Precision forming of the 3D curved structure parts in flexible multi-points 3D stretch-bending process.

The lightweight aluminum 3D curved structure part has the characteristics of high structural strength, excellent aerodynamic performance, and flowing geometric shape. It is increasingly used in the fields of railway transportation, aerospace, and other high-end vehicle manufacture industry. However, with the increase of forming dimensions, as well as the large, thin-walled, complex forming features, it is urgent to study the precise plastic forming method for this kind of difficult-to-deform materials. Based on the new type of flexible multi-points 3D stretch-bending (3D FSB) process, the precision forming method for these hard-to-deform parts was studied in this paper. Extensive numerical simulations for the 3D FSB forming of the target parts have been performed by finite element methods. The simulation results show good agreement with the experiment results, and the max shape error of springback prediction is less than 0.3 mm. Then, based on the measured shape error of the 3D formed parts, an iterative overbending method for envelope surface of the multi-point die (MPD) is proposed to realize precise forming of the 3D curved structure parts. After four times adjustment of MPD, the simulation results show that the contour error is reduced from 1.01 to 0.06%, the maximum springback error changes from 30.16 to 1.66 mm. According to the adjustment parameters acquired in the optimization process, the actual experimental measured contour error is 0.05%, the maximum springback error is 1.41 mm, which achieved the forming requirements of the target parts and verified the effectiveness of the compensation method. [ABSTRACT FROM AUTHOR]