• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 추계학술발표대회 개요집
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• pp.126-128
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• 2005

This paper presents a 3-D finite element analysis of a magneto-thermal coupled problem with moving conductor. In the magnetic and thermal analyses, temperature-dependent magnetic and thermal material properties were considered. Transient finite element method for analysis of moving conductor needs many number of elements and much time to make calculation. Therefore, in this paper, finite element formulation derived from quasi-state is adopted. Finite element results were compared with the experimental results. The results demonstrate that this approach is suitable to solve the magneto-thermal coupled problem.

• 대한기계학회논문집B
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• 제23권2호
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• pp.243-253
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• 1999

The dual reciprocity boundary element method (DRBEM) is used to solve the Graetz problem of laminar flow inside circular duct. In this method the domain integral tenn of boundary integral equation resulting from source term of governing equation is transformed into equivalent boundary-only integrals by using the radial basis interpolation function, and therefore complicate domain discretization procedure Is completely removed. Velocity profile is obtained by solving the momentum equation first and then, using this velocities as Input data, energy equation Is solved to get the temperature profile by advancing from duct entrance through the axial direction marching scheme. DRBEM solution is tested for the uniform temperature and heat flux boundary condition cases. Local Nusselt number, mixed mean temperature and temperature profile inside duct at each dimensionless axial location are obtained and compared with exact solutions for the accuracy test Solutions arc in good agreement at the entry region as well as fully developed region of circular duct, and their accuracy are verified from error analysis.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1996년도 춘계공동학술대회논문집; 공군사관학교, 청주; 26-27 Apr. 1996
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• pp.121-124
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• 1996

In general, cellular manufacturing system can be constructed by the following two steps. The first step forms machine cells and part families, and the second step determines cell layout based on the result of first step. Cell layout has to be considered when cell is formed becauese the result of cell formation affects it. This paper presents a cell formation algorithm and proposes an integrated mathematical model for cell formation and cell layout. The cell formation algorithm minimizes the number of exceptional element in cellular manufacturing system. New concept for similarity and incapability is introduced, based on machine-operation incidence matrix and part-operation incidence matrix. One is similarity between the machines, the other is similarity between preliminary machine cells and machines. The incapability identifies relations between machine cells and parts. In this procedure, only parts without an exceptional element are assigned to machine cell. Bottleneck parts are considered with cell layout design in an integrated mathematical model. The integrated mathematical model determines cell layout and assigns bottleneck parts to minimize the number of exceptional element and intercell moving distance, based on linearixed 0-1 integer programming. The proposed algorithm is illustrated by using numerical examples.

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2008년도 학술대회 1부
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• pp.78-84
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• 2008

이 논문에서는 부채꼴 모양을 가진 요소의 집합으로 3 차원 도자기 모델을 구성하고 사용자가 촉감을 느끼면서 가상공간의 도자기를 제작할 수 있도록 하는 새로운 모델을 제안한다. 변형체를 다루기 위해 기존에 사용하던 유한 요소법(finite element method)과 같은 방법은 모델이 복잡하고 연산량이 많아 실시간 햅틱 렌더링(haptic rendering)에 사용하기에는 많은 제약이 있다. 제안한 모델에서는 도자기 모양의 특징에 착안하여 부채꼴 모양을 가진 요소들이 원통 형태로 모여 쌓여있는 구조를 이용하였다. 이를 통해 요소의 개수를 줄이고 복잡한 연산을 최대한 단순화면서 효율적인 모델링이 가능하도록 하였다.

• Journal of Mechanical Science and Technology
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• 제16권12호
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• pp.1687-1692
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• 2002

The problem analyzed here is a sheet metal forming process which requires a drawbead. The drawbead provides the sheet metal enough tension to be deformed plastically along the punch face and consequently, ensures a proper shape of final products by fixing the sheet to the die. Therefore, the optimum design of drawbead is indispensable in obtaining the desired formability. A static-explicit finite element analysis is carried out to provide a perspective tool for designing the drawbead. The finite element formulation is constructed from static equilibrium equation and takes into account the boundary condition that involves a proper contact condition. The deformation behavior of sheet material is formulated by the elastic-plastic constitutive equation. The finite element formulation has been solved based on an existing method that is called the static-explicit method. The main features of the static-explicit method are first that there is no convergence problem. Second, the problem of contact and friction is easily solved by application of very small time interval. During the analysis of drawbead processes, the strain distribution and the drawing force on drawbead can be analyzed. And the effects of bead shape and number of beads on sheet forming processes were investigated. The results of the static explicit analysis of drawbead processes show no convergence problem and comparatively accurate results even though severe high geometric and contact-friction nonlinearity. Moreover, the computational results of a static-explicit finite element analysis can supply very valuable information for designing the drawbead process in which the defects of final sheet product can be removed.

