• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.531-534
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• 1997

A design system of dies for hot extrusion of structural shapes such as Z' s, L' s, T' s, U' s and H' s from aluminum alloys was developed in this study. The developed design system of dies is based of established die design rule system. The design rules for die design are obtained from the handbooks, plasticity theories and relevant references. The environment of the system is AutoCAD and AutoLISP, the graphic programming language was used for the configuration of the system. This system includes five major modules such as section shape design module, die opening number module. die opening layout module, die correction module and die bearing design module that are used to determine design variables. This system would be used to design of dies for hot extrusion from aluminum alloys and widely used in manufacturing course..

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.4
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• pp.327-332
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• 2008

The effectiveness of vehicle parts made through extrusion is in the limelight because of the advantages of high strength stiffness materials can be produced and the number of processes can be drastically reduced. Therefore, the parts should have sufficient stiffness and be lightweight enough to improve fuel efficiency. However, the application of extruded aluminum requires pre-bending technologies that can manufacture the complex designs profiles demanded by vehicle parts. The aim of this research is that the development of the variable curvature extrusion technology that can produce a variety of curvature. In order to produce a variable curvature, the guide transfer speed and transfer time should be controlled properly. The guide transfer speed and transfer time were examined by the theoretical analysis. A model was developed to simulate the deformation behaviors of extrusion and bending process from the symmetric bumper with range of radii from 1863mm to 2163mm. The theoretical analysis and FE analysis were verified through experimental method.

• Transactions of Materials Processing
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• v.16 no.7
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• pp.555-560
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• 2007

This paper shows some achievements at bending of extruded aluminum profiles during the extrusion process. The conventional process for the production of bent profiles involves a successive extrusion, stretching, and bending of the profiles. Conventional bending methods can not meet demands far precision and cost-effective production in some cases, due to cross sectional deformation, irregular decrease of tube wall thickness and a complication of the process design. An estimation of spring-back required for precision of the bending radius can not always be achieved by the over bending of the profile. Since the profile is hot during the bending process, the spring-back phenomenon can be avoided. This means that an additional bending process is not necessary. Consequently, flexible bending can be achieved with cost reduction and quality improvement. Experimental tests were completed to study the relationship between curvature radius of profile and position of guide on the extrusion for vehicle bumper. A7108 is applied as a billet material in order to increase strength. The overall correlation between the experimental and numerical results is good. It is therefore concluded that the present method provides an efficient means for the constant curvature extrusion process.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.4 s.193
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• pp.102-108
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• 2007

The characteristic properties of aluminum, high strength stiffness to weight ratio, good formability, good corrosion resistence, and recycling potential make it the ideal candidate to replace heavier materials in the car to respond to the weight reduction demand within the automotive industry. In this paper, FE simulation was carried out to design an appropriate extrusion die for the automobile control arm. Based on the FE simulation result, a new die design has been proposed for uniform material flow in the cross section of extruded product. And then the welding pressure, extrusion load, and the tendency of mandrel deflection were estimated to verify high quality. In the extrusion experiment, it was possible to produce sound product without defects.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2644-2649
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• 2011

The purpose of this study is to propose the modular design of hybrid lightweight carbody structures made of sandwich composites and aluminum extrusion. The sandwich composites were used for secondary structures to minimize the weight of carbody, and the aluminum extrusions were applied to primary structures to improve the stiffness of carbody and manufacturability. Key requirements were defined for the modular design of hybrid carbody, and the applied parts of sandwich composites were determined through the topology optimization analysis. Consequently, feasibility of enhancing mass saving and maintainability in modular hybrid carbody design were presented, comparing with the carbody structures made of aluminum extrusion or sandwich composites only.

