• Transactions of Materials Processing
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• v.17 no.7
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• pp.511-516
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• 2008

A drawbead die for the experimental determination of drawbead forces was newly introduced in this paper. While the conventional Nine's drawbead die inevitably includes effects of a blank holding force on the measured drawbead forces, the new drawbead die excludes it by removing the blank holder contact in the dieface. Therefore, the new drawbead die can provide more realistic drawbead forces without considering somewhat arbitrary effect of blank holder with the computational procedure of forming process. The drawbead opening force and restraining force obtained by adopting the two experimental dies were compared for the validation of accuracy in the FEM simulation of automotive fender forming process. The compared section strains and draw-ins confirmed that the present drawbead die provides better drawbead forces for an accurate FEM simulation of sheet metal forming process.

• Transactions of Materials Processing
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• v.18 no.5
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• pp.371-376
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• 2009

An equivalent drawbead model(EDM) for sheet metal forming analysis, which replaces complex drawbead geometries with drawbead forces in modeling the stamping dies with finite elements, is experimentally verified and applied to the numerical simulation of auto-panel stamping process. The drawbead restraining and opening forces of elliptical drawbead, circular drawbead, square drawbead, and step drawbead are obtained by performing the drawbead pulling test and compared with those of EDM and commercial code models(CCM). Better agreement with experimental measurements is found in EDM than CCM. Furthermore, the excellence of EDM is demonstrated in its application to the auto-body stamping analysis.

• Transactions of Materials Processing
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• v.7 no.1
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• pp.12-22
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• 1998

An expert drawbead model is developed for the finite element analysis of stamping processes. The expert model calculates drawbead restraining forces and bead-exit thinnings with the forming condi-tions and drawbead size. The drawbead restraining forces and bead-exit thinnings of a circular draw-bead and stepped drawbead are computed by mathematical models and corrected by the multiple lin-ear regression method based on experimental measurements. The squared drawbead preventing the sheet from drawing-in inside die cavity is assumed to have a very huge drawbead restraining force and no pre-strain just after drawbead. The combined beads are considered as a combination of basic draw-beads such as circular a drawbead stepped drawbead and squared drawbead so that the drawbead restraining forces and bead-exit thinnigs are basically sum of those of basic drawbeads.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.367-369
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• 2008

A theoretical model of equivalent drawbead for sheet metal forming analysis is experimentally verified in this paper. After the theoretical drawbead models improved a material description for the accurate calculation of drawbead forces are briefly introduced, they are verified by showing the good agreement of their drawbead forces with experimental measurements. Furthermore, the excellence of theoretical models is demonstrated by the comparison with those of commercial codes.

• Transactions of Materials Processing
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• v.11 no.5
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• pp.394-404
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• 2002

The drawbead model for a three-dimensional a finite element analysis of sheet metal forming processes is developed. The mathematical models of the basic drawbeads like circular drawbead, stepped drawbead, and squared drawbaed are first derived using the bending theory, belt-pulley equation, and Coulomb friction law. Next, the experiments for finding the drawing characteristics of the drawbead are performed. Based on mathematical models and drawing test results, expert models of basic drawbeads are then developed employing a linear multiple regression method. For the expert models of combined drawbeads such as the double circular drawbead, double stepped drawbead, circular-and-stepped drawbead, etc., those of the basic drawbeads are summed. Finally, in order to verify the expert models developed, the drawing characteristics calculated by the expert models of the double circular drawbead and circular-and-stepped drawbead are compared with those obtained from the experiments. The predictions by expert models agree well with the measurements by experiments.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.431-433
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• 2007

The drawbeads, which is used for controlling the flow of the sheet by imposing the tension and for preventing the springback in the sheet metal forming process, affects a lot the formability because of the differences in the restraint and opening forces according to the drawbead shapes and dimensions. In this study, the experimental device enabling to measure the drawbead restraining and opening forces was manufactured and the drawing forces of circular, square, and step drawbeads are measured. The drawbead restraining and opening forces of a circular drawbead are increased as its drawbead height is increased. Similarly, those of a square drawbead are increased as its height is increased and shoulder radii decreased. Also, those of a step drawbead are increased as its height and difference in their heights are increased.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.04a
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• pp.26-29
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• 2000

drawbead expert models are developed for calculating drawbead restraining force and drawbead-exit thinnings which are boundary conditions in FEM stamping simulation employing the linear multiple regression method by which the deviation of drawing characteristics between drawing test and mathematical model is minimized. In order to show the efficiency and accuracy of an expert drawbead model a finite element simulation of auto-body panel stamping is carried out. The finite element simulation shows that the expert drawbead model provides the accurate solution guarantees the stable convergence and the merit in the computation time.

• Transactions of Materials Processing
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• v.16 no.6
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• pp.457-462
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• 2007

The drawbeads, which are used for controlling the flow of the sheet into die cavity by imposing the tension and for preventing the forming defects like wrinkling, springback, etc. during the sheet forming process, affect the formability strongly because of the differences in the restraint and opening forces according to the drawbead shapes and dimensions. In this study, the experimental device enabling to measure the drawbead restraining and opening forces is manufactured and the drawing forces of circular, square, and step drawbeads are measured. The drawbead restraining and opening forces of a circular drawbead are increased as its drawbead height is increased. Similarly, those of a square drawbead are increased as its height is increased and shoulder radii decreased. The drawbead forces obtained from the experiment were compared with those calculated in the numerical simulation of stamping process of automotive fender. Good agreement was found so that the experimental measurements can be used in the simulation of auto-body stamping process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.557-561
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• 1997

In this study, using DEFORM and PAM-STAMP drawbead analysis is carried out for the commercial code availability. The three drawbead types, single circular drawbead, single square drawbead and double circular drawbead, are examined. The clamping force, drawing force and effective strain of sheet metal which is passed by drawbead are checked on each drawbeads.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.203-206
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• 2006

The drawbeads, which is used for controlling the flow of the sheet by imposing the tension and for preventing the springback in the sheet metal forming process, affects a lot the formability because of the differences in the restraint and opening forces according to the drawbead shapes and dimensions. In this study, the experimental device enabling to measure the drawbead restraining forces and the drawbead opening forces associated with various drawbead shapes and dimensions and their theoretical evaluation are introduced and verified through the experimental measurement of those of a circular drawbead.