Thermal Analyses of Electrically Assisted Forming

Abstract

Electrically assisted manufacturing (EAM) is defined as the direct application of electricity to a workpiece in situ with a manufacturing process. This is commonly used in forming to reduce the flow stress and increase the ductility of metals. Under certain conditions, there seem to be effects of the electricity that occur in addition to the inherent resistive heating in metals. This electroplastic effect is often deduced by estimating temperatures through analytical or numerical simulations and comparing this to the temperatures required to effect thermal stress reductions observed in experimental tests. For tests which utilized pulsed or AC currents, an RMS current value may be used to simplify simulations since current transience can be averaged to a constant representative value. However, there is often no justification of this assumption and it is possible that assumption could lead to erroneous results. Various assumptions applied to EAM research are explicitly explored herein to determine their validity in thermal estimations. It was concluded that AC, square wave, and sawtooth currents at frequencies greater than 1 Hz, or pulses from power supplies with significant ripple, can be approximated with a DC current of similar RMS value to obtain similar thermal estimations. Simulation geometries should incorporate as much of the experimental setup as possible. An example from literature was used to test several other assumptions as well, including the use of analytical simulations, rather than numerical.