Magnetic Medium-Assisted Inverse Bulge Pre-Forming and Deep Drawing Composite Forming Process for Improving Forming Performance of the Cylindrical Parts

Abstract

Due to the poor plasticity of aluminum alloy at room temperature, it is difficult to form thin-walled and complex curved parts. This paper proposes a composite method of inverse bulge pre-forming deep drawing based on intelligent magnetorheological (MR) fluid materials. Through the experiments and finite element modeling of cylindrical parts with drawing ratios of K1=2.125 and K2=2.25 were carried out under different forming conditions. The effect of soft mold medium on the drawing forming of cylindrical parts was studied. The research results show that the uniformity of the wall thickness of the parts is enhanced after using the soft mold medium. When the inverse bulge height is about 9mm and 5mm, the wall thickness variance of the cylindrical part is 0.0023 and 0.0025 pectively, which is reduced by 86.31% and 82.8% respectively. In the pre-forming stage, as the height of inverse bulge is increased, the maximum equivalent stress moves from the fillet area of the blank holder to the outer surface of the highest point of the bulging area. Taking drawing ratio of K1=2.125 as an example, the circumferential compressive stress in the flange area decreases and is distributed unifomly under the back pressure and soft drawbeads, the radial stress gradient and equivalent stress gradient at the fillet of die are reduced; For cylindrical parts with drawing ratios of K1=2.125 and K2=2.25, when the inverse bulge height is 9mm and 5mm, the forming effect of the part is the best.