Investigation of thermal and mechanical effects during electrically-assisted microbending

The application of electrical current to conductive metals during deformation processes has been shown to reduce the flow stress required, increase the potential elongation prior to failure, and decrease the springback observed. These are believed to be beyond what can be explained by elevated temperatures due to resistive heating alone, i.e., an additional electro-plastic effect is supposed to be relevant. Further experimental data (including force, strain distribution, and temperature) for a standard deformation process would provide insight into the effects involved. In this paper, results from electrically-assisted (EA), three-point bending of C260 (brass) sheet metal with a 0.5mm thickness are presented. The strain distributions are measured using a stereomicroscope system with digital imaging correlation (DIC) while temperature was measured using a thermal imaging camera. Results show that the strain distribution through the thickness was more uniform for the EA case (in particular for coarse grain structures) which has not been shown in past literature. Also, the bending force decreased only during a temperature spike at the beginning of the process. Therefore for this specific application, an electroplastic effect was not observed with 40A/mm2 being applied to the specimens, and variations observed were simply caused by temperature effects.