Numerical prediction of springback in U-channel forming of aluminum tailor welded blanks

The results from an investigation of the numerical prediction of springback behaviour of AA5754 and AA5182 sheet after forming are presented. A series of tooling geometries and blank sizes were considered for the U-channel forming process for both monolithic (uniform thickness) and tailor welded blanks (TWBs) with dissimilar thickness. The effects of a number of process and material parameters on springback were simulated by the sequential use of an explicit FEM code (LS-DYNA) to model the forming stage, and an implicit code (LS-NIKE3D) to simulate springback after forming.; Experiments designed to assess the accuracy of the numerical predictions were conducted on a series of tooling geometries for a variety of monolithic blanks and TWBs of AA5754 and AA5182. The FEM predictions obtained using the explicit and implicit FEM models demonstrated reasonably good agreement with experiments. The comparisons show that the numerical model using the Barlat constitutive formulation accurately simulated the forming phase, with the punch force time history agreeing well with the experiments. The comparisons also demonstrate that the numerical model was capable of reasonably accurate prediction of the springback stage after unloading for both monolithic and TWBs, with the predicted general trends of springback versus the process and material parameters considered being consistent with the experimental results.; TWBs exhibited a different springback trend from that demonstrated by monolithic blanks due to the change of the interface friction behaviour and the redistribution of the binder force (BHF). The delicate combination of BHF and frictional coefficient (COF), as well as the COF itself, has a strong influence on springback. Some concern exists that the predicted magnitudes of both the flange and the sidewall springback angles tend to be lower than the measured.