• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 춘계학술발표회논문집(1)
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• pp.600-605
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• 1997

Sandia National Laboratories(SNL)에서 수행된 원자로 용기의 고온, 고압 크리프 파괴 실험의 하나인 Lower Head Failure-1(LHF-1)에 대한 코드 해석을 수행하였다. 해석 코드로는 범용 유한요소 구조해석 코드인 ABACUS를 사용하였고, Idaho National Engineering Laboratory(INEL)의 크리프 데이터를 이용하였다. 크리프 해석에는 strain hardening 식을 적용하였고, 크리프 데이터를 적용하기 위해서 user subroutine을 개발하였다. 민감도 분석의 일환으로 내부 압력을 1.2배로 증가시킨 경우에 대해 수행한 해석 결과가 실험 결과와 유사하였다 해석 결과를 분석하여 현 크리프 데이터의 절대적 부족을 확인하였고, 크리프데이터 생산을 위한 크리프 시험을 계획하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.228-232
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• 2010

In this paper, various operating parameters of stream reforming process from methane in preconverter for MCFC is studied by numerical method. Commercial code is used to simulated the porous catalyst with user subroutine to model three dominant chemical reactions which are Stream Reforming(SR), Water-Gas Shift(WGS), and Direct Stram Reforming(DSR). The hydrogen production is tested with different wall temperature, Gas Hourly Space Velocity(GHSV), and different reactor shapes.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1986년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 17-18 Oct. 1986
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• pp.337-340
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• 1986

A software package CARDS for general purpose robot design, control, and simulation has been developed and is presented here. CARDS (Computer Aided Robot Design and Simulation) consists of a collection of standardized subroutine modules that carry out typical kineamatic, dynamic, and control computations so that the user only needs to write a main program that further defines a particular robot configuration and the task to be performed. It provides users a complete simulation environment, so that it will be a valuable engineering tool for mechanical designers as well as electric control designers.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.409-414
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• 2003

This paper develops a relatively comprehensive and sophisticated constitutive model of concrete for finite element analysis of concrete structures. The present model accounts for the hydrostatic pressure sensitivity and Lode angle dependence behavior of concrete, not only in its strength criterion, but also in its hardening characteristics. The implementation is carried out through incorporating the developed concrete model in User Subroutine Material(UMAT) of the general-purpose FE program ABAQUS(v.5.8). It is found that the model can sufficiently predict the hardening as well as the softening behaviour of concrete under high confining pressure.

• International Journal of Aeronautical and Space Sciences
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• 제7권1호
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• pp.91-98
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• 2006

The thermomechanical behaviors of SMA thin film actuator and their application are investigated. The numerical algorithm of the 2-D SMA thermomechanical constitutive equation is developed and implemented into the ABAQUS finite element program by using the user defined material (UMAT) subroutine. To verify the numerical algorithm of SMAs, the results are compared with experimental data. For the application of SMA thin film actuator, the methodology to maintain the precise configuration of inflatable membrane structure is demonstrated.

• 한국정밀공학회지
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• 제17권1호
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• pp.164-170
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• 2000

Important factors in a casting mold are strength at the mold surface and gas permeability of the mold. This study investigates the effects of pre-pressure and sand particle hardness on gas permeability, with a constraint that the norm of a stiffness array at the mold surface should be higher than a certain value. The constitutive relation is obtained using a hypoplasticity model. This study is firstly attempted to investigate sand behavior in mold fabrication, and will give a theoretical base for fabricating better molds.

• 한국자동차공학회논문집
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• 제11권3호
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• pp.145-154
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• 2003

Occupant simulation models have been used to study trends or specific design changes in several typical crash situations. The ATB, Articulated Total Body, was developed and used to predict gross human body responses to vehicle crashes and pilot ejections. Since the ATB source code is open to public, the user can add their own defined modules and functions. The introduction of seat belts into cars significantly decreased the injury risk of passengers in frontal impacts. In this paper, a new seat belt model was developed and implemented into the ATB. For this purpose, a subroutine of the new seat belt was constructed. A force-deflection function was added to replace an existing function to consider energy absorption. The function includes hysteresis effects of the experiment data of the loading and unloading parts of the seat belt load-extension curve. Moreover, this belt model considers a slip between ellipsoid and belt segments. This paper attempted to validate the ATB program which includes the subroutine of new belt models comparing with the real car frontal crash experiments and MADYMO frontal models. The analysis focusses on the human movement and body accelerations.

• Computers and Concrete
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• 제30권4호
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• pp.289-299
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• 2022

Based on the random cracking theory, the cylinder RVE model of reinforced concrete is established and the damage process is divided into three stages as the evolution of the cracks. The stress distribution along longitude direction of the concrete and the steel bar in the cylinder model are derived. The equivalent elastic modulus of the RVE are derived and the user-defined field variable subroutine (USDFLD) for the equivalent elastic modulus is well integrated into the ABAQUS. Regarding the tensile rebars and the concrete surrounding the rebars as the equivalent homogeneous transversely isotropic material, and the FEM analysis for the reinforced concrete beams is conducted with the USDFLD subroutine. Considering the concrete cracking and interfacial debonding, the macroscopic damage process of the reinforced concrete beam under four-point bending loading in the simulation. The volume fraction of rebar and the cracking degree are mainly discussed to reveal their influence on the macro-performance and they are calibrated with experimental results. Comparing with the bending experiment performed with 8 reinforced concrete beams, the bending stiffness of the second stage and the ultimate load simulated are in good agreement with the experimental values, which verifies the effectiveness and the accuracy of the improved finite element method for reinforced concrete beam.

• 한국해양공학회지
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• 제29권6호
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• pp.454-462
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• 2015

An extended study was conducted on the fracture criterion by Choung et al. (2011; 2012) and Choung and Nam (2013), and the results are presented in two parts. The theoretical background of the fracture and the results of new experimental studies were reported in Part I, and three-dimensional fracture surface formulations and verifications are reported in Part II. How the corrected true stress can be processed from the extrapolated true stress is first introduced. Numerical simulations using the corrected true stress were conducted for pure shear, shear-tension, and pure compression tests. The numerical results perfectly coincided with test results, except for the pure shear simulations, where volume locking appeared to prevent a load reduction. The average stress triaxialities, average normalized lode parameters, and equivalent plastic strain at fracture initiation were extracted from numerical simulations to formulate a new three-dimensional fracture strain surface. A series of extra tests with asymmetric notch specimens was performed to check the validity of the newly developed fracture strain surface. Then, a new user-subroutine was developed to calculate and transfer the two fracture parameters to commercial finite element code. Simulation results based on the user-subroutine were in good agreement with the test results.

• 한국전산구조공학회논문집
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• 제22권4호
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• pp.363-370
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• 2009

본 논문에서는 비선형 유한요소해석 기법을 이용하여 API-X80 강재 라인파이프의 대변형 비선형 거동을 모사하였다. 강재의 구성방정식을 작성하기 위해 GTN(Gurson-Tvergaard-Needleman) 모델을 사용하였다. 대변형 해석을 위해 범용 유한요소해석 프로그램인 ABAQUS과 연계해서 사용할 수 있는 사용자 서브루틴(User Subroutine)의 사용자 재료모델(UMAT)을 개발하였다. 유한요소해석 결과와 일축인장실험의 결과와의 비교를 통해 GTN 모델에서 사용되는 재료모델상수를 도출하였다. 도출된 모델상수를 이용해 API-X80 강재 라인파이프의 소성 좌굴변형해석을 실시하여 실험결과와 비교하였고 소성 좌굴변형에서 발생하는 거동 특성을 성공적으로 모사하였다.