Improving the uniformity and controllability of tube deformation via a three-coil forming system

The Lorentz force distribution on a tube is the dominant factor that determines the tube deformation behavior in the electromagnetic forming process. However, the existing forming technologies in this field are mainly based on a single-coil system, which results in a relatively fixed Lorentz force distribution and makes it difficult to control the forming process or the final tube shape. To solve this problem, a three-coil forming system composed of three sub-coils and two pulsed power supplies is developed for tube forming in this work. Both numerical simulation and experimental results show that the three-coil system can be easily applied to alter the Lorentz force distribution through adjusting the discharge voltage of sub-coils, providing an effective way to improve the deformation uniformity and control the deformation shape. It is found that an AA6061-O aluminum alloy tube with an inner diameter of 76 mm and a thickness of 2 mm can be deformed with a homogeneous deformation range of about 23.56 mm via the three-coil system in the experiments, while the range is only about 11.48 mm under the same conditions when using the conventional single-coil system. Meanwhile, it is demonstrated that the three-coil system can achieve a variety of tube shapes including concave and convex profiles with different uniformity. The developed method and obtained results are of good value for expanding the application of electromagnetic tube forming.