• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.38-38
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• 2003

최근 나노기술의 발달과 더불어 나노재료에 대한 특성평가 요구가 높아지고 있고, 따라서 나노스케일로 재료의 기계적 거동을 분석할 수 있는 나노인덴테이션 기법이 심도있게 연구되고 있다. 본 연구에서는 나노인덴테이션을 이용하여 여러 가지 재료의 탄성 소성 변형 거동을 관찰 조사하고 이를 다시 유한요소법(FEM)으로 모사하여 해석하였다. 나노인덴테이션으로 재료 표면에 압입하여 탄소성 변형을 일으켰으며 이때의 가하중과 변형깊이를 측정하여 하중-변형 곡선을 얻었다. 매우 작은 접촉응력 조건하에서는 탄성변형의 비율이 매우 높았는데 하중-변형 곡선으로부터 재료의 나노 경도와 탄성 계수값을 얻을 수 있었다. 실험적으로 얻은 하중-변형 곡선을 3 차원의 유한요소법(FEM)을 이용하여 모사하였는데 상호간에 매우 근접한 결과를 얻을 수 있었다. 이 때 압자의 모양, 압입 깊이, 재료의 종류, 둥을 변수로 하여 여러 가지 조건하에서 압입실험을 하였으며 그 결과를 유한요소법으로 모사하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.464-469
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• 2017

This study evaluated the displacements of a Cu bar in the Y-direction and the relationship between swaging pressures and total contact forces to increase the productivity of the rotor core swaging process. Elastic-plastic numerical analyses of four different Cu bar shapes were performed with a constant swaging pressure to evaluate the displacements of the Cu bar in the Y-direction and the contact force distributions at the contact surfaces during the swaging process. Based on the numerical analysis results, the following conclusions were obtained. First, a simplified 2-dimensional cyclic symmetric analysis model was developed for the numerical analysis of the rotor core swaging process. Second, the final displacements of the Cu bar in the Y-direction were nearly the same as the change of the Cu bar size at a constant swaging pressure. Third, a linear relationship between the swaging pressures and the total contact forces, the so called resistance forces, was suggested.

• Geotechnical Engineering
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• v.10 no.3
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• pp.97-110
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• 1994

Interaction between an unlined tunnel may cause a serious stability both the tunnel and the overlying and unli Red tunnel interaction meta study on the three dimensional bets a three dimensional elasto plastic the program, a wide range of blur puter analysis such as stress distr menu and tunnel deformation were footing and unlined tunnel. The yes traces the ultimate bearing capacity only on the tunnel size and location revealed is that an unlined tunnel under a square footing is subjected to three dimensional stress pattern along the tunnel axis, and that the magnitudes of stresses in the foundation soil and around tunnel perimeter are considerably smaller when loaded with a square than with a strip footings and the difference varies with the location and the type of stress. It is also revealed that the footing failure mechanism varies with the degree of footing and tunnel interaction.

• Journal of Korean Association for Spatial Structures
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• v.11 no.4
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• pp.37-47
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• 2011

This article aims to analytically research for influence of residual stresses on bending moment responses against welded steel pipes subjected to quasi -static or dynamic loadings. The residual stresses of the welded steel pipe are computed by three-dimensional welding simulation. The bending moment responses of the welded and seamless steel pipes are determined by using three-dimensional dynamic elastoplastic FE analysis as a function of loading rate. It is seen from analytical results that the welded steel pipe shows lower moment response comparing to the seamless steel pipe, and moment difference between seamless and welded steel pipes tends to decrease as loading rate increases.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.1
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• pp.81-84
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• 2004

A water-cooled calorimeter chamber with 8 cooling channels based on KSR-III sub-scale chamber has been designed and manufactured. One dimensional empirical correlation has been used at the design stage and full three-dimensional CFD analysis has been conducted to confirm the cooling condition for hot fire test is safe. Predicted heat flux is accurate around the nozzle throat when the thermal resistance of carbon deposit is considered. However relatively large difference is observed in chamber part.

