• Journal of the Korean Society for Precision Engineering
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• v.18 no.1
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• pp.154-161
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• 2001

A UBET analysis has been carried out to predict the forming load and the extruded length of forward and backward extrusion of hexagonal and trochoidal wrench colts. For the upper bound load and the average length of the extruded billets are determined by minimizing the total energy consumption rate which is a function of unknown velocities and parameters at each element. Experiments are carried out with antimony-lead billets at room temperature using hexagonal and trochoidal shaped punches. The theoretical predictions of the forming load and the extruded length are in good agreement with the experimetal results.

• Transactions of Materials Processing
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• v.28 no.3
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• pp.123-129
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• 2019

Hypereutectic Al-Si alloys have been widely utilized for wear-resistant components in the automotive industry. In order to expand the application of Hypereutectic Al-Si alloys, the addition of alloying elements forming a stable precipitate at high temperature is required. Thermally stable inter metallic compounds can be formed through the addition of transition elements such as Fe, Ni to Al alloys. However, the amount of transition element to be added to Al alloys is limited due to their low solid solubility. Also, hypereutectic Al-Si-Fe alloys form coarse primary Si phases and needle-shaped intermetallic compounds during solidification in the general casting processes. In this study, the effects of the destruction of Intermetallic compound and Si phase are investigated via hot extrusion. Both the microstructure and mechanical properties are discussed under different extrusion conditions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.593-596
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• 2001

In the previous work, the effect of blending with two kinds of low density polyethylene (LDPE) on physical and electrical properties have been investigated. From the results, blending with two kinds of LDPE was effective method on changing the morphology of LDPE and improving the high-field characteristics in high temperature region. Especially, it suggested that the F$\_$BImp/ was associated with the changes of the crystal size. In this work, the relationship between the morphology and the high-field characteristics of blended LDPE was discussed. In addition, the physical and electrical properties of blended LDPE with extrusion treatment were investigated. The two groups of specimen were prepared; Group 1 was prepared by passing 1 time through the extruder included in the film-blowing process, and Group 2 was prepared by passing 2 times through the extruder. From the relation between the crystal size which was perpendicular to the (020) plane and the F$\_$BImp/ of blended LDPE, it was confirmed that the F$\_$BImp/ was associated with the changes of crystal size due to the blending. Moreover, the F$\_$BImp/ of blended LDPE in Group 2 was higher than that of blended LDPE in Group 1. The crystal size of the (020) plane became smaller according to the extrusion treatment. These results suggest that the uniform distribution and dispersion of crystalline occurred due to the extrusion treatment and the morphological change due to the extrusion treatment influenced on the electrical properties of blended LDPE.

• Korean Journal of Materials Research
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• v.15 no.1
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• pp.25-30
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• 2005

The microstructural changes by hot extrusion of AZ31B magnesium alloy were observed, and the relation to the tensile property was examined. The tensile properties as oriented longitudinal(L), half transverse(HT) and long transverse(LT) to the extrusion direction were investigated at $20^{\circ}C,\;100^{\circ}C,\;200^{\circ}C,\;300^{\circ}C\;and\;400^{\circ}C$, respectively. As the results, many recrystallized small grains distributed uniformly in large banded microstructures formed along the extrusion direction. The grain size of as-extruded specimen was around $30\~150\;{\mu}m$. As increasing the test temperature the tensile and yield strength with respect to the angle between the axis of the tensile and the longitudinal direction in extrusion was decreased, but their elongation were increased and their deviation between L and LT specimens have disappeared from $300^{\circ}C$. This mechanical anisotropy was reduced at elevated temperatures and almost disappeared at $400^{\circ}C$. It was considered that the homogenization was occured by the recrystallization and the change of slip system was occurred during tensile test process in elevated temperatures.

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.6
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• pp.921-927
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• 2015

The aim of this study was to investigate the effect of die temperature and repeated extrusion on physical properties of extruded white ginseng (EWG). The die temperature was adjusted to 100, 120, and $140^{\circ}C$, and extrusion was repeated under the same conditions with their corresponding samples. Specific mechanical energy input decreased as die temperature increased during extrusions. The secondary extruded white ginseng (SEWG) at a die temperature of $120^{\circ}C$ showed a higher expansion index than other extrudates. Elevation of both die temperature and repeated extrusion increased the specific length of extrudates. The highest apparent elastic modulus, breaking strength, and water solubility index obtained from SEWG at a die temperature of $100^{\circ}C$ were $7.53{\times}10^8N/m^2$, $7.49{\times}10^5N/m^2$, and 39.02%, respectively. When die temperature increased, water absorption index (WAI) decreased. The WAI of SEWG was higher than that of EWG. In conclusion, repeated extrusion affected physical properties of white ginseng and could be applied to produce improved quality of ginseng products.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.254-257
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• 2007

