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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Transactions of Materials Processing
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Journal DOI :
The Korean Society for Technology of Plasticity
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Volume & Issues
Volume 25, Issue 4 - Aug 2016
Volume 25, Issue 3 - Jun 2016
Volume 25, Issue 2 - Apr 2016
Volume 25, Issue 1 - Feb 2016
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Evaluation of the Static Strength of a Mg-Sn-Al-Zn Alloy Used for an Automotive Control Arm
Lee, S.I. ; Kim, B.M. ; Lim, S.G. ; Lee, J.H. ;
Transactions of Materials Processing, volume 25, issue 3, 2016, Pages 155~160
DOI : 10.5228/KSTP.2016.25.3.155
Magnesium(Mg) alloys have been evaluated as replacements for steel or aluminum parts in the automobile industry because of the fuel economy they can provide through reducing weight. The application of Mg alloys has been limited due to its low formability at room temperature, which results from a small number of active slip systems. In the current study, an extruded TAZ711(Mg-7Sn-1Al-1Zn) alloy was warm forged into an automotive control arm to evaluate its formability at various forging temperature. Warm forging was conducted at temperatures of 200, 250, 350 and 450℃. Static strength evaluation was performed on the as-forged specimen at 250℃. The results showed good static strength.
Development of a Flexibly-reconfigurable Roll Forming Apparatus for Curved Surface Forming
Yoon, J.S. ; Park, J.W. ; Son, S.E. ; Kim, H.H. ; Kim, J. ; Kang, B.S. ;
Transactions of Materials Processing, volume 25, issue 3, 2016, Pages 161~168
DOI : 10.5228/KSTP.2016.25.3.161
Sheet metals are often required to be formed into three dimensional curved shapes for use as skin structures. As a result various sheet metal forming methods, such as press die forming, stretch forming, and line heating have been used over the years in industrial production lines. Although they are extensively used in industry, these methods are not suitable for small quantity batch productions. Studies have been conducted to improve or replace these methods with plausible flexible forming technologies. As a part of these studies, we developed a new and more efficient forming device named flexibly-reconfigurable roll forming (FRRF). The current study presents the process development and experimental verification for the applicability of this device. To improve the efficiency of the FRRF apparatus, several hardware components were invented and a suitable operating program was developed using MFC of visual C++. The ways to make the FRRF apparatus fully functional are also described. Sheet metal was formed into three dimensional shapes using the FRRF apparatus and the final products are presented as evidence for the applicability of the developed device.
Finite Element Analysis of Thermal Stresses on a Hearth Roll Surface Depending on Changes in the Neck Shape
Na, D.H. ; Lee, Y. ;
Transactions of Materials Processing, volume 25, issue 3, 2016, Pages 169~175
DOI : 10.5228/KSTP.2016.25.3.169
The hearth roll, which transfers the cold-rolled strip sheet in a Continuous Annealing Line (CAL), is always subjected to changes in the surface temperature and subsequently experiences thermal stress in service. These variations lead to the generation of thermal cracks on the hearth roll surface as well local plastic deformation. We performed finite element analysis to predict the thermal stress changes on the hearth roll surface and designed the collar shape of the hearth roll to minimize these thermal stresses. Results show that the hearth roll with a collar having an obtuse angle is much more effective than a hearth roll with collar having a right angle when the tangential stress, which is one of main causes leading to surface cracks, is compared for the various conditions. It was found that the tangential stress and the temperature on the surface of hearth roll can be reduced by 51.9% and 26℃ if the shape of roll on collar is re-designed.
