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임세영(Seyoung Im),최강혁(Kanghyouk Choi) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
In this paper, a finite element analysis of arc-welding processes is presented for large structures. We use an implicit numerical implementation for Leblond’s transformation plasticity constitutive equations, which are widely used in steel-structure welding. Several numerical examples, particularly including a large structure undergoing significant elastic-plastic deformations before welding, are presented to demonstrate the effectiveness of the three-dimensional analysis of welding processes.
B-bar aided edge-based smoothed finite elements of hexahedron type for elasto-plasticity
Son, Youngtak,Im, Seyoung 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.2
<P>The purpose of this study is to perform elastoplastic analysis using an edge-based smoothed finite element of hexahedron type. The edge-based smoothed finite element method has the best performance among the smoothed finite element methods, but has the problem of the volumetric locking phenomenon. Since plastic deformation is an isochoric process, it is accompanied by volumetric locking. In this study, the B-bar approach was introduced in the ESFEM to solve the volumetric locking phenomenon, and to enable elastoplastic analysis. The proposed method was verified to be efficient and accurate by comparison with results from the conventional finite element method.</P>
Kim, Moonhong,Im, Seyoung Elsevier 2017 Computer methods in applied mechanics and engineer Vol.325 No.-
<P><B>Abstract</B></P> <P>An equivalent continuum model for multilayer graphene sheets (MLGSs) and its plate model are developed to analyze the deformation behavior of MLGSs. Hyperelastic material models are introduced for the MLGS continuum model by examining the atomistic structures of MLGSs and obtaining their mechanical properties by means of molecular statics simulations. The MLGS plate model, a structural model for MLGSs, is developed by applying kinematics assumptions to the MLGS continuum model subjected to infinitesimal deformation. Finite element methods (FEM) with the corotational formulation are adopted to analyze the mechanical behavior of MLGSs under small-strain deformation and large rotation conditions. The MLGS plate element passes several basic numerical tests, including patch tests, eigenvalue analyses, and geometrically nonlinear benchmark problems. Finally, the deflections of a plane-strain cantilever and spherical indentations are analyzed by the proposed MLGS plate element and molecular dynamics (MD) simulations. These results show that the MLGS plate element properly represents the deformation behaviors of MLGSs from the atomic scale to the macroscopic continuum scale.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We present a plate finite element able to analyze deformation of MLGSs. </LI> <LI> Interlayer slip and layer deformation are described by kinematics assumptions. </LI> <LI> Corotational formulation is employed for small-strain deformations & large rotations. </LI> <LI> The element is verified as a structural element and a continuum description of MLGSs. </LI> </UL> </P>
용접공정에서 발생하는 변태 소성 구성방정식의 수치적 구현에 관한 연구
김주완(Juwan Kim),임세영(Seyoung Im),김현규(Hyun-Gyu Kim),최강혁(Kanghyouk Choi) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
Finite element analysis of welding processes, which entail phase evolution, heat transfer and deformations,<br/> is considered in this paper. Attention focuses on numerical implementation of the thermo-elastic-plastic<br/> constitutive equation proposed by Leblond in consideration of the transformation plasticity. Based upon the<br/> multiplicative decomposition of deformation gradient, hyperelastic formulation is employed for efficient<br/> numerical integration, and the algorithmic consistent moduli for elastic-plastic deformations including<br/> transformation plasticity are obtained in the closed form. The convergence behavior of the present<br/> implementation is demonstrated via a couple of numerical examples.
Higher Order Eigenfields in Mode Ⅱ Cracks Under Elastic-Plastic Deformation
Insu Jeon,Yongwoo Lee,Seyoung Im 대한기계학회 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.2
The explicit formulation of the J-integral and the M-integral is constructed in terms of the stress intensity factor and the higher order stress coefficients for Mode II cracks under small or large scale yielding. Furthermore, the stress intensity factor and the higher order stress coefficients as well are computed with the aid of the two-state J-and the M-integral, which is found to be accurate and efficient. It is found that the contribution from the higher order singularities to the J-integral is closely related to the configuration of the plastic zone.<br/>