• 한국지반공학회논문집
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• 제20권3호
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• pp.85-96
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• 2004

본 연구는 점토층위의 모래지반에 위치하는 표면기초의 극한지지력에 대해 이론적으로 조사하였다. 실용적인 적용을 위하여 표면기초의 지지력에 관한 연구들에 대한 검토와 논의가 제시되며, 한계해석(Limit Analysis)의 운동학적 접근방법을 이용하여 정해의 극한 지지력이 계산되었다. 운동학적 해는 상한값이며 해의 정확성은 파괴메카니즘의 형상에 달려 있다. 이러한 방법은 설계도표를 만드는데 편리할 뿐만 아니라 물성치의 영향을 추정할 수 있다. 본 연구에서는 범용 유한요소해석 프로그램인 ABAQUS를 사용하여 탄소성 이론에 근거하여 극한지지력을 계산하였다. 운동학적 방범으로 계산된 결과와 유한요소 해석, 한계평형론에 근거한 몇몇 알려진 식들(Yamaguchi, Meyerhof와 Okamura 등)에 의한 결과를 비교하였다. 아울러, 운동학적 방법에 의한 제안식과 유한요소해석 결과와 한계평형해석 결과의 유효성에 대하여 검증하였다.

• Biomaterials and Biomechanics in Bioengineering
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• 제2권4호
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• pp.207-223
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• 2015

In this paper a method for simultaneous swift non-linear analysis and optimal design/posture of mechanical/biomechanical systems is presented. The method is developed to get advantages of iterations in non-linear analysis and/or generations in genetic algorithm (GA) for the purpose of efficient analysis within the optimal design/posture. The method is applicable for both size and geometry optimizations wherein material and geometry non-linearity are present. In addition to established mechanical systems, the method can solve biomechanical models of human musculoskeletal system. Optimization-based procedures are popular methods for resolving the redundancy at joints wherein the number of unknown muscle forces is far more than the number of equilibrium equations. These procedures involve optimization of a cost function(s) which is assumed to be consistent with the central nervous system's strategy when activating muscles to assure equilibrium. However, because of the complexity of biomechanical problems (i.e., due to non-linear biomaterial, large deformation, redundancy of the problem and so on) efficient analysis are required within optimization procedures as suggested in this paper.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.135-137
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• 2014

Excess enthalpy flame propagating an porous inert medium, which recirculate exhaust heat to the upstream cold mixture, is theoretically analyzed. Using the activation-energy asymptotics, the flame structure is divided into the thin reaction and the gas-phase preheat zone, as is traditionally done. Ahead and behind of the two, there exist an outer preheat zone, where heat is convectively transferred from solid to gas, and a downstream re-equilibrium zone, where thermal equilibrium between phases is established. Asymptotic solutions of species and energy equations in each zone are obtained and then matched to each other, and finally the mass burning rate is obtained as a function of the flame propagation velocity with respect to the solid phase and physical properties of gas and solid.

• 대한전기학회논문지:전력기술부문A
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• 제54권7호
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• pp.337-344
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• 2005

An energy function is derived on the basis of the EMM(Equivalent Mechanical Model) to take account of the effects of tap changer, and then the VC(Voltage Collapse) criteria is proposed to predict the voltage collapse in Power systems. The VC criterion can be evaluated by using the energy margin given by the energy gap between UEP(Unstable Equilibrium Point) and SEP(Stable Equilibrium Point) of the energy function adopted, in which it is noted that the energy contour should be considered due to energy discontinuity associated with tap changing. This paper shows that the proposed VC criterion improves the accuracy of voltage stability analysis with application to a two-bus sample system.

