Forming limit of TWBs with material damage consideration - Finite element simulation and experiments

Forming limit of tailor-welded blanks (TWBs) is studied experimentally and numerically. TWBs made of JIS G3141 steel were manufactured with laser-welding. Three sets of different thickness ratios were chosen for the investigation. The mechanical properties and damage parameters of the material required for the simulation were measured. A damage coupled plastic model and the damage criterion for localized necking were coded in LS-DYNA through a user-defined material subroutine with detailed procedures. By means of input cards of LS-DYNA, the user-defined history variables can be properly stored and displayed. To illustrate the application of the damage coupled LS-DYNA, the simulation of the TWB forming process was performed. The predicted forming limit strains were found to compare satisfactorily with those obtained from the tests.