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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Transactions of Materials Processing
Journal Basic Information
Journal DOI :
The Korean Society for Technology of Plasticity
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Volume & Issues
Volume 23, Issue 8 - Dec 2014
Volume 23, Issue 7 - Nov 2014
Volume 23, Issue 6 - Oct 2014
Volume 23, Issue 5 - Aug 2014
Volume 23, Issue 4 - Jul 2014
Volume 23, Issue 3 - Jun 2014
Volume 23, Issue 2 - Apr 2014
Volume 23, Issue 1 - Feb 2014
Selecting the target year
Evaluation of Analytical Parameters on Forming Limit Diagram based on Initial Geometrical Instability
Noh, H.G. ; Lee, B.E. ; Kim, J. ; Kang, B.S. ; Song, W.J. ;
Transactions of Materials Processing, volume 23, issue 4, 2014, Pages 199~205
DOI : 10.5228/KSTP.2014.23.4.199
The current study examines the effect of the analytical parameter values on the theoretical forming limit diagram (FLD) based on the Marciniak-Kuczynski model (M-K model). Tensile tests were performed to obtain stress-strain curves and determine the anisotropic properties in the rolling, transverse and diagonal direction of SPCC sheet materials. The experimental forming limit curve for SPCC sheet material was obtained by limiting dome stretching tests. To predict the theoretical FLD based on the M-K model, the Hosford 79 yield function was employed. The effects of three analytical parameters - the exponent of the yield function, the initial imperfection parameter and the fracture criterion parameter - on the M-K model, were examined and the results of the theoretical FLD were compared to the experimentally measured FLD. It was found that the various analytical parameters should be carefully considered to reasonably predict the theoretical FLD. The comparison of the acceptable forming limit area between the theoretical and experimental FLD is used to compare the two diagrams.
Press and Die Deformation for a Precise Semiconductor Lead Frame
Hong, S. ; Yoon, Y. ; Eom, S. ; Hwang, J. ; Lee, D. ;
Transactions of Materials Processing, volume 23, issue 4, 2014, Pages 206~210
DOI : 10.5228/KSTP.2014.23.4.206
The metal lead frame, a semiconductor component, has product tolerances in micro units as compared to products made with a larger size mold. Therefore, small deflections of the mold and of the press as well as the press molding process itself have a strong influence on accuracy of the product. Hence, it is necessary for the process design to consider the structural response of the mold and the press during deformation. In the current study, the mold deflection and pressure on the punch is examined using the finite element modeling (FEM) program ABAQUS. The results from the simulation were verified with the dynamic deformation measurement equipment using digital image correlation (DIC).
Process Modification and Numerical Simulation for an Outer Race of a CV Joint using Multi-Stage Cold Forging
Kang, B.S. ; Ku, T.W. ;
Transactions of Materials Processing, volume 23, issue 4, 2014, Pages 211~220
DOI : 10.5228/KSTP.2014.23.4.211
The outer race of a constant velocity (CV) joint having six inner ball grooves has traditionally been manufactured by multi-stage warm forging, which includes forward extrusion, upsetting, backward extrusions, necking, ironing and sizing, and machining. In the current study, a multi-stage cold forging process is examined and an assessment for replacing and modifying the conventional multi-stage warm forging is made. The proposed procedure is simplified to the backward extrusion of the conventional process, and the sizing and necking are combined into a single sizing-necking step. Thus, the forging surface of the six ball grooves can be obtained without additional machining. To verify the suitability of the proposed process, a 3-dimensional numerical simulation on each operation was performed. The forging loads were also predicted. In addition, a structural integrity evaluation for the tools was carried out. Based on the results, it is shown that the dimensional requirements of the outer race can be well met.
