• Laser Solutions
• /
• v.2 no.3
• /
• pp.42-51
• /
• 1999

This research was conducted as a fundamental study to apply tailored blank welding technique into automotive production process. The materials used in this study were 2.0mm thickness low carbon steel sheets and 1.2mm Zn-coated low carbon steel sheets. To ensure the reproducibility and to consider various factors, experiments were. conducted by applying Taguchi experimental method with 6 factors. Every welding process was repeated 3 times to offset the effect of uncontrolled factors. Elongation and LDH(Limited Dome Height)were measured to evaluate formability of specimens and Optical microscopy, XRD, SEM, and EDS analysis were performed to observe the microstructures and to determine the solidification mode in the weld. The elongation of specimen welded with optimum condition was 83% of base metal, and LDH was 84% of base metal. In case of laser treated specimen where Zn coating was removed, elongation was 85% of base metal, and LDH was 85% of base metal. In fusion zone, phases were consisted of quasi-polygonal ferrite, banitic ferrite, and martensite.

• Laser Solutions
• /
• v.2 no.1
• /
• pp.51-60
• /
• 1999

In this paper, weldability and formability of Tailored-Blank (TB) and the structural impact testing of bump beam were investigated to apply TB to automobile bumper beam. The optimal $CO_2$ laser welding condition for TB of SPFC and SPRC steel plates with different thicknesses was obtained. Before welding, the cross section of butt joint was prepared only by shearing without milling process. Real type bump beam was produced by two kind of forming processes such as roll-forming and press-forming, and the good formability of TB was obtained. Impact test results of bump by using pendulum and barrier were satisfied the impact regulation of bump. Finally. It may be confirmed that laser welded TB is well-balanced material in both weight reduction and production cost of automobile bump.

• Laser Solutions
• /
• v.2 no.1
• /
• pp.61-67
• /
• 1999

This study introduces the new concept in the evaluation criteria of the $CO_2$ laser Tailored Blank weldability, The materials used are 0.7mm, 1.5mm thick low carbon automotive galvanized steels. Welding tests were conducted for both similar thickness(0.7mm-0.7mm, 1.5mm-1.5mm) and dissimilar thickness(0.7mm-1.5mm) cases. The criteria developed for optimum welding conditions were based on relationship between results of die press forming test, weld transverse tensile test Erichsen test and weld penetration measurements. Application of the developed criteria(fracture ratio, strength ratio and D/To) in obtaining optimum welding condition revealed that a weld which satisfied any of the criteria did not fracture during actual die press test.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1998.03a
• /
• pp.36-39
• /
• 1998

To predict strain distributions and weld line movements in the forming processes of tailored blank sheets, the 2-dimensional finite element formulation is developed. The welding zone is modelled with the several, narrow finite elements. The material properties of weld elements are calculated from those of base metals, based on the experimental evaluation. To verify the finite element formulation developed, the forming process of an autobody door inner panel section is simulated. FEM predictions are compared and showed good agreements with experimental measurements.

• Journal of Welding and Joining
• /
• v.20 no.4
• /
• pp.538-543
• /
• 2002

M/S TB(Mash Seam Tailored Blank) is a production method for blanks by welding together blanks of different material, thickness and coating, and is an attractive method for manufacturing car body because it makes parts lighter and can save the cost and time to manufacture. However, there have not been quantified criteria to evaluate the quality of TB weld. This study introduced FHR (failure height ratio) in order to assess formability or/and weldability of the M/S welds and the applicability of FHR was confirmed by actual auto body forming and FLD tests. Furthermore, a new parameter, HN(heat number) based on the heat input of "$Q=I^2Rt$" was proposed and assessed. It was found that the concept of HN could be utilized to evaluate the soundness of M/S welds without any destructive tests.ive tests.

• Journal of Welding and Joining
• /
• v.18 no.3
• /
• pp.5-11
• /
• 2000

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

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1998.06a
• /
• pp.95-101
• /
• 1998

The steel door inner was manufactured via a new route, tailored blanking process, to remove hinge reinforcement parts, using thicker panels laser welded, instead. It is very important, first of all, in this process, to design optimum configuration of tailored blanks and determine the optimum process control for the stamping. Generally, it was found that the severe deformation reduction behavior during stamping in the thinner panel around weld line caused cracks and the other troubles in formability. It is our purpose of this investigation to introduce how the process control parameters, such as tailored blank configuration, size, location in the die, the position of weld line, BHF, bead configuration, work on the formability. In addition, causes of cracks and movement of weld line after forming were analyzed and compared with computer simulation work.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1999.03a
• /
• pp.45-48
• /
• 1999

The optimal blank design method by sensitivity analysis has been applied to the formings of oil-pan, tailored blank and front panel have been chosen as the examples. Die shape is prepared by a commercial CAD system. Excellent results has been obtained between the numerical results and the target contour shapes. Through the investigation, the proposed systematic method of optimal blank design is found to be effective in the practical forming processes.

• Transactions of Materials Processing
• /
• v.9 no.3
• /
• pp.226-232
• /
• 2000

The optimal blank design method by sensitivity analysis has been applied to the formings of oil-pan, tailored blank and front panel as the examples. Die geometry is prepared by a commercial CAD system. Excellent results has been obtained between the numerical results and the target contour shapes. Through the investigation, the proposed systematic method of optimal blank design is found to be effective in the practical forming processes.