• Journal of Ocean Engineering and Technology
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• v.18 no.2
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• pp.52-57
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• 2004

Preflex beam is a method of construction designed to hold the pre-compressive stresses over the concrete pier by the preflexion load. During the fabrication of the girder, welding causes residual stresses. The welding residual stresses must be relieved in order to generate the accurate compressive pre-stresses. In this study, to determine the thermal distribution characteristics on the girder by welding, both three-dimensional finite element analysis and two-dimensional finite element analysis, in a quasi-steady state, is carried out. After comparing each result between the three-dimensional analysis and the two-dimensional analysis, finite element analysis is carried out against the actual girder, and the welding thermal distribution characteristic over the preflex beam is analyzed. It is possible to provide the input data for the analysis of the welding residual stresses.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.5
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• pp.43-49
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• 2015

Most of agricultural structures located in seashore could not avoid rapid deterioration of concrete because chloride-ion and $CO_2$ gradually penetrate into concrete. However, since most of models can be able to describe the phenomenon of penetration by using one or two dimensional models based on finite difference method (FDM), those modes can not simulate the real geometry and it takes a lot of computational time to complete even the calculation. To overcome those weaknesses, three dimensional numerical model considering time dependent variables such as surface concentration of chloride and diffusion coefficient of domain based on finite element method (FEM) was suggested. This model also included the neutralization occurred by the penetration of $CO_2$. Because the model used various sizes of tetrahedral mesh instead of equivalent rectangular mesh, it reduced the computational time to compare with FDM. As this model is based on FEM, it will be easily extended to execute multi-physics simulation including water evaporation and temperature change of concrete.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.5
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• pp.1095-1105
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• 1993

Shape rolling processes to produce H-section beams are numerically simulated by the simplified three-dimensional finite element method. The 2-dimensional finite element method, used for the generalized plane strain condition, is combined with the slab method. Computer simulation results of the 19-passes in H-section beam rolling in practice include the grid distortions, the cross-sectional area changes, the roll separating forces, and the roll torques. Also, the amount of side spread can be found during the multi-pass rolling simulations. The finite element mesh system is remeshed with I-DEAS whenever the billet distorts severely. This study would contribute to CAD/CAM of shape rolling process through the optimal roll pass schedule.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.110-113
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• 2002

As a preliminary study for the three dimensional failure analysis of composite joints, the three dimensional stress analysis on a pin-loaded unidirectional-fabric hybrid composite joints are performed. The contact and frictions between composite plate and metal bush are considered in the finite element method by NASTRAN. Experiments are conducted to validate the accuracy and feasibility of the finite element technique for 25 specimens with 5 different geometries. The finite element and experimental results show the bush cap induces the unsymmetric deformation, stress distribution, and failure behavior through the thickness. The experiment also shows the failure loads are higher in the joint with bush cap than without it.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.3
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• pp.116-122
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• 2003

This paper proposes an efficient method for computing the 3-dimensional capacitance of complex structures. The proposed method Is based on Finite Element Method(FEM) and expands the conventional FEM by adopting variable division. This method improves the extraction efficiency 50 times when compared to the conventional FEM with equal division. The proposed method can be used efficiently to extract electrical parameters of on/off-chip interconnects in VLSI systems.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2401-2405
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• 2008

In the present study, a three-dimensional least square/level set based two-phase flow code was developed for the simulation of three-dimensional sloshing problems using finite element discretization. The present method can be utilized for the analysis of a free surface flow problem in a complex geometry due to the feature of FEM. Since the finite element method is employed for the spatial discretization of governing equations, an unstructured mesh can be naturally adopted for the level set simulation of a free surface flow without an additional load for the code development except that solution methods of the hyperbolic type redistancing and advection equations of the level set function should be devised in order to give a bounded solution on the unstructured mesh. From the numerical experiments of the present study, it is shown that the proposed method is both robust and accurate for the simulation of three-dimensional sloshing problems.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.1
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• pp.54-59
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• 1999

High-speed electronic digital computers have enabled engineers to employ various numerical discretization techniques for solutions of complex problems. The Finite Element Method is one of the such technique. The Finite Element Method is one of the numerical analysis based on the concepts of fundamental mathematical approximation. Three dimensional plate structures used often in partition of ship, box girder and frame are analyzed by Finite Element Method. In design of structures, the static deflections, stress concentrations and dynamic deflections must be considered. However, these problem belong to geometrically nonlinear mechanical structure analysis. The analysis of each element is independent, but coupling occurs in assembly process of elements. So, to overcome such a difficulty the shell theory which includes transformation matrix and a fictitious rotational stiffness is taken into account. Also, the Mindlin's theory which is considered the effect of shear deformation is used. The Mindlin's theory is based on assumption that the normal to the midsurface before deformation is "not necessarily normal to the midsurface after deformation", and is more powerful than Kirchoff's theory in thick plate analysis. To ensure that a small number of element can represent a relatively complex form of the type which is liable to occur in real, rather than in academic problem, eight-node quadratic isoparametric elements are used. are used.

• Journal of the Korean Institute of Intelligent Systems
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• v.8 no.4
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• pp.1-7
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• 1998

This paper describes a meshless of element-free method based on fuzzy knowledge processing. To efficiently simulate complicated physical phenomena with dynmics and non-linear ploblem using computational mechanics, special method is required such as parallel processing or adaptive analysis techniques. However, the conventional finite element method is too complicated to be employed in the above cases. In order to reduce the above complexity of the conventional finite element analysis systms, the so called meshles finite elements as an input information have been stuided. Node is generated if its distance form existing node points is similar to the node spacing fuction at the point. The node spacing function is well controlled by the fuzzy knowledge processing Practical performances of the present system are demonstrated through several three-dimensional(3D) problems.

• Journal of the Korean Society of Safety
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• v.18 no.3
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• pp.39-45
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• 2003

The failure mode of a pipe due to local wall thinning is increasingly more attention in the nuclear power plant industry. To assess the integrity of locally wall thinned pipe, it is necessary to perform many simulations under various conditions. Because the modeling for locally wall thinned elbow is more complicated than that of straight pipe the efficient modeling method for finite element analysis is necessary. In this study, the more simple efficient modeling method of three-dimensional finite element analysis for locally wall thinned elbow has been suggested and verified. And using the method, the failure mode of local wall thinned elbows that have different thinning lengths and circumferential angles is evaluated. From the results, we concluded that the collapse load of elbows has been decreased by the increase of wall thinning shape factors such as thinning lengths and circumferential angles.

• Computers and Concrete
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• v.1 no.3
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• pp.285-302
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• 2004

A FE-(FE-HE)-BE procedure is presented for dynamic analysis of concrete arch dams. In this technique, dam body is discretized by solid finite elements, while the reservoir domain is considered by a combination of fluid finite elements and a three-dimensional fluid hyper-element. Furthermore, foundation rock domain is handled by three-dimensional boundary element formulation. Based on this method, a previously developed program is modified, and the response of Morrow Point arch dam is studied for various conditions. Moreover, the effects of canyon shape on response of dam, is also discussed.