Research on the Optimization of the Structure and Parameters of Uniform Pressure Coils in the Warm Electromagnetic Sheet Forming

Abstract: Flat spiral coils is generally used for forming flat sheet. As a result of uneven distribution of the electromagnetic force, the range of applications is restricted very much, is only suitable for simple stamping, indentation and blanking. The uniform pressure coils are not only able to provide uniform pressure, but also the efficient of magnetic field energy are improved. In addition, since the coils are reacted by the metal sheet and the conductive outer channel, help to improve the life of the coils. So compared with flat spiral coils, the uniform pressure electromagnetic coils take a distinct advantage in the plate forming and can be widely used.During the electromagnetic forming, the working condition of the coil is hard. It not only must bear the impact of current up to thousands of security and thousands of volts of input voltage, but also need to bear the acceleration of nearly a thousand times of magnitude. On the other hand, in order to meet the security needs of operation, the insulation must be closed shell, which will lead to difficulty in cooling coil. Especially in the warm electromagnetic forming environment, the work coils’ temperature will affect the strength of the material, thereby accelerating the coils to failure. Therefore it must be taken into account from the coil strength, mechanical strength, heat resistance and conversion efficiency etc, for the optimization of the coils’structure and parameters.The article discusses the characteristics of the magnetic field of the uniform pressure coils in the electromagnetic forming, and uses the finite element analysis software ANSYS to simulate the magnetic field of the uniform pressure coils in the electromagnetic forming, and gets the distribution of the uniform pressure coils magnetic field and magnetic field intensity. The research results show:in addition to a slightly divergent appear due to the sheet edge effects of the electromagnetic force, the magnetic field intensity is uniform in the most areas of the sheet. Also discusses the different structural parameters (the sharp of coil, the height of coil, coil and sheet length ratio, distance between coil and sheet) on the sheet and the electromagnetic force of the coils, the coils’structure and parameters were optimized.In the electromagnetic forming process it will produce the heat, and with the temperature rising, conductivity and magnetic permeability of the coils and sheet would be changed, thereby affecting the electromagnetic force. In this paper, base on the magnetic field-the temperature field full coupling, magnetic field intensity is revised.Then through the magnetic field-stress coupling,achieve the stress distribution and work load spectrum of the coil. And based on coil fatigue stress-life approach, through the Fatigue Tool fatigue analysis module, considering the stress and load conditions such as fatigue and fatigue strength coefficient factors according to uniform linear cumulative damage theory to calculate the pressure coil fatigue, fatigue life estimates obtained. Original uniform pressure on the coil compared to verify the optimized structural parameters of the fatigue life increased.
Key words: Electromagnetic Forming; Uniform Pressure Coils; Structure Optimization; Fatigue Life;

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