An Experimental and Modelling Study of Cyclic Tension-Compression Behavior of Aa7075-T6 Under Electrically-Assisted Condition

Abstract

Electrically-assisted (EA) forming is an effective method to improve forming quality of sheet metal. In order to reveal the effects of current on material’s behavior under complex strain paths and develop corresponding constitutive model, the EA tension-compression cyclic loading tests with particularly designed setup, and a new constitutive model were developed. The electroplasticity was verified by warm and EA uniaxial tensions and microstructure observation. Further, the effects of current on the elastic modulus degradation and cyclic deformation were investigated. The results showed that the flow stress under EA uniaxial tension was lower than that under warm uniaxial tension. Moreover, the current-induced growth of precipitate and the decrease of dislocation occur under EA uniaxial tension, which is more obvious than those under warm uniaxial tension. Regarding the EA cyclic deformation behavior, the elastic modulus decreases with the increase of plastic strain, temperature and current density, which is described by a proposed modified model. The Bauschinger effect and permanent softening effect are weakened with the increase of temperature and current density. The asymmetric tension-compression behavior becomes more obvious with the increase of temperature and current density. Based on above results, a modified Y-U model was established and verified with EA draw-bending process.

Keywords: Electroplasticity, Cyclic deformation, Bauschinger effect, Permanent softening, Modified Y-U model