• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.81-84
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• 2001

An inverse finite element approach is employed for more capability to design the optimum blank shape from the desired final shape with small amount of computation time and effort. In some drawing or stamping simulation with inverse method, it is difficult to apply inverse scheme due to the large aspect ratio or steep vertical angle of inclination. The reason is that initial guesses are hard to make out with present method for those cases. In this paper, a direct mesh marring scheme to generate initial guess on the sliding constraint surface described by finite element patches is suggested for one step inverse analysis to calculate initial blank shape. Radial type mapping is adopted for the simulation of rectangular cup drawing process with large aspect ratio and parallel type mapping for the simulation of S-Rail forming process with steep vertical angle of inclination.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.4
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• pp.38-47
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• 2000

Recently, finite element method has been used as an effective tool in the design process of sheet metal forming. In the present study, an implicit method and an explicit method have been developed for 2D analysis and 3D analysis, respectively, and applied to several processes including plane strain draw bending and TWB sqaure cup drawing. Also, commercial codes are used for geometrically complex problems, such as tube hydroforming, "L" cup deep drawing and side frame forming. In this paper, basic formulations used in the methods are introduced and results obtained from the applications are discussed.discussed.

• Transactions of Materials Processing
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• v.10 no.3
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• pp.235-245
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• 2001

Deep drawing process, one of sheet metal forming methods, is very useful in the industrial field because of its efficiency The deep drawing is affected by many process variables, such as blank shapes, shape radii of the punch and die, formability of materials and so on. Especially, blank shape is very important formability factor. In this study, in order to investigate the effects of blank shape, we suggested three kinds of blank shapes and examined friction test about three conditions. We measured punch load distribution according to punch stroke under the conditions of each punch and die shape radii and observed punch load of elliptical cup forming.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.235-238
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• 2005

In this study, it is investigated that the effect of material properties such as strength coefficient and strain hardening exponent on formability of AZ31 alloy sheet in square cup deep drawing process. Mechanical properties of AZ31 alloy sheet at elevated temperature $250^{\circ}C$ are obtained from uniaxial tensile tests and based on these results, a series of square cup deep drawing tests at the same temperature condition are carried out. Also, the possibilities of necking initiation is predicted by the FEM and FLD and compared with experimental results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.42-45
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• 1997

Weldline movement of tailored blanks originates from two sources, primary and secondary. Primary movement occurs by geometrical reason, that is, just scratched lines on the no-weld blanks move during drawing to be fitted to geometrical change. Secondary movement is induced by the characteristics of tailored blanks itself. The primary movement was mainly dependent on the weldline location and not affected by the type of material. The secondary movement caused by laser welding and/or small strength difference in this study was not dominant compared with primary movement. The formability of tailored blanks always inferior to those of original blanks. This is due to the existence of hardened weld bead. The closer a weldline is to punch corner where drawing is most active, the worse its formability becomes. This is because the weldline prohibits the drawing process. It was confirmed by measuring diagonal length at the blank corner. The mode of fracture was changed form wall break to draw break when the weldling was close to the punch corner.

• Transactions of Materials Processing
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• v.5 no.4
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• pp.288-296
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• 1996

A method of determining an optimum blank shape for non-circular deep drawing process is extended to the multi-stage deep drawing process. As an example concentric two-stage square deep drawing process is considered and the ideal blank shape with uniform cup height and without flange part after the process is constructed by the backward tracing of rigid plastic FEM. The conventional square blank shapes are also adopted for the comparison of two cases. As a result it is confirmed that the drawn products with better thickness strain distribution and deeper cup depth could be obtained by the suggested ideal blank shapes.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.30.1-33
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• 1999

Finite element simulation with experimental analysis of Taguchi's orthogonal array was carried out to know the effects of material and forming parameters on the cup earing and skewness. It was revealed that the planar anisotropy was the most influencing factor in the cup ear formation whereas blank holding force and material properties such as strength and thickness deviation at the coil edge had a relatively high effect on the cup skewness.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.10
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• pp.2653-2663
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• 1994

The design of sheet metal working processes is based on the knowledge about the deformation mechanism and the influence of the process parameters. The typical geometric process parameters are the die geometry, the initial sheet thickness, the initial blank shape, and so on. The initial blank shape is of vital importance in the most sheet metal forming operations, especially in the deep drawing process, since the forming load and the strain distribution are significantly affected by the shape of an initial blank. The influence of the initial blank shape on a square cup deep drawing process is investigated by the numerical simulation and the experiment. The numerical simulation is carried out by a modified membrane finite element method which takes bending deformation into account. The numerical and experi-mental results show that the initial blank shape have strong influence on the forming load and the strain distribution. The numerical results are compared with the experimental results and other numerical results which are calculated with the membrane theory.

• Korean Journal of Metals and Materials
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• v.47 no.5
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• pp.274-282
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• 2009

To investigate the evolution of deformation texture in dual phase (DP) steels during deep-drawing deformation, deep-drawing experiments were performed. Microtexture measurements were conducted using electron backscattered diffraction (EBSD) to analyze texture evolution. A rate-sensitive polycrystal model was used to predict texture evolution during deep-drawing deformation. In order to evaluate the strain path during deep-drawing deformation, a steady state was assumed in the flange part of a deep-drawn cup. A ratesensitive polycrystal model successfully predicted the texture evolution in DP steels during deep-drawing deformation. The final stable orientations were found to be strongly dependent on the initial location in the blank. Texture analysis revealed that the deep drawability of DP steels decreases as the true strain in the radial direction of the deep-drawn cup increases during deep-drawing deformation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.1171-1172
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• 2010