• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.7
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• pp.1314-1321
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• 1992

In analyzing the plastic flow of axisymmetric tube extrusion a new method of formulation using the stream function approach and upper-bound theorem is proposed which permits the prediction of plastically deformed zone in analytic expression as well as metal flow. It is shown that the formulation proposed in this work covers the solid extrusion and tube extrusion in axisymmetric case. The effect of some process parameters such as area reduction, the ratio of radii(inner radius to outer radius) and friction factor on extrusion pressure, deformation zone and plastic flow through stream-lined dies has been studied. The presented theoretical analysis can be effectively used for the prediction of deformation zone and plastic flow.

• Transactions of Materials Processing
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• v.3 no.3
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• pp.291-301
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• 1994

In the simultaneous forward-backward extrusion the effects of some process variables including area reduction, stroke advance, materials(Al 2024 and commercial pure copper) on the extrusion load, plastic flow and height ratio of upper to lower extruded parts are experimentally investigated and analyzed. Grid-marking technique is employed to visualize the plastic flow. The influence of using split and original specimen on the extrusion load and height ratio is evaluated by experiments. Experimental results show that the plastic flow if oriented to the part of lower area reduction in the begining but it is usually variated during the overall process. The configurations of plastic deformation and plastic flow are dependent on the working materials and the lubricational conditions.

• Transactions of Materials Processing
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• v.18 no.1
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• pp.80-86
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• 2009

This paper presents the plastic inhomogeneous deformation behavior of bimetal composite rods during the axisymmetric and steady-state extrusion process through a conical die. The rigid-plastic FE model considering frictional contact problem was used to analyze the co-extrusion process with material combinations of Cu/Al. Different cases of initial geometry shape for composite material were simulated under different conditions of co-extrusion process, which includes the interference and frictional conditions. From the simulation results, the sleeve cladding rate at the core/sleeve interface was recorded as a distribution of diameter ratio and interference conditions, which will be useful for the investigations of the bonding process during co-extrusion process. In addition, the results of the co-extrusion, connected with the results of the variations of diameter rate and average contact pressure, demonstrate a good agreement and present the possibility of describing the parameters of the plastic zones in non-uniform deformation of these type of composite materials.

• Transactions of Materials Processing
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• v.10 no.6
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• pp.485-492
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• 2001

The paper is concerned with plastic flow in the port and welding chamber of rectangular hollow section extrusion through the porthole die. The extrusion process is analyzed by numerical simulation and experiments in the unsteady state. The effects of types of inlet with and without taper on the flow and extrusion load are mainly discussed and compared by FEA and experiments. Experiments are carried out by using the plasticine as a model material at room temperature. To visualize the plastic flow in the extrusion process, some split dies and punches are designed and manufactured by EDM. The theoretical predictions by FEM are reasonable agreements with experimental results on the deformed configurations and welding lines.

• Transactions of Materials Processing
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• v.15 no.7 s.88
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• pp.512-517
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• 2006

In this paper, the cold extrusion process for internal spline forming using a thin and long tube has been analyzed by using a rigid plastic finite element code. The internal spline consists of 10 tooths. The cold extrusion process has been focused on the comparisions of load-stroke relation and filling states of the teeth according to design parameters. The design parameters involve extrusion ratio, extrusion angle and friction factor. The internal spline forming can cause the buckling and folding during the cold extrusion process because of using a thin and long tube. The optimum design parameters have been obtained through rigid-plastic finite elements analysis. The extrusion ratio and extrusion angle have great effects on the deformation characteristics of the cold extrusion process.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.03a
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• pp.175-182
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• 1994

Effect of some process variables including area reduction, stroke advance, materials on the extrusion load, plastic flow and height ratio of upper to lower extruded parts in the cup-cup axisymmetric extrusion were experimentally investigated and analyzed. Deformed pattern is visualized by grid-marking technique using half-cut billets splitted. The influence of using split specimen and original specimen on the extrusion load and height ratio is examined by experiment.

• 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.

• Transactions of Materials Processing
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• v.21 no.3
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• pp.164-171
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• 2012

This paper focuses on the development of a new SPD (severe plastic deformation) process named HCAE (half channel angular extrusion). HCAE technology is based on principled similar to ECAE, but imposes a larger amount and more effective plastic deformation on materials. The amount of shear deformation can be altered by varying the process parameters. Finite element analyses of HCAE were conducted in order to investigate the characteristics of deformation during HCAE and the simulated results show that the predicted value of imposed plastic strain in a single pass reaches 2.5.

• Transactions of Materials Processing
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• v.9 no.3
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• pp.242-248
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• 2000

This paper is concerned with the family of parts that generally feature a central hub with radial protrusions. Radial Extrusion is usually used in order to produce complex parts, which is combined with upsetting and/or forward and backward extrusion. Typical parts that fall into this category include cross pieces for universal joints, key-shaft type parts, tube fittings, and differential gears. In this paper, the forming characteristics of radial extrusion combined with forward extrusion is investigated by comparing the punch and mandrel loads. The design factors during radial extrusion combined with forward extrusion are applied to the simulation to see how much those factors have effect on the forming loads. The rigid-plastic FEM is applied to the simulation.

• Transactions of Materials Processing
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• v.9 no.5
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• pp.486-493
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• 2000

Extrusion die-lip buildup has direct and negative impact on the properties of the final product. At the present time there is no absolute method of die-lip prevention. However, a Periodical shut down of extrusion line for the removal has been the general practice throughout the industry in concern. In this study the die-lip buildup was Investigated with a particular attention paid to the influence of die exit geometry and dimensions on the stresses produced at the point of die exit. To demonstrate the relationship between the stress state and the magnitude of the die-lip buildup, a method of virtual manufacturing was performed, assuming elastic-plastic material behavior for the high-density polyethylene under investigation. The overall numerical results suggested that the longer the die-land and/or the smaller the areal reduction of the die would reduce the tendency for the die-lip formation. Similarly, haying a fillet around the circumferential edge of the die exit would be favorable in decreasing the die-lip buildup.