Classification of Electrical Current Used in Electroplastic Forming

Electrically assisted manufacturing (EAM) is the direct application of an electric current to a workpiece during manufacturing. This advanced manufacturing process has been shown to produce anomalous effects which extend beyond the current state of modeling of thermal influences. These purported non-thermal effects have collectively been termed electroplastic effects (EPEs). While there is a distinct difference in results between steady-state (ideal DC) testing and pulsed current testing, the very definition of these two EAM methods has not been well established. A long pulse may be considered DC current; a short pulse may produce electroplastic effects; and even steady-state current shapes are highly dependent on the underlying operating principles of the power supply used. The definition of long and short pulses and steady current is therefore ambiguous. This research aims to discover the relationships underlying the characteristics of an electrical current and the resultant heat generation and electroplastic behavior. Deformation effects of pulsed and DC current in tension were characterized using pure tungsten. Precipitate effects were characterized using AA7075 and were investigated on a bulk-scale using resistivity measurements and on a nano-scale through in situ TEM observation. Skin, pinch, and magnetic vector potential effects were fully characterized. From this work, no distinctions could be made between pulsed and DC current. This result provides support that electroplastic effects do not significantly contribute to any deformation effects. Additionally, precipitate effects of electric currents can be explicitly attributed to joule heating