Bidirectional electromagnetic impact hydroforming for improved forming accuracy and material flow control in aluminum alloys

Abstract

Impact hydroforming technology has emerged as a promising approach for enhancing the forming performance of lightweight components. However, all existing methods in this area are constrained by unidirectional loading, which leads to critical challenges such as excessive thinning and low forming accuracy, particularly when forming complex geometries with large drawing ratios and curvatures. To overcome these limitations, this study introduces an innovative bidirectional electromagnetic impact hydroforming method for shaping aluminum alloy sheet metals, which combines axial and radial pulsed Lorentz forces to achieve remarkable control over material flow and forming accuracy. Comprehensive mechanical analyses reveal that the radial magnetic pressure optimizes wall thickness and deformation uniformity by reducing radial tensile stress and enhancing circumferential compressive stress in the flange. This approach results in a remarkable 44 % improvement in the maximum forming height of sheet metals in a free bulging process under the test conditions, compared to conventional unidirectional methods. Furthermore, the proposed method is successfully applied to form concave-bottomed cylindrical components, where radial magnetic pressure significantly suppresses localized thinning, mitigates necking, and prevents cracking. Notably, the maximum die-fitting gap is reduced from 8 mm to just 0.3 mm, while maintaining a thinning rate below 20 %, demonstrating good forming performance. These results highlight that the novel process, which integrates high strain rate loading, liquid medium, and highly controllable electromagnetic characteristics, offers a new forming method for achieving high accuracy, low-thinning ratio, and high-efficiency manufacturing of complex thin-walled components. This method holds significant potential for applications in industries such as aerospace, automotive, and advanced manufacturing.