• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.31-36
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• 1997

Various methods of finite element modeling for welded part are examined and the stamping simulation of automotive body is presented by using the explicit finite element code PAM-STAMPTM. The process of stamping simulation is suggested step by step, and then the gravity, binder wrap, forming, trimming and springback of front door inner are analyzed. It shows good agreements with real product in the aspects of deformed shape and failure area. The door inner with laser-tailor welded blank is simulated, in which deformed shape, movement of welde line and formability are predicted.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1331-1332
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• 2011

• Journal of the Korean Society for Heat Treatment
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• v.23 no.4
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• pp.183-190
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• 2010

There are many methods to reduce the weight and the cost of the automobile body, among them, Tailor Welded Blank (TWB) is new welding method applied to body structure. It is necessary to evaluate mechanical properties of TWB structures or sheets for the application to automobile body parts. In this study, the stiffness of T-type and L-type joint structures, composite of TWB panel, which simplified two portions of side structure in automobile body were investigated. Additionally, the fatigue properties of TWB panels were obtained. Two types of welding technologies, laser and mash seam welding, were used to join mild panels with different thickness. This results are compared with conventional structures. The results are as follows: 1) The stiffness of joint structures, composite of TWB panel, is approximately 17% higher than that of conventional ones. 2) The location of welding line in TWB had a effect on the in plane bending stiffness, but not on the out of plane bending stiffness. 3) In terms of welding technology type, the mash seam welding show higher stiffness than the laser welding for in plane bending stiffness. But minimal differences in both types are revealed for out of plane bending stiffness. 4) The fatigue strength, composite of TWB panel, is lower than that of base steel. It is thought that defects in the welding zone had the action of notch in the fatigue test.

• Transactions of Materials Processing
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• v.18 no.1
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• pp.73-79
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• 2009

In order to investigate the formability of friction stir welded(FSW) tailor welded blanks(TWB) with respect to the base material's directional combination, aluminum alloy AA6111-T4 sheets were welded with three different conjoining types: RD-RD, TD-RD and TD-TD. Here, RD and TD represent rolling and transverse directions, respectively. For experimental formability study, three tests with gradual complexity were performed: the simple tension test with various weld line directions for uni-axial elongation, the hemisphere dome stretching test for biaxial stretching and the cylindrical cup deep drawing test. As a result, all three forming tests showed that RD-RD type samples exhibited the best formability, while TD-TD type sheets showed the least formability performance.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.151-155
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• 2001

The purpose of this study is to investigate the weldline movement of the laser welded sheets during the warm deep drawing process. For this investigation, Five steps of temperature ranges, from room temperature to $200^{\circ}C$, and two kinds of thickness combination, 0.8 mm${\times}$1.2 mm and 0.8 mm${\times}$1.6 mm SCP1 material sheets, were adopted. Also, the numerical analysis using the PAM-STAMP has been carried out with the same models as the specimens. As a result the higher temperature was adopted, the less weld-line movement was observed.

• Transactions of Materials Processing
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• v.10 no.3
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• pp.193-199
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• 2001

Forming more than two parts of sheet metal in a single stamping operation lowers production costs, reduces weight, and heightens dimensional accuracy. The tailored blank (TB) is a laser-welded or mash-seam-welded sheet metal with different thicknesses, different strengths, or different coatings. Recently, automotive manufacturers have been interested in tailored blanks because of their desire to improve the rigidity, weight reduction, crash durability, and cost savings. Therefore the application to auto-bodies has increased. However, as tailored blanks do not behave like un-welded blanks in press forming operations, stamping engineers no longer rely on conventional forming techniques. Field try-outs are very important manufacturing processes for an economic die-making. In the field try-outs, the rounded geometries of tool and the drawbead shape and size in die face are generally modified when the forming defects can not be removed by the adjustment of forming process parameters. In this study, the field try-outs of tailored door inner panel are introduced and evaluated. The behaviours of laser tailored blank associated with different thickness combinations in the forming process of door inner panel are described focusing on terms of experimental investigations on the formability.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.477-478
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• 2007

• 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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• 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 the Korean Society of Automotive Engineers
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• v.9 no.3
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• pp.181-189
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• 2001

For the Tailor Welded Blank sheet used fur automobile body panel, the characteristics of fatigue crack propagation behavior were studied. The thickness of specimen was machined to be same (0.9+0.9mm) and different (0.9+2.0mm). As a base test, mechanical properties around welding zone were examined. The results indicated that there were no significant decreases in mechanical properties, but hardness around welding bead is 2.3 times greater than base material. The crack propagation rate was noticeably decreased around welding line and rapidly increased as it passed by welding line. Reviewing the shape of the crack propagation, crack width around welding line was wide around the welding zone due to retardation of crack growth, but it became narrow passing welding line due to decreased toughness. Elasto-Plastic analysis was performed by finite element analysis fur explaining the test results.