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The long-life driving coil is the prerequisite for electromagnetic forming industrial application. Up to date, the temperature rise is one of the major factors that restrain its working life. For the purpose of reducing the temperature rise of the driving coil, this paper proposes a new coupled cooling method, in which an extra cooling coil is placed on one side of the driving coil, then the Joule heating is coupledly transferred by delaying the breakover control of the driving coil. To achieve this purpose, a finite element simulation model of Electrical Circuit- Electromagnetic Field-Thermal Coupling in the plates setting of the electromagnetic forming is established, after which the influence rules of coil turns, cross-sectional area and materials of cooling coil on temperature rise are analyzed. Then, this paper also establishes a coupled cooling circuit model, in which the influence of cooling coil structure parameters on the Joule heating of driving coil is analyzed. Furthermore, Simulation results show that effective Joule heating transfer can be reached by the best optimization scheme of the cooling driving coil. Specifically, the average temperature rise reduces by 13 degrees, namely 22.8% by using this new method. [ABSTRACT FROM AUTHOR]

Low forming accuracy is the main defects in electromagnetic forming process of sheet metal. One of the main reasons is that shapes of the coil and required workpiece are cylindrical and deep concave respectively. The distance between the coil and the side wall of deformed sheet metal is too far in forming process, which leads to a consequence that electromagnetic force in the side wall is not enough. To solve this problem, a solenoid field shaper was introduced to enhance the electromagnetic force at the side wall, and then improve forming accuracy of electromagnetic forming of sheet metal. To verify the effectiveness of the method, a series of simulations based on circuit-electromagnetic-structure were finished. The results showed that the maximum electromagnetic force with field shaper increased more than 10 times at the side wall. And the maximum deformation was 1.18 mm which can improve forming accuracy effectively. The presented method and results can be helpful in designing electromagnetic forming systems of sheet metal. [ABSTRACT FROM AUTHOR]

The concept of capacity coefficient is introduced to evaluate the processing capacity of electromagnetic forming (EMF). An EMF system design method, including capacity coefficient design, inductance design and strength design, is developed by a finite element method. The geometry and size of the driving coil are optimized by the capacity coefficient design. The inductance design is aimed at obtaining a reasonable pulse width of EMF. Finally, the strength design of the driving coil is presented with respect to the reinforcement. With this design method, a high strength driving coil is designed and wound. The height, inner radius, and outer radius of the driving coil are 25 mm, 5 mm, and 50 mm respectively. The number of turns is 40, resulting in reasonable pulse width of 380 \mus. Experiments with different driving coils and pulse width were carried out. The results show that the processing capability of EMF is improved due to the high strength driving coil. [ABSTRACT FROM PUBLISHER]

The application of an attractive electromagnetic force for small tube bulge forming is a meaningful but challenging issue because it is almost impossible to do so with the traditional electromagnetic bulging method, in which the electromagnetic force is always repulsive. A new method has been proposed to solve this problem, in which an attractive electromagnetic force was generated by controlling the discharge current in a high strength forming coil with two pulse width power systems. To validate the effectiveness of the expanding tube by an attractive electromagnetic force, electromagnetic bulging equipment has been designed and manufactured. A series of simulations and experiments have proven that the attractive electromagnetic force can effectively expand the tubes. As shown in the obtained results, an annealed 1060 aluminum tube with a 28 mm inner diameter and a 1 mm thickness can be attracted towards a coil with a maximum height of approximately 2.55 mm and with a strain in the middle area of the tube of more than 15%. The method and results presented here will facilitate the development of electromagnetic forming systems. [ABSTRACT FROM AUTHOR]

How to reduce the temperature rise of coil winding is an important issue for improving the production and lifetime performance of the tool coil in electromagnetic forming system. To address the problem, this paper proposes a new discharge circuit configuration with a crowbar circuit to control the discharge current flowing in the tool coil and then to reduce the Joule heating generated without affecting the forming efficiency. A detailed numerical analysis of the mechanism of the temperature rise reduction was first carried out, and then numerical simulation and experimental investigation of the effects of the crowbar circuit on the coil current and surface temperature rise were investigated. The simulation results show that the Joule heating in the coil winding can be reduced from 4.62 kJ to 2.07 kJ when a crowbar circuit with a resistor of 0.3 Ω was applied, and the corresponding temperature rise in the coil can also be effectively reduced. Meanwhile, the experimental results show good agreements with the simulation results, further verifying the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In order to overcome the limitations of the existing electromagnetic forming systems for deep drawing, a dual-coil system has been developed for deep drawing of sheet metal with large drawing ratio. In addition to the conventional driving coil that generates the axial Lorentz force on the workpiece, a radial inward force in the flange region is generated by a second coil that is energized by an individual power supply. The axial force pushes the sheet into the die in axial direction, while the radial Lorentz force enhances the material flow of the flange. The effectiveness of the novel system is validated by a series of experiments for deep drawing a cup of AA1060-H24 with drawing ratio of 3.25. It is demonstrated that with the dual-coil system the material flow of the flange can be significantly enhanced, and the maximum forming depth without failure is greatly increased from 8.44 mm to 20.28 mm. The new electromagnetic forming method is expected to break through the bottleneck of deep drawing and enable major advances in forming metallic parts and components that are difficult to form, by developing driving coils with advanced design. [ABSTRACT FROM AUTHOR]