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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 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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Compressive and Bending Behaviors of the Shielded Slot Plate Considering Forming Effect for Fuel Cell Application
Lee, C.W. ; Yang, D.Y. ; Kang, D.W. ; Chang, I.G. ; Lee, T.W. ;
Transactions of Materials Processing, volume 21, issue 6, 2012, Pages 341~347
DOI : 10.5228/KSTP.2012.21.6.341
The metallic bipolar plates of the molten carbonate fuel cell(MCFC) are composed of shielded slot plates and a center-plate. The shielded slot plates support the center-plate and the membrane electrode assembly. Compressive forces are applied to the shielded slot plate in order to increase the contact area between shielded slot plates and the membrane electrode assembly (MEA). In the design of the shielded slot plate, it is necessary to predict the mechanical behavior of the shielded slot plate. The shielded slot plates are manufactured by a three-stage forming process consisting of slitting, preforming and the final forming process. The mechanical behavior of the shielded slot plate is largely affected by the forming process. In this study, the simulation of the three-stage forming process was used to predict the mechanical behavior of the shielded slot plate. The present simulation approach showed good agreements with the experimental results.
Influence of Drawing Speed and Blank Holding Force in Rectangular Drawing of Ultra Thin Sheet Metal
Lee, J.H. ; Chung, W.J. ; Kim, J.H. ;
Transactions of Materials Processing, volume 21, issue 6, 2012, Pages 348~353
DOI : 10.5228/KSTP.2012.21.6.348
Micro-drawn parts have received wider acceptance as products become smaller and more precise. The subject of this study was the deformation characteristics of ultra thin sheet metal in micro drawing of a rectangular shaped part. The influence of drawing speed and blank holding force on the product quality was investigated in micro-drawing of ultra thin sheet of beryllium copper (C1720) alloy. The specimen had a diameter of 4.8 mm and a thickness of
. Experiments were carried out in which, different blank holding force and drawing speed were considered. The product quality was evaluated by measuring the thickness and hardness along two specified directions, namely, the side and diagonal directions. The distribution of the thickness strain showed severe thinning especially around the punch radius in both directions. In the diagonal direction, thickening occurred in the flange area due to the axi-symmetric drawing mode. The increase of blank holding force and/or drawing speed was found to cause severe thinning around the punch radius. The blank holding force had a greater effect on thinning of the product than the drawing speed.
Tensile and High Cycle Fatigue Properties of Ion-nitrided and Nitro-carburized SCr430B Steels
Park, S.H. ; Lee, C.S. ;
Transactions of Materials Processing, volume 21, issue 6, 2012, Pages 354~359
DOI : 10.5228/KSTP.2012.21.6.354
Effects of a nitriding treatment on the tensile and high cycle fatigue properties were investigated by conducting ion-nitriding and gas nitro-caburizing treatments on the spheroidized SCr430B medium-carbon steel and performing tensile and tension-tension high cycle fatigue tests. The nitrided samples showed much lower strength and ductility compared to those in the initial as-spheroidized state and premature fracture occurred at the hardened layers. The micro-voids in the compound layer caused fatigue crack initiation. Thus, the removal of the compound layer with micro-voids remarkably improved the fatigue resistance to even beyond that of the as-spheroidized sample.
Effects of Forming Depth on the Deformation Behavior of Cup-like Tubes in Tube Spinning Process
Shin, Y.C. ; Yoon, D.J. ; Lim, S.J. ; Choi, H.J. ;
Transactions of Materials Processing, volume 21, issue 6, 2012, Pages 360~365
DOI : 10.5228/KSTP.2012.21.6.360
The aim of this study was to investigate the effects of forming depth on the deformation behavior of cup-like tubes made of AISI1020 steel in tube spinning process. Spinning process was performed on cup-like tubes, which had an inner diameter of 34mm and thicknesses of 7, 8.5 or 11.5mm. The forming depths achieved were 3, 4, and 5.5mm. The complex deformation behaviors occurring during the tube spinning process was explained using the experimental results. Also analyzed were the causes of the material buildup and the bulge defect of inner surface, observed on cross section of tubes. The relationship between tube spinning conditions and the height of bulge defect was examined. The results indicate that bulge defect is increased with a decrease of the forming depth. Moreover, a critical forming depth exists for preventing the generation of the bulge defect in the tube spinning process. The present results will be useful for future decisions of forming depths for successful tube spinning of cup-like tubes.
