• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.343-346
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• 2003

In order to construct the extrusion die surface of arbitrarily shaped sections, an automatic surface construction method based on NURBS surface and area mapping method is proposed in the present work. In the present study, a center point for area mapping is determined by introducing the marring concept based on constant area proportionality between original billet and final product. The characteristic points of inlet profile is determined using the traditional area mapping method and the root finding numerical method. The inlet and outlet profiles are precisely described with NURBS curves using the characteristic points of entry and exit sections. For the construction of NURBS surface, an interpolation method for the pre-determined two section curves has been developed to be used in the generation of interior control points and weights. To show the validity of the proposed method, automatic die surface generation is carried out for the several kinds of shaped sections.

• Transactions of Materials Processing
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• v.12 no.4
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• pp.348-357
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• 2003

In order to construct the extrusion die surface of arbitrarily shaped sections, an automatic surface construction method based on NURBS surface and area mapping method is proposed in the present work. A center point fur area mapping is determined by introducing the mapping concept based on constant area proportionality between original billet and final product. The characteristic points of inlet profile are determined using the traditional area mapping method and the root finding numerical method. The inlet and outlet profiles are precisely described with NURBS curves using the characteristic points of entry and exit sections. For the construction of NURBS surface, an interpolation method for the pre-determined two section curves has been developed to be used in the generation of interior control points and weights. To show the validity of the proposed method, automatic die surface generation is carried out for the several kinds of shaped sections.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.311-320
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• 2009

Most advanced countries are researching to apply light weight materials far rolling stock because weight reduction for railway body derives cost-saving, energy-saving, and high-speed. Likewise, current Korea rolling stock field makes arduous effects of weight-reduction, miniaturization, and high-efficiency to achieve a high-speed railway. Aluminum becomes suitable material for these projects because it is much lighter than steel or stainless. Manufacturing the railway car body by using the Aluminum is increasing because Aluminum is not bringing the corrosion by unique oxidation-passivate. Aluminum extrusion profile far railway body requires a high mechanical property, accurate shape dimension, and stable quality because the railway body is composed with many different kinds of extruded profiles. Therefore, it is necessary to research about Aluminum precision-extrusion technology to maintain exit temperature and die load. The goal of this project is applying the Aluminum extrusion profile to next-generation railway car body by developing the Aluminum extrusion profile according to precision-extrusion technology which may maintain isothermal exit temperature.

• Proceedings of the Korean Society of Rheology Conference
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• 2000.11a
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• pp.83-86
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• 2000

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.03b
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• pp.145-155
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• 1996

The extrusion velocity of billet through a die and the shapes of the die are the important factors in the metal forming process of the extrusion of billet. in recent years, the life cycle of products is goingfaster. Although the former finite element method was capable of yielding a detailed analysis, it requires lots of time and extensive coding effort. Then, some simple devices were developed and based on upper bound method. For this purpose , a kinematically admiasible velocity field is formulated for extrusion of cylinders with arbitrary cross section and die profile on their outer surfaces by using a modified upper bound approach, which configures simulataneous extruding speeds in three directions . Also, In order to display mesh of the cold forward extrusion process using the approach , the automatic three-dimentional mesh generation produced by the approach coupled finite element method with upper bound method.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.10
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• pp.208-217
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• 2003

In order to construct the extrusion die surface of T -shaped sections, an automatic surface construction method based on NURBS surface and area mapping method is proposed in the present work. In the present study, a center point for area mapping is determined by introducing the mapping concept based on constant area proportionality between original billet and final product. The characteristic points of inlet profile are determined using the traditional area mapping method and the root finding numerical method. The inlet and outlet profiles are precisely described with NURBS curves using the characteristic points of entry and exit sections. For the construction of NURBS surface, an interpolation method for the pre-determined two section curves has been developed to be used in the generation of interior control points and weights. To show the validity of the proposed method, automatic die surface generation is carried out for the T-shaped section and T-shaped section with rounded corners.

• Journal of the Semiconductor & Display Technology
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• v.12 no.2
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• pp.19-25
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• 2013

Extrusion is one of the most important operations in the polymer-processing industry. Balancing the distribution of flow through a die to achieve a uniform velocity distribution is the primary objective and one of the most difficult tasks of extrusion die design. If the manifold in a coat-hanger die is not properly designed, the exit velocity distribution may be not uniform; this can affect the thickness across the width of the die. Yet, no procedure is known to optimize the coat hanger die with respect to an even velocity profile at the exit. While optimizing the exit velocity distribution, the constraint optimization used in this work with allowable pressure drop in the die; according to this constraint we can control the pressure in the die. The computational approach incorporates three-dimensional finite element simulations software STAR-CCM+. These simulations are used with numerical optimization to design polymer coat hanger dies with pressure drop, uniform velocity and temperature variation across the die exit.

• Transactions of Materials Processing
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• v.16 no.4 s.94
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• pp.260-265
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• 2007

Rubber compounds have high viscoelastic property. One of the viscoelastic behaviors during profile extrusion is the swelling of extrudate. In this study, die swells of rubber compounds at the capillary die have been investigated through experiment and computer simulation. Experiments and simulations have been performed using fluidity tester and commercial CFD code, Polyflow respectively. Die swells of rubber compounds in a capillary die were predicted using non-linear differential viscoelastic model, Phan-Thien-Tanner(PTT) model for various relaxation times and relaxation modes. The results of simulation were compared with the experiments. Pressure and velocity distribution, and circulation flows at the comer of capillary die have been investigated through computer simulation. It is concluded that the PTT model successfully represented the amount of the die swell of rubber compounds for various relaxation times at different modes.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.209-212
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• 2007

Rubber compounds have high viscoelastic property. One of the viscoelastic behaviors during profile extrusion is the swelling of extrudate. In this study, die swell of rubber compounds at the capillary die have been investigated through an experiment and computer simulation. They have been performed using fluidity tester in experiment and commercial CFD code, Polyflow in computer simulation. Die swell of rubber compounds for relaxation time at several modes under same conditions with the experiment were predicted using non-linear differential viscoelastic model, Phan-Thien-Tanner (PTT) model. The simulation was analyzed compared with the experiment. Viscoelastic behaviors for pressure, velocity and shear rate distribution were analyzed at the capillary die. It is concluded that the PTT model successfully represented the amount of the optimal die swell of rubber compounds for relaxation time at different modes.

• Transactions of Materials Processing
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• v.5 no.4
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• pp.269-280
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• 1996

A new approach to die shape optimal design in extrusion is presented. The approach consists of a FEM analysis model to predict the value of the objective function a design model to relate the die profile with the design variables and a genetic algorithm based optimaization procedure. The approach was described in detail with emphasis on our modified micro genetic algorithm. Comparison with theoretical solutions was made to examine the validity of the predicted optimal die shapes. The approach was then applied to revealing the optimal die shapes with regard to various objective functions including those for which the design sensitivities can not be deter-mined analytically.