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유리섬유강화형 폴리우레탄폼의 재료비선형해석을 위한 이방성 점탄소성손상모델 개발 및 유한요소 적용
이치승,김명현,이제명 한국해양환경·에너지학회 2012 한국해양환경공학회 학술대회논문집 Vol.2012 No.5
In the present study, the anisotropic viscoplastic?damage model is proposed to estimate and predict the material non-linearity and damage growth of reinforced polyurethane foam (RPUF). The developed model is independent on the yield criterion and the loading path. It is dependent on the plastic work and softening-hardening parameters. In addition, the damage growth is calculated based on the multi-axial stress function which is function of maximum tensile principal stress and first stress invariant. The developed viscoplastic-damage model is formulated based on the Algorithmic Tangential Stiffness (ATS) method during stress update and is implemented into ABAQUS user defined subroutine (UMAT). The analysis results of material behavior and damage growth of RPUF is compared to the uniaxial tensile and compressive tests Of RPUF.
이치승,김영환,김태우,이제명 대한용접접합학회 2007 대한용접·접합학회지 Vol.25 No.1
Once assessment of material failure characteristics is captured precisely in a unified way, it can be directly incorporated into the structural failure assessment under various loading environments, based on the theoretical backgrounds so called Local Approach to Fracture. The aim of this study is to develop a numerical fatigue test method by continuum damage mechanics applicable for the assessment of structural integrity throughout crack initiation and structural failure based on the Local Approach to Fracture. The generalized elasto-visco-plastic constitutive equation, which can consider the internal damage evolution behavior, is developed and employed in the 3-D FEA code in order to numerically evaluate the material and/or structural responses. Explicit information of the relationships between the mechanical properties and material constants, which are required for the mechanical constitutive and damage evolution equations for each material, are implemented in numerical fatigue test method. The material constants selected from constitutive equations are used directly in the failure assessment of material and/or structures. The performance of the developed system has been evaluated with assessing the S-N diagram of stainless steel materials.
이치승,Haeng-Sung Heo,Young-Nam Kim,김명현,김상현,이제명 대한조선학회 2012 International Journal of Naval Architecture and Oc Vol.4 No.2
In the present study, the structural response of breakwaters installed on container carriers against green water impact loads was numerically investigated on the basis of the fluid-structure interaction analysis. A series of numerical studies is carried out to induce breakwater collapse under such conditions, whereby a widely accepted fluidstructure interaction analysis technique is adopted to realistically consider the phenomenon of green water impact loads. In addition, the structural behaviour of these breakwaters under green water impact loads is investigated simultaneously throughout the transient analysis. A verification study of the numerical results is performed using data from actual collapse incidents of breakwaters on container carriers. On the basis of the results of a series of numerical analyses, the pressure distribution of green water was accurately predicted with respect to wave mass and velocity. It is expected that the proposed analytical methodology and predicted pressure distribution could be used as a practical guideline for the design of breakwaters on container carriers.
유리섬유강화형 폴리우레탄폼의 재료비선형해석을 위한 이방성 점탄소성손상모델 개발 및 유한요소 적용
이치승,김명현,이제명 대한조선학회 2012 대한조선학회 학술대회자료집 Vol.2012 No.5
In the present study, the anisotropic viscoplastic-damage model is proposed to estimate and predict the material nonlinearity and damage growth of reinforced polyurethane foam (RPUF). The developed model is independent on the yield criterion and the loading path. It is dependent on the plastic work and softening-hardening parameters. In addition, the damage growth is calculated based on the multi-axial stress function which is function of maximum tensile principal stress and first stress invariant. The developed viscoplastic-damage model is formulated based on the Algorithmic Tangential Stiffness (ATS) method during stress update and is implemented into ABAQUS user defined subroutine (UMAT). The analysis results of material behavior and damage growth of RPUF is compared to the uniaxial tensile and compressive tests of RPUF.
