Increasingly strict fuel efficiency standards have driven the aerospace and automotive industries to improve the fuel economy of their fleets. A key method for feasibly improving the fuel economy is by decreasing the weight, which requires the introduction of materials with high strength to weight ratios into airplane and vehicle designs. Many of these materials are not as formable or machinable as conventional low carbon steels, making production difficult when using traditional forming and machining strategies and capital. Electrical augmentation offers a potential solution to this dilemma through enhancing process capabilities and allowing for continued use of existing equipment. The use of electricity to aid in deformation of metallic materials is termed as electrically assisted manufacturing (EAM). The direct effect of electricity on the deformation of metallic materials is termed as electroplastic effect. This paper presents a summary of the current state-of-the-art in using electric current to augment existing manufacturing processes for processing of higher-strength materials. Advantages of this process include flow stress and forming force reduction, increased formability, decreased elastic recovery, fracture mode transformation from brittle to ductile, decreased overall process energy, and decreased cutting forces in machining. There is currently a lack of agreement as to the underlying mechanisms of the electroplastic effect. Therefore, this paper presents the four main existing theories and the experimental understanding of these theories, along with modeling approaches for understanding and predicting the electroplastic effect.

The electroplastic effect can be predicted and modeled as a 100% bulk heating/softening phenomenon in the quasi-steady-state; however, these same models do not accurately predict flow stress in transient cases. In this work, heterogeneous Joule heating is examined as the possible cause for the transient stress drop during quasi-static pulsed tension of 7075-T6 aluminum. A multiscale finite element model is constructed where heterogeneous thermal softening is explored through the representation of grains, grain boundaries, and precipitates. Electrical resistivity is modeled as a function of temperature and dislocation density. In order to drive the model to predict the observed stress drop, the bulk temperature of the specimen exceeds experiment, while the dislocation density and grain boundary electrical resistivity exceed published values, thereby suggesting that microscale heterogeneous heating theory is not the full explanation for the transient electroplastic effect. A new theory for explaining the electroplastic effect based on dissolution of bonds is proposed called the Electron Stagnation Theory.

One of the largest issues for sheet metal forming techniques such as stamping and incremental forming is springback. Springback is the elastic recovery of a material after it has been formed resulting in distorted part geometries. Springback can be compensated for during the forming process, however, this often requires forming the metal further than the desired shape. Unfortunately, if a formed part is designed such that it is close to its forming limit, compensation could push the material too far and cause fracture. It has been shown that by pulsing electric current throughout an entire workpiece during forming, springback can be greatly reduced and sometimes eliminated. This paper examines the effect of pulsing direct electric current, through localized points of a workpiece after it has been deformed into a 90-degree bend, but prior to the reversal of the bending die (i.e., while the part is still constrained). It was found that, with a high current density for a short amount of time, springback could be greatly reduced without the need to run a larger current through the entire workpiece. The largest springback reduction was seen when the electric current was forced to flow across the bend in the specimen. This finding is advantageous for industry as it will allow springback reduction in large parts that would normally require much larger power sources to generate the correct current density, if current is run through the entire part. A potential barrier between industry and this technology is that machines would need to be either created or modified to apply electric current at known places at a specific current density and time. To modify an existing machine may be difficult because the machine would need to be insulated from the electric current.

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Driven by the automotive industry’s drive towards lightweighting, electrically assisted forming (EAF) is one of the most rapidly growing research fields in bulk deformation, and is classified under the general term “Electrically-Assisted Manufacturing (EAM)”. In EAF electric current (continuous or intermittent) is applied to a metallic sheet during the forming process, leading to numerous advantageous effects that have been studied and proven by several research groups and for different structural metals, such as reduced forming load and flow stress, increased formability, and reduction (or even elimination) of springback. Electrically-assisted bending (EAB) is a recent evolution of EAF technique, with the aim of capitalizing on the aforementioned advantages of EAF technique. In this work the effects of the EAB process on the final springback in an air bending test are identified, with the metal sheet being bent under different electrical field conditions. In addition, a comparison between the effects of applying the current during forming versus post forming are investigated. It was found that in general, higher current density (amount of current through cross sectional area of specimen (A/mm2), more frequent pulse period, and longer pulse duration all resulted in a greater degree of springback reduction. A microstructural evaluation showed no change in grain size in the presence of electric current.