Electromagnetic attractive forming of aluminum alloy tubes utilizing a dual-frequency current: New circuit design and forming process analysis

Electromagnetic attractive forming is meaningful for expanding the applications of electromagnetic forming, but it has been a challenge due to the fact that electromagnetic repulsive forces always dominate during the forming process with conventional RLC circuits. To solve this problem, a new discharge circuit topology is proposed in this work to generate a dual-frequency current for significantly increasing electromagnetic attractive forces, where only a single coil and a single power supply are required. Both numerical and experimental results demonstrate that the proposed method is more beneficial for attractive forming compared to the existing methods. Furthermore, it is shown that the developed forming system with the new circuit can be applied to achieve attractive forming of AA6061-O aluminum alloy tubes with a diameter of 33 mm both in the absence and presence of an inner solid die, where the generated attractive force can be larger than the repulsive force. Meanwhile, an interesting observation is the promotion of material flow due to the axial compressive force in the proposed attractive forming process, thus improving the forming ability and inhibiting the thinning. At the end, as an example, the developed circuit for attractive forming is further applied to the tube joint disassembly. These results could have great significance in understanding electromagnetic attractive forming process and promote its practicality. [Display omitted] •A new circuit is proposed to achieve attractive forming of small-diameter tubes.•The circuit can produce an attractive force that is larger than the repulsive force.•The attractive forming behavior and mechanism of tubes are revealed.•The axial compressive force can promote material flow and improve tube forming limit.•The developed attractive forming method can achieve the disassembly of tube joints.