• Transactions of Materials Processing
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• v.6 no.5
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• pp.446-455
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• 1997

A Combined extrusion operation consists of forward and backward extrusion forming and it is possible to make the process be simple by employing it. But the metal flow pattern induced by the operation is hard to analyze accurately because the flows are non-steady, which have at least two directions dependent upon each other. So engineers in the industrial factories had conducted the two extrusion operations separately. A new process was designed by the industrial expert for forming of an alu-minum preform using the combined extrusion operation. In this study, experiments and finite element analysis was carried out to determine the process parameters. Through the preliminary experiment, it was shown that warm forming condition was more desirable than cold or hot ones. And optimal shape of initial billet could be also determined. From the compatibility test, bonde-lube was chosen as the optimal lubricant and 20$0^{\circ}C$ as the material temperature by the inspection of micro-structure. The operation was simulated by the rigid-plastic finite element method to examine the metal flow. Disap-pearing of dead metal zone was observed as the punch fell down and desirable shape was obtained from the one operation. As a result of this study, 7 operations could be reduced and 225% of material saved.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.7
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• pp.673-680
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• 2009

In this study, die cooling system using the nitrogen gas has been applied to hot aluminum extrusion process for refining grains and reducing of grain growth. Computational fluid dynamics(CFD) has been carried out to evaluate die cooling effect by nitrogen gas, and the results of CFD have been used to FE-simulation for the prediction of the extrudate temperature in hot extrusion process. Experimental hot extrusion has been performed to observe microstructure and to measure temperature of extrudate. The results of FE-Simulation have been good agreement with those of experiment. Finally, process condition of hot extrusion can be established to reduce grain growth of Al6061 through the experiment.

• Korean Journal of Materials Research
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• v.5 no.8
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• pp.953-959
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• 1995

It was investigated that reinforced species, billet condition and extrusion variation in Al 6061 composite material effected on extrusion process of particulate reinforced composite material. The strength of composite material with reinforcement species revealed SiC$\sub$w/> A1$_2$O$\sub$3f/ > A1$_2$O$\sub$3f/ > A1$_2$O$\sub$3f/ orderly. K$\sub$w/ increased as volute fraction increased in all composite material. The composite materials reinforced by A1$_2$ $O_3$required the larger pressure in hot extrusion process than those by SiC$\sub$p/ at all condition. Extrusion process tended to decrease as the semi-angle of extrusion dies increased because larger contact area caused larger shear friction. Extrusion temperature went up about 50$^{\circ}C$ in low elevated deformation temperature. In extrusion temperature above 500$^{\circ}C$, severe tearing occurred on extrusion surface. More reinforcement in volume fraction, more hot tearing.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.261-264
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• 2003

Semi-solid processing is now becoming of great interest for the production of various parts by pressure die casting. Many advantages are associated with this forming process at the condition that the forming operation is performed under appropriate conditions. The thixoforming process, which needs a suspension of a globular, non-dendritic solid phase in the liquid phase, is characterized by three major steps. The first step is casting of billets with a microstructure suited for thixoforming. The second step is reheating of slugs cut from these billets. The third step is injection of the semi-solid slugs into a die. In this paper, the horizontal reheating machine to obtain the optimal conditions suitable for semiu-solid die casting process was used and applied to extrusion material. It is estimated the possibility of application on semi-solid die casting with extrusion material through various results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.136-139
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• 1997

Applications of commercial software DEFORM-3DTM for 3-D simulation in extrusion process are developed for the analysis of twisting of extruded products. Because the elliptical shape has at least one line symmetry, the twisting is not occured during the extrusion. But, the results of extrusion simulation of the elliptical shape show that the twisted boundary of the die surface makes the material inside die surface rotate with the constant angular velocity. Otherwise, the simulation results of the S shaped product show that the twisting can be occured by the only 180$^{\circ}$rotation symmetry of S shape without no line symmetry and show that the angular velocity increases by the only 180$^{\circ}$rotation symmetry without no twisted die surface between on the die entrance section and on the die exit section. The results of the analysis show that the angular velocity of the extruded product changes with die length and friction condition.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.111-114
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• 1999

The twisting and extrusion process of the product with involute helical fin from the round billet is developed by the upper bound analysis. The twisting of extruded product is caused by the twisted die surface connecting the die entrance section and the die exit section linearly. In the analysis, the internal shear surface is defined as the curved twisted plane from the taisting of die surface and the shear work is calculated by the consumption of shear energy The increase rate of angular velocity is determined by the minimization of plastic work. The results of the analysis show that the angular velocity of the extruded product increases with the die twisting angle, the reduction of area, and decreases with the die length, the friction condition.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.115-118
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• 1999

The twisting and bending extrusion process is developed by the $DEFORM^TM$-3D. Because the rectangular section of the extruded product has the symmetry line of cross-section area, the twisting and the bending of extruded product has not occurred. The product with the rectangular section is applied to the twisting and bending extrusion process through the twisted die surface and eccentricity die section. It is shown that the twisting of extruded product is caused by the twisted die surfaces and the bending of extruded product is causd by the eccentricity between the die section. The results by the analysis show that the twisting angle and the curvature of extruded products increases by the die twisting angle, the eccentricity, but decreases by the die length, and friction condition

• Transactions of Materials Processing
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• v.16 no.1 s.91
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• pp.67-74
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• 2007

This study is aimed to find out the optimal forming conditions by comparing and analyzing material flow, deformation pattern, and a forming load through rigid-plastic FEM for a flange using pipe. Flanges are widely used for various purposes as connectors of industrial steel pipes which are manufactured by drawing process. The forming feature of flange was reviewed through both heading process and radial extrusion process in a cold working condition. As a result of simulation, the shape of flange can not be made by heading process, but made by radial extrusion process. The effects of design factors, such as gap-height, die-comer radius, and frictional factors on maximum forming load and deformation pattern are investigated for radial extrusion process.

• Transactions of Materials Processing
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• v.8 no.2
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• pp.160-168
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• 1999

This paper is concerned with the process sequence design of longneck flange forming by using cold extrusion with thick hollow pipe. The conventional hot forming process to produce a longneck flange is investigated by thermo-viscoplastic finite element method to observe the metal flow in detail and evaluate design requirements. Based on the results of simulation of the current hot forming process, design strategy for improving the process sequence are developed using the thick hollow pipe. The main goal is to obtain an appropriate improved process sequence which can produce the required product most economically without tensile cracking, workpiece buckling, and overloading of tools. Newly process condition such as semi-die angle, reductio ratio of cross-sectional area of axisymmetrical extrusion process. The final designed process can provide very useful guidelines to other flange forming industries.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.440-445
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• 2003

Maglev is the vehicle which can run in levitated condition by the electro-magnets, and propelled by linear induction motors. The Maglev is divided in two parts such as carbody and bogies, and the bogies are the driving device of the vehicle. The frame of the bogie must endure many loads occurred in the operation of the vehicle. So the bogie frame is designed and manufactured in the view of good safety and maintainability. The methods of design of frames are developed in regards of stresses and weights of structures. In this research, the extrusion of bogie frame is re-designed by the process of topology optimization with the ANSYS. By this process, the optimal shape of extrusion is acquired and additional optimization researches would be required in the view of size and shape of the members in the extrusion.