Analysis and elimination for drum warpage of U-shaped workpiece with super length and large opening of sheet metal

To study the mechanism of workpiece warpage under air-bending forming, a method combined experiment with numerical simulation is proposed in this paper. Based on Hill’s yielding criterion and plane strain condition, 3D ABAQUS finite element models, used to form the semiellipse-shaped workpiece with super length and large opening of sheet metal, are established. The multistep incremental air-bending forming and non-uniform springback processes are simulated. It is pointed out that a large bending force and bed deformation of press brake can lead to warpage defect of workpiece. A technique used reverse deflection compensation for bed deformation of press brake, and female die with a large opening is found to eliminate warpage defect of workpiece. Manifested by the experiment for incremental air-bending forming of this workpiece, the proposed method yields satisfactory performance in improving forming accuracy and eliminating warpage defect of a large workpiece.