• Journal of the Korean Geotechnical Society
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• v.19 no.3
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• pp.65-74
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• 2003

The dragload on pile groups in consolidating ground was investigated based on a numerical analysis. The case of a single pile and subsequently the response of groups were analyzed by 2D and 3D finite element studies. Conventional continuum elements and special slip elements were used in the analyses for comparison. Based on a limited parametric study, it is shown that dragload for a single pile and group effect are normally overestimated by continuum analyses, compared with the predictions by the slip analyses. The group effect was examined from the slip analysis by considering various factors such as pile configurations, surface loading, interface friction coefficient, and axial loading on piles. An examplary analysis and one previous experimental observation of dragload and group effects were back-analysed. The case histories demonstrated that the slip analysis might predict a better estimate of dragload and group effect compared to the no-slip continuum analysis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.2
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• pp.245-255
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• 1994

A two-dimensional Lagrangian finite-difference computer program is developed for the wave propagation analysis of impact phenomena. The numerical scheme is the standard method originally proposed by Von Neuman and Richtmyer, using artificial viscosity to smooth shock fronts. The material model used in the study is the standard hydrodynamic-elastic-plastic relations with Von-Mises yield criterion. A test configuration consisted of a target and a projectile were calculated to understand the response of a colliding event. However, the computer code is in plane strain, the calculations were intended for generating the qualitative features of the model behaviors. Nevertheless, the computational results were consistent with the experimental observations and provided a rational basis to interpret the modes of failures.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1995.11a
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• pp.171-177
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• 1995

추진기관 연소관 제작시 발생하는 결함등에는 주로 표면결함의 형태의 것이 많은데 연소관 설계시 이러한 결함들의 영향을 고려하는 것이 구조물의 안정성에 있어 중요한 요소가 된다. 따라서 본 논문에서는 연소관에 발생할수 있는 결함들에 대한 파단하중 및 파단압력에 대한 탄성 및 탄소성해석을 통하여 파괴 매개변수인 J적분을 유한요소 프로그램인 ABAQUS를 이용하여 3차원 비선형해석을 수행하여 5가지의 균열모델을 사용하여 평판, 양단개방 압력용기(open tube) 및 양단막힘 압력용기 (closed tube)의 파단하중하에서의 J적분의 영향을 분석하였다. 평판 결함시편의 J적분으로부터 압력용기의 손상허용설계를 할 수 있는 방안을 조사 하였으며 추진기관 연소관에 적용하여 발생가능한 크기의 결함에 대한 안정성을 조사한결과 충분한 안정성을 확보하고 있음을 알수 있었다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.5
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• pp.437-447
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• 2016

In a nuclear power plant, the fuel assembly, which is composed of fuel rods, burns, and the high temperature can generate power. The fuel rod consists of pellets and a cladding that covers the pellets. It is important to understand the pellet-cladding mechanical interaction with regard to nuclear safety. This paper proposes simulation of the PCMI. The gap between the pellets and the cladding, and the contact pressure are very important for conducting thermal analysis. Since the gap conductance is not known, it has to be determined by a suitable method. This paper suggests a solution. In this study, finite element (FE) contact analysis is conducted considering thermal expansion of the pellets. As the contact causes plastic deformation, this aspect is considered in the analysis. A 3D FE module is developed to analyze the PCMI using FORTRAN 90. The plastic deformation due to the contact between the pellets and the cladding is the major physical phenomenon. The simple analytical solution of a cylinder is proposed and compared with the fuel rod performance code results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.8 s.179
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• pp.2015-2021
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• 2000

In order to evaluate the integrity of nuclear power plant components, the analysis based on fracture mechanics is crucial. For this purpose, finite element method is popularly used to obtain J-integral. However, it is time consuming to design the finite element model of a cracked structure. Also, the J-integral should be verified by alternative methods since it may differ depending on the calculation method. The objective of this paper is to develop a three-dimensional elastic-plastic J-integral analysis system which is named as EPAS program. The EPAS program consists of an automatic mesh generator for a through-wall crack and a surface crack, a solver based on ABAQUS program, and a J-integral calculation program which provides DI (Domain Integral) and EDI (Equivalent Domain Integral) based J-integral calculation. Using the EPAS program, an optimized finite element model for a cracked structure can be generated and corresponding J-integral can be obtained subsequently.