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CHABOCHE 통합 점소성 구성방정식을 이용한 재료거동해석
곽대영,임용택,김종범,이형연,유봉,Kwak, D.Y.,Im, Y.T.,Kim, J.B.,Lee, H.Y.,Yu, B. 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.11
Service conditions for structures at elevated temperatures in nuclear power plant involve transient thermal and mechanical load levels that are severe enough to caeuse inelastic deformations due to creep and plasticity. Therefore, a systematic mehtod of inelastic analysis is needed for the design of structural components in nuclear poser plants subjected to such loading conditions. In the present investigation, the Chabodhe model, one of the unified viscoplastic constitutive equations, was selected for systematic inelastic analysis. The material response was integrated based on GMR ( generallized mid-point rule) time integral scheme and provided to ABAQUS as a material subroutine, UMAT program. By comparing results obtaned from uniaxial analysis using the developed UMAT program with those from Runge-Kutta solutions and experimentaiton, the validity of the adopted Chaboche model and the numerical stability and accuracy of the developed UMAT program were verified. In addition, the developed material subroutine was applied for uniaxial creep and tension analyses for the plate with a hole in the center. The application further demonstrates usefulness of the developed program.
액체금속로 Y-구조물의 비탄성 열응력 해석 및 손상평가에 관한 유한요소해석
곽대영,임용택,김종범,이형연,유봉,Kwak, D.Y.,Im, Y.T.,Kim, J.B.,Lee, H.Y.,Yoo, B. 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.7
LMFBR(Liquid Metal Fast Breeder Reactor) vessel is operated under the high temperatures of 500-550.deg. C. Thus, transient thermal loads were severe enough to cause inelastic deformation due to creep-fatigue and plasticity. For reduction of such inelastic deformations, Y-piece structure in the form of a thermal sleeve is used in LMFBR vessel under repeated start-up, service and shut-down conditions. Therefore, a systematic method for inelastic analysis is needed for design of the Y-piece structure subjected to such loading conditions. In the present investigation, finite element analysis of heat transfer and inelastic thermal stress were carried out for the Y-piece structure in LMFBR vessel under service conditions. For such analysis, ABAQUS program was employed based on the elasto-plastic and Chaboche viscoplastic constitutive equations. Based on numerical data obtained from the analysis, creep-fatigue damage estimation according to ASME Code Case N-47 was made and compared to each other. Finally, it was found out that the numerical predictio of damage level due to creep based on Chaboche unified viscoplastic constitutive equation was relatively better compared to elasto-plastic constitutive formulation.
한영원(Y.W.Hahn),곽대영(D.Y.Kwak),임용택(Y.T.Im) 한국자동차공학회 1995 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1995 No.6_2
In order to substitute steel for new material in fabrication of automotive hood, proper stiffness according to the constructed geometry should be guaranted. For this purpose, numerical analyses of self-weight deflection, oil canning test, and torsional deflection were carried out using steel and SMC (Sheet Molding Compound). For optimization of manufacturing cost and structural benefit, several geometries were considered for the arbitrarily selected hood design type. The current approach will be beneficial in determining the proper design parameters for fabrication of hood with new material such as composites or aluminium alloys.<br/>