• Transactions of Materials Processing
• /
• v.14 no.2 s.74
• /
• pp.147-152
• /
• 2005

The objective of this study is to develop an optimal drawing die for the clad wire drawing process. Cu-clad wire, which has the advantages of the high strength of a steel core and the electro-conductivity, corrosion resistance of a copper layer, is widely being used in the field of the telecommunications, electric-electronic and military technology industries. It is important to obtain uniformly coated rate when producing clad wires. Drawing process of clad wire will be influenced on damage and coated rate of core and sleeve for process variables such as semi-die angle and reduction in area. Therefore, in this study, the finite-element result obtained in this study was analyzed to the effect of the various forming parameters, which included the semi-die angle and reduction in area. The coated rate will be predicted with observation of copper coated rate variation according to total reduction in area and the optimal pass schedule will be set up through proper reduction in area and semi-die angle variation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1997.03a
• /
• pp.55-58
• /
• 1997

In automotive industries, stamping of laser-welded blank gives many merits which brings about dimensional accuracy, strong body assembly and high productivity. However the welding of blanks with different thickness or/and different strength materials introduces many challenging formability problems for process development and tool design. In this paper, the deformation characteristics for deep drawing process of laser-welded blank with different thickness sheets are investigated by experiment and FEM simulation. And also the optimal location of weld line in laser-welded blank with different thickness sheets is calculated to compensate for the movement of weld line on deep drawing process. In addition, the effect of location of weld line is clarified using FEM simulation.

• Proceedings of the KWS Conference
• /
• 2003.11a
• /
• pp.103-105
• /
• 2003

Currently, duplex and superduplex stainless steels are widely used for piping system in offshore unit because of its excellent combination of strength and corrosion resistance properties. Also, the usage of duplex and superduplex stainless steel is steadily increasing with getting into step with development of offshore industries. In spite of excellent merits in mechanical and chemical properties of base materials, sometimes stringent requirements in welding procedure qualification and fabrication of duplex class material have regulated not only the application of various high-efficiency welding processes but also applicable welding parameters. This study is focused on hardness requirement which is known as one of the most stringent factor in duplex class material welding and this study aims to evaluate the effects of cutting and welding methodology on hardness values of duplex and superduplex stainless steel weldments.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.967-972
• /
• 2003

In recent years building floors has become larger and more spacious due to the development of new design methods and high strength and light weight materials. However, such long span floor systems may provide smaller amount of damping and have longer period so that they would be more vulnerable to the floor vibration. This study attempts to evaluate the performance of the floors in typical apartment buildings. Four different floors with the area of 43.2$m^2$, 41.44$m^2$, 34.5$m^2$, and 28.89$m^2$ were investigated. The guideline provided by AISC(997) and human perception level of Korean people proposed by S. W. Han(2003) are used to check the acceptability of the floor vibration.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.217-222
• /
• 2003

The steel slag, a by-product which is produced during the manufacture of steel by refining pig iron, is mainly used as road materials after aging it. It is necessary to age steel slag for long time in air because the reaction with water and free-CaO in steel slag could make the expansion of volume. This problem prevents steel slag from being used as aggregate for concrete. But steel slag used in this study was controled by an air-jet method which rapidly cools substance melted at a high temperature. Rapid cooling prevents from generation of free-CaO in steel slag. In this study, properties of steel slag manufactured by air-jet method and mortar used it were investigated. As results of this study, free-CaO contents were controled under 1%. Mortar used this steel slag demanded to lower water contents, higher compressive strength and lower drying shrinkage than the basic mortar in the same condition.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.255-260
• /
• 2003

The corrosion of steel rebars has been the major cause of the reinforced concrete deterioration. It is FRP rebar that is developed to solve problem of such steel rebar. FRP rebar in concrete structures should be used as a substitute of steel rebars for that cases in which aggressive environment produce high steel corrosion, or lightweight is an important design factor, or transportation cost increase significantly with the weight of the materials. But FRP rebar have only linearly elastic behavior; whereas, steel rebar has linear elastic behavior up to the yield point followed by large plastic deformation and strain hardening. Thus, the current FRP rebars are not suitable concrete reinforcement where a large amount of plastic deformation prior to collapse in required. The main objective of this study was to develop new type of hybrid FRP rebar. The manufacture of the hybrid FRP rebar was achieved pultrusion, braiding and filament winding techniques. Tensile and interlaminar shear test results of hybrid FRP rebar can provide its excellent tensile strength-strain behavior and interlaminar stress-strain behavior.

