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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Transactions of Materials Processing
Journal Basic Information
Journal DOI :
The Korean Society for Technology of Plasticity
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Volume & Issues
Volume 21, Issue 8 - Dec 2012
Volume 21, Issue 7 - Nov 2012
Volume 21, Issue 6 - Oct 2012
Volume 21, Issue 5 - Aug 2012
Volume 21, Issue 4 - Jul 2012
Volume 21, Issue 3 - Jun 2012
Volume 21, Issue 2 - Apr 2012
Volume 21, Issue 1 - Feb 2012
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Biaxial Compressive Deformation Characteristics of Round Aluminum Pipe
Yoo, C.K. ; Kim, K.J. ; Won, S.T. ;
Transactions of Materials Processing, volume 21, issue 2, 2012, Pages 89~95
DOI : 10.5228/KSTP.2012.21.2.89
To examine the deformation characteristics of round aluminum pipe under biaxial compression, a horizontal biaxial compression die was fabricated. The change of material properties, punch load and deformation behavior were monitored in experiments using various compressive deformation rates in the range of 1mm/min.~400mm/min. The tensile and compressive strains were estimated from Vickers microhardness results. The punch load and deformation characteristic of the round aluminum pipes were found to change greatly at a deformation rate of about 200mm/min. The punch load decreased with increasing compressive deformation rate. Results of numerical simulation using Deform-2D were in good agreement with experimental results, and the measured hardness variation with the strain variation was predicted well by the simulation.
Cycle Time Reduction with Automated Gate Cutting Mechanism and Injection/Compression Molding for Producing Mobile LGP
Min, I.K. ; Kim, J.S. ; Yoon, K.H. ;
Transactions of Materials Processing, volume 21, issue 2, 2012, Pages 96~100
DOI : 10.5228/KSTP.2012.21.2.96
Conventional injection molding system for producing extremely thin-wall parts such as Light Guide Plates(LGP's) for mobile displays is at the limit of its capability due to its tendency to develop frozen layers and the critical speed of injection. The molten polymer in the cavity freezes quickly as its heat is rapidly transferred to the mold base. Many attempts have been tried in the past to overcome this problem. The present study used the injection/compression molding technology to produce a thin-wall part, with enhanced features such as an automated mechanism for cutting gates. As a result, the total cycle time was reduced by almost 35 seconds, resulting in a productivity increase by 30%.
A multi Step Cure Process to Prevent Residual Bubbles in LED Encapsulation Silicone Resin
Song, M.J. ; Kim, H.K. ; Yoon, G.S. ; Kim, K.H. ;
Transactions of Materials Processing, volume 21, issue 2, 2012, Pages 101~106
DOI : 10.5228/KSTP.2012.21.2.101
Generally, rapid cure reaction of LED encapsulation silicone resin causes serious defects in cured resin products such as warpage, residual bubbles, and reduced wettablility. In order to prevent residual bubbles in silicone resin, the step cure process was examined in the present paper. Three kinds of step cure processes were applied, and bubble-free phenomenon was observed. Most of the bubbles were removed under
, the minimum temperature for activating cure reaction. In addition, degree of cure(DOC) and temperature distribution were predicted by using FEM analysis of heat transfer. It was concluded that maintaining cure temperature which provide a DOC under 0.5~0.6 effectively reduces residual bubbles.
The Effects of Processing Variables on Gas Penetration in Gas-Assisted Powder Injection Molding(GAPIM)
Kim, D.H. ; Park, H.P. ; Lee, K.H. ; Cha, B.S. ; Choi, J.H. ; Rhee, B.O. ; Tovar, Jorge A. ;
Transactions of Materials Processing, volume 21, issue 2, 2012, Pages 107~112
DOI : 10.5228/KSTP.2012.21.2.107
Gas-assisted injection molding(GAIM) produces parts with hollow internal sections. The technique offers benefits to powder injection molding(PIM), with lower material usage and reduced time for de-binding processes. In this study, the effects of processing parameters on gas penetration length of gas-assisted powder injection molding(GAPIM) were investigated for SUS316L stainless steel powder feedstock. Experiments were planned based on the Taguchi method, involving processing variables such as melt temperature, shot size, gas pressure, and gas delay time. The most significant parameters affecting gas penetration length were gas delay time and shot size, while the effects of melt temperature and gas pressure was relatively insignificant.