Development of Tube Hydroforming for a Tail Pipe Using FE Analysis
Han, S.S. ;
Transactions of Materials Processing, volume 25, issue 3, 2016, Pages 176~181
DOI : 10.5228/KSTP.2016.25.3.176
The exhaust tail pipe is the only visible part of the exhaust system on a vehicle. The conventional way to make the tail pipe is welding after stamping. There are various problems that occur during the stamping of stainless steel sheets such as scratching and local fracture. Problems during welding can also occur due to poor weldability. Tube hydroforming can be a solution, which eliminates these problems. The current study deals with the development of tube hydroforming for a vehicle tail pipe using finite element analysis for a free-feeding method. The current study focuses on the development of a proper load path for the tail pipe hydroforming and how bending influences the subsequent processing steps. The FE analysis results were compared with experimental results. This study shows the importance of bending and the necessity of considering bending when performing a tube hydroforming analysis.
Shape Prediction of Flexibly-reconfigurable Roll Forming Using Regression Analysis
Park, J.W. ; Yoon, J.S. ; Kim, J. ; Kang, B.S. ;
Transactions of Materials Processing, volume 25, issue 3, 2016, Pages 182~188
DOI : 10.5228/KSTP.2016.25.3.182
Flexibly-reconfigurable roll forming (FRRF) is a novel sheet metal forming technology conducive to producing multi-curvature surfaces by controlling the strain distribution along longitudinal direction. In FRRF, a sheet metal is shaped into the desired curvature by using reconfigurable rollers and gaps between the rollers. As FRRF technology and equipment are under development, a simulation model corresponding to the physical FRRF would aid in investigating how the shape of a sheet varies with input parameters. To facilitate the investigation, the current study exploits regression analysis to construct a predictive model for the longitudinal curvature of the sheet. Variables considered as input parameters are sheet compression ratio, radius of curvature in the transverse direction, and initial blank width. Samples were generated by a three-level, three-factor full factorial design, and both convex and saddle curvatures are represented by a quadratic regression model with two-factor interactions. The fitted quadratic equations were verified numerically with R-squared values and root mean square errors.
Spring-back Prediction of DP980 Steel Sheet Using a Yield Function with a Hardening Model
Kim, J.H. ; Kang, G.S. ; Lee, H.S. ; Kim, J.H. ; Kim, B.M. ;
Transactions of Materials Processing, volume 25, issue 3, 2016, Pages 189~194
DOI : 10.5228/KSTP.2016.25.3.189
In the current study, spring-back of DP980 steel sheet was numerically evaluated for U-bending using a yield function with a hardening model. For spring-back prediction, two types of yield functions - Hill`48 and Yld2000-2d - were considered. Additionally, isotropic hardening and the Yoshida-Uemori model were used to investigate the spring-back behavior. The parameters for each model were obtained from uniaxial tension, uniaxial tension-compression, uniaxial tension-unloading and hydraulic bulging tests. The numerical simulations were performed using the commercial software, PAM-STAMP 2G. The results were compared with experimental data from a U-bending process.
Effect of Powder Morphology on the Deposition Quality for Direct Laser Melting
Lee, S.H. ; Kil, T.D. ; Han, S.W. ; Moon, Y.H. ;
Transactions of Materials Processing, volume 25, issue 3, 2016, Pages 195~202
DOI : 10.5228/KSTP.2016.25.3.195
Direct laser melting(DLM) is an additive manufacturing process that can produce parts by solidification of molten metallic powder layer by layer. The properties of the fabricated parts strongly depend on characteristics of the metallic powder. Atomized powders having spherical morphology have commonly been used for DLM. Mechanical ball-milling is a powder processing technique that can provide non-spherical solid powders without melting. The aim of the current study was to investigate the effect of powder morphologies on the deposition quality in DLM. To characterize the morphological effect, the performances of spherical and non-spherical powders were compared using both single- and multi-track DLM experiments. DLM experiments were performed with various laser process parameters such as laser power and scan rate, and the deposition quality was evaluated. The surface roughness, cross-section bead shape and process defects such as balling or non-filled area were compared and discussed in this study.
CFRP Compression Forming Technology
Lee, J.M. ; Kim, B.M. ; Ko, D.C. ;
Transactions of Materials Processing, volume 25, issue 3, 2016, Pages 203~208