• Carbon letters
• /
• v.14 no.3
• /
• pp.131-144
• /
• 2013

The carbon nanotube (CNT) represents one of the most unique inventions in the field of nanotechnology. CNTs have been studied closely over the last two decades by many researchers around the world due to their great potential in different fields. CNTs are rolled graphene with $SP^2$ hybridization. The important aspects of CNTs are their light weight, small size with a high aspect ratio, good tensile strength, and good conducting characteristics, which make them useful as fillers in different materials such as polymers, metallic surfaces and ceramics. CNTs also have potential applications in the field of nanotechnology, nanomedicine, transistors, actuators, sensors, membranes, and capacitors. There are various techniques which can be used for the synthesis of CNTs. These include the arc-discharge method, chemical vaporize deposition (CVD), the laser ablation method, and the sol gel method. CNTs can be single-walled, double-walled and multi-walled. CNTs have unique mechanical, electrical and optical properties, all of which have been extensively studied. The present review is focused on the synthesis, functionalization, properties and applications of CNTs. The toxic effect of CNTs is also presented in a summarized form.

• Journal of the Korean Ceramic Society
• /
• v.40 no.12
• /
• pp.1159-1164
• /
• 2003

Two processing routes (i.e., the gel casting and polymer preform routes) using polymer beads were studied to fabricate porous ceramics with a cellular structure. The gel casting route, comprising the gel casting of a ceramic slurry mixed with polymer beads, was found to be inadequate to produce porous ceramic bodies with a interconnected pore structure, due to complete coating of the slurry on the polymer beads, which left just isolated pores in the final sintered bodies. The polymer preform route, involving the infiltration of a polymer beads preform with the ceramic slurry, successfully produced porous ceramics with a highly interconnected network of spherical pores. The pore size of 250-300 $\mu\textrm{m}$ was demonstrated and the porosity ranged from 82 to 86%. This process is advantageous to control the pore size because it is determined by the sizes of polymer beads used. Another feature is the avoidance of hollow skeleton, giving a high strength.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.7 no.4
• /
• pp.31-36
• /
• 2008

Sheet metal forming has some merits that are less loss of materials in process, less time-consuming and it makes mass product possible. The product produced by sheet metal forming process has high strength compared to the weight and better surface characteristics. Therefore, sheet metal forming process is a lot used in automobiles, aircrafts, electronics and appliances. This paper made the process design for forming Bracket Front Back Frame Lower, determined the blank shape and size using PAM-STAMP, commercial software and evaluated formability. It has been proved that the optimal blank through the result forming analysis has advantage in terms of formability and spring back compared to the rectangular blank.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2004.10a
• /
• pp.22-27
• /
• 2004

Super-duralumin has widely been used as the part materials of aerospace and automobile industry because it has high specific strength and also is light. But, we have little design data about the creep behaviors of the alloy. Therefore, in this study, every creep test under four constant stress conditions have been conducted for four temperature conditions. A series of creep tests had been performed to get the basic design data and life prediction of super-duralurnin products and we have gotten the following results. First, the stress exponents showed the descending trend as the test temperatures increase. Secondly, the creep activation energy gradually decreased as the stresses become bigger. Thirdly, the constant of Larson-Miller parameters on this alloy was estimated about 6. And last, the fractographs at the creep rupture showed both the brittle fracture due to the transgranular rupture.