Formability and Fatigue Behavior of Tailor (Laser) Welded Blanks for Automotive Applications
The drive towards weight reduction in the automotive industry has led to the use of tailor welded blanks (TWBs). This work is aimed at evaluating the forming and fatigue behavior of the TWBs with different thickness combinations and compositions. Forming tests were carried out to determine the forming limit diagrams (FLDs) of the TWBs, and compared with those of the individual steel sheets. The results showed that the FLDs of the TWBs lie in-between those of the individually formed steel sheets that comprise the TWBs. A semi-empirical relation based on the mean values of the strain-hardening exponents (n-values) and of the thickness of the base metals was developed to calculate the FLDo of the TWBs. The calculated FLDo values were found to be in good agreement with the experimentally determined values. The fatigue tests showed that TWBs made from zinc coated/galvanized steels exhibited a lower fatigue limit, as compared with the TWB combinations from comparable uncoated steel. This was attributed to the intergranular cracking in the galvanized TWBs, caused by the presence of zinc penetrating beneath the sheet surface.