Experimental Study on Multi-Stage Cold Forging for an Outer Race of a CV Joint
Kang, B.S. ; Ku, T.W. ;
Transactions of Materials Processing, volume 23, issue 4, 2014, Pages 221~230
DOI : 10.5228/KSTP.2014.23.4.221
This study deals with a series of experimental investigations on multi-stage cold forging of an outer race used for a constant velocity (CV) joint with six inner ball grooves. The multi-stage cold forging, which consists of forward extrusion, upsetting, backward extrusion, and combined sizing-necking including ironing, was used to produce a prototype of the outer race. The cold forging tools such as forging punches and dies required in this multi-stage cold forging were also designed and fabricated. For the combined sizing-necking, especially, the longitudinally six-segmentallized punches were developed to easily eject from the necked inner groove of the outer race with consideration of the operating mechanism. Spheroidized SCr420H billet was used in the experimental study. To verify the suitability of the proposed process, the obtained parts were obtained from each forging operation, and the geometries were compared with the target dimensions. It was confirmed that the outer race with six inner ball grooves was well forged by adopting the proposed multi-stage cold forging, and the dimensional accuracy of the forged outer race matched well with the requirements.
Prediction of Deformation Texture in BCC Metals based on Rate-dependent Crystal Plasticity Finite Element Analysis
Kim, D.K. ; Kim, J.M. ; Park, W.W. ; Im, Y.T. ; Lee, Y.S. ;
Transactions of Materials Processing, volume 23, issue 4, 2014, Pages 231~237
DOI : 10.5228/KSTP.2014.23.4.231
In the current study, a rate-dependent crystal plasticity finite element method (CPFEM) was used to simulate flow stress behavior and texture evolution of a body-centered cubic (BCC) crystalline material during plastic deformation at room temperature. To account for crystallographic slip and rotation, a rate-dependent crystal constitutive law with a hardening model was incorporated into an in-house finite element program, CAMPform3D. Microstructural heterogeneity and anisotropy were handled by assigning a crystallographic orientation to each integration point of the element and determining the stiffness matrix of the individual crystal. Uniaxial tensile tests of single crystals with different crystallographic orientations were simulated to determine the material parameters in the hardening model. The texture evolution during four different deformation modes - uniaxial tension, uniaxial compression, channel die compression, and simple shear deformation - was investigated based on the comparison with experimental data available in the literature.
Design for Warm Forming of a Mg El-cover Part Using a Ductile Fracture Criterion
Kim, S.W. ; Lee, Y.S. ;
Transactions of Materials Processing, volume 23, issue 4, 2014, Pages 238~243
DOI : 10.5228/KSTP.2014.23.4.238
Recently, magnesium alloys have been widely used in the automotive, aerospace and electronics industries with the advantages of high specific strength, excellent machinability, high electrical conductivity, and high thermal conductivity. Deep drawn magnesium alloys not only meet the demands environmentally and the need for lighter products, but also can lead to remarkably improved productivity and more rapid qualification of the product The current study reports on a failure prediction procedure using finite element modeling (FEM) and a ductile fracture criterion and applies this procedure to the design of a deep drawing process. Critical damage values were determined from a series of uniaxial tensile tests and FEM simulations. They were then expressed as a function of strain rate and temperature. Based on the plastic deformation histories obtained from the FEM analyses of the warm drawing process and the critical damage value curves, the initiation time and location of fracture were predicted. The proposed method was applied to the process design for fabrication of a Mg automotive compressor case and verified with experimental results. The final results indicate that a Mg case part 39% lighter than an Al die casting part can be produced without any defects.
Fabrication of a Joint Node for an Aluminum Frame for a Low Speed Electric Vehicle using Thixoforming Technology
Lee, S.Y. ;
Transactions of Materials Processing, volume 23, issue 4, 2014, Pages 244~249
DOI : 10.5228/KSTP.2014.23.4.244
The thixoforming process has been applied to forming of a joint node for the aluminum frame of a low speed electric vehicle. A joint node should connect three aluminum extruded chassis showing different profiles. The MHS(magnetohydrodynamic stirring) A357 billet was selected because homogeneous globular grains are necessary as the billet materials for thixoforming. A careful design of joint node has been performed by the considerations of structural demands and the simulation results for the thixoforming process using the MAGMAsoft. Optimum heating temperature for the A357 billet was between 580 and
corresponding to the semi-solid temperatures showing 20-30% of liquid fraction. An injection speed of around 100mm/s and preheating of die at temperatures of
were also necessary conditions to obtain reasonable thixoformed parts.