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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 18, Issue 8 - Dec 2009
Volume 18, Issue 7 - Nov 2009
Volume 18, Issue 6 - Oct 2009
Volume 18, Issue 5 - Aug 2009
Volume 18, Issue 4 - Jul 2009
Volume 18, Issue 3 - Jun 2009
Volume 18, Issue 2 - Apr 2009
Volume 18, Issue 1 - Feb 2009
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A Study on Cross Sectional Shape Design of Intermediate Pass in the Multi-Stage Shape Drawing
Lee, J.E. ; Lee, T.K. ; Lee, S.K. ; Kim, S.M. ; Kim, B.M. ;
Transactions of Materials Processing, volume 18, issue 4, 2009, Pages 283~289
DOI : 10.5228/KSPP.2009.18.4.283
The multi-stage shape drawing is used to obtain long shaped products with high levels of dimensional accuracy and quality. It is important to design the cross sectional shapes of the intermediate passes to meet the required dimensional accuracy of the final product in the multi-stage shape drawing. Until now, the cross sectional shapes of the intermediate passes have been designed by the experiences. It is still remained unsolved problem to design the cross sectional shapes of intermediate pass drawing dies in the multi-pass shape drawing. In this study, a new technique is proposed to design the cross sectional shapes of intermediate passes. The proposed method is applied to a multi-stage shape drawing for a LM-guide which is one of the representative shape drawing products. In order to verify the effectiveness of the proposed method, FE-simulation and experiments have been carried out. The dimensional accuracy of the proposed method is compared with that of the conventional shape drawing process designed by the industrial engineers.
A Study on the Roll Gap Set-up to Compensate Thickness Variation at Top-end in Plate Rolling
Yim, H.S. ; Joo, B.D. ; Lee, G.Y. ; Seo, J.H. ; Moon, Y.H. ;
Transactions of Materials Processing, volume 18, issue 4, 2009, Pages 290~295
DOI : 10.5228/KSPP.2009.18.4.290
The roll gap set-up in the finishing mill is one of the most important technologies in the hot plate rolling process. As the target thickness can be obtained by the correct set-up of the roll gap, improving the roll gap set-up technology is very critical for plate thickness accuracy. The main cause of thickness variation in hot plate mills is the non-uniform temperature distribution along the length of the slab. The objective of this study is to adjust the roll gap set-up for the thickness accuracy of plate in hot rolling process considering top-end temperature drop. Therefore this study has concentrated on determining the correct amounts of thickness variation according to top-end temperature drop and roll gap to compensate thickness variation. The control method of roll gap set-up which can improve the thickness accuracy was proposed. The off-line simulation of compensated roll gap significantly decreases top-end thickness variation.
Effect of Porosity on the High-Cycle Fatigue Behavior of Al-Si-Mg Casting Alloy
Lee, Young-Jae ; Kang, Won-Guk ; Euh, Kwang-Jun ; Cho, Kyu-Sang ; Lee, Kee-Ahn ;
Transactions of Materials Processing, volume 18, issue 4, 2009, Pages 296~303
DOI : 10.5228/KSPP.2009.18.4.296
The effect of porosity on the high-cycle fatigue properties of Al-Si-Mg casting aluminum alloys was investigated in this study. Microstructure examination, tensile and high-cycle fatigue test were conducted on both Al-Si-Mg casted (F) and heat-treated (T6) conditions. Porosity characteristics on the fracture surfaces of fatigue-tested samples were examined using SEM and image analysis. The microstructure observation results showed that eutectic Si particles were homogeneously dispersed in the matrix of the Al-Si-Mg casting alloys, but there were porosities formed as cast defects. The high-cycle fatigue results indicated that the fatigue strength of the 356-T6 alloy was higher than that of the 356-F alloys because of the significant reduction in volume fraction of pores by heat treatment. The SEM fractography results showed that porosity affected detrimental effect on the fatigue life: 80% of all tested samples fractured as a result of porosity which acted as the main crack initiation site. It was found that fatigue life decreased as the size of the surface pore increased. A comparison was made between surface pore and inner pore for its effect on the fatigue behavior. The results showed that the fatigue strength with the inner pores was higher than that of the surface pore.
