Predicting the forming limit strains of tailor-welded blanks

Abstract

This work aims at predicting the forming limit strains of welded blanks using a thickness gradient-based necking criterion. In order to reduce the complexity and synergistic effect of tailor-welded blank (TWB) parameters, the same material and thickness sheets are considered for the entire work. The forming limit curve (FLC) of welded blanks for varied weld conditions - namely, weld orientation and location - are predicted by simulating the limit dome height (LDH) test using PAM-STAMP (ESI Group, PAM System International), a finite element code. The un-welded blank and TWB FLCs thus predicted by the thickness gradient-based necking criterion are compared with the experimental FLCs obtained by LDH test. Dome height at failure and failure location data of TWBs from experiments and prediction are also compared for varied weld conditions. It is found from the analyses that limit strain predictions correlate well (less than five per cent error) with the experimental results in the drawing region of the forming limit diagram, with the stretching region showing considerable difference. Dome height at failure and failure location prediction correlate well with those of experimental observation in most of the cases. In a few TWB cases, where considerable difference in limit strains are seen, predicted dome height at failure values deviates from experimental results.