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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 25, Issue 4 - Aug 2016
Volume 25, Issue 3 - Jun 2016
Volume 25, Issue 2 - Apr 2016
Volume 25, Issue 1 - Feb 2016
Selecting the target year
Use of Processing Maps to Evaluate the Forming Condition during Ring Rolling
Lee, H.J. ; Kang, G.P. ; Kim, Y.H. ;
Transactions of Materials Processing, volume 25, issue 1, 2016, Pages 5~11
DOI : 10.5228/KSTP.25.1.5
The control of the roll velocities is essential in maintaining stability during ring rolling, but such control is difficult. The determination of the best roll velocities can be helped with the use of FE simulations and processing maps, which give the useful information such as power dissipation and flow instability for hot metal forming processes. In the current study, the workability of 7050 aluminum alloy is evaluated by using processing map. With the developed information, the stability of the ring rolling condition, called the Constant Growth Velocity Condition (CGVC), is evaluated.
Evaluation of Formability Dependent on Reconfigurable Roller Types for 3D Curved Sheet Forming
Son, S.E. ; Yoon, J.S. ; Kim, H.H. ; Kim, J. ; Kang, B.S. ;
Transactions of Materials Processing, volume 25, issue 1, 2016, Pages 12~20
DOI : 10.5228/KSTP.25.1.12
Press machines and dies are commonly used for 3D curved sheet forming. Using conventional die forming can cause economic problems since various modifications of the die shape are required depending on the product shape. Various types of flexible forming such as multi-point dieless forming (MDF), flexible incremental roll forming have been developed to improve the needed process flexibility. Although MDF can reduce the production cost using reconfigurable dies, it still has significant material loss. Drawbacks such as wrinkling, dimpling, and forming errors can also occur despite continuous investigations to mitigate these defects. A novel sheet forming process for 3D curved surfaces, a flexibly-reconfigurable roll forming (FRRF), has been recently proposed to overcome the economic and technical limitations of current practice. FRRF has no limitation on blank size in the longitudinal direction, and also minimizes or eliminates forming defects such as wrinkling and dimpling. Feasibility studies of FRRF have been conducted using FE simulations for multi-curved shapes and various sheet thicknesses. Therefore, the fabrication of a FRRF apparatus is required for any follow-up studies. In the current study, experiments with reconfigurable rollers were conducted using a simple design pre-FRRF apparatus prior to fabricating the full size FRRF apparatus. There are three candidates for the reconfigurable roller: a bar-type shaft, a flexible shaft, a ground flexible shaft. Among these candidates, the suitable reconfigurable roller for FRRF is determined through various forming tests.
Change in Springback Tendency during Forming of a Hat-type Product with High Strength Steel Using a Digital Servo Press
Kang, K.H. ; Kim, S.H. ; Ro, H.C. ;
Transactions of Materials Processing, volume 25, issue 1, 2016, Pages 21~28
DOI : 10.5228/KSTP.25.1.21
In the current study, reduction of springback is quantified and the reasons for the reduction are investigated. The testing involved a digital servo motion applied to a U-draw bending to produce a hat-type product from high strength steels such as DP780 and DP980. The change in springback is compared between the constant speed motion and three kinds of servocontrolled motions during forming experiments. In order to predict the springback for the servo-controlled tool motion, a finite element method was utilized for the springback analysis considering a kinematic hardening model for the steel. The comparison of springback between the analysis and the experiments shows that they have similar tendencies. Also, the analysis results indicate that the springback reduction is greatly influenced by a decrease in the friction coefficient, which originates from the contact and detach phenomena between the tooling and the blank during the up-and-down motion of the upper die following the servo-controlled motion.
Finite Element Analysis and Parameter Optimization for the Press Hemming of Automotive Closures
Kim, J.H. ; Kwak, J.H. ; Kim, S.H. ; Ju, Y.H. ; Shin, H.S. ;
Transactions of Materials Processing, volume 25, issue 1, 2016, Pages 29~35
DOI : 10.5228/KSTP.25.1.29
In the current study, finite element analysis was conducted for the press hemming of automotive panels in order to predict various hemming defects such as roll-in and turn down. The analysis used the exact punch movement based on the cam location and considered the sealer between the inner and outer panels with an artificial contact thickness. The analysis results quantify the hemming defects especially at the flange edge in the matching region of the head lamp. A design of experiments along with the parameter study was used to obtain the optimum process parameters for minimizing hemming defects. The optimization process selects the intake angle, bending angle of the hemming punch, and the flange height of the outer panel. The optimum design process determines an appropriate tool angle and flange height to reduce the roll-in and turn-down as compared to the initial design.
