Study on constitutive relationship of 6061 aluminum alloy based on Johnson-Cook model

Uniaxial tensile tests are conducted on 6061 aluminum alloy sheets at different strain rates of a certain temperature and different temperatures of a certain strain rate. The true stress-strain curves show that the flow stresses are negatively correlated with strain rates and temperatures. Based on the Johnson Cook (J-C) constitutive model, the modified J-C model is constructed by replacing the strain term with a Voce hardening model and correcting the strain rate sensitivity coefficient and the thermal softening exponent. Compared with the J-C model, the modified J-C model has a smaller average absolute error and more accurately describes the plastic stress-strain relationship of 6061 aluminum alloy under various deformation conditions. Furthermore, the modified J-C model is also used for numerical simulation of uniaxial tension. The good agreement between the experimental and simulated load-displacement curves further verifies the usefulness of the modified J-C model. Finally, the microscopic mechanism by which deformation speeds affect ductility is analyzed by scanning electron microscopy (SEM).