Development of High Strength Steel Body by Hot Stamping
Lee, D.H. ; Kim, T.J. ; Lim, J.D. ; Lim, H.J. ;
Transactions of Materials Processing, volume 18, issue 4, 2009, Pages 304~309
DOI : 10.5228/KSPP.2009.18.4.304
Quenchable boron steel is a new type of high strength steel to reduce the weight of automobiles and maintain the safety conditions. Quenchable blanks can be hot-stamped and hardened in a water-cooled tool to achieve high strength. In this paper, new alloy for hot stamping is designed based on requirement of mechanical properties and two types of surface coating are investigated in viewpoints of oxidization and exfoliation. An automotive part of center pillar is manufactured by hot-stamping using Al-Si coated sheet. The performance of developed part is compared by static compression test and side impact crash test.
A Study on Rapid Fabrication of Micro Lens Array using 355nm UV Laser Irradiation
Je, S.K. ; Park, S.H. ; Choi, C.K. ; Shin, B.S. ;
Transactions of Materials Processing, volume 18, issue 4, 2009, Pages 310~316
DOI : 10.5228/KSPP.2009.18.4.310
Micro lens array(MLA) is widely used in information technology(IT) industry fields for various applications such as a projection display, an optical power regulator, a micro mass spectrometer and for medical appliances. Recently, MLA have been fabricated and developed by using a reflow method having the processes of micro etching, electroplating, micro machining and laser local heating. Laser thermal relaxation method is introduced in marking of microdots on the surface of densified glass. In this paper, we have proposed a new direct fabrication process using UV laser local thermal-expansion(UV-LLTE) and investigated the optimal processing conditions of MLA on the surface of negative photo-resist material. We have also studied the 3D shape of the micro lens obtained by UV laser irradiation and the optimal process conditions. And then, we made chrome mold by electroplating. After that, we made MLA using chrome mold by hot embossing processing. Finally, we have measured the opto-physical properties of micro lens and then have also tested the possibility of MLA applications.
A Study on the Superplasticity of Zn-Al Alloy using Dynamic Materials Model
Jung, J.Y. ; Ha, T.K. ; Chang, Y.W. ;
Transactions of Materials Processing, volume 18, issue 4, 2009, Pages 317~322
DOI : 10.5228/KSPP.2009.18.4.317
Superplastic deformation behavior of a Zn-0.3 wt.% Al was investigated. Grain sizes of
were obtained by a thermomechanical treatment. A series of load relaxation and tensile tests were conducted at various temperatures ranging from RT (
. A large elongation of 1400% was obtained at room temperature in the specimens with the grain size of
. In the case of specimens with the grain size of
, relatively lower elongation at room temperature was obtained and, as the temperature increases above
, a high elongation of about 400 % has been obtained at
under the strain rate of
. Dynamic materials model (DMM) has been employed to explain the contribution from GBS of Zn-Al alloy. Power dissipation efficiency for GBS was evaluated as above 0.4 and found to be very close to the unity as strain rate decreased and temperature increased, suggesting that GBS could be regarded as Newtonian viscous flow.
Prediction of Drawing Load in the Shape Drawing Process
Lee, T.K. ; Lee, C.J. ; Lee, S.K. ; Kim, B.M. ;
Transactions of Materials Processing, volume 18, issue 4, 2009, Pages 323~328
DOI : 10.5228/KSPP.2009.18.4.323
The prediction of drawing load is very important in the drawing process. However, it is not easy to calculate the drawing load for the shape drawing process through a theoretical model because of a complex arbitrary final cross section shape. The purpose of this study is to predict drawing load in shape drawing process. The cross section of product is divided with small angle as much as similar with fan-shape. The drawing load of each section was calculated by theoretical model of round to round drawing process. And the shape drawing load was determined by summation of drawing load of each section. The effectiveness of the proposed method was verified through the FE analysis and shape drawing experiment. It had a good agreement between proposed method, FE analysis and experiment within about 3% errors.
Springback Prediction of Friction Stir Welded DP590 Steel Sheet Considering Permanent Softening Behavior
Kim, J. ; Lee, W. ; Chung, K.H. ; Park, T. ; Kim, D.G. ; Kim, Chong-Min ; Kim, D. ;
Transactions of Materials Processing, volume 18, issue 4, 2009, Pages 329~335
DOI : 10.5228/KSPP.2009.18.4.329
In order to better predict the springback for friction stir welded DP590 steel sheet, the combined isotropic-kinematic hardening was formulated with considering the permanent softening behavior during reverse loading. As for yield function, the non-quadratic anisotropic yield function, Yld2000-2d, was used under plane stress condition. For the verification purposes, comparisons of simulation and experiments were performed here for the unconstrained cylindrical bending, the 2-D draw bending tests. For two applications, simulations showed good agreements with experiments.
