• Transactions of Materials Processing
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• v.5 no.2
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• pp.156-164
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• 1996

To investigate the behavior of plastic deformation in axisymmetric extrusion through square dies, experimental works with the plasticine as a model material are carried out at the room temperature. Some mechanical properties of the model material are determined by compression and ring compression tests. Visioplasticity method using expermental grid distortion in extrusion is introduced to analyze the plastic flow strain rate and strain distribution. In spite of severe deformation during the extrusion through square die the visioplasticity method shows good results for the distribution of effective strain rate and effective strain.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.280-283
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• 1999

Square dies are widely used for hot extrusion processes with high production rate. However the design and manufacture of square dies mainly relies on experience of industrial engineers To overcome such difficulty this study develops a method of automatic generation of NC-codes for the manufacture of extrusion square dies. The result shows that the method can reduce the lead time for the design and manufacture of square dies as well as eliminating engineers ow experience.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.12
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• pp.136-141
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• 1996

In this paper, the design variables of the extruded parts involving flat die through model experiment are investigated to overcome some current problems such as bending and twisting and get more improved quality products. Above all, the deformation behavior is analyzed in experiment and investigated flow charactristics inside container. Finally, the straight extruded product is obtained by modified bearing land width on the basis of the exit velocities distribution from bended and twisted products.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.11
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• pp.1912-1920
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• 1997

In the analysis of metal forming process, ALE(Arbitrary Lagrangian Eulerian) finite element methods have been increasingly used for the capability to control mesh independently from material flow. The methods can be divided into two groups i.e., coupled and split formulations. In the present work, the split ALE formulation is used for computational efficiency. A split ALE finite element method developed for rigid-viscoplastic materials and applied to the analysis of hot square die extrusion. Since thermal state greatly affects the product quality, an ALE scheme for temperature analysis is also presented. As computational examples, profile shapes as square and cross-like sections are chosen.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.3
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• pp.130-136
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• 1997

The velocity distrubution at the exit of extrusion die depends on the width of bearing land very much. When uniform bearing land without flow guide is used, the material which is extended through the same die does not, deflect to the constant direction, but when the flow guide is equipped and then the volume compensation is done accurately, the material deflects to one constant direction. Therfore, the part of problem can be known exactly, and extrusion products of straight shape can be produced by the corrected bearing land width.

• Transactions of Materials Processing
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• v.7 no.4
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• pp.375-381
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• 1998

This paper presents development of finite element simulation program and analysis of hot extrusion through square dies with a mandrel. The design of extrusion dies is still an art rather than science. Die design for a new extrusion process is developed from through in-plant trials. In the present paper, a three-dimensional steady-state finite element simulation program is developed. Steady-state assumption is used for both the analyses of deformation and temperature. The developed program is effectively used to simulate hollow extrusion of several sections. Distributions of temperature effective strain rate, mean strain rate and mean stress are studied for an effective design of extrusion dies.

• Transactions of Materials Processing
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• v.5 no.1
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• pp.55-60
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• 1996

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 an ALE(arbitrary Lagrangian-Euleria) finite element formulation for deforma-tion analysis are presented fro rigid-viscoplastic materials. The developed finite element program is applied to the isothermal analysis of square die extrusion of a square section. The computational results are compared with those by the updated Lagrangian finite element analysis.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.11
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• pp.91-97
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• 1995

In this study, a deformation model for the regular polygonal-shaped tubes from hollow-cylindrical billets is proposed and a kinematically admissible velocity field is obtained from this deformation model. The final stage upper-bound extrusion load and the average extruded length are determined by minimizing the total power consumption with respect to chosen parameters. Experiments have been carried out with hard solder billets at room temperature. The theoretical predictions of the extrusion load are in good agreements with the experimental results and there is generally reasonable agreement in average extruded height between theory and experiment.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.10a
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• pp.64-73
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• 1994

An updated Lagrangian finite element analysis with automatic remeshing scheme is applied to the three-dimensional hot extrusion through landless square dies. In the remeshing procedure, it is very difficult that the meshes are generated automatically with consideration of physical characteristics. In the presented study, the mesh generation is accomplished by modular concept. The generated meshes by modular concept have advantages, especially for three-dimensional problems, such as economized computational time and consideration of physical characteristic. In the problem, orifice shapes of square die are divided into two for the extrusion of solid sections. The orifice adaptive modules are developed for each type and the numerical examples are carried out for each type.

• Transactions of Materials Processing
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• v.5 no.2
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• pp.97-104
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• 1996

It is very important to obtain the knowledge of loads and flow patterns in most processes because these information are the fundamental data of die design and process design. The objective of present study is to investigate loads and metal flow patterns for various process conditions in flat die extrusion of square-bars from circular billets. For analyzing the metal flow patterns of the billets photo etching is used on sections of split specimen. From this method metal flow patterns are analyzed for various area reductions friction factors and punch stroke through the process from initial-stage to final-stage. Experiments are carried out with hard solder billets at room temperature.