• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.94-97
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• 2001

An inverse finite element approach is employed for more capability to design the optimum blank shape from the desired final shape with small amount of computation time and effort. For multi-stage deep-drawing processes, numerical analysis is extremely difficult to carry out due to its complexities and convergence problem as well as tremendous computation time. In this paper, multi-stage finite element inverse analysis is applied to multi-stage rectangular cup drawing processes to calculate intermediate blank shapes and strain distributions in each stages. Deformation history of the previous stage is considered in the computation. Finite element patches are used to describe arbitrary intermediate sliding constraint surfaces.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.158-161
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• 2000

An inverse finite element approach is employed for more capability to design the optimum blank shape from the desired final shape with small amount of computation time and effort. For multi-stage deep-drawing processes, numerical analysis is extremely difficult to carry out due to its complexities and convergence problem as well as tremendous computation time. In this paper, multi-stage finite element inverse analysis is applied to multi-stage rectangular cup drawing processes to calculate intermediate blank shapes and strain distributions in each stages. Finite element patches are used to describe arbitrary intermediate sliding constraint surfaces.

• Journal of the Korean Ceramic Society
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• v.37 no.6
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• pp.589-595
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• 2000

Densification behavior of SiC powder was investigated under cold compaction. A special form of the Cap model was proposed from experimental data of SiC powder under triaxial compression. To compare with experimental data of SiC powder under cold compaction, the proposed constitutive model was implemented into a finite element program (ABAQUS). Finite element calculations from the Cam-Clay model and the modified Drucker-Prager model were also compared with experimental data of SiC powder. The agreements between experimental data and finite element results obtained from the proposed constitutive model are reasonably good. In die pressing, finite element results obtained from the Cam-Clay model and the modified Drucker-Prager model, however, show lower average density of SiC powder compacts compared to experimental data.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.2
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• pp.228-234
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• 2013

This study focuses on development of a finite element model for analysis of thermal characteristics of a direct-connection spindle of a machining center by joint simulation of heat transfer and thermal deformation. Two finite element analyses were carried out procedurally for heat transfer, first, to identify temperature distribution of components of the spindle and then for thermal deformation to identify their structural behavior based on the temperature distribution. It was assumed that the heat transfer between a component revolving and the surrounding air is identical to that between a flat plate and the running air on it and the heat transfer is based on a uniform surface heat flux for turbulent flow. The results from the analyses were compared with those from experiments to validate the finite element model.

• Journal of Mechanical Science and Technology
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• v.14 no.4
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• pp.401-407
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• 2000

An elastic-plastic finite element analysis is performed to investigate detailed closure behavior of fatigue cracks and the numerical results are compared with experimental results. The finite element analysis performed under plane stress using 4-node isoparametric elements can predict fatigue crack closure behavior. The mesh of constant element size along crack surface can not predict the opening level of fatigue crack. The crack opening level for the constant mesh size increases linearly from initial crack growth. The crack opening level for variable mesh size, is almost flat after crack tip has passed the monotonic plastic zone. The prediction of crack opening level using the variable mesh size proportioning the reversed plastic zone size with the opening stress intensity factors presents a good agreement with the experimental data regardless of stress ratios.

• Structural Engineering and Mechanics
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• v.6 no.8
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• pp.921-937
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• 1998

A new four-node degenerated shell element with drilling degrees of freedom (DOF) is proposed. Allman-type displacement approximation is incorporated into the formulation of degenerated shell elements. The approximation improves in-plane performance and eliminates singularities of system matrices resulted from DOF deficiency. Transverse shear locking is circumvented by introducing assumed covariant shear strains. Two kinds of penalty energy are considered in the formulation for the purpose of suppressing spurious modes and representing true drilling rotations. The proposed element can be applied to almost all kinds of shell problems including composite laminated shell structures and folded shell structures. Numerical examples show that the element is of good accuracy and of reasonably fast convergence rate.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.159-164
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• 1997

The optimal conditions were investigated in order to manufacture the light automotive body parts using the semi-solid forging process by the finite element nalysis. Considering about macro-segregation cause to difference of relative velocity between solid phase and liquid phase, solidificational phenomenon cause to heat transfer from die and export of the latent heat, so solid fraction updating algorithm can be proposed. The rigid thermo-viscoplastic finite element analysis was carried out according to die temperature with proposed algorithm, so availability of forming part were understood. The finite element program can be used to the analysis of semi solid forging process.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.10a
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• pp.150-156
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• 1995

In the finite element analysis of metal forming processes, the updated Lagrangian approach has been widely and effectively used to simulate the non-steady state problems. However some difficulties have arisen from abrupt flow change as in extrusion through square dies. In the present work, a ALE(arbitrary Lagrangian-Eulerian) finite element formulation for deformation analysis are presented for rigid viscoplastic materials. The developed finite element program is applied to the analysis of square die extrusion of a square section. The computational results are compared with those from the updated Lagrangian finite element analysis.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.10a
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• pp.20-28
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• 1996

An Eulerian finite element method for the analysis of steady state rolling/extrusion of sintered powder metals is presented. Initial guess of the porosity distribution in an Eulerian mesh is obtained from the velocity and scaled pressure field computed by the Consistent Penalty finite element formulations-the standard one and the consistent penalty type one-are invoked for the analysis of strain hardening, dilatant viscoplastic deformation of porous metals. Comparisons of the predicted distributions of porosity to those by a Lagrangian finite element method and by experiments reported in the articles prove the effectiveness and validity of the proposed method.

• Structural Engineering and Mechanics
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• v.49 no.6
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• pp.727-743
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• 2014

Geometrically nonlinear analysis of planar beam and frame structures made of functionally graded material (FGM) by using the finite element method is presented. The material property of the structures is assumed to be graded in the thickness direction by a power law distribution. A nonlinear beam element based on Bernoulli beam theory, taking the shift of the neutral axis position into account, is formulated in the context of the co-rotational formulation. The nonlinear equilibrium equations are solved by using the incremental/iterative procedure in a combination with the arc-length control method. Numerical examples show that the formulated element is capable to give accurate results by using just several elements. The influence of the material inhomogeneity in the geometrically nonlinear behavior of the FGM beam and frame structures is examined and highlighted.