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 gradientbased 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.

Experimental evaluation and prediction of forming limit of FSW blanks made of AA 6061 T6 sheets at different weld orientations and weld locations

“…The transverse welded sheets with offsets at 20 mm and 30 mm showed a reduction in forming limit compared to that of the unwelded blank. The forming limit of laser welded sheets with different weld orientations and locations were predicted by thickness gradient based necked criterion and validated with experimental results [8]. Panda et al fabricated TWBs with different dissimilar material combinations including high strength low alloy (HSLA), dual phase steels DP980 and DP600 with 1.14 mm and 1.2 mm thickness by laser welding [9].…”

A variable strain hardening model for anisotropic sheet metals

“…9,17,[20][21][22][23][24][25][26][27][28][29][30][31] The observations from the experimental data ( Figure 2) suggest that the value of n varies with orientation with respect to the rolling direction. Appropriate modelling of n described above, accounting for the anisotropy effect, can be used for realistic predictions of hardening during plastic deformation.…”

Prediction of Tensile and Deep Drawing Behaviour of Aluminium Tailor-Welded Blanks

“…In case of deep drawing simulation since both 0º and 90º orientations will be similar, an orientation of 60º was chosen as the third level. The weld zone yield strength was chosen such that it is higher or lower when compared to that of base materials as seen in most of the steel and aluminium alloy TWBs (Ganesh & Narasimhan, 2008;Miles et al, 2004;Stasik & Wagoner, 1998). Generally weld zone exhibits lesser ductility when compared to that of base materials (Ganesh & Narasimhan, 2008;Stasik & Wagoner, 1998) and hence strain-hardening exponent (n) of weld zone was selected such that it is lower than that of base materials.…”

“…5.) as this has been reported to validly predict the forming limit of TWBs acceptably in Ganesh & Narasimhan (2008). The material properties were assigned to weld zone and base metals according to the different parameter levels (Tables 1 and 2) in the orthogonal array.…”