Abstract: The high-performance aluminum 3D stretch-bending part has the characteristics of smooth geometric modeling, excellent aerodynamic performance, and high structural strength, so it is widely used in the manufacture of high-end equipment. Such parts usually have the characteristics of geometric asymmetry, and they are always used in pairs and arranged mirror-symmetrically. For the forming of such parts, multiple sets of dies and equipment are often required, the forming efficiency is low, and the springback deformation is difficult to predict and control. In order to improve the forming efficiency and forming accuracy, the precision forming method for the lower beams of the high-speed trains is studied based on the proposed multi-point 3D stretch-press-bending technology. The asymmetric 3D structural parts are connected as a whole symmetric part. The 3D stretch-press-bending process realizes the pairwise forming of mirror-symmetrical structural parts, which improves the material utilization rate by 6.79% and doubles the production efficiency. In addition, a numerical simulation model for predicting the forming process and the springback deformation was established. In the case of post-stretching applied, the springback prediction error was less than 2 mm, which indicates that the simulation results have a good agreement with the experimental data and successfully predict the overall trend of springback deformation. At last, by using the springback direct compensation method, the maximum errors in the horizontal and vertical directions reduced to 1.33 mm and 0.73 mm under two times iterations, which realizes the pairwise precision forming of the lower beam for the high-speed trains.

Key words: multi-point forming, 3D stretch-bending, springback prediction, springback compensation, precision forming