Prior sheet buckling leading to wrinkling formation in a gas forming a V-trough with wavy bottom

When the amount of stretching strain exceeds material's intrinsic capability in gas forming a complex shape metallic sheet, gas pressurization operation can fail due to sheet material's perforation. A hot-bent assisted gas forming method for shaping a long V-trough with deep bottom of longitudinal wavy shape is proposed for obtaining the product with harmless wrinkle and relatively uniform thickness. This method consists of three sequential actions - an instant hot V-shape bending together with die closing followed by controlled pressurized gas blowing for a period of time. For this method, the depth of hot bending is varied as a parameter to generate pre-forms bearing various contours which consequently determine wrinkling situation in the subsequent gas forming product. Two groups of specimens differing in sheet size are adopted. Regular AA5052 (coarsely grained) and superplastic grade AA5083 (fine grained) alloys are used for experimental works.