Improvement in limiting drawing ratio of aluminum tailored friction stir welded blanks using modified conical tractrix die

In the present work, aluminum tailor friction stir welded blanks (TFSWBs) of dissimilar grade and gauge combinations were fabricated successfully with optimized parameters. The tensile tests of TFSWBs were conducted perpendicular to the weld orientation to confirm the weld quality, and it was found that the failure occurred in the weaker base metal side. Subsequently, the limiting drawing ratios (LDR) of the base metals as well as TFSWBs were evaluated and compared using a conventional cylindrical die (CCD) and a modified conical tractrix die (MCTD) setup. Approximately, 27% and 14% improvements in LDR were recorded respectively for the dissimilar grade and the dissimilar gauge TFSWBs while using the MCTD setup. The finite element (FE) simulations of the improvements in LDR were carried out using LS-DYNA solver. For identifying the failure steps, the thickness true strain gradient (TTSG) method was incorporated successfully in the FE model. The predicted LDR and thickness distribution of the deep drawn cups of TFSWBs and the base metals were validated with the experimental data. Also, the strain envelope progression profiles and thinning development predicted from the validated FE models were analyzed rigorously to get an insight into the improvement in the material flow during deep drawing operation using MCTD.