• Advances in aircraft and spacecraft science
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• 제10권2호
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• pp.179-202
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• 2023

This article presents a numerical analysis to investigate the natural frequencies and harmonic response of a perforated cantilever beam attached to two layers of piezoelectric materials by using the finite element method for the first time. The bimorph piezoelectric is composed of 3 layers; two of them at the outer are piezoelectric, and the inner isotropic material. A higher order 3-D 20-node solid element that exhibits quadratic displacement behavior is exploited to discretize the isotropic layer, and coupled piezoelectric 3D element with twenty nodes is used to mesh the top and bottom layers. CIRCU94 element is added to act as a resistor part of the model. The proposed model is validated with previous works. The numerical parametric studies are presented to illustrate the effects of perforation geometry, the number of rows, the resistance on the natural frequencies, frequency response, and power. It is found that the thickness has a positive relationship with the natural frequency. Perforations help in producing higher voltage, and the best shape is rectangular perforations, and to produce higher voltage, two rows of rectangular perforations should be applied.

• 한국멀티미디어학회논문지
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• 제23권11호
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• pp.1361-1371
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• 2020

Fonts have developed as a visual element, and their influence has rapidly increased around the world. Research on font automation is actively being conducted mainly in English because Hangul is a combination character and the structure is complicated. In the previous study to solve this problem, the stroke element of the character was automatically extracted by applying the object detection by component. However, the previous research was only for similarity, so it was tested on various print style fonts, but it has not been tested on other characters. In order to extract the stroke elements of all characters and fonts, we performed a performance analysis experiment according to the expansion character in the Hangul stroke element extraction training. The results were all high overall. In particular, in the font expansion type, the extraction success rate was high regardless of having done the training or not. In the character expansion type, the extraction success rate of trained characters was slightly higher than that of untrained characters. In conclusion, for the perfect Hangul stroke element extraction model, we will introduce Semi-Supervised Learning to increase the number of data and strengthen it.

• 대한기계학회논문집A
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• 제24권4호
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• pp.972-981
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• 2000

The phased array transducer has two distinct advantages. One is rapid scanning comparing with the conventional mechanical or manual scanning system. Therefore, output image is represented in real-time. The other is the dynamic focusing and the dynamic steering of ultrasonic beam. Only the delay times that are controlled electrically are used to focus and to steer beam without any lenses or wedges. In this study, the profile of the ultrasonic beam for the phased array transducer has been simulated in the Huygens principle with varying the inter-element spacing of the linear phased array transducer. From the result of this study, it was found that the ultrasonic beam spread wider as the inter-element spacing was decreased. However, the focusing effect was improved, even when the number of the element was not big. In addition, there was grating lobes that are constructed when the inter-element spacing is more than half wavelength. However, this grating lobe has lower amplitude than the main lobe.

• 한국자동차공학회논문집
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• 제3권3호
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• pp.19-28
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• 1995

The explicit scheme for finite element analysis of sheet metal forming problems has been widely used for providing practical solutions since it improves the convergency problem, memory size and computational time especially for the case of complicated geometry and large element number. The explicit schemes in general use are based on the elastic-plastic modelling of material requiring large computation time. In the present work, rigid-plastic explicit finite element method is introduced for analysis of sheet metal forming processes in which plane strain normal anisotropy condition can be assumed by dividing the whole piece into sections. The explicit scheme is in good agreement with the implicit scheme for numerical analysis and experimental results of auto-body panels. The proposed rigid-plastic explicit finite element method can be used as robust and efficient computational method for prediction of defects and forming severity.

• 대한기계학회논문집
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• 제18권12호
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• pp.3127-3135
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• 1994

An approach to the simultaneous optimal design of structure and control system for large free-free flexible beam is presented. The flexible beam is modeled by the finite element method. And the reduced model of small degree of freedom is constructed by use of modal analysis. The tapered beam is considered so that the number of design variables is not dependent on the increasing number of finite elements. The width of several points of tapered beam and control gain are taken as design variables. The shape of beam and control gain are optimized simultaneously for the minimum weight of total structure including control system subject to the constraints of the magnitude of displacement of beam. It is shown that the simultaneous optimal design of structure and control systems is indeed useful.