Numerical investigation of controllable non-uniform deformation of tailor-welded blanks using heterogeneous pressure-carrying medium

Severe non-uniform deformation occurs in the forming of tailor-welded blanks (TWBs) with a large difference in properties or shell thickness of base materials, which lowers deformability of tailored shell components. Establishing a non-uniform pressure field and using it to form sheet blanks with non-uniform deformability such as TWBs may be a potential solution. In this work, the non-uniform pressure field established by heterogeneous elastomers and mechanism for controlling the deformation of TWBs using this pressure field were studied numerically. Concretely, a modified three-region model was proposed to describe the structure of TWBs based on the sectional distribution of microhardness. Finite element models of TWBs and heterogeneous elastomers were established and validated accordingly. The "higher"and "lower" pressure generated by different partitions of the heterogeneous elastomer were employed to form the "stronger"and "weaker" regions of TWBs, respectively. Forming processes using heterogeneous elastomers with different ratios of Shore hardness (zeta) as the flexible dies were simulated. The results showed that with the decrease of zeta, excessive deformation in the "weaker"side was alleviated and deformation uniformity of TWBs was greatly improved. Stress triaxiality at three characteristic regions (i.e., the "stronger"side, the "weaker"side, and the transition region) was increased simultaneously. Stress localization in the weld seam and its heat-affected zones (HAZs) was alleviated as well. In addition, results of failure analysis showed that deformation uniformity of TWBs could be greatly improved (+19.62%) on the premise of sacrificing a few forming limits (-4.34%) by using the optimal heterogeneous elastomer.