• 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.

• International Journal of Precision Engineering and Manufacturing
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• v.2 no.2
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• pp.5-10
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• 2001

This paper attempt to explore the shape of stress wave propagation of 3-dimensional stress field which in made in the process of the time increment. A finite element program about 3-dimensional stress wave propagation is developed for investigating the changing shape of the stress by the impact load. The finite element program, which is the solution for the 3-dimensional stress wave analysis, based on Galerkin and Newmark-${\beta}$ method at time increment step. The tensile stress and compressive stress become larger with the order of the middle , the upper and the opposite layers when the impact load is applied. In a while the shear stress become larger according to the order of the upper, the middle and the opposite layers when impact load applied.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.1
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• pp.97-107
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• 1995

Global postbuckling analysis is accomplished for one-dimensional and two-dimensional delaminations. A new finite element model, which can be used to model the global postbuckling analysis of one-dimensional and two-dimensional delaminations, is presented. In order to calculate the strain energy release rate, geometrically nonlinear analysis is accomplished, and the incremental crack closure technique is introduced. To check the effectiveness of the finite element models and the incremental crack closure technique, the simplified closed-form sloution for a through-the-width delamination with plane strain condition is derived and compared with the finite element result. The finite element results show good agreement with the closed-foul1 solutions. The present method was extended to calculate the strain energy release rate for two-dimensional delamination. For a symmetric circular delamination, the strain energy release rate shows great variation along the delamination front. and the delamination growth appears to occur perpendicular to the loading direction.

• 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.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1852-1855
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• 1997

A three-dimensional biomechanical modle is proposed in order to simulate human pharyngeal function based on the FEM(Finite Element Method) utilizing optimization procedure.

• 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 for Precision Engineering
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• v.15 no.7
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• pp.119-128
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• 1998

In this paper, nonsteady state shaped drawing process has been investigated using the three-dimensional rigid-plastic finite element method. In order to analyze the shaped drawing process, a method to define straight converging die considering straight die part, die radius part and bearing part has been proposed. In addition, the modeling of initial billet and the generation procedure of mesh system have been suggested. The three-dimensional rigid-plastic finite element simulation has been performed for a square sectional drawing process and its result has been confirmed in comparison with the existing experimental one. Also, for the same process conditions, the effect of perimeter ratio in the shaped drawing process has been investigated.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.05a
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• pp.5-8
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• 1999

The present work is concerned with three-dimensional finite element analysis of the hollow section extrusion process using a porthole die. For economic computation, mismatching refinement, an efficient domain decomposition method with different mesh density for each subdomain, is implemented. The proposed method improves the computational efficiency significantly, especially fur the three-dimensional analysis of extrusion problems. As a numerical example, extrusion of the underframe part of a railroad vehicle are analyzed. For three-dimensional mesh generation of a complicated shape with hexahedral elements, a modified grid-based approach with the surface element layer is utilized. The analysis results are then successfully reflected on the industrial porthole die design.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.638-643
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• 1993

The three dimensional finite element models for the basic deflection of linear motion guides and ball screws were developed. Form the comparison of the results calculated by the finite element method with those by the experiment, it was proved that the modeling method might be applied to real machine tool structures. Form the structural analysis of the headstock of the machine tool, it was found that the static stiffness was calculated within 6.5% error

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.3-9
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• 2001

In this study, the geometric modeling has been conducted for the current lower end fitting and 2 candidates using three-dimensional solid modeler, Solidworks. Then, the three-dimensional stress analysis using the finite element method has been performed. The evaluation for the mechanical integrity of 2 candidates has been performed based on the stress distribution obtained from the finite element analysis.