Forming method and cross-section deformation of transition section of finned special-shaped tubes in 3D free bending technology

Abstract

In 3D free-bending technology, the bending forming of the tube consists of the transition section and the stable forming section. However, because of the continuous movement of the bending die and tube in the transition section, the forming mechanism of the tube in the transition zone is relatively complex and still unclear. In addition, due to the complexity of the cross-section deformation of the finned special-shaped tube (FSST), its application in the heat dissipation pipeline of aerospace vehicles is severely hindered. To address the above issues, in this paper, a 3D free-bending forming process method, which can effectively coordinate the movement of FSST and the bending die in the transition section, was proposed. Meanwhile, an analytical model of FSST bending forming was established, which can effectively characterize the elastic-plastic evolution of the FSST cross-section and match the bending radius with the cross-sectional bending moment effectively. Then, the effectiveness of the process method and analytical model was verified by finite element model (FEM), and experiments. Further, FEM and experiments were used to investigate the influence of the process parameters of the transition section on the forming radius and cross-section deformation of FSST after springback. The results from this study show that reasonable coordination of the rotation speed of the bending die and the advancing speed of FSST in the transition zone can improve the forming quality of FSST.