• Transactions of Materials Processing
• /
• v.12 no.4
• /
• pp.314-319
• /
• 2003

In the micro hole punching, the size and shape of burr and burnish zone are very important factors to evaluate quality of micro holes which depend on punch-die clearance, strain rate, workpiece material and etc. To get micro holes with small burr and wide burnish zone for industrial demands, not only the parametric study but also a study on fracture behavior in shear band are necessary. In this study, 100 $\mu$m, 25 $\mu$m micro holes in diameter were fabricated on brass (Cu63/Zn37) and SUS 316 foils as aspect ratio 1:1, and the characteristics of micro holes was investigated comparing with those of macro holes over several mm by scanning electron microscopic views and section views. Like macro hole, micro hole is also composed of 4 portions, rollover. burnish zone, fracture zone and burr, and it shows similar fracture behavior in shear band. But by high strain rate (10$^2$∼10$^3$s$^{-1}$ ) condition unlike that of macro hole fabrication and by the increment of relative grain size in the direction of the workpiece thickness, fracture zone is not observed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2003.10a
• /
• pp.237-240
• /
• 2003

Deformation surrounding the hole in the tube during the hydro-piercing process has been investigated in this study. The tube is expanded and internally pressurized between upper and lower dies, and a piercing punch is driven forcefully through a cross passage in the die and through the wall of the tube. The pressurized fluid within the tube provides support to the wall of the tube during a piercing step to form a hole in the tube having less deformation surrounding the hole in the tube. The deformation area may be fully retracted to a substantially flat form or partially retracted to a countersunk form. In this study, a mathematical model that can predict deformation surrounding the hole has been proposed and experimentally verified by actual hydro-piercing test.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.11 no.5
• /
• pp.88-93
• /
• 2012

This paper describes the machinability of the sintered carbide and tool-die steel(STD-11) by electric discharge drilling with various tubular electrodes which have multi-holes. Various types of electrode which have different diameters and materials are used with the application of continuous direct current and axial electrode feed. Inner part of electrodes are inserted with smaller tubes or Y-channel or bar. In ED-Drilling, the dielectric flushed down the interior of the rotating tube electrode, in order to remove machining debris from the hole. As result of experiments, the bigger the diameter of the electrode is, the lower the material removal rate is. Machinability of copper electrode is higher than that of brass. In machining of sintered carbide, to use oil is better than distilled water as dielectric.

• Transactions of Materials Processing
• /
• v.14 no.3 s.75
• /
• pp.277-281
• /
• 2005

LTCC(Low temperature co-fired ceramic) is being recognized as a significant packaging material of electrical devices for the advantages such as relatively low temperature being needed for process, low conductor resistance and high printing resolution. In the process of LTCC electrical devices, the punched via-hole quality is one of the most important factors on the performance of the device. However, its mechanism is very complicated and optimization of the process seems difficult. In this paper, to clarify the process, via-hole punching experiments were carried out and the punched holes were examined in terms of their burr formation. The effects of thickness of PET sheet, ceramic sheet and punch-to- die clearance on via-hole quality were also discussed. Optimum process conditions are proposed and a factor $\kappa$ is introduced to express effect of the process variables.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.6
• /
• pp.1478-1485
• /
• 1993

A shape optimization problem is formulated to determine the optimal position of heating lines in a compression molding die. The objective of the problem is that the cavity surface would be maintained by a prescribed uniform temperature. A boundary integral equation for the sensitivity of the temperature in terms of hole position is derived using the method of shape design sensitivity analysis. The boundary element method is employed to analyze the temperature and sensitivity field of the die. The sensitivity calculation algorithm is incorporated in an optimization routine. To demonstrate a numerical implementation, an example problem arising in thermal design of a compression molding die is dealt with, showing that the number of heating lines chosen for the die strongly affects the ultimate uniformity of the cavity surface temperature.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2003.05a
• /
• pp.230-235
• /
• 2003

In the micro hole punching, the size and shape of burr and burnish zone are very important factors to evaluate quality of micro holes which depend on punch-die clearance, stain rate, workpiece material and etc. To get micro holes with small burr and wide burnish zone for industrial demands, not only the parametric study but also a study on fracture behavior in shear band are necessary. In this study, 100 $\mu\textrm{m}$, 25 $\mu\textrm{m}$ micro holes in diameter were fabricated on brass (Cu63/Zn37) and SUS 316 foils as aspect ratio 1:1, and the characteristics of micro holes was investigated comparing with man holes over several mm by scanning electron microscopic views and section views. Like macro hole, micro hole is also composed of 4 portions, rollover, burnish zone, fracture zone and it shows similar fracture behavior in shear band, but？ by high strain rate (10$^2$∼ 10$^3$s$\^$-1/) unlike macro hole fabrication and increment of relative grain size several different results are shown.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.5 no.2
• /
• pp.27-35
• /
• 2006

Al used in automobiles is mostly material, and according to the innovation of technique is in rapid development. Al die casting is an important field as today's trend of lightweight on automobiles. Valve housing in steering system improves driver's controling. The valve housing which is widely reliable to the most automobiles are developed this moment in our automobile industry. Therefore, they are produced by casting method which cost three times or even more expensive in production. If valve housing which is a part of steering system is produced by gravity casting, the space for manufacturing equipment will be increased, and more time and workers would be brought into service. For such reason, die casting would replace gravity casting in order to minimize cost of time, manpower, and working space. This study is the forming analysis of the 2 cavity die casting for automobile valve housing.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2003.10a
• /
• pp.313-317
• /
• 2003

Porthole die extrusion is the method which put the billet in the container and push it between die hole by ram. This method make it possible that product manufacture which have complex shape of area with excellent induction of area, in addition that this is economical. So this method is used as the basic manufacturing method of many industrial materials. The subject of this research is the forming technology development of heat sink which is being produced by extrusion process in my country. Flow condition of extrusion for heat sink, and metal flow of billet in the die are estimated by the means of rigid-plasticity finite element method.

• Carbon letters
• /
• v.3 no.1
• /
• pp.33-38
• /
• 2002

Petroleum based isotropic pitch was spun into short fiber by melt-blown spinning technology. The processing parameters chosen were air velocity, die temperature, and throughput rate of the pitch within the ranges of experimental tolerances. The fiber diameter was reduced to $6{\mu}m$ by increases of hot air velocity, and spin die temperature. Also, the fiber diameter was strongly dependent on the throughput rate of the pitch and jet speed of hot air through the spinnerets. Even fibers with $10{\mu}m$ diameter were produced at throughput rate of $0.17g/min{\cdot}hole$ and at die temperature of $290^{\circ}C$.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.5 no.4
• /
• pp.79-85
• /
• 2006

Multi-filament hydrostatic extrusion was developed as a fine wire manufacturing process and wire forming experiments were conducted. Also, single wire stretch forming process was proposed in the possibility of obtaining long wire with constant cross-section. In the multi filament extrusion since the workpiece, die and forming facility are in the macro forming circumstance, fine wire and fine hole structure with less than a few micrometer can be easily obtained. Although stretch forming does not use a die in order to avoid the friction problem between the workpiece and the die, it is necessary to have high level of technology to maintain cross-sectional shape and measure in longitudinal direction.