Methods of assessing influence of weld properties on formability of laser welded tailored blanks

Abstract

Small scale forming limit tests and modified stretch draw (MSD) tests have been conducted on laser welded high strength steels to compare the formability of laser welded tailored blanks (LWTBs) with that of unwelded specimens. Using an alternative strain analysis technique, which was shown to be 20%more accurate than the standard technique, it has been demonstrated that the forming limit curve (FLC) of a dissimilar strength/ thickness LWTB, with the weld orientation transverse to the major strain axis, can be estimated using the FLC of the weaker/thinner parent material. In conjunction with miniature tensile tests, a method has also been developed that can provide the material properties (stress– strain data) of the weld metal. The weld material properties determined by this method have been validated by finite element analysis (FEA) models of the miniature tensile test and the MSD test. The results indicate that close correlation can be achieved between practical formability tests on LWTBs and FEA, and that the models now provide the opportunity to overcome difficulties which can occur when pressforming LWTBs.