• Journal of Powder Materials
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• v.15 no.3
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• pp.204-209
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• 2008

Aluminum alloys are not only lightweight materials, but also have excellent thermal conductivity, electrical conductivity and workability, hence, they are widely used in industry. It is important to control and enhance the densification behavior of metal powders of aluminum. Investigation on the extrusion processing combined with equal channel angular pressing for densification of aluminum powders was performed in order to develop a continuous production process. The continuous processing achieved high effective strain and full relative density at $200^{\circ}C$. Optimum processing conditions were suggested for good mechanical properties. The results of this simulation helped to understand the distribution of relative density and effective strain.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1533-1534
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• 2013

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.11
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• pp.1010-1015
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• 2008

In this study, the characteristics of aluminum tube hydroformed products at different extrusion type and heat treatment conditions 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, free bulge test was performed at room temperature to $300^{\circ}C$. Also mechanical properties of hydroformed products at various pre- and post-heat treatments were estimated by hexagonal prototype hydroforming test at $250^{\circ}C$. And the tensile test specimens were obtained from hexagonal prototype hydroformed tube. As a results, hydroformability of full annealed tube is $5{\sim}8%$ higher than that of extruded and T6-treated tube. The tensile strength and elongation of T6-post heat treated indirect extrusion tube were more than 330MPa and 12%, respectively. However, T6 pre treated hydroformed product represents high strength, 330MPa and low elongation, 8%. Therefore, Hydroformability of Al6061 tube showed similar value for both extrusion types. However flow stress of direct tube showed $20{\sim}50MPa$ lower value than indirect tube.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.10
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• pp.1093-1100
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• 2014

The purpose of this paper is to suggest a weight-reduction design method for the hybrid carbody of a high-speed maglev train that uses aluminum extrusion profiles and sandwich composites. A sandwich composite was used on the roof as a secondary member to minimize the weight. In order to assemble the sandwich composite roof and aluminum extrusion side frame of the carbody using welding, a guide aluminum frame located at the four sides of the sandwich composite roof was introduced in this study. The clamping force of this guide aluminum frame was verified by three-point bending test. The structural integrity and crashworthiness of the hybrid carbody of a high-speed maglev train were evaluated and verified according to the Korean Railway Safety Law using a commercial finite element analysis program. The results showed that the hybrid carbody composed of aluminum extrusion frames and a sandwich composite roof was lighter in weight than a carbody made only of aluminum extrusion profiles and had better structural performance.

• Journal of the Korean institute of surface engineering
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• v.41 no.3
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• pp.121-128
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• 2008

High strength 7xxx aluminum alloys have been applied to automotive bump back beam of the some limited model for light weight vehicle. The aluminum bump back beam is manufactured through extrusion, bending and welding. The residual stress given on these processes combines with the corrosive atmosphere on the road spreaded with corrosive chemicals to melt snow to occur the stress corrosion cracking. The composition of commercial 7xxx aluminum has Zn/Mg ratio about 3 and Cu over 2 wt% for better strength and stress corrosion cracking resistivity. But this composition isn't adequate for appling to the automotive bump back beam with high resistance to extrusion and bad weldability. In this study the composition of 7xxx aluminum alloy was modified to high Zn/Mg ratio and low Cu content for better extrusion and weldability. To estimate the resistivity against stress corrosion cracking of this aluminum alloy by slow strain rate test, the corrosion atmosphere and strain rate separate the stress corrosion cracking from conventional corrosion must be investigated. Using 0.6 Mol NaCl solution on slow strain rate test the stress corrosion cracking induced fracture was not observed. By adding 0.3% $H_2O_2$ and 0.6M $Na_2SO_4$ to 1M NaCl solution, the corrosion potential and current density of polarization curve moved to active potential and larger current density, and on the slow strain rate test the fracture energy in solution was lower than that in pre-exposure. These mean the stress corrosion cracking induced fracture can be estimated in this 1M NaCl + 0.3% $H_2O_2$ + 0.6M $Na_2SO_4$ solution. When the strain rate was below $2{\times}10^{-6}$, the stress corrosion cracking induced fracture start to be observed.