Research Progress of Combined Electromagnetic Forming Technology

Electromagnetic forming (EMF) is a special forming method with high energy and high speed for metal materials by using pulsed electromagnetic force. Unlike traditional mechanical stamping, EMF is not limited by force transfer medium properties and is simple in device design. The application had significant limitations because the early electromagnetic forming scheme essentially realized the repulsive force forming effect of the workpiece, and the repulsive force was primarily dominated by the electromagnetic force analysis. With its many benefits, combined electromagnetic forming technology is currently gaining traction in the media. In order to achieve more flexible, accurate, and efficient forming, the combined electromagnetic forming technology combines drive-coils, force fields, and forming processes to diversify the magnetic field configuration and forming force field. Based on the EMF principles and electromagnetic force control methods, the latest research results are divided into three parts according to the different application levels: drive-coil combined type, electromagnetic force combined type and forming process combined type. This review focuses on the implementation concepts, technological solutions and application implications of the three types. The first part is the drive-coil combined type. Due to the limited strength of a single coil and the poor uniformity of the electromagnetic force generated during the forming process, another option is a more flexible combined drive-coil method. Multiple drive-coils provide the electromagnetic force required for forming and improving the magnetic force distribution. The drive-coil combined electromagnetic forming is presented separately from the combined coil repulsive forming and attractive forming. The drive-coil combined electromagnetic forming method skillfully neutralizes the harsh requirements on the coil. The second part is electromagnetic force combined type. The application of electromagnetic force in traditional electromagnetic forming is all in a single direction, a single attraction or repulsion force, and the combined effect of electromagnetic force has not broken through. In practical applications, the electromagnetic force can be used for both single-directional and multi-directional loading and forming; it can be used as a forming force as well as an auxiliary force (blank holding force, transmission force); and the attractive electromagnetic force can be combined with the repulsive electromagnetic force. The third part is forming process combined type. Pure electromagnetic forming technology's range of applications is restricted by its limitations in real-world manufacturing. Many experts and scholars have proposed a process that combines electromagnetic forming technology with welding and mechanical manufacturing. A new type of combined forming scheme combined with traditional stamping, electro-hydraulic forming, and welding is introduced respectively. Lastly, research hotspots on the EMF are predicted and the technology's future is explored. At present, there are still many unsolved problems in the existing electromagnetic forming technology. How to obtain a universal drive-coil forming scheme, how to make use of the flexible point of the electromagnetic force, and how to combine two or even multiple manufacturing processes to fully utilize various forming process advantages are meaningful. This will provide important reference and guidance for further in-depth research of the EMF and will accelerate its promotion and application in key application fields such as lightweight integration of aerospace and automotive. © 2024 China Machine Press. All rights reserved.