The Effect of Weld Design on the Formability of Laser Tailor Welded Blanks

Abstract

Tailor welded blanks (TWBs) are used in the automotive industries as a method to meet economic, environmental and governmental demands. Conventionally, TWBs incorporated mild and low strength steels such as interstitial free and draw quality steels because of their excellent formability traits. However, due to their low strength they are unsuitable for energy absorption applications; thus, the interest of incorporating advanced high strength steels (AHSS) into the TWBs. Dual phase (DP) steel is a type of AHSS that is of interest because of its combination of high strength and good formability that is comparable to high strength low alloy (HSLA) steels. However, welding DP steel causes softening in the heat affected zone (HAZ), which leads to premature failure and reduces formability. The aim of this thesis was to study the effect of weld design on the formability of TWBs with DP steels and with HSLA steel. This thesis is divided into three parts; the first part examines TWBs with different weld line positions, weld line orientations and strain paths. The second part investigates bead-on plate curvilinear blanks and its effect on formability of the blanks. The last part examines the effects of multiple welds on the formability of TWBs.