Multi-scale Modeling of Plasticity for Single Crystal Iron
Jeon, J.B. ; Lee, B.J. ; Chang, Y.W. ;
Transactions of Materials Processing, volume 21, issue 6, 2012, Pages 366~371
DOI : 10.5228/KSTP.2012.21.6.366
Atomistic simulations have become useful tools for exploring new insights in materials science, but the length and time scale that can be handled with atomistic simulations are seriously limiting their practical applications. In order to make meaningful quantitative predictions, atomistic simulations are necessarily combined with higher-scale modeling. The present research is thus concerned with the development of a multi-scale model and its application to the prediction of the mechanical properties of body-centered cubic(BCC) iron with an emphasis on the coupling of atomistic molecular dynamics with meso-scale discrete dislocation dynamics modeling. In order to achieve predictive multi-scale simulations, it is necessary to properly incorporate atomistic details into the meso-scale approach. This challenge is handled with the proposed hierarchical information passing strategy from atomistic to meso-scale by obtaining material properties and dislocation mobility. Finally, this fundamental and physics-based meso-scale approach is employed for quantitative predictions of the mechanical response of single crystal iron.
Evaluation of Anisotropic Hardening Models using Two-Step Tension Tests
Ha, J. ; Lee, M.G. ; Barlat, Frederic ;
Transactions of Materials Processing, volume 21, issue 6, 2012, Pages 372~377
DOI : 10.5228/KSTP.2012.21.6.372
In this study, the plastic flow behaviors of extra deep drawing quality (EDDQ) steel subjected to non-proportional strain paths were investigated. Two-step uniaxial tension tests, in which the first step was performed in the rolling direction (RD) and the subsequent test in different directions in
increments from the RD, were conducted. The experiments clearly showed that stress overshooting and strain hardening stagnation were the dominant features, which were captured reasonably well using a recently proposed distortional hardening model.
Bending Characteristics of DP980 Steel Sheets by the Laser Irradiation
Song, J.H. ; Zhang, Y. ; Lee, J.S. ; Park, S.J. ; Choi, D.S. ; Lee, G.A. ;
Transactions of Materials Processing, volume 21, issue 6, 2012, Pages 378~383
DOI : 10.5228/KSTP.2012.21.6.378
Laser forming is an advanced process in sheet metal forming in which a laser heat source is used to shape the metal sheet. This is a new manufacturing technique that forms the metal sheet only by a thermal stress. Analyses of the temperature and stress fields are very important to identify the deformation mechanism in laser forming. In this paper, temperature distributions and deformation behaviors of DP980 steel sheets are investigated numerically and experimentally. FE simulations are first conducted to evaluate the response of a square sheet in bending. The effects of process parameters such as laser power and scanning speed are then analyzed numerically and experimentally. It is observed that experimental and numerical results are in good agreement. These results provide a relationship between the line energy and the angles for laser bending of DP980 steel sheets.
Investigation of Springback Behavior of DP780 Steel Sheets after the U-bending Process
Choi, M.K. ; Huh, H. ;
Transactions of Materials Processing, volume 21, issue 6, 2012, Pages 384~388
DOI : 10.5228/KSTP.2012.21.6.384
Sheet metal forming processes induce residual stress in the final product due to plastic deformation. The residual stress leads to elastic recovery of the formed part called springback, which causes shape errors in the final product. This error is a serious issue, especially for high strength steels, which are widely used in auto-body structures. Therefore, the evaluation of the amount of springback becomes critical for high strength steels. This paper investigates the springback behavior of DP780 steel sheets after the U-bending process using the geometry of the standard U-shape tool from the NUMISHEET`93 benchmark problem. The amounts of springback were measured as a function of the intrusion direction, forming speed and blank holding force.