Eddy current measurement in hollow conducting tube in electromagnetic forming process

Abstract

Abstract Electromagnetic forming (EMF) is a high strain rate metal deformation process that utilizes Lorentz force to expand or compress the conducting tube. Stored electrostatic energy of capacitor bank is discharged through solenoid coil which surrounds the conducting tube. Capacitor bank and solenoid coil form a series R-L-C circuit during current discharge through the coil and hence, the coil current is damped sinusoidal. Coil current produces time varying magnetic field which induces eddy current in conducting tube. Interaction of eddy current in the tube and magnetic field in air gap between tube and coil causes Lorentz force to expand or compress the conducting tube. The eddy current is a vital parameter in electromagnetic forming study and its measurement is almost unfeasible owing to very few mm gap between coil and conducting tube. Here we establish a novel method to determine the eddy current in a cylindrical tube, using a superposition theorem, when a damped sinusoidal current is passed through a finite solenoid coil. The present study uses a Al-Mg alloy tube to demonstrate this method of eddy current determination.