• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.2
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• pp.507-514
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• 1991

A penalty finite element method has been developed for accurately predicting stress distributions at the tool-workpiece interfaces. The basic formulation is described, with the emphasis on the algorithm to deal with the normal stress and the frictional stress at the interface. Comparison with the experimental data and the theoretical solutions found in the literature is made for the forming processes selected.

• Journal of Power System Engineering
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• v.4 no.2
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• pp.46-51
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• 2000

The contact stress characteristics of the domestic CPF pin when inserted into the rigid PTH was analyzed using the finite element method. The model geometry was based on the shape of the existing pin and the two different PTH diameters were used in the analysis. The stress distributions with respect to the friction coefficients were compared and the stress variations of the compliant part of the pin, which have an influence on the performance, were displayed with the time and the arc length on complete connection.

• Transactions of Materials Processing
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• v.14 no.1 s.73
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• pp.29-36
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• 2005

In this paper, a useful rigid-plastic finite element method with various numerical schemes is presented for simulation of an orbital forming process. A new approach to reduce volume change during simulation is presented and an approximation method to reduce computational time is also presented. An actual orbital forming process found in a bearing making industry is simulated by the presented approach. The simulated results of the orbital forming process are compared with the experimental results.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.1
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• pp.57-65
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• 2008

Superplastic forming/diffusion bonding(SPF/DB) processes with inner contact were analyzed using a 3-D rigid visco-plastic finite element method. A constant-triangular element based on membrane approximation and an incremental theory of plasticity are employed for the formulation. The hierarchical search algorithm for the contact searching has been applied. The algorithms for contact force processing were designed to handle equally well contact between deformable bodies, as well as rigid bodies. The plate of three and four sheets for 3-D SPF/DB model are analyzed using the developed program. The validity for the analysis is verified by comparison between analysis, experiment and results in the literature.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.546-550
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• 1996

A fully automatic computer simulation technique of axisymmetric multi-stage compound forging processes was presented in this paper. A penalty rigid-viscoplastic finite element method was employed together with an improved looping method for automatically remeshing with quadrilateral finite-elements only. An application example of six-stage axisymmetric forging processes involving one cold and two hot forging processes, two piercing processes and a sizing process was given with emphasis on automatically tracing the metal flow lines through the whole simulation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.4
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• pp.876-886
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• 1994

Process design in superplastic forming to produce a Nickel-base jet engine disk has been carried out using the rigid-viscoplastic finite element method. This study aims at deriving systematic procedures in forging of superalloy engine disk, and develops a simple scheme to control strainrate within a range of superplastic deformation during the forging operation. The new process, a pancake type preform being used, is designed to have less manufacturing time, and more even distribution of effective strain in the final product, while the conventional superplastic forging of an engine disk has been produced from a cylindrical billet. The jet engine company, Pratt & Whitney, provided the basic information on the manufacturing process of superplastic forging of a jet engine disk.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.1
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• pp.129-137
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• 1994

A rigid-viscoplastic finite element method has been used for modeling superplastic stretch/blow process design to improve thickness distribution. Punch velocity-time relationship of the stretch forming and pressure-time cycle of the blow forming for a given strain rate are calculated. A superplastic material is assumed to be isotropic and a plane-strain line element based on membrane approximation is employed for the formulation. The effects of the width, corner radius and height of the punch during stretch forming are examined for the final thickness distribution, and the process design to improve thickness distribution can be established.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.246-249
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• 1998

In the present study, domain decomposition using the substructuring method is developed for the computational efficiency of the finite element analysis of metal forming processes. In order to avoid calculation of an inverse matrix during the substructuring procedure, the modified Cholesky decomposition method is implemented. As obtaining the data independence by the substructuring method, the program is easily parallelized using the Parallel Virtual Machine(PVM) library on a workstation cluster connected on networks. A numerical example for a simple upsetting is calculated and the speed-up ratio with respect to various domain decompositions and number of processors. Comparing the results, it is concluded that the improvement of performance is obtained through the proposed method.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.103-107
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• 1999

In this paper, a computer simulation technique for the forging process having a floating die is presented. The penalty rigid-plastic finite element method is employed together with an iteratively force-balancing method, in which the convergence is achieved when the floating die part is in force equilibrium within the user-specified tolerance. The force balance is controled by adjusting the velocity of the floating die in an automatic manner. An application example of a three-stage cold forging process is given.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.110-114
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• 1996

The objective of this study is to consider the induction heating process and to develop the finite element program to analyze the behaviour of semi-solid materials. The semi-solid material is assumed to be composed of solid region as rigid visco-plastic model and liquid region following Darcy's law. Induction heating process is analyzed using finite element software, ANSYS, and also the behaviour of a semi-solid material considering induction heating is analyzed using developed finite element program.