A Comparative Study of Failure Criteria for Magnesium Alloy Sheet under Warm Press Forming Condition
Kim, H.K. ; Kim, J.D. ; Heo, Y.M. ; Kim, W.J. ;
Transactions of Materials Processing, volume 21, issue 2, 2012, Pages 113~118
DOI : 10.5228/KSTP.2012.21.2.113
Magnesium sheet alloys possess limited plastic formability at room temperature but their formability is substantially improved at elevated temperatures and optimum strain rates. In the present paper, three different types of failure criteria, namely, strain-based, stress-based, and work-based criteria, are compared for their applicability to warm press forming of magnesium sheet alloys. Warm deep-drawing experiments were conducted on AZ31 alloy sheet, and the results were used to assess the strength and weakness of the failure criteria.
Effect of Material Flow Direction on the Replication Characteristics of the Ultrasonic Patterning Process
Seo, Y.S. ; Lee, K.Y. ; Park, K. ;
Transactions of Materials Processing, volume 21, issue 2, 2012, Pages 119~125
DOI : 10.5228/KSTP.2012.21.2.119
The present study addresses a direct patterning process on a plastic film using ultrasonic vibration energy. In this process, a tool horn containing micro-patterns is attached to an ultrasonic power supply, and is used with ultrasonic vibration to replicate micro-patterns on the surface of a plastic film. To improve the replication characteristics of the micro-patterns, the effect of the die shape of the ultrasonic patterning process was investigated with respect to the flow direction control. Finite element analyses were performed to predict the flow characteristics of the polymer with variations in die design parameters. Experiments were conducted using the optimally-designed die, from which it was possible to attain much improved pattern replication.
Influence of Micro-Pattern Replication Ratio of Injection-Molded Light Guide Plate on Optical Aspect of LCD
Hong, J.P. ; Joo, B.Y. ;
Transactions of Materials Processing, volume 21, issue 2, 2012, Pages 126~130
DOI : 10.5228/KSTP.2012.21.2.126
Accurate optical texturing of light guide plate over the entire surface area is an important technical issue in LCD TV industry. Injection molding process has the potential to produce large light guide plates having highly efficient optical textures such as micro-prism array. This study is focused on the effect of the degree of replication of the micro texture of the 40" injection molded light guide plates on the overall optical performance of the display panel. Measured replication ratios of the micro-textures formed with three different types of injection molding process were considered in the modeling of prismatic micro segment array. Optical simulation was conducted and results were discussed.
Development of Fin Expansion Type Cooling System using Heat Pipes for LED Lightings
Jung, T.S. ; Kang, H.K. ;
Transactions of Materials Processing, volume 21, issue 2, 2012, Pages 131~137
DOI : 10.5228/KSTP.2012.21.2.131
With the advantages of power savings, increased life expectancy and fast response time over traditional incandescent bulb, LEDs are increasingly used for many applications including automotive, aviation, display, and special lighting applications. Since the high heat generation of LED chips can reduce service life, degrade luminous efficiency, and cause variation of color temperature, many studies have been carried out on the optimization of LED packaging and heat sinks. In this study, a fin expansion type cooling device using heat pipe, instead of a solid aluminum heat sink, was designed for LED security lightings based on thermal resistance analysis. Numerical analysis and experimental validation were carried out to evaluate its cooling performance.
Characteristics of MR Polishing using Carbonyl Iron Particles Coated with Xanthan Gum
Lee, J.W. ; Ha, S.J. ; Shin, B.C. ; Kim, D.W. ; Cho, M.W. ; Choi, H.J. ;
Transactions of Materials Processing, volume 21, issue 2, 2012, Pages 138~143
DOI : 10.5228/KSTP.2012.21.2.138
A polishing method using magnetorheological (MR) fluid has been developed as a new precision technique to obtain a fine surface. The process uses a MR fluid that consists of magnetic carbonyl iron (CI) particles, nonmagnetic polishing abrasives, water and stabilizers. But the CI particles in MR fluids cause a severe corrosion problem. When coated with Xanthan gum, the CI particles showed long-term stability in corrosive aqueous environment. The surface roughness obtained from the MR polishing process was evaluated. A series of experiments were performed on fused silica glass using prepared slurries and various process conditions, including different polishing times. Outstanding surface roughness of Ra=2.27nm was obtained on the fused silica glass. The present polishing method could be used to produce ultra-precision micro parts.