• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.1
• /
• pp.49-54
• /
• 2010

Rotor pole for AC(alternating current) generator is manufactured through transfer warm forging die. As soon as the material is heated at the warm manufacturing process, it is transferred to the first stage for upsetting work and then to the second stage for lateral extrusion work. The processes at the lateral extrusion work such as die block, die bushing, center punch, and side punch make severe condition and abrasion which leads to shorten the die life. This causes production decrease, long maintenance time, and low level of precision. Research on the die material selection, heat process cycle improvement, electric discharge machining trouble solution, and re-construction of main parts is expected to find a method to lengthen the die life up to 40 - 50%.

• Polymer(Korea)
• /
• v.29 no.2
• /
• pp.198-203
• /
• 2005

Melt extrusion foaming process for the preparation of poly(L-lactic acid) (PLLA) scaffolds was carried out and the effects of foaming conditions on the pore structure of PLLA scaffolds and their mechanical properties were investigated. The porosity and mechanical properties of fabricated scaffolds were compared with the scaffolds obtained from the salt leaching method as well. It was found that the optimum pore structure was achieved when the PLLA melt was kept in extruder for the maximum decomposition time of blowing agent. In order to maintain the proper scaffolds structure, the blowing agent content should be less than $10\;wt\%$. It can be concluded that melt extrusion foaming process allows for the production of scaffold having higher mechanical properties with reasonable pore size and open cell structure for hard tissue regeneration even though it has less porosity than scaffolds made by salt leaching process.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.3
• /
• pp.251-258
• /
• 2014

Sunroof tracks are manufactured by press-forming extruded aluminum sheets. During press forming, cracking occurs along the sharply bent edge. The final positions of the punch and die were measured on the section, and their relation to cracking was investigated. Finite element simulation of bending to the final position was done to find the critical strains. Three-point bending tests with different material orientations, hardnesses, bending edge lengths, and bending radii were carried out in the laboratory, and finite element simulation of the three-point bending tests was performed to find the critical strains.

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

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.9 s.174
• /
• pp.49-59
• /
• 2005

This paper describes a development of the extrusion process and estimation of the weldability for multi cell tubes used to cooling system of automobiles. A study on extrusion process is performed through the 3D FE simulation in non-steady state and extrusion experimentation. Also, nano-indentation test is employed to estimate the weldability of tubes. Especially, An evaluation of the weldability using the nano-indentation is accomplished as compared with nano-hardness in welded part and in the others. Finally, the pattern of the mandrel defection is investigated according to shapes of the porthole and/or chamber.

• Journal of the Korean Society for Precision Engineering
• /
• v.18 no.6
• /
• pp.166-173
• /
• 2001

Composite materials consists of two or more different material layers. The usefulness of clad metal rods forms the possibilities of combination of properties of different metals. Copper clad aluminum composite materials are being used for economic and structural purpose. In this study, composite billet consists of commercially pure copper and aluminum(A6061) and experimental conditions consist of the combinations of clad thickness, extrusion ratio, and semi-cone angle of die. In order to investigate the influence of these parameters on the hot direct extrudability of the copper clad aluminum composite material rods, the experimental study have been performed with various extrusion temperatures, extrusion ratios, semi-cone angles of die, and composition rate of Cu:Al.

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.762-767
• /
• 2007

As a macromolecule material, melted rubber flow shows characteristics of shear thinning fluid. The dynamic viscosity of this rubber fluid is influenced by temperature and shear strain rate. In this study, the numerical simulation of rubber extrusion forming process has been performed using commercial CFD code, Polyflow. Power-law model considering the effect of shear rate is used for the computer simulation of this non-Newyonian flow. Also Non-isothermal behavior is considered as Arrhenius-law model. Distributions of velocity and temperature are predicted through the simulation.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2000.11a
• /
• pp.437-440
• /
• 2000

Composite material consists of more than two materials and make various kinds of composite materials by combining different single materials. Copper clad aluminum composite material is composed of Al and Cu, and it has already been put to practical use in Europe because of its economic benefits. This paper presents the interface bonding according to the variation of extrusion ratio and semi-angle die by observing the interface between Cu and Al using metal microscope. By that result, we can predict the conditions of the interface bonding according to the extruding conditions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1999.03b
• /
• pp.80-83
• /
• 1999

Rigid Plasticity Finite Element Analysis is developed for the shapes of dead metal zone and the curving velocity distribution in the eccentric square dies extrusion. The shape of dead metal zone is defined as the boundary surface with the maximum friction constant between the deformable zone and the rigid zone. The curving phenomenon in the eccentric square dies is caused by the eccentricity of square dies. The deviated velocity is changed with the distance form the center of cross-section of the workpiece. The results show that the curving of products and the shapes of the dead metal zone are determined by Rigid Plasticity Finite Element Analysis and that the curvature of the extruded products increases with the eccentricity.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2004.05a
• /
• pp.101-101
• /
• 2004

초미세 발포 플라스틱(MCPs; Microcellular Plastics)공정은 기존 발포 플라스틱의 장점을 보존하면서도 그 동안 발포 플라스틱의 단점으로 지적되어온 충격강도, 인성, 경도 등의 기계적 특성저하를 개선하기 위하여 개발되었다. 플라스틱 내에 지름 수 십 $\mu\textrm{m}$ 내외의 기포를 $10^{9}$-$10^{15}$cel1/㎤의 밀도로 발생시키는 초미세 발포공법은 내부의 미세 구조로 인하여 재료비를 절약하면서 우수한 기계적 특성을 나타내는 플라스틱 재료를 성형할 수 있게 하며, 발포제로 초 임계 상태의 불활성 기체($CO_2$, $N_2$, etc)를 사용하기 때문에 기존의 발포 공정에서 발포제로 사용했던 유해 화학 물이나 프레온, 부탄으로 인해 발생할 수 있는 환경 문제를 해결할 수 있다는 장점을 지닌다.(중략)