이치승,이성철 한국화학공학회 2004 Korean Journal of Chemical Engineering Vol.21 No.6
To analyze the physical phenomena occurring in the Proton Exchange Membrane Fuel Cell (PEMFC)using Computational Fluid Dynamics (CFD) technique under an isothermal operating condition, four major governingequations such as continuity equation, momentum conservation equation, species transport equation and charge con-servation equation should be solved. Among these governing equations, using the interfacial boundary condition isnecessary for solving the water transport equation properly since the concept of water concentration in membrane/elec-trode assembly (MEA) and other regions is totally different. It was first attempted to solve the water transport equationdirectly in the MEA region by using interfacial boundary condition; and physically-meaningful data such as watercontent, proton conductivity, etc. were successfuly obtained. A detailed problem-solving methodology for PEMFCis presented and result comparison with experimental data is also implemented in this paper.
D-24 : Numerical Analysis of Physical and Electrochemical Phenomena in PEM Fuel Cell
이치승,이성철 한국화학공학회 2007 화학공학의이론과응용 Vol.10 No.2
A mathematical model for PEMFC simulation was developed and improved in order to analyze physical and electrochemical phenomena using Computational Fluid Dynamics(CFD) technique. In this model, momentum conservation equation, speceis transport euquation(H2, O2, N2, H2O_vap., water content) and charge conservation equation are solved simultaneously. In this study, we mainly focus on physical and electrochemical behavior in PEMFC system in accordance with its various operating condtions; (i) H2, O2, H2O_vap. distribution and their effects on electrochemical reaction in anode and cathode catalyst layer (ii) water content and proton conductivity distribution and their effects on current density distribution in MEA (iii) EOD(Electro Osmotic Drag) effect on water profile in MEA (iv) prediction of polarization curve and cell efficiency based on various operating conditions.
이치승,이제명,Lee, Chi-Seung,Lee, Jae-Myung 대한용접접합학회 2009 대한용접·접합학회지 Vol.27 No.6
In this study, the numerical analysis model for fatigue life prediction of welded structures are presented. In order to evaluate the structural degradation of welded structures due to fatigue loading, continuum damage mechanics approach is applied. Damage evolution equation of welded structures under arbitrary fatigue loading is constructed as a unified plasticity-damage theory. Moreover, by integration of damage evolution equation regarding to stress amplitude and number of cycles, the simplified fatigue life prediction model is derived. The proposed model is compared with fatigue test results of T-joint welded structures to obtain its validation and usefulness. It is confirmed that the predicted fatigue life of T-joint welded structures are coincided well with the fatigue test results.
이치승,김영환,김태우,유병문,이제명,Lee, Chi-Seung,Kim, Young-Hwan,Kim, Tae-Woo,Yoo, Byung-Moon,Lee, Jae-Myung 대한용접접합학회 2008 대한용접·접합학회지 Vol.26 No.3
Fatigue life evaluation of welded structures in a range of high cycles is one of the most difficult problems since extremely small plastic deformation and damage occur during the loading cycles. Moreover, it is very difficult to identify the strong non-linearities of welding, inducing residual stress. In this paper, numerical fatigue test method for welded structures was developed using continuum damage mechanics with inherent strain. Recently, continuum damage mechanics, which can simulate both crack initiation at the micro-scale level and crack propagation at the meso-scale level, has been adopted in the fracture related problem. In order to consider the residual stresses in the welded strictures, damage calculation in conjunction with welding, inducing inherent strain, was proposed. The numerical results obtained from the damage calculation were compared to experimental results.
이치승,조진래,김화수,노병재,김명현,이제명 대한조선학회 2013 International Journal of Naval Architecture and Oc Vol.5 No.1
In the present paper, the sloshing resistance performance of a huge-size LNG carrier’s insulation system is evaluated by the fluid-structure interaction (FSI) analysis. To do this, the global-local analysis which is based on the arbitrary Lagrangian-Eulerian (ALE) method is adopted to accurately calculate the structural behavior induced by internal LNG sloshing of a KC-1 type LNG carrier insulation system. During the global analysis, the sloshing flow and hydrodynamic pressure of internal LNG are analyzed by postulating the flexible insulation system as a rigid body. In addition, during the local analysis, the local hydroelastic response of the LNG carrier insulation system is computed by solving the local hydroelastic model where the entire and flexible insulation system is adopted and the numerical analysis results of the global analysis such as initial and boundary conditions are implemented into the local finite element model. The proposed novel analysis techniques can potentially be used to evaluate the structural integrity of LNG carrier insulation systems.