In this study, hydroformability and mechanical properties of pre- and post- heat treated Al6061 tubes at different extrusion type were investigated. For the investigation, as-extruded, full annealed and T6-treated Al 6061 tubes at different extrusion type were prepared. To evaluate the hydroformability, uni-axial tensile test and free bulge test were performed at room temperature and $200^{\circ}C$. Also mechanical properties of hydroformed part at various pre- and post-heat treatments were estimated by tensile test. And the tensile test specimens were obtained from hexagonal prototype hydroformed tube at $200^{\circ}C$. As for the heat treatment, hydroformability of full annealed tube is 25% higher than that of extruded tube. The tensile strength and elongation were more than 330MPa and 12%, respectively, when hydroformed part was post-T6 treated after hydroforming of pre- full annealed tube. However, hydroformed part using T6 pre treated tube represents high strength and low elongation, 8%. Therefore, the T6 treatment after hydroforming for as-extruded tube is cost-effective. Hydroformability of Al6061 tube showed similar value for both extrusion types. But flow stress of seam tube showed $20{\sim}50MPa$ lower value.

• Korea-Australia Rheology Journal
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• v.13 no.2
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• pp.97-106
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• 2001

Three-dimensional flow analysis was performed by using the control volume finite-element method for design of a profile extrusion die. Because polymer melt behavior is complicated and cross-sectional shape of the profile extrusion die is changing continuously, the fluid flow within the die must be analyzed three-dimensionally. A commercially available polypropylene is used for theoretical and experimental investigations. Material properties are assumed to be constant except for the viscosity. The 5-constant modified Cross model is used for the numerical analysis. A test problem is examined in order to verify the accuracy of the numerical method. Simulations are performed for conditions of three different screw speeds and three different die temperatures. Predicted pressure distribution is compared with the experimental measurements and the results of the previous two-dimensional study. The computational results obtained by using three dimensional CVFEM agree with the experimental measurements and are more accurate than those obtained by using the two-dimensional cross-sectional method. The velocity profiles and the temperature distributions within several cross-sections of the die are given as contour plots.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.05a
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• pp.24-37
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• 1999

A comprehensive methodology to consolidate the hypereutectic Al-27Si-X alloy via spray forming was investigated in an attempt to judge the feasiblilty of this alloy in applying wear resistant components. Billets having desired shape and microstructures were fabricated using forming parameters obtained from numerical calculations. Prior to tube extrusion of the spray formed billets, effects of various extrusion conditions, such as extrusion ratio, die temperature, and die configuration, on microstructures of the billet were studied. Based on results obtained from the preliminary extrusion tests, the formed billets were then hot extruded into a tubular shape. Various material properties of the extruded billet were measured and compared with the other candidate materials for anti-wear applications.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.184-187
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• 2006

The effects of scandium content and extrusion parameters on Al-Zn-Mg-(Sc) alloys were examined. Three kinds of Al-Zn-Mg-(Sc) alloys with up to 0.30 wt.% Sc were prepared. The compression test was conducted to investigate the microstructure evolution during hot deformation. Despite of microstructural differences in the alloys, deformation behaviors were very similar. After extrusion at $350^{\circ}C$ with the ram speed of 15mm/sec, AA7075 showed a moderate surface quality compared with other Sc containing alloys, which was attributed to low flow stresses. AA7075 showed coarse-grained bands in surface region. With the ram speed of 1.5mm/sec at $350^{\circ}C$, the surface quality of the alloys was sound due to low friction stresses and deformation heating. As the Sc content increased, tensile strengths and elongations at room temperature improved.

• Transactions of Materials Processing
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• v.13 no.1
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• pp.53-58
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• 2004

The microstructural changes of Al-Zn-Mg-Cu alloy containing Sc during hot extrusion and post heat treatment were investigated. Two kinds of Al-Sc alloys with different alloying elements (B1, B2) were hot extruded to make T-shape bars at extrusion temperature of $380^{\circ}C$, then the bars were solution treated at $480^{\circ}C$ for 2hrs followed by artificial aging at $120^{\circ}C$ for 24hrs. The interior microstructure of as extruded bar consisted of elongated grains, however, fine equiaxed grains were also observed around surface. The microstructural gradient suggested that different restoration process could proceed during the hot extrusion. For B1 and B2, different grain growth behaviors were found around the surface during the post heat treatment. Rapid grain growth behavior was observed for B1 around the surface, however, it was not observed for B2. Orientation pinning, which was related with the evolution of preferred orientation, and precipitation were thought to be responsible for the rapid grain growth.