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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.

Due to the fact that geometrical structure of tube electromagnetic bulging process with field shaper does not conform to the axisymmetric property, three-dimensional (3D) model is usually used to analyze the process which is complicated and time consuming. Therefore, on the basis of understanding the working principle of the field shaper, a two-dimensional (2D) model with current constraint is proposed in this paper to analyze the electromagnetic bulging process of a tube fitted with a field shaper. COMSOL finite element analysis software is used to develop three models for performance analysis and comparison, these are: conventional 3D model and the proposed 2D model with and without current constraint. Simulation results show that the induced eddy current density, magnetic flux density and electromagnetic body density of the two-dimensional model with current constraint are in good agreement with the results of the three-dimensional model. This provides an alternative and effective way to analyze the performance of the tube electromagnetic bulging with field shaper using a simple but yet reliable 2D model.

The attractive electromagnetic bulging is a novel technology which has unique advantages in the formation of small tube fittings. To generate the attractive electromagnetic force, a dual-frequency current method has been proposed in the existing research on the attraction bulging of the small tube fittings. This method, however, has a flaw that the tube fittings are subjected to a large repulsion electromagnetic force before the attraction, which will lead to a negligible effect on the final forming results. To solve this problem, a non-uniform solenoid coil structure is proposed in this paper to suppress the repulsion to improve the attraction. On this basis, a finite element model is built to analyze the process of an aluminum tube with an inner diameter of 20 mm and an outer diameter of 22 mm and the thickness of 1 mm. The influences of the coil structure on the magnetic induction intensity B, eddy current density Je and the stress of the coil have been studied. The results show that the expansion of the tube can be improved when the non-uniform solenoid coil is used. The maximum expansion in this dissertation is achieved with a 28 turns non-uniform solenoid, and its expansion uniformity standard deviation is only 0.156. These simulations have a significant outcome to the design of the coils and the application of electromagnetic bulging in small tube fittings.

Electromagnetic forming is a method of high-speed metal workpiece forming technology that uses electromagnetic force pulses generated from the interaction of the magnetic flux density and workpiece induced eddy current. The main challenge of this technology is the control of the eddy current and magnetic flux density to perform various forming processes. This paper is aimed at overcoming this challenge by introducing a new electromagnetic sheet forming method based on discretely driven rings. In this method, a set of discrete conducting rings are placed between the driving coil and the metal workpiece to enhance the shaping process of the workpiece. By changing the number and position of the rings, the induced eddy current can be adjusted, and different electromagnetic force distribution profiles can be realized. COMSOL software is used to develop an electromagnetic field-structure coupling model of the proposed electromagnetic forming method. The characteristics of the electromagnetic force distribution and its effect on the workpiece forming process are analyzed. Results show that the electromagnetic force distribution profile can be controlled by adjusting the rings physical parameters such as diameter, material, and position. The proposed method can effectively improve the performance of the conventional electromagnetic forming technology and has the potential for implementation in wide industry applications.

Electromagnetic tube expansion has been given much attention due to its superior cold forming properties. The traditional electromagnetic coil is of single structure, which results in substantial tube wall thinning and mechanical strength reduction. This shortcoming restricts further development of the electromagnetic tube expansion technology in various industrial applications. This paper proposes an axial-radial electromagnetic force bidirectional loading method to increase the axial fluidity of the material and eliminate the wall thinning issue that currently exists in the traditional method. Furthermore, the performances of three proposed structures for the axial compression electromagnetic tube expansion using three-coil, two-coil and one-coil are analyzed and compared. In this context, the electromagnetic force distribution and the wall thinning of the tube during the expansion process are analyzed based on finite element modelling. Results show that with the proposed modified structure of the traditional single coil, the axial electromagnetic force can be substantially increased which results in reducing the tube wall thinning significantly. The proposed technique in this paper paves the way for further development and more industrial applications of the electromagnetic expansion technology.

In the conventional electromagnetic tube expansion, tube wall thickness tends to decrease significantly while the workpiece is expanded. This paper is aimed at introducing a new technique using three-coil electromagnetic tube bulging with axial compression as an innovative solution for this issue. To validate the feasibility of the proposed technique and investigate the electromagnetic force distribution along the workpiece, COMSOL software is used to construct a detailed finite element analysis model for the proposed electromagnetic coupling model. Results show that the ratio of the axial and the radial electromagnetic forces increases linearly with the increase of the height and the outer diameter of the top and bottom coils. Furthermore, the tube deformation profile and the wall thickness are compared with two different coil structures. Comparison analysis reveals that for the same axial to radial electromagnetic forces ratio, the effect of prohibiting the wall thickness reduction using different coil structures is quite similar. The new method is expected to have a good potential in enhancing the tube-forming performance.