A Study on the Bendability of Stainless Steel Tubes
Lee, G.Y. ; Lee, H.J. ; Yi, H.K. ; Kim, Y.K. ; Moon, Y.H. ;
Transactions of Materials Processing, volume 18, issue 4, 2009, Pages 336~341
DOI : 10.5228/KSPP.2009.18.4.336
Hydroformed parts have higher dimensional accuracy, structural strength, and dimensional repeatability. Particularly in the automotive industry, manufacturing of parts with complex shapes from tubular materials sometimes requires one or more pre-forming operations such as bending before the hydroforming process. The pre-bending process is an important process for the successful hydroforming in the case where the perimeter of the blank is nearly the same as that of final product. The bendability of a tube depends on the parameters such as the bending radius, welding methods, mechanical properties and hardness. Through the stainless steel tubes bent by rotary draw bending machine, this study shows the following : (1) The influence on spring back ratio variation with stress level in the welded bent tube. (2) The Cross-section ovality variation with weld seam position and bending radius. (3) The relation between elongation and thickness reduction of tension zone with weld seam position and bending radius. (4) Workability evaluation of bent stainless steel tubes through the hardness of materials and hardness increment. The results of this study may help to understanding of characteristics on bendability of stainless steel tubes.
Forming Characteristics for the Bundle Extrusion of Cu-Ti Bimetal Wires
Lee, Y.S. ; Kim, J.S. ; Yoon, S.H. ; Lee, H.Y. ;
Transactions of Materials Processing, volume 18, issue 4, 2009, Pages 342~346
DOI : 10.5228/KSPP.2009.18.4.342
Forming characteristics for the bundle extrusion of Cu-Ti bimetal wires are investigated, which can identify the process conditions for weak mechanical bonding at the contact surface during the direct extrusion of a Cu-Ti bimetal wire bundle. Bonding mechanism between Cu and Ti is assumed as a cold pressure welding. Then, the plastic deformation at the contact zone causes mechanical bonding and a new bonding criterion for pressure welding is developed as a function of the principal stretch ratio and normal pressure at the contact surface by analyzing micro local extrusion at the contact zone. The averaged deformation behavior of Cu-Ti bimetal wire is adopted as a constitutive behavior at a material point in the finite element analysis of Cu-Ti wire bundle extrusion. Various process conditions for bundle extrusions are examined. The deformation histories at the three points, near the surface, in the middle and near the center, in the cross section of a bundle are traced and the proposed new bonding criterion is applied to predict whether the mechanical bonding at the Cu-Ti contact surface happens. Finally, a process map for the direct extrusion of Cu-Ti bimetal wire bundle is proposed.
The Effect of Surface Treatment on Creep Behaviors of Mg Alloy
Kang, Dae-Min ; An, Jung-O ; Kang, Min-Cheol ;
Transactions of Materials Processing, volume 18, issue 4, 2009, Pages 347~353
DOI : 10.5228/KSPP.2009.18.4.347
The apparent activation energy, the applied stress exponent, and rupture life have been measured from creep experiments over the range of
and the applied stress range of 64MPa to 94MPa. The materials were used AZ31 magnesium alloys treated by plasma electrolytic oxidation of
at surface to investigate the its influence on creep behavior, and creep tests were carried out under constant applied stress and temperature. The experimental results showed that the dipper the thickness of surface treatment the higher the activation energy and stress exponent. And the higher temperature and applied stress, the lower stress exponent and activation energy, respectively. Also the dipper the thickness of surface treatment the longer creep rupture time.
Hot Forging Design of Titanium Compressor Wheel for a Marine Turbocharger
Yeom, J.T. ; Na, Y.S. ; Lim, J.S. ; Kim, J.H. ; Hong, J.K. ; Park, N.K. ;
Transactions of Materials Processing, volume 18, issue 4, 2009, Pages 354~360
DOI : 10.5228/KSPP.2009.18.4.354
Hot-forging process and die design were made for a large-scale compressor wheel of Ti-6Al-4V alloy by using the results of 2-D FEM simulation. The design integrated the geometry-controlled approach and the processing contour map based on the dynamic materials model and the flow stability criteria. In order to obtain the processing contour map of Ti-6Al-4V alloy, compression tests were carried out in the temperature range of
and the strain rate range of
. In the die design of the compressor wheel using the rigid-plastic FEM simulation, forging dimensional accuracy, the capacity of the forging machine and defect-free forging were considered as main design factors. The microstructure of hot forged wheel using the designed die showed a typical alpha-beta structure without forging-defects.