• 항공우주기술
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• 제7권2호
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• pp.157-161
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• 2008

본 연구에서는 액체로켓엔진의 가스발생기와 연소기의 연소현상을 화학평형의 관점으로 접근하여 주어진 압력과 혼합비 하에서 연소가스의 화학조성을 Gibbs 자유에너지 최소화기법을 이용하여 계산할 수 있는 프로그램의 개발을 다루었다. 기존에 개발되어 연소해석에 광범위하게 사용되고 있는 NASA의 CEA code와의 해석결과 비교를 통하여 새로 개발된 연소해석 프로그램의 정확성을 검증하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제26회 춘계학술대회논문집
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• pp.7-10
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• 2006

본 논문에는 준평형 모델을 사용하는 PAD(propellant actuated device) 시스템의 거동 및 추진제 형상설계에 관하여 기술하였다. 준평형 모델의 검증을 위해 PAD 시스템 시험이 수행되었다. 시험과 해석 결과를 비교하여 상호 경향이 유사함을 확인함으로써 준평형 모델적용치 타당성을 입증하였고, 사용된 시스템의 열손실 및 마찰계수를 얻을 수 있었다. 개발된 설계기법은 향후 PAD 시스템 설계시에 유용하게 사용될 것이다.

• Structural Engineering and Mechanics
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• 제12권1호
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• pp.35-50
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• 2001

A numerical methodology is presented in this paper for the geometrically non-linear analysis of slender uni-dimensional structural elements under unilateral contact constraints. The finite element method together with an updated Lagrangian formulation is used to study the structural system. The unilateral constraints are imposed by tensionless supports or foundations. At each load step, in order to obtain the contact regions, the equilibrium equations are linearized and the contact problem is treated directly as a minimisation problem with inequality constraints, resulting in a linear complementarity problem (LCP). After the resulting LCP is solved by Lemke's pivoting algorithm, the contact regions are identified and the Newton-Raphson method is used together with path following methods to obtain the new contact forces and equilibrium configurations. The proposed methodology is illustrated by two examples and the results are compared with numerical and experimental results found in literature.

• Journal of Welding and Joining
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• 제16권5호
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• pp.67-75
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• 1998

This study aimed at he experimental and finite element analytic investigation of the effect of preheating on he residual stress of weldment. In this study, an autogenous arc welding was used on type 304 stainless steel and MARC as F.E.M. common code was utilized in analysis The analyses include transient and moving heat source and thermal properties as function of temperature. During welding, the thermal cycles of four locations in the weldment were recorded to investigate of the behavior of thermal stress and residual stress. The experimental and analytic results had good coincidence and show that there are two factors influencing the formation of welding residual stress in preheat process. One is the elevation of welding equilibrium temperature and the other is the increase of amount of heat input. The former decrease welding residual stress and the latter increase welding residual stress. Therefore, the cumulative effects result in the welding residual stress not being improved significantly with preheating in 304 stainless steel.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.1279-1285
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• 2010

Our country has a tendency to build many structures by cutting mountainous areas due to geographical features. Among these construction done in our country, road construction take the first spot in rank. As the construction is done, fractured inclining plane is created inevitability because of the natural properties of mountainous areas. The stability of the fractured inclining planes and slope formed in the opening, which are developed at the time of construction, need to be evaluated. Also, reinforcement plans for these matters are necessary. This paper is to go through an examination on the fractured inclining surface that is developed at the time of construction, especially the composite inclining plane that consists of soil and rocks. Furthermore, evaluating the stability by performing an analysis on stereographic projection and limit equilibrium, based on the examination results. using the stability evaluations, applications were explored for reinforcement methods of construction that fits the geological characters of this inclining surface.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 추계 학술대회논문집
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• pp.13-17
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• 2006

RoeM and AUSMPW+ schemes are two of the most accurate and efficient schemes which are recently developed for the analysis of single phase gas dynamics. In this paper, we developed two-phase versions of these schemes for the analysis of gas-liquid large density ratio two-phase flow. We adopt homogeneous equilibrium model (HEM) using mass fraction to describe different two phases. In the Eulerian-Eulerian framework, HEM assumes dynamic and thermal equilibrium of the two phases in the same computational mesh. From the mixture equation of state (EOS), we derived new shock-discontinuity sensing term (SDST), which is commonly used in RoeM and AUSMPW+ for the stable numerical flux calculation. The proposed two-phase versions of RoeM and AUSMPW+ schemes are applied on several air-water two-phase test problems. In spite of the large discrepancy of material properties such as density, enthalpy, and speed of sound, the numerical results show that both schemes provide very satisfactory solutions.