Prediction and Verification of Lateral Joining Strength for Tapered-Hole Clinching using the Taguchi Method
Kang, D.S. ; Park, E.T. ; Tullu, A. ; Kang, B.S. ; Song, W.J. ;
Transactions of Materials Processing, volume 25, issue 1, 2016, Pages 36~42
DOI : 10.5228/KSTP.25.1.36
Fiber metal laminates (FMLs) are well known for improved fatigue strength, better impact resistance, superior damage tolerance and slow crack growth rate compared to traditional metallic materials. However, defects and loss of strength of a composite material can occur due to the vertical load from the punch during the joining with a dissimilar material using a conventional clinching method. In the current study, tapered-hole clinching was an alternative process used to join Al 5052 and FMLs. The tapered hole was formed in the FML before the joining. For the better understanding of static and dynamic characteristics, a clinched joining followed by a tensile-shear test was numerically simulated using the finite element analysis. The design parameters were also evaluated for the geometry of the tapered hole by the Taguchi method in order to improve and compare the lateral joining strength of the clinched joint. The influence of the neck thickness and the undercut were evaluated and the contribution of each design parameter was determined. Then, actual experiments for the joining and tensile-shear test were conducted to verify the results of the numerical simulations. In conclusion, the appropriate combination of the design parameters can improve the joining strength and the cross-sections of the tapered-hole clinched joint formed in the actual experiments were in good agreement with the results of the numerical simulations.
BDM Rolling of Middle Sized H-beams from a Bloom
Kim, J.M. ; Kim, K.W. ; Kim, B.M. ;
Transactions of Materials Processing, volume 25, issue 1, 2016, Pages 43~48
DOI : 10.5228/KSTP.25.1.43
H-beams are generally produced by hot rolling composed of a Break Down Mill (BDM) and a Finishing Mill (FM). The goal of the current study was to develop BDM rolling of H300ｘ300 beams from blooms slit from slabs. In order to manufacture H300ｘ300 beams, the caliber design and the pass schedule of BDM rolling were proposed for a bloom instead of a beam blank. The proposed BDM caliber design and pass schedule were tested using FE-simulation and pilot tests. For the major shape dimensions, such as flange width, web height, web thickness, as well as BDM rolling loads, a comparative analysis between the FE-simulation and the pilot rolling tests was conducted. The results of FEM analysis and pilot rolling tests showed good consistency. Moreover, BDM rolling loads were predicted to be in the range of allowable rolling loads. It was concluded that the designed BDM rolling is suitable for implementation within current manufacturing capacity.
Numerical Study of Electrohydraulic Forming Using an Arbitrary Lagrange-Eulerian Method
Woo, M.A. ; Noh, H.G. ; Song, W.J. ; Kang, B.S. ; Kim, J. ;
Transactions of Materials Processing, volume 25, issue 1, 2016, Pages 49~55
DOI : 10.5228/KSTP.25.1.49
Electrohydraulic forming (EHF) is a high-speed forming process that uses an electric arc discharge in water. Shock waves resulting from the electric arc discharge are propagated to the blank through water and the blank moves toward the die. Advantages of EHF include improved formability due to the high-speed process and reduction of the bouncing effect. In the current study, a numerical simulation of EHF was developed using LS-DYNA. In the simulation, the model for the electric arc was assumed as an adiabatic gas expansion and an Arbitrary Lagrange-Eulerian (ALE) multi material formulation was used to describe the interaction between the electric arc and the water. In order to model the Fluid-Structure Interaction (FSI), a coupling mechanism was used. The blank of Al 1100-O was simulated using shell elements. The results of the simulation showed that the blank was deformed due to the pressure propagation of water and the bouncing effect did not affect the formability of blank.
Prediction of Steady-state Strip Profile during Hot Rolling - PartⅠ: FEM Analysis
Lee, J.S. ; Hwang, S.M. ;
Transactions of Materials Processing, volume 25, issue 1, 2016, Pages 56~60
DOI : 10.5228/KSTP.25.1.56
Precise prediction and control of the strip profile is crucial for automatic process set-up and operation of a hot strip mill. In the current study, we present the effect of post-deformation on the steady-state strip profile. The process was simulated by a 3-D elastic-plastic finite element (FE) analysis. Comparisons are made between the strip profile measured at the roll exit and the steady-state strip profile. The results raised an issue with regard to the importance of taking into account the effect of post-deformation.
Prediction of Steady-state Strip Profile during Hot Rolling - PartⅡ: Development of a Mathematical Model
Lee, J. S. ; Hwang, S. M. ;
Transactions of Materials Processing, volume 25, issue 1, 2016, Pages 61~66
DOI : 10.5228/KSTP.25.1.61
In the current study, we present a new model for the prediction of the strip profile and the residual stresses. This new approach is an analytical model that predicts the residual stresses from the effect of post-deformation. Since the residual stress cannot exceed the yield strength of the material, post-yielding may possibly occur in the post-deformation zone prior to the strip reaching the steady-state zone. The prediction accuracy of the proposed model is examined through comparison with the predictions from 3-D finite element (FE) simulations.
Review on Profile Drawing Process
Lee, S.K. ; Lee, I.K. ; Kim, B.M. ;
Transactions of Materials Processing, volume 25, issue 1, 2016, Pages 67~74