• Journal of the Korean Society for Precision Engineering
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• v.10 no.4
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• pp.109-117
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• 1993

Force balance method is employed to predict forging information such as forging load, tool pressure and normal stress at the surface of tangential velocity discontinuity. The incipient stages of deformation for the plane strain forging of rectangular billets in V-shaped dies of different semi-angles are analysed. To construct an approximate model for the analysis of deformation by the force balance method in the incipient deformation stages, slip-line field is used. When the deformation mode by slip-line method is the same as that by force balance method, the slip-line method and the force balance method give identical solutions. The effects of die angle, coefficient of friction, billet geometries and deforma- tion characteristics are also investigated. In order to verify the validity of force balance analysis, the rigid-plastic finite element simulation for the various forgig parameters are performed and performed and find to be in good agreement.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.5
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• pp.653-660
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• 1986

Two uppor bound solutions, by the force balance method and by a kinematically admissible velocity field, are compared for the metal forming problems in plane strain. It is concluded that these two approaches always give identical results when the geometrical configurations of the deformation model reman the same. By detailed derivations for plastic bending of a notched bar, closed die forging, compression of a rectangular block, machining with a restricted contact tool and plane strain backward extrusion, the identity of both approaches is verified.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.1
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• pp.87-95
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• 2011

A rational method for determination of initial cable forces in cable-stayed bridges without complicated nonlinear analysis is presented. Initial shape analysis for cable-stayed bridges should be able to find optimizated initial cable forces and unstrained length that minimize deflection and vending moments of the deck and pylon. A presented method utilizing the idea of force equilibrium organizes initial shape analysis for each types of cable-stayed bridges. The results of that analysis were compared to several existing methods for 2D numerical examples. And for 3D actual bridges, the improved TCUD method was performed to demonstrate the accuracy of this study.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.212-217
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• 1993

A 2-dimensional FEM/GEM program was developed for analyzing forming processes of an arbitrarily shaped draw-die, in which plane strain condition is assumed and linear line elements are employed. FEM formulation adopted a new algorithm for solving force equilibrium as well as non-penetration condition simultaneously. For the case of numerical divergence at nearly final forming stages and the initial guess in Newton-Raphson iterations, geometric force equilibrium method(GEM) is also introduced. The developed program was tested with the simulation of stamping processes of automotive bonnet inner pannel in order to verify the usefulness and validity of FEM/GEM formulation.

• Transactions of Materials Processing
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• v.7 no.6
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• pp.594-602
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• 1998

The design analysis of axisymmetric, multi-stage deep drawing dies was performed using the rigid-viscoplastic finite element formulation. In the formulation the axisymmetric CFS algorithm was employed. Hill's non-quadratic normal anisotropic yield criterion and isotropic hardening rule were considered. For trial initial displacements and tool contact points. the geometric force equilibrium method was adopted. In order to see the validity of the formulation, the multi-stage deep drawing processes of shell-cylinder front part of hydraulic booster were simulated. The simulation showed good agreements with measurments and PAM-STAMP results.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.3
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• pp.80-93
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• 1996

A 2-dimensional FEM/GEM program was developed under the plane strain assumption using linear line elements for analyzing stretch/draw forming operations of an arbitrarily shaped draw-die. FEM formulation adopted a new algorithm for solving force equilibrium as well as non-penetration condition simultaneously. Also, a rigid-viscoplastic material model with Hill's normal anisotropic yield condition and rate-sensitive hardening law is assumed, along with the Coulomb friction law in the contact regions. For the case of numerical divergence at nearly final forming stages, geometric force equilibrium method(GEM) is also introduced. The developed program was tested by simulating the forming processes of cylindrical punch/open die, and the drawing processes of automotive oilpan and hood inner panel in order to verify the usefulness and validity of FEM/GEM formulation. The numerical simulation verified the validity and robustness of developed program.