Bending effect on fracture of 5A06 aluminum alloy plate during reverse deep drawing

The reverse deep drawing of a plate is more difficult than that of a sheet due to the bending effect. In order to solve this difficulty, experiments and simulations were conducted to investigate the deformation behavior of forming a deeper cup using a 4.5-mm-thickness 5A06 aluminum alloy plate. Three die corner shapes were used to analyze the bending effect on the fracturing. The stress and strain distribution considering the bending effect was obtained by the simulation. It is shown that the fracture occurs at the inside flange corner and it can be avoided by changing the die corner shape. The limit drawing depth can be increased from 79 to 118 mm as the reasonable die corner shape was used. The reason for the fracturing is that a bigger tensile stress was induced by the bending effect at the inside flange corner, which leads to a stress gradient along the thickness. When the semicircle die corner shape was applied, the increment of the tensile stress at the inside area of the flange can be significantly reduced so that a deeper cup can be formed.