• 한국정밀공학회지
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• 제15권4호
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• pp.58-67
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• 1998

A sectional analysis of sheet metal forming process with an arbitrary tool shape is proposed in the present work. To improve the numerical convergence in the conventional membrane sectional analysis, the Bending Energy Augmented Membrane (BEAM) elements had been developed. The BEAM elements particularly improve the stability and convergence of the finite element method for the case of deep drawing. In this work, the FERGUBON spline (C$^2$-continuous) was used to fit the deformed mesh to smooth the given curves and calculate the local curvature of the deformed sheet. The fittings of the deformed sheet and tool surface profile ensure the stability and the convergence of the finite element analysis of highly nonlinear stamping processes. A center floor section and front fender section are analyzed to show the accuracy and robustness of the approach. The results obtained by the proposed approach are compared with the available experimental data.

• Journal of Welding and Joining
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• 제25권5호
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• pp.36-44
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• 2007

This paper is the first part of the study on the accuracy improvement of numerical analysis of steel welds. The aim of this paper is to raise the accuracy of thermal analysis results, such as the shape and size of the weld cross section and the hardness distribution in HAZ(Heat-Affected Zone). It is known that the factors affecting on the accuracy are thermal properties, metallurgical properties and welding heat source model. It was found that the arbitrary distributed heat source model should be used to predict practical weld cross section shape and size. Also, in order to improve the prediction accuracy of HAZ hardness distribution, it was essential to consider 2 CCT(Continuous Cooling Transformation) diagrams in calculating volume fraction of transformed phases. One is the peak temperature being around melting temperature. The other is the peak temperature being around metallurgical transformation temperature.

• 한국정밀공학회지
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• 제8권3호
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• pp.55-63
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• 1991

Transforming small ultrasonic energy into large mechanical energy is the essential feature of ultrasonic vibration in various application fields. This energy amplification can be obtained by achieving resonance condition between booster or tool horn and transducer. When it has uniform section with small sectional area, one dimensional analysis provides good estimation of the natural frequency of the horn. But, for arbitrary shape of horn, one dimensional analysis can no longer be applied. At present, designing tool horn whose natural frequency is identical to that of transducer requires serveral stages of trial and error in actual manufacturing process. In this paper, frequency analysis program is developed to easily predict the natural frequency of ultrasonic vibration cutting tool with axisymmetry and 3- dimensional shape using finite element method.

• 한국지리정보학회지
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• 제11권1호
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• pp.90-104
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• 2008

높은 정확도와 고밀도의 자료를 제공하는 레이저 스캐닝 기술은 공간정보 분야를 포함한 여러 분야에서 폭 넓게 활용되고 있으며 특히, 레이저 스캐닝 기술의 개발은 건설공학분야에 있어서 방대한 정보 추출을 가능케 하여 그 활용성이 매우 높은 실정이다. 본 연구에서는 지상 레이저 스캐닝 기법에 의해 취득된 자료를 이용하여 보다 정확한 터널 내공단면을 결정하고, 이를 실무에서 활용할 수 있는 터널단면관리시스템을 개발한 결과, 다음과 같은 결론을 얻을 수 있었다. 지상 레이저 스캐너를 이용하여 고정밀도의 3차원 자료를 신속 정확하게 취득할 수 있었으며, 자료 처리 단계를 거쳐 0.1m, 0.5m, 1.0m 간격의 임의 단면을 신속히 결정할 수 있었다. 따라서 레이저 스캐닝 기법을 활용함으로써 각 단면의 여굴량과 미굴량 뿐만 아니라, 전체 터널 연장에서 발생한 여굴량과 미굴량을 신속하고 정확히 산정할 수 있었다. 또한, 터널 굴착단계에서 보다 정확한 여굴량과 미굴량을 산정하고, 이를 모니터링 할 수 있는 터널단면관리시스템을 개발하였다. 개발된 GUI 프로그램은 실무에서 더욱 효율적이고 경제적인 터널 굴착관리 및 모니터링을 가능하게 하며 향후, 임의 단면의 자료 추출로 터널 유지 관리에 대한 중요한 기반 자료의 제공 및 활용에 기여할 것으로 판단된다.

• 한국자동차공학회논문집
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• 제13권3호
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• pp.146-153
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• 2005

Structural design of the torsion beam rear suspension is investigated by calculating warping of the torsion beam. Since the longitudinal displacement in the cross section of the torsion beam due to torsional moment causes normal stress across the beam restrained from outside at both ends, the profile of torsion beam needs to be designed considering the warping. Warping function of the beam is derived with the parameters of cross section fur the arbitrary shapes of torsion beam profiles assuming thin-walled open section. From comparing the warping calculated for two different beam profiles, the design method for the torsion beam in the view point of low stress is discussed. It is shown that the gusset used to reinforce the torsion beam can be optimized in accordance with warping shape. The method to fix the end point of the gusset is proposed to minimize the stress concentrated on the end point of the gusset produced during torsional moment. The result from finite element analysis shows the stress is minimized when the height of gusset end point is coincident with the point where warping of the beam is minimized.

