• 소성∙가공
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• 제6권4호
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• pp.346-356
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• 1997

The fiber orientation distribution and interface bonding in hot extrusion process have an effect on the maechanical properties of metal matrix composites(MMC's). Aluminium alloy matrix composites reinforced with alumina short fibers are fabricated by compocasting method. MMC's billets are extruded at high temperature through conical and curved shaped dies with various extrusion ratios and temperature. This present study was directed to describe the systematic correlation between extrusion die shape and subsequent results such as fiber breakage, fiber orientation and tensile strength to hot extruded MMC's billet. Extrusion load, tensile strength and hardness for variation of extrusion ratios and temperature are investigated to examine mechanical properties of extruded MMC's SEM fractographs of tensile specimens are observed to analyze the fracture mechanism.

• 한국분말재료학회지
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• 제2권1호
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• pp.44-52
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• 1995

Effects of the extrusion temperature and die angle on the tensile properties of SiCIyAl composites in powder extrusion have been investigated. SiCP/Al composites were extruded at various extrusion temperatures (450, 500, $550^{\circ}C$) under the extrusion ratio of 25 : 1. The ram speed was maintained at 13 cm/min for all the extrusion conditions. The surface of the extruded rod appeared to be smooth without tearing at 450 and 50$0^{\circ}C$, whereas it was very rough due to tearing at $550^{\circ}C$. It was found that the tensile strength and elongation of the composites extruded at $500^{\circ}C$ are greater than those of composites extruded at $450^{\circ}C$ This is due to the easier plastic deformation of composite extruded at $500^{\circ}C$, compared with the composites extruded at $450^{\circ}C$. The effect of die angle was examined under 20=60, 120, $180^{\circ}$die angles at extrusion temperature of $500^{\circ}C$ under 25:1 extrusion ratio. The tensile strength of the composites extruded with 20=$60^{\circ}$approved to be higher than that of the composties extruded with 28 : 120 and $180^{\circ}$This is attributable to the higher extrusion pressure, which mixed composite powders could be densely consolidated at elevated temperatures, resulting from high friction force between billet and sliding surface of conical die.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.329-332
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• 2002

The upper bound analysis by stream function is used to study the torsional forward extrusion. The torsional forward extrusion process not only reduces forming load but also increase optimal die angle. Optimal die angle is determined by the optimization technique. The advantages of this process are that the low capacity of pressing machine can be used and the process with a large die angle can be applied. To verify the theoretical result, we have carried out experiments using model material (plasticine) and FE simulations using DEFORM3D.

• 한국안전학회지
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• 제15권4호
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• pp.28-34
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• 2000

Copper clad aluminum composite materials are being used for economic and structural purposes, The development of an efficient production method of copper clad aluminum composite material rods by extrusion is very important. This paper describes experimental investigations in the direct extrusion of copper clad aluminum rods through conical dies. There are several parameters that have an influence on determining a sound clad extrusion. These variables are extrusion temperature, extrusion ratio, semi-cone angle of die, extrusion force, extrusion velocity, friction of between the container and billet, percentage of copper used and ratio of flow stress of copper to aluminum. In order to investigate the influence of extrusion temperature, extrusion ratio, semi-cone angle of die on the hot direct extrudability of the copper clad aluminum composite material rods, the experimental study have been performed with these variation.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.759-765
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• 2000

A composite material consists of two or more different material layers. Copper clad aluminum composite materials are being used for economic and structural reasons. This study is concerned with experimental investigation in the direct extrusion of copper clad aluminum rods through conical dies. The suggestion are given for the proper extrudability of copper clad aluminum rods via hot direct extrusion. This paper presents the variation of flow state and hardness at a variable of extrusion ratio and semi-angle of die. By measuring after and before extrusion radius ratio of Cu sleeve and Al core, proportional flow state has been considered. And also by measuring hardness, through extrusion way, a variation of hardness has been considered.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 춘계학술대회 논문집
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• pp.102-105
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• 2001

The bending process for the curved tube can be developed by the hot metal extrusion machine with the multiple punches moving in the different velocity. The bending phenomenon has been studied to be occurred by the different of velocity at the die extrusion. The difference of velocity at the die exit section can be obtained by the different velocity of billets through the multi-hole container and by the welding of billets inside the porthole die chamber. The multiple billets are moving differently by the multiple extrusion punches controlled by PLC with the servo mechanism units. The results of the experiments show that the curved tube can be bended by the extrusion process and that the defects such as the distortion of section and the thickness change of thick tube, tile folding and wrinkling of thin tube can not be shown after the bending processing by the extrusion bending machine.

• 한국정밀공학회지
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• 제9권2호
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• pp.116-121
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• 1992

The optimal extrusion process for the rate sensitive materials have been developed in this study. The preliminary designs of the die shapes have been carried out to maintain constant strain rate during extrusion and the upper bound approach has been applied to define the process variables (the die entrance velocity and the die length) including the rheology during deformation. The result for the axisymmetric extrusion process has been verified with rigid-viscoplastic finite element analysis. It has been confirmed that the optimal die has wider band of constant strain rate than the conical one does.

• 소성∙가공
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• 제14권2호
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• pp.160-167
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• 2005

In the present study about extru-bending of angle product, the bending of extruded angle products with the $'\Lambda'$ section and 'ㄱ', section can be obtained using two extrusion billets by the hot metal extru-bending machine with the two punches moving in the different velocity. The bending curvature can be controlled by the different velocity of billets through the two-hole container. This paper describes simulations and experiments of extru-bending process that can make bending during extruding by the difference of stem velocities. And they are applied to two kinds of dies, that is, one of them is conical dies with symmetry $'\Lambda'$ section and the other one is conical dies with asymmetry 'ㄱ' section. The results of the forming simulation by $DEFORM^{TM}-3D$ and results of experiments show that the bending phenomenon at the die exit during extrusion can be obtained with two extrusion billet by the two stems moving in the different velocity. And it was known that it is possible to design the structure of conical cavity of extrusion dies and to control the curvature of product through the simulation and experiment of extru-bending process.

• 대한기계학회논문집
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• 제8권1호
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• pp.57-64
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• 1984

Forward extrusion of sintered porous metal through conical converging die is analyzed using slab method on the basis of plasticity theory for porous metal. It is taken into consideration in the analysis that the material in the container is continuously recompressed on densified until the process reaches steady state. Extrusion pressure and distribution of relative density from the die inlet to the outlet are calculated under various process variables. The results are useful in finding initial relative density of the billet, reduction of area and cone angle of the die in order to get required final products. Experiments are done for porous copper and then compared with the computed results.

• 대한기계학회논문집
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• 제7권2호
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• pp.168-174
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• 1983

The study is concerned with an analysis on the hydrofilm extrusion through conical dies. The upper bound method is adopted for the analysis of metal deformation in connection with hydrodynamic lubrication theory for the lubricant in order to determine the extrusion pressure for some variables such as reduction of area, die cone angle. In the upper bound method, a kinematically admissible velocity field is found by assuming proper streamlines and applying the flow function concept to the region of plastic deformation. The effect of work hardening is incorporated approximately by calculating the strains at the exit of the die. The experiments are carried out with the commercially pure aluminium for some chosen variables at room temperature. It is shown that the theoretical predictions are in good agreement with the experimental observations.