Formability Issues in the Application of Tailor Welded Blank Sheets

The use of tailor welded blank sheets for body-in-white applications has brought many new forming challenges. Mechanical properties of tailor welded blanks measured from the tension test showed significantly higher strengths and lower elongations than in the base metal. The forming limit of tailor welded blanks was significantly reduced when compared to that in the base metal. For the weld made from materials with dissimilar thicknesses/strengths, additional formability issues were also raised in addition to those for the weld made from materials with similar thickness/strength. These issues increase the potential for failure in the lesser thickness/lower strength material in the area immediately adjacent to the weld when the difference in thicknesses or strengths of the two materials increases. It was demonstrated both in laboratory and in forming of a door inner panel that the maximum formability performance for this type of weld could be achieved by minimizing the isolation of deformation in the lesser thickness or lower strength material side by allowing more metal flow near the weld from the greater thickness or higher strength material side.