Investigation of the Electroplastic Effect Through Nominally Equal Energy Deformation

To increase the fuel economy of their fleets, automotive OEMs are turning to lightweighting their vehicles through multi-material bodies. This involves forming and joining of materials with high strength to weight ratios such as aluminum and advanced high strength steels. These metals come with the downside of decreased formability and increased springback compared to conventional automotive steels. Electrical augmentation has been shown to decrease springback and increase formability in sheet forming and represents a potential solution to the use of new lightweight metals. Applied electricity is traditionally measured as a current density, however this measure struggles to represent elevated strain rate manufacturing processes. This paper examines other predictors of electrically assisted process performance such as electrical energy and power through comparison of nominally equivalent waveforms. It is found that energy is a better predictor of process performance than current density, but is dependent on the ability to predict process temperature. The leading predictive electrically assisted temperature model is examined in depth through testing of 13 different parameter sets. It is found that the model is unable to predict the correct temperature at a high current density and that the transient stress drop cannot predicted for any of the electrical cases.