Abstract
Electromagnetic forming is a novel technology in which a coil is used to generate a pulsed Lorentz force for shaping sheet metal pieces. However, the Lorentz force between the coil and the sheet metal is generally repulsive due to the Lenz’s Law, which limits the practical application of this technology. To break this bottleneck, a dual-coil method is proposed to generate attractive Lorentz force, which is then used to form sheet metals. The theoretical principle of this method is presented, and an infinite element model is established to simulate the forming effect. The simulation results show that an A1060-O plate with a diameter of 140 mm and thickness of 1 mm can be attractively shaped under this method. The maximum axial displacement of the plate reaches 2.74 mm. Unfortunately, a dent exists in this situation. Further analysis indicates that this dent can be eliminated by increasing the inner and outer diameters of the coils. Further, it is found that when the capacitance value of the long pulse-width discharge circuit is set to 5.6 mF and the initial discharge voltage is set to 10.690 kV, the sheet metal attains the best shape.
Highlights
Owing to its unique advantages of high-speed plastic deformation and non-contact ability and the high-plastic effect. electromagnetic forming (EMF) technology has garnered considerable attention in shaping tubes and sheet metals
1) COIL CURRENT, EDDY CURRENT, AND MAGNETIC FIELD To further clarify the dynamics of EMF of sheet metal, the initial discharge voltages of the inner and outer coils were set to 6.8 kV and 10 kV, respectively
Comparing the results of the models with different parameter values, it can be inferred that when the discharge energy of the long pulse-width circuit is constant, there is an optimal set of voltage and capacitance values, which facilitate the best attraction forming of the sheet metal
Summary
Owing to its unique advantages of high-speed plastic deformation and non-contact ability and the high-plastic effect. electromagnetic forming (EMF) technology has garnered considerable attention in shaping tubes and sheet metals. BASIC PRINCIPLE OF ELECTROMAGNETIC ATTRACTIVE FORMING OF SHEET METAL Sheet metal forming technology based on electromagnetic repulsive force is widely used in several applications such as deep forming of sheet metals assisted by radial force [16], deep forming of large sheet metals under axially movable coils [17], and optimization of forming precision of sheet metals [18], [19] These studies indicated that when a pulsed current is circulated in the coil, a time-varying magnetic field with constant direction and varying strength is generated. Current pulse with short pulse width is applied, the direction of eddy current in the workpiece is reversed (the value is relatively large), but the direction of magnetic field is not changed It can be inferred from Eq (3) that an attractive force is generated between the coil and the workpiece. FR and fA indicate repulsive and attractive force on the workpiece, respectively
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