Real-time and selective control of shell deformation based on dynamic and subregional pressure response of flexible dies under magnetic field

Abstract Pressure-carrying properties of traditional flexible materials can hardly be controlled during the process that they serve as pressure-carrying medium to form shell components. In this work, a forming method based on the subregional and dynamic pressure response of property-adjustable forming medium was proposed, aiming at achieving the flexible control of shell deformation in different regions and stages. Elastic composites with iron particles selectively dispersed in pre-designed location, i.e., heterogeneous magneto-rheological elastomers (MREs), were fabricated and employed as the flexible dies in the bulge tests of Al1060 sheet in the presence of external magnetic field. Deformation behaviors of sheet metal were dynamically measured, and loading and stress conditions were numerically studied. The results showed that local shell deformation could be controlled in a nearly monotonic way by adjusting the distribution pattern and content (φ) of iron particles. In the case that heterogeneous MRE with φ = 0/30% was employed and magnetic field with flux density (B) of 1950 Gs was applied, difference of bulge height and strain on both sides of the deformed shell increased by 6.5% and 16%, respectively. In the presence of magnetic field with B = 1240Gs, difference of bulge height on both sides of the sheet metal increased by 9% compared with the condition that no magnetic field is applied. But, the influence of magnetic field is not monotonous. Changed stress paths of sheet metal, which was induced by non-uniformly distributed and dynamically controllable pressure field of heterogeneous MREs, was used to clarify the forming mechanism.