• 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 the Korean Society of Automotive Engineers
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• v.11 no.1
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• pp.143-150
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• 2003

Experimental research has been carried out to investigate the characteristics of the fatigue crack initiation and propagation behavior of Tailor Welded Blank(TB) sheet used for vehicle body. We used three types of specimens which were machined of the same base metal: one is 1.4mm thick, another is 1.6mm thick, and the third(TB specimen) is laser-welded of two specimens(1.4mm and 1.6mm thick ones). The results of tensile and hardness test indicate that the yield strength of the TB specimen is the highest, and the hardness around welding bead is higher than that of base metal. Fatigue strength and fatigue limit of the TB specimen are much superior to those of the base metal up to $10^6$ cycles. The fatigue crack propagation of the heat-affected zone of the TB specimen is slower than that of the base metal. Welding bead has the fastest crack Propagation in the low stress intensity factor range$(\DeltaK)$ region, but the slowest in the high $\DeltaK$ region. The fatigue propagation characteristic of the TB specimen is relatively stable in comparison with that of the base metal in the high ${\Delta}K$ region around over $28MPa\sqrt{m}$.