In order to investigate the influence of mandrel on the forming quality of bending L-shaped hollow parts, three types of mandrels, which are polyurethane rubber mandrel, low-melting-point mandrel, and ball bearing mandrel. Polyurethane rubber mandrel and low-melting-point mandrel, which supposed as elastic–plastic deformable part in the numerical simulation. The effect of different forms of mandrel on the forming quality of L-shaped hollow parts, such as section deformation and wall thickness variation, were compared with push bending without a mandrel. The results show that the low-melting-alloy mandrel leads to a better formability and a more uniform tube thickness distribution compared with the polyurethane rubber mandrel and ball bearing mandrel, for the low-point-melting mandrel brings about smaller stress in the bending process. Cold push-bending trials of rectangular cross-section tubes were conducted successfully based on the finite element simulation results. The experimental results showed that the formability and quality of L-shaped tubes greatly improved compared to no mandrel, ball bearing mandrel, and rubber mandrel when the low-melting-point-alloy mandrel was used as the flexible mandrel.
L-shaped hollow parts Cold push-bending Low-melting-point-alloy mandrel Numerical simulation
The authors greatly acknowledge the financial support from the Natural Science Foundation of Jiangsu Province (grant No. BK20151469), the Research Fund of Nanjing University of Aeronautics and Astronautics (grant No. YAH17019), the Fundamental Research Funds for the Central Universities (grant No. NJ20150023, No. NJ20160035, and No. NJ20160036), and the Project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.