• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.4
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• pp.207-218
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• 1997

A new blank design method is introduced to predict the blank shape and the strain distribution in the sheet metal forming process. This method deals with only one step from the final shape to the initial blank using the ideal forming theory. Based on this theory, a three-dimensional membrane finite element code has been developed to design an initial blank in the sheet metal forming process. In this paper, the designs of initial blanks for forming a cylindrical cup, a rectangular cup, and a front fender are presented as examples. Also, it compares the two shapes, the target shape with the shape which is deformed from the initial blank using the FEM analysis code. The results illustrate the information that this direct design code is useful in the preliminary design state.

• Transactions of Materials Processing
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• v.8 no.5
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• pp.454-464
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• 1999

A new blank design method is proposed to predict the optimum initial blank shape in the sheet metal forming process. The rollback method for blank shape design takes the difference between the deformed blank contour and the target contour shape into account. the minimization object function R is proposed. Based on the method, a computer program composed of blank design module, FE-analysis module and mesh generation module is developed. The rollback method is applied to square cup, reentrant cross section, L-shaped cup drawing process with the flange of uniform size around its periphery to confirm its validity. The optimum initial blank shape is obtained from an arbitrary blank shape after several modifications. Good agreements are recognized between the numerical results and the published experimental results for initial blank shape and thickness strain distribution. It is concluded that the rollback method is an effective and convenient method for an optimum blank shape design.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.185-195
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• 1998

A new blank design method is proposed to predict the optimum initial blank shape in the sheet metal forming process. The rollback method for blank shape design takes the difference between final deformed shape and target contour shape into account. Based on the method, a computer program composed of blank design module, FE-analysis program and mesh generation module is developed. The rollback method is applied to square cup drawing process with the flange of unifiorm size around its periphery to confirm its validity. The optimum initial blank shape is obtained from an arbitrary square blank after three modifications. Good agreements are recognized between the numerical results and the published results for initial blank shape and thickness strain distribution. The optimum blank shape for two parts of automobile sub-frame is designed. The thickness distribution and the level of punch load is improved. Also, the method is applied to design the weld line in the tailor-welded blank. It is concluded that the rollback method is an effective and convenient method for an optimum blank shape design.

• Transactions of Materials Processing
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• v.12 no.3
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• pp.208-213
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• 2003

The methodology to design initial blanks considering the reduction of both springback and flange trimming amounts is studied. Three dimensional forming analysis of a trial blank Is first carried out using FEM and the tentative Initial blank shape is then determined by cutting the outer edge of the trial blank whose shape is nearly matched with the trimming line. During the shaping the blank edge, tile movement of blank outer line is described with random variables to reduce the sensitivity of initial blank geometry. After performing 2-D FEM forming and springback simulations for selected sections and optimizing the trimming and springback amounts in terms of section length of the blank, the initial blank is finally determined. In order to see tile springback reduction in the initial blank determined by the proposed method, a stepped s-rail is stamped and the sppingback is measured. The springback of newly designed initial blank of stopped s-tail is tremendously reduced.

• Transactions of Materials Processing
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• v.7 no.3
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• pp.260-273
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• 1998

A new blank design method is proposed to predict the optimum initial blank shape in the sheet metal forming process. The rollback method for blank shape design takes the difference between final deformed shaped and target contour shape into account. Based on the method a computer program composed of blank design module FE-analysis program and mesh generation module is developed. The rollback method is applied to square cup drawing process with the flange of unifiorm size around its periphery to confirm its validity. The optimum initial blank shape is obtained from an arbitrary square blank after three modification. Good agreements are recognized between the numerical results and the published results for initial blank shape and thickness strain distribution. The optimum blank shape for two parts of automobile sub-frame is designed, The thickness distribution and the level of punch load is improved. Also the method is applied to design the weld line in the tailor-welded blank. It is concluded that the rollback method is an effective and convenient method for an optimum blank shape design.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.77-81
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• 2002

A new method of optimal blank shape design using the initial nodal velocity (INOV) has been proposed for the drawings of arbitrary shaped cups. With the given information of tool shape and the final product shape, corresponding initial blank shape has been found from the motion of boundary nodes. Although the sensitivity method, the past work of Hynbo Shim and Kichan Son, has been proved to be excellent method to find optimal blank shapes, the method has a problem that a couple of deformation analysis is required at each design step and it also exhibits an abnormal behaviors in the rigid body rotation prevailing region. In the present method INOV, only a single deformation analysis per each design stage is required. Drawings of practical products as well as oil-pan have been chosen as the examples. At every case the optimal blank shapes have been obtained only after a few times of modification without predetermined deformation path. The deformed shape with predicted optimal blank almost coincides with the target shape at every case. Through the investigation the INOV is found to be very effective in the arbitrary shaped drawing process design.

• Transactions of Materials Processing
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• v.11 no.6
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• pp.487-494
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• 2002

A new method of optimal blank shape design using the initial nodal velocity (INOV) has been proposed for the drawings of arbitrary shaped cups. With the given information of tool shape and the final product shape, corresponding initial blank shape has been found from the motion of boundary nodes. Although the sensitivity method, the past work of the present authors, has been proved to be excellent method to find optimal blank shapes, the method has a problem that a couple of deformation analysis is required at each design step and it also exhibits an abnormal behaviors in the rigid body rotation prevailing region. In the present method INOV, only a single deformation analysis per each design stage is required. Drawings of practical products as well as oil-pan, have been chosen as the examples. At every case the optimal blank shapes have been obtained only after a few times of modification without predetermined deformation path. The deformed shape with predicted optimal blank almost coincides with the target shape at every case. Through the investigation the INOV is found to be very effective in the arbitrary shaped drawing process design.

• Journal of Ocean Engineering and Technology
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• v.13 no.3 s.33
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• pp.21-28
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• 1999

In this paper, a finite element method for the determination of initial blank shape in sheet metal forming process will be introduced. The initial blank shape is determined by the only one step from the final to the initial blank. The used finite element inverse method adopted Henky's deformation theory, Hill's anisotropic yield criterion and simplified boundary conditions. Based on this theory. a three-dimensional membrane finite element code was developed. The developed code will be applied to several sheet metal forming examples for the demonstration of its validity.

• 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.

• Transactions of Materials Processing
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• v.6 no.5
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• pp.400-407
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• 1997

Geometric mapping technique has been used to find the shape of initial blank for sheet forming. The method was chosen because of its simplicity and numerical efficiency. Error in blank shape were measured along deformation path by FE analysis of forming. Blank shape was modified by volume additionaddition/Subtractiontraction method with taking with taking into account of deformation path. Modified blank shape shows an acceptable result, showing the current method can be an useful tool for predicting blank shape in the practical application. More test will be done to verify the validity of the method.