• Korean Journal of Materials Research
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• v.11 no.2
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• pp.115-119
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• 2001

The electrical properties of heavily drawn bundled Cu- Nb filamentary microcomposite wires were examined and correlated with the microstructural changes caused by thermomechanical treatments. The cross sectional shape of Nb filaments in wires fabricated by bundling and drawing appear straight or slightly curved. The different shape of Nb filaments is attributed to the break- up and cylinderization of Nb filaments during the bundling process at high temperatures. The resistivity of Cu-Nb microcomposites is predominantly controlled by electron scattering at Cu-Nb interfaces. The decrease of the conductivity below the annealing temperature of $400^{\circ}C$ is due to the increasing contribution of the scattering associated with coherency strains of needle- shaped precipitates. The slight decrease of the resistivity ratio (${\rho}_{295K}/{\rho}_{75K}$) is also due to the precipitation of Nb atoms. The increase in conductivity in Cu-Nb microcomposites at an annealing temperature of 50$0^{\circ}C$ is due to the coarsening and spheroidization of Nb filaments.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.35-38
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• 2004

In general, tube drawing process is composed of two steps, so called first drawing and second drawing. Drawing cracks are mainly occurred during the 2nd drawing process due to the improper drawing process. In order to analyze the reduction distribution in successive two-step drawing process, tube drawing process was simulated by finite element method. From the finite element analysis, the balance between first and second reduction is proved to be important factor to prevent drawing cracks. Hence the numerical expression was developed for tube drawing process to distribute even strain and criteria curves that can predict the safe drawing region were also proposed using this numerical formula.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.95-98
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• 1999

In this study, a method to find the optimal intermediate die geometry for the multi-stage drawing process for the rectangular rod from a round bar is proposed and a program using the proposed method is developed. On the stage of the design of the intermediate die geometry, the virtual die was constructed using the initial billet as a inlet of the drawing die and the final product as a exit of that and the virtual die was divided by the number of pass. Divided die was transformed into the rectangular one which is the intermediate die geometry for the multi-stage rectangular drawing process. In order to verify the application of the proposed method on the real industrial product, the drawing of the rectangular rod from a round which composed two stage has been performed and simulated by the three dimensional rigid plastic finite element method.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.11
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• pp.124-130
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• 2009

In the multi-stage shape drawing process, the most important aspect for the economy is the correct design of the various drawing stage. For most of the products commonly available round or square materials can be used as initial material. However, special products should be pre-rolled. This study proposes a process design method of multi-stage shape drawing process for producing cross roller guide. Firstly, a standard classification of shape drawing process is suggested based on the requirement of pre-rolling process. And a design method is proposed to design the intermediate die shape. The process design method is applied to design the multi-stage shape drawing process for producing cross roller guide. Finally, the effectiveness of the proposed design method is verified by FE-analysis and shape drawing experiment.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.2
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• pp.191-200
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• 2005

To develop composite bridge deck, comparative study on the flexural characteristics of deck fabricated with filament winding and pultrusion was performed. In this study, composite deck of triangular shape was fabricated with filament winding process and flexural tests were conducted along with pultruded 'Duraspan' deck. Failure load, maximum deflection and strains were compared with each other. Also finite element analysis for filament winding deck was carried out and the results were compared with those from experiments.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.3
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• pp.377-382
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• 2011

Up to now, process design of multistage profile drawing from initial round material is performed through trial-and-error based on experience of industrial experts. This means the increase in production cost and excessive time consuming. In this study, process design program was developed for multistage profile drawing from initial round material. The program was made using VisualLISP. Therefore, the program can be operated by AutoCAD program. In order to verify the effectiveness of the program, two stage profile drawing process for producing heavy duty guide rail was design by using the program. In addition FE analysis and profile drawing experiment were performed. As a result, the program can be used in order to design profile drawing process design.

• Journal of the Korean Society for Precision Engineering
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• v.34 no.2
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• pp.77-81
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• 2017

CP (Commercially Pure) titanium has been widely used in various industries such as in energy plants and bio-materials because of an excellent corrosion resistance and its non-toxicity to the human body. But there are limitations for usage as structural materials due to low strength. The tensile properties of CP titanium could be improved by microstructure refinement such as in a SPD (Severe Plastic Deformation) process. However, high strengthening of CP titanium wire is impossible by SPD processes like ECAP (Equal Channel Angular Pressing), HPT (High-Pressure Torsion), and the ARB (Accumulative Roll Bonding) process. The study purposes are to increase the strength of CP titanium wire by optimization of the cold drawing process and the harmonization with mechanical properties by heat treatments for the next forming process. The optimization process was investigated with regard to the design of drawing dies and the reduction ratio of cross sections. The elongations of high strength CP titanium were controlled by heat treatment.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.12
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• pp.27-32
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• 2008

• Journal of the Korean Society for Precision Engineering
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• v.13 no.1
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• pp.116-122
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• 1996

In forming processes, die failure must be considered before die design. One of the main reasons of die failure in industrial application of metal forming technologies is wear. The die wear affects the tolerances of formed parts, metal flow and costs of processes etc. The only way to control these failures is to develop methods which allow prediction of the die wear and which are suited to be used in the design state in order to optimize the process. In this paper, wire drawing processes were simulated using the rigid-plastic finite element method and its results were used for predicting the die wear by Archard's wear model. The effects of the temperature rising on the wear profiles of die were also investigated. The simulation results were compared with the measured die profiles.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.821-825
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• 2000

Drawing is one of the oldest metal forming operations and has major industrial significance. This process allows excellent surface finishes and closely controlled dimensions to be obtained in long products that have constant cross sections. In drawing of the high carbon steel wire, exit speeds of several hundreds meters per minute are very common. Drawing is usually conducted at room temperature using a number of passes or reductions through consequently located dies. In multi-stage drawing process like this, temperature rise in each pass affects the mechanical properties of final product such as bend, twist and tensile strength. In this paper, therefore, to estimate the wire temperature in multi-stage wire drawing process, wire temperature prediction method was mathematically proposed. Using this method, temperature rise at deformation zone as well as temperature drop between die exit and the next die inlet were calculated.