-rates. Results show that the superelastic behaviors of SMAs may significantly be changed depending on the variation of strain-rate.

• Applied Chemistry for Engineering
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• v.23 no.1
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• pp.65-70
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• 2012

Structural changing materials which can induce the physical deformation of materials are interesting research topics with various potential applications. Particularly, light among many driving mechanisms is a non-contact energy source, hence the light-responsive system can be used where non-destructive, local irradiation, and remote control is needed. Here, a mainchain azobenzene polymer is synthesized and its physical and optical properties are observed and compared to that of a polymer having a light-responsive azobenzene moiety on its side chain. Further dispersion onto polyvinylalcohol hydrogel is made and its dual stability and actuation are observed upon UV-visible light irradiation. Extended azobenzene polymer blend films show an anisotropic light-actuation with non-polarized UV light at room temperature. This physical shape change is quite reversible and occurs at lower temperature than that of any other reported systems including liquid crystalline elastomers. It is successfully demonstrated that the simple physical azobenzene/polymer blending has a very good actuation compared to that of LCEs which need an elaborate chemical design and it can be further used in the areas requiring a dimensional shape change.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.10
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• pp.209-216
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• 1999

일반적으로 힘 제어는 힘 센서의 사용 여부에 따라 능동적 힘 제어와 피동적 힘 제어로 분류시킬 수 있다. 능동적 힘 제어는 힘 세서를 이용하여 구속력을 목표한 힘에 근접하도록 제어한다. 유연 매니퓨레이터의 함수(위치, 속도, 가속도)를 이용하여 일정한 힘에 근접하도록 제어한다. 유연 매티퓨레이터에 있어서 링크 선단의 강성 증대는 힘 제어뿐만이 아니라, 링크의 진동을 크게 유발함으로서 위치 제어에 불리하게 작용한다. 주로 사용되고 있는 힘 센서는 많은 변형 게이지(strain gauge)로 구성되어 있다. 유연 매니퓨레이터 또한 링크 선단의 변형을 측정하기 위해 변형 게이지를 사용하고 있다. 본 논문에서는 이점에 착안하여, 유연 매니퓨레이터의 선단의 탄성 변형을 측정하기 위해 장착한 변형 게이지를 이용한 위치/힘 제어를 제안한다. 먼저, 유연 매니퓨레이터의 집중 정수 모델로부터 링크의 탄성 변형과 구속력 관계를 도출한 후 이 관계를 이용하여 3차원 실험 유연 매니퓨레이터를 실시간 위치/힘 제어 실험을 수행하였다. 또한 범용 동력학 해석 소프트웨어인 ADAMS FEM 을 이용하여 해석하였다. 마지막으로, 실험 결과와 해석 결과를 비교 분석하여 본 논문에서 제안한 유연 매니퓨레이터의 위치/힘 제어의 타당성을 입증시켰다.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.5
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• pp.356-361
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• 2005

A temperature-compensating double fiber Bragg grating(FBG) sensor having two different FBGs in one fiber line was proposed for real time measurement of mechanical normal strain in structures. Measurement of mechanical strains of the aluminum beam surface by the double FBG sensor was performed under various thermal conditions, and the results were compared with those of electrical resistance strain gage. The FBG sensor fabricated in this study was able to measure accurately the mechanical strains without containing any thermal strain component.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.528-535
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• 2011

In the present, the formation of shear band under a simple shear deformation is investigated using a rate-independent elastic-plastic constitutive relations. Moreover, the strain gradient terms are incorporated to obtain a non-local plastic constitutive relation, which in turn represented using combined two-back stress hardening model. Then, the continuum damage model is also included to the proposed model. The post-localization behavior are studied by introducing a small imperfection in a work piece. The strain gradient affects the shear localization significantly such that the intensity of shear band decreases as the strain gradient coefficient increases when the J2 flow theory is employed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.2021-2026
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• 2013

In this study, the effect on the welding angle distortion was reviewed by carrying out a thermal elastic-plastic analysis while changing the cooling condition(width, length, and distance from weld torch to cooling torch) the back of the welding zone for the butt weld joint. The review results revealed that maximum 57% of reduction in the angle distortion was achieved when the distance between weld torch and cooling tip of 25mm, cooling length of 80mm, and cooling width of 30mm were maintained.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.7
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• pp.707-712
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• 2015

During the welding process, welding distortion is caused by the non-uniformity of the temperature distribution in the weldment. Welding distortion is redistributed because the residual stress and rigidity change according to the removal of the welded structure. In shipbuilding in particular, this phenomenon may be observed during the cutting process of lugs that are attached to blocks for transfer. The redistribution of welding distortion also causes problems, such as damage to the cutting tool. The aim of this study is to experimentally analyze the redistribution of welding distortion because of the partial removal of the welded structure. In the experiments conducted in this study, fillet welding and cutting were performed, and longitudinal bending and angular distortion in the welded structures were then investigated and analyzed.