A new method of determining forming limit diagram for sheet materials by using the magnetorheological elastomer forming process

The sheet forming using flexible-die has been presented the great development potential, which uses the liquid, polyurethane rubber, rubber bladder, viscous medium, or magnetorheological fluid as the force transmission medium and shows some advantages. In this paper, the new method on the sheet flexible-die forming using the magnetorheological elastomer (MRE) is proposed. The MRE consists of magnetically polarizable particles locked into an elastomer matrix and has the magnetorheological effect under the action of a magnetic field. The mechanical property like the shear modulus of MRE can up to 160% in microseconds when the magnetic field is applied. Therefore, the performance behavior of MRE is controllable and adjusted, which can adapt the force requirements at different positions during the sheet metal forming process. Finite element analysis of Al1060 sheet bulge using MRE with different shear modulus was carried out. Results show that the right side of the FLD is obtained by using elliptical dies with different length–width ratios. On the basis of that a new method is proposed to obtain forming limit diagrams of sheet metal using the magnetorheological elastomer forming process at variable magnetic fields, bulging tests of the Al1060 sheet under different magnetic fields were implemented. FLD at different elliptical dies under the action of MRE is determined. An increase in forming limits of Al1060 with the increase in the magnetic field is observed.