• Steel and Composite Structures
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• 제13권1호
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• pp.71-89
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• 2012

The paper investigates beam lateral buckling stability according to linear and non-linear models. Closed form solutions for single-symmetric cross sections are first derived according to a non-linear model considering flexural-torsional coupling and pre-buckling deformation effects. The closed form solutions are compared to a beam finite element developed in large torsion. Effects of pre-buckling deflection and gradient moment on beam stability are not well known in the literature. The strength of singly symmetric I-beams under gradient moments is particularly investigated. Beams with T and I cross-sections are considered in the study. It is concluded that pre-buckling deflections effects are important for I-section with large flanges and analytical solutions are possible. For beams with T-sections, lateral buckling resistance depends not only on pre-buckling deflection but also on cross section shape, load distribution and buckling modes. Effects of pre-buckling deflections are important only when the largest flange is under compressive stresses and positive gradient moments. For negative gradient moments, all available solutions fail and overestimate the beam strength. Numerical solutions are more powerful. Other load cases are investigated as the stability of continuous beams. Under arbitrary loads, all available solutions fail, and recourse to finite element simulation is more efficient.

• 물과 미래
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• 제20권4호
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• pp.249-256
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• 1987

유한수심의 해역중에 잠겨있는 고정된 2차원 구조물에 작용하는 파력을 경계요소법의 선형요소에 의해 해석하였다. 파력은 2차원 선형과 이론으로부터 해석하였으며, 입사파 방향은 무한히 긴 구조물의 직각방향으로 진행한다고 가정하였다. 본 연구에서는 바닥위에 놓여있는 반원 및 원형 단면 송유관, 수중에 잠겨있는 단면 송유관 그리고 임의 형상의 잠제에 작용하는 파력에 관해 해석하였다. 본 계산의 신뢰도를 검증하기 위하여 기존의 실험적, 이론적 결과 및 수치결과와 각각 비교하였다.

• 한국정보통신학회논문지
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• 제7권3호
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• pp.478-484
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• 2003

본 논문에서는 비 등방성 복합 산란체의 전자파 산란문제를 surface integral equation을 적용하여 정식화하는 절차를 보였다. 산란체에는 평면파가 입사하는 것으로 가정하고, 산란체의 표면에 유기되는 등가 표면 전류 및 자류 밀도를 계산하기 위하여 모멘트법을 이용하여 산란체의 표면을 삼각 요소로 이산화하여 적절한 경계조건하에서 몇 가지 수치계산 모델에 대하여 계산을 수행하고 그 유효성을 검증하였다. 계산된 후방산란단면적의 결과는 측정결과와 잘 일치하였다.

• Structural Engineering and Mechanics
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• 제65권4호
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• pp.389-400
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• 2018

An exact solution for the title problem was obtained in closed-form fashion considering general boundary conditions. The expressions of moment, shear and shear coefficient (or shear factor) of cross section under the effect of arbitrary temperature distribution were first derived. In view of these relationships, the differential equations of Timoshenko beam under the effect of temperature were obtained and solved. Second, the characteristic equations of Timoshenko beam carrying several spring-mass systems under the effect of temperature were derived based on the continuity and force equilibrium conditions at attaching points. Then, the correctness of proposed method was demonstrated by a Timoshenko laboratory beam and several finite element models. Finally, the influence law of different temperature distribution modes and parameters of spring-mass system on the modal characteristics of Timoshenko beam had been studied, respectively.

• Structural Engineering and Mechanics
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• 제80권5호
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• pp.625-643
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• 2021

In this paper, we present a new method to calculate interface warping functions for the analysis of beams with geometric and material discontinuities in the longitudinal direction. The classical Saint Venant torsion theory is extended to a three-dimensional domain by considering the longitudinal direction. The interface warping is calculated by considering both adjacent cross-sections of a given interface. We also propose a finite element procedure to simultaneously calculate the interface warping function and the corresponding twisting center. The calculated interface warping functions are employed in the continuum-mechanics based beam formulation to analyze arbitrary shape cross-section beams with longitudinal discontinuities. Compared to the previous work by Yoon and Lee (2014a), both geometric and material discontinuities are considered with fewer degrees of freedom and higher accuracy in beam finite element analysis. Through various numerical examples, the effectiveness of the proposed interface warping function is demonstrated.