Electromagnetic shielding forming: A facile approach for Lorentz force regulation and its application in tube forming

The Lorentz force distribution is crucial in determining the deformation of workpieces in electromagnetic forming, with its spatial distribution directly influencing the resulting shape. However, achieving flexible control over this force to accommodate diverse forming requirements poses a significant challenge. To address this, an innovative electromagnetic shielding forming (EMSF) technique is proposed, which introduces a conductive metal ring positioned around the coil-tube assembly to modulate the Lorentz force distribution through its eddy current shielding effect during pulsed discharge. On this basis, we systematically explore how variations in the ring's thickness, length, electrical conductivity, and positioning affect the shielding performance. Applying this forming method to long tubes, short tubes, and variable-diameter tubes, it is demonstrated that conventional EMF processes typically result in long tubes deforming into convex shapes and short tubes into concave shapes. In contrast, the method improves the uniformity of long-tube forming and offers the flexibility to shape short tubes into concave, flat, or convex profiles. Additionally, the method enhances the precision of variable-diameter tube forming by optimizing ring placement, enabling the production of high-accuracy tubes of various sizes. This advancement introduces a versatile and effective strategy for managing the Lorentz force via electromagnetic shielding effect, which enables more precise and flexible control over the deformation of workpieces during the electromagnetic forming process.