A physically-based constitutive model applied to AA6082 aluminium alloy at large strains, high strain rates and elevated temperatures

Abstract

This paper presents a physically-based constitutive model applied to an AA6082 aluminium alloy subjected to large strains, high strain rates and elevated temperatures. The model accounts for thermo-elasticity, thermo-viscoplasticity, and strain-rate and temperature dependent work hardening, using the dislocation density as an internal variable without relating it to a detailed characterization of the microstructure evolution. The parameter identification is based on previously reported experimental results from quasi-static and dynamic tensile tests performed at temperatures from 20 to 350°C. The equivalent stress-strain curves were determined beyond necking by monitoring the cylindrical specimens with a digital camera and applying the Bridgman correction to account for the triaxial stress state. The results revealed a distinct increase of the work hardening at high strain rates, indicating a change of strengthening mechanism. A new formulation for the dynamic recovery provided reasonable predictions over the considered range of strains, strain rates and temperatures. Finite element simulations of the quasi-static and dynamic tensile tests were made to assess the accuracy of the Bridgman correction. The simulations reproduced the complex behaviour observed in the tests and validated the constitutive model and the associated parameter identification procedures in the entire range of strains, strain rates and temperatures investigated.