• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.409-413
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• 2005

Even though the relative importance of length scale of flow system allow us to simplify three dimensional flow problem to one or two dimensional representation, many systems still require three dimensional analysis. The objective of this study is to develop an efficient and accurate finite element model for analyzing and predicting three dimensional flow features in natural rivers and to offend to model spreading of pollutants and transport of sediments in the future. Firstly, three dimensional Reynolds averaged Navier-Stokes equations with the hydrostatic pressure assumption in generalized curvilinear coordinates were combined with the kinematic free-surface condition. Secondly. to simulate realistic high Reynolds number flow, the model employed the Streamline Upwind/Petrov-Galerkin(SU/PG) scheme as a weighting function for the finite element method in conjunction with an appropriate turbulence model(Smagorinsky scheme for the horizontal plain and Mellor-Yamada scheme for the vertical direction). Several tests is performed for the purpose of validation and verification of the developed model. A simple rectangular channel, 5-shaped and U-shaped channel are used for tests and comparisons are made with RMA-10 model. Runs for each case is converged stably without a oscillation and calculated water-surface deformation, longitudinal and transversal velocities, and velocity vector fields are in good agreement with the results of RMA-10 model.

• Transactions of Materials Processing
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• v.21 no.4
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• pp.252-257
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• 2012

Crystallographic texture evolution during forming processes has a significant effect on the anisotropic flow behavior of crystalline material. In this study, a crystal plasticity finite element method (CPFEM), which incorporates the crystal plasticity constitutive law into a three-dimensional finite element method, was used to investigate texture evolution of a face-centered-cubic material - an aluminum alloy. A rate-dependent polycrystalline theory was fully implemented within an in-house program, CAMPform3D. Each integration point in the element was considered to be a polycrystalline aggregate consisting of a large number of grains, and the deformation of each grain in the aggregate was assumed to be the same as the macroscopic deformation of the aggregate. The texture evolution during three different deformation modes - uniaxial tension, uniaxial compression, and plane strain compression - was investigated in terms of pole figures and compared to experimental data available in the literature.

• Transactions of Materials Processing
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• v.11 no.2
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• pp.179-186
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• 2002

In the finite element analysis of metal forming Processes using general Lagrangian formulation, element nodes in the mesh move and elements are distorted as the material is deformed. The excessive degeneracy of mesh interrupts finite element analysis and thus increases the error of plastic deformation energy, In this study, a remeshing scheme using so-called mesh compression method is proposed to effectively analyze the flash which is generated usually in hot forging processes. In order to verify the effectiveness of the method, several examples are tested in two-dimensional and three-dimensional 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.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.1
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• pp.16-22
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• 2001

In this study for reduction degree of freedom of dynamic model, a mixed method to combined finite element method and transfer matrix method is presented. This offers the advantages of an automatic reduction in the size of the eigenvalues problem and of a straightforward means of dynamic substructuring. The analytical procedure in this method for dynamic analysis of 3-dimensional cantilevered box beam are described. the result of numerical example is shown to demonstate the efficiency and accuracy of this method. The result form this example agree well those obtained by ANSYS, By using this technique, the number of nodes required in the regular finite element method is reduced and therefore a smaller com-puter can be used.

• Interaction and multiscale mechanics
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• v.4 no.4
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• pp.257-271
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• 2011

The analysis of interfacial stresses in structural component has been the subject of several investigations but it still requires more effort and studies. In this study a general three-dimensional interface element has been formulated for stress and displacement analyses in the interfacial area between two adjacent plate bending element and brick element. Interface element has 16 nodes with 5 degrees of freedom (DOF) in each node adjacent to plate bending element and 3 DOF in each node adjacent to brick element. The interface element has ability to transfer three translations from each side of interface element and two rotations in the side adjacent to the plate element. Stiffness matrix of this element was formulated and implemented in three-dimensional finite element code. Application of this element to the reinforced concrete (RC) beam strengthened with fiber reinforced polymer (FRP) including variation of deflection, slip between plate and concrete, normal and shear stresses distributions in FRP plates have been verified using experimental and numerical work of strengthened RC beams carried out by some researchers. The results show that this interface element is effective and can be used for structural component with these types of interface elements.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.3
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• pp.344-352
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• 2002

In the analysis of the 3 dimensional plate structures by the finite element method, the triangular elements are generally used for the global stiffness matrix of the analyzed system. But the triangular elements of the plates have some problems in the process of formulation and in the precision of analysis. The formulation of the finite element method to analyze 3 dimensional plate structures using quadrilateral elements is presented in this paper. The degree of freedom off nodal point is 6, that is, the displacements in the direction off-y-z is and the rotations about x-y-z axis and then the degree of freedom off element is 24. For the comparison of the analysis using triangular elements and quadrilateral elements, the rectangular plates subjected to the uniform load and a concentrated load on the centroid of the plate, for which the theoretical solutions have been obtained, are analyzed. The calculated deflections of the rectangular plates using the finite element method by the triangular elements and the quadrilateral elements are also compared with the deflections of the plates calculated by theoretical solutions. The defections of the rectangular plates calculated by the finite element method using the quadrilateral elements are closer to the theoretical solutions than the defections calculated by the finite element method using the triangular elements. The deflection of the centroid of plate, calculated by the finite element method, converges to that of theoretical solution as the number of elements is increased. This convergence is much more rapid for the case of using the quakrilateral elements than fir the case of using triangular elements.

• 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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.2414-2418
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• 2014

This study carried out three-dimensional finite element analysis and structural safety evaluation of attachable roadside barriers. The effects of diaphragm distance and the number of bolts on displacements and maximum stresses for various parameters are studied using the LS-DYNA finite element program for this study. In this study, the existing finite element analysis of barriers using the LS-DYNA program is further extended to study static behaviors and structural safety of the barrier with module structures connected by anchor bolt inserted through concrete bridge decks. The numerical results for six parameters are verified by comparing different models with displacements and stress distribution occurred in the barrier and shows good structural performance.

• 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.