Some metals present high ductility and slight springback under electromagnetic force. Moreover electromagnetic forming can form parts rapidly and is easy to realize automation. So electromagnetic forming has gained more and more researchers' attention. But electromagnetic forming involves complex coupling among the electromagnetic, deformation and thermal response of the deforming workpiece and other system structure. A loose coupling method is adopted to solve electromagnetic forming in this paper. Analysis of electromagnetic field is conducted by ANSYS/Emag, structural field is solved by explicit module ANSYS/Lsdyna, and data transfer from electromagnetic field to structural field is realized by APDL program. Effect of discharge voltage and discharge frequency on electromagnetic tube bulging is considered. Strain state of deformed workpieces under different voltages and the reasons for existing an optimum frequency on the condition of fixed discharge energy is discussed. A series of experiments under different voltage and frequency is conducted, experimental results agree with the calculated results.
The sky-screen is an instrument to measure the parameter of flying projectile in the ranger, it is often interfered by the external fake projectile signals that can cause equipments to trigger mistakenly and lead to work abnormally in the measurement system. The character of detection screen thickness is used in the sky-screen to analyze the signal on the projectile and fake projectile when it pass the screen, and calculate the pulse width that the projectile and fake projectile generates. According to the feature of the pulse width, the technology of CPLD was used to recognize projectile signal and eliminate the fake signal, the logic circuit of recognizing and eliminating was designed, the method was applied in the across screen fire measuring system, the result proves the method can identify projectile signal and eliminate the fake signal.
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