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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.
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.
탄소나노튜브를 위한 준연속체와 양자역학 계산과의 결합 연구
박종연(Jong Youn Park),임세영(Seyoung Im) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
We propose a fully non-local quasicontinuum in order to observe more realistic behaviors for mechanical deformations of carbon nanotubes(CNTs) on the viewpoint of length-scale. This coarse-graining model using high order interpolation function is adopted for finding the positions of atoms and for describing deformation on the curved structure. Cluster-based summation rule and inner displacement are used for approximating energy of reduced system and for assuring more exact equilibrium configuration of CNT, respectively. Furthermore, as we combine the QC algorithm with first principles calculation, the hybrid scheme makes it possible to enlarge the length scale for simulation and to predict more accurately the configuration as well as to obtain the electronic structure of the system.
이용우(Yongwoo Lee),임세영(Seyoung Im) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
Singular stress fields around three-dimensional wedges are examined, and the near-tip intensity is calculated via the<br/> two-state M-integral with the aid of the domain integral representation. A numerical example demonstrates the<br/> effectiveness and accuracy of the present scheme for computing the stress intensities of singular stresses near the generic<br/> three-dimensional wedges.
Harmonic Fourier Beads 방법을 이용한 최소 자유에너지 경로 계산
이영민(Youngmin Lee),임세영(Seyoung Im) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
Harmonic Fourier Beads (HFB) method is used for computing minimum free energy paths under finite temperature condition. This methoduses the Fourier representation of a path in an appropriate coordinate space. Molecular dynamics method is used to generate positions for the next path. Discrete path points are restrained by harmonic force field. Utilizing HFB method, we calculate the minimum free energy path of conformational change of carbon structures, which is among the rare event phenomena.
변형률 완화법 기반 다면체 요소를 이용한 불일치 격자망의 연결
손동우(Dongwoo Sohn),임세영(Seyoung Im) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
In the framework of cell-based smoothed finite element method, arbitrary polyhedral elements are applied for connection of nonmatching meshes, because they have exterior polygonal faces and nodes on the faces. When individual meshes with different resolutions meet, the nonmatching interfaces may be composed with combinations of several polygonal shapes, according to configurations of the individual meshes. In this case, only the elements on the nonmatching interfaces are converted into the polyhedral elements, and thus it leads to direct and compatible connection of the nonmatching meshes. Strain smoothing technique is introduced to resolve difficulties in formulating shape functions of the polyhedral elements, and it facilitates an efficient analysis without the explicitly defined shape functions. The effectiveness of the proposed scheme is demonstrated throughout numerical examples involving the nonmatching meshes.
김성엽(Sung Youb Kim),임세영(Seyoung Im) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
We examine the mobility of an edge dislocation pair in Si crystal using action-derived molecular dynamics. The various structural changes of dislocation cores with atomic resolution and their corresponding energy barriers, the so-called Peierls barriers, are evaluated during the dislocation motion. The dislocation movement is achieved by sequential bond-breaking and re-bonding processes of concerned atoms, which occur layer by layer in contrast with the assumption in Peierls-Nabarro model. The energy barrier for the movement of an edge dislocation pair on shuffle plane is higher than 0.20 eV, if bond-breakages occur first. However, it is significantly reduced to be about 0.08 eV, when five-fold bonds are formed before bond-breakages. When the dislocation moves via this mechanism, energy barrier for the dislocation movement does not depend on the length of dislocation line.
ANALYSIS OF THE SINGULAR STRESS AT 3-D WEDGES VIA TWO-STATE M-INTEGRAL
Yongwoo Lee(이용우),Seyoung Im(임세영) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.3
Singular stress fields around three-dimensional wedges are examined, and the near-tip intensity is calculated via the two-state M-integral with the aid of the domain integral representation. A numerical example demonstrates the effectiveness and accuracy of the present scheme for computing the stress intensities of singular stresses near the generic three-dimensional wedges.