Mechanism of pre-deformation effect on sheet deep-drawing forming under magnetic field condition using a magnetorheological fluid (MRF) medium

Due to the poor plasticity of an 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-deformation deep-drawing based on intelligent magnetorheological (MR) fluid material. The experiments and FEM modeling of cylindrical parts with drawing ratios of K-1 = 2.125 and K-2=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, respectively, which is reduced by 86.31% and 82.8%, respectively. In the pre-deformation stage, as the height of the 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 a drawing ratio of K-1 = 2.125 as an example, the circumferential compressive stress in the flange area decreases and is distributed uniformly under the back pressure and soft draw beads; the radial stress gradient and equivalent stress gradient at the fillet of die are reduced. For cylindrical parts with drawing ratios of K-1 = 2.125 and K-2 = 2.25, when the inverse bulge height is 9mm and 5mm, the forming effect of the part is the best.

Automated summary

This paper proposes a composite method of inverse bulge pre-deformation deep-drawing based on intelligent magnetorheological (MR) fluid material. The research results show that the uniformity of the wall thickness of the parts is enhanced after using the soft mold medium, and the distribution of equivalent stress changes as the height of the inverse bulge increases.