Stress-state-dependent constitutive model and fracture criterion of annealed 6056 aluminum alloy

The high strength and formability of heat-treated 6056 aluminum alloys offer great potential for use in automotive components. To investigate the mechanical properties of annealed 6056 aluminum alloy, tensile tests were conducted on both standard and notched specimens. A modified hardening model, derived from the JC and Voce constitutive models, was proposed to accurately describe the mechanical behavior of the annealed alloy under quasi-static tensile loading. Based on the experimental results of notched specimens, it was determined that the material's constitutive behavior is dependent on the stress state. Therefore, a stress-state-dependent constitutive model, incorporating stress triaxiality and the Lode parameter, was developed to describe the alloy's mechanical behavior under multiaxial stress conditions. The average relative error between the simulation and experimental results was ∼2.31%. The ASCE fracture criteria of the annealed 6056 aluminum alloy were determined utilizing a parameter inversion method focused on the most failure-prone regions. The average error between the simulated displacements based on the ASCE fracture criterion and the displacements in the experiment was 6.39%, which is better than the average error of 20.83% when using the surface fitting method. This study shows the proposed constitutive model and fracture criteria can simulate annealed 6056 aluminum alloy behavior effectively.