A Novel Continuum Damage Constitutive Model for Predicting the Formability of AA7075 Alloy at Elevated Temperatures

Hot forming has been proposed to improve the formability of high-strength aluminum alloys. The main objective of this paper is to formulate a continuum damage model and to describe the damage evolution features of AA7075 alloy at elevated temperatures. Hot uniaxial tensile tests and hot Nakajima tests were conducted. Subsequently, a novel continuum damage model was proposed and incorporated into a set of multi-axial visco-plastic constitutive equations to describe the thermal flow behaviors and predict the thermal forming limit diagram (TFLD) of AA7075. Material constants were determined based on the experimental data with a genetic algorithm. Moreover, the TFLD of AA7075 was numerically simulated by implementing the multi-axial continuum damage constitutive equations (CDCEs) via the user material subroutine VUMAT in commercial software ABAQUS. Simulation results agree well with experimental results and theoretically predicted results, which indicates the set of multi-axial CDCEs is capable of predicting the formability of AA7075 at elevated temperatures.