Constitutive modelling and validating of annealed copper under various stress states, strain rates and temperatures

Metallic materials and structures are often subjected to a wide range of strain, strain rate, temperature and stress state during the engineering application. In order to study the plastic and deformation characteristics of metallic materials under complex stress states, it is necessary to use a constitutive model that considers the effects of stress states. Based on shear specimens suitable for hydraulic Instron testing machines and Hopkinson bar systems (SHPB and SHTB), the compression-shear and tension-shear specimens are designed to achieve complex stress states. Through a combination of test and parallel finite element simulation, stress–strain curves of the material under various stress states were obtained. Additionally, mechanical property tests were conducted on specimens under typical stress states (uniaxial compression, uniaxial tension, and shear) at a wide range of strain rates and temperatures. To describe the plastic mechanical behavior of materials, a new plastic constitutive model considering temperature, strain rate, and stress state is proposed. Then the model was embedded into the ABAQUS/Explicit finite element software through the VUMAT user material subroutine for numerical simulation. The performance of the new model was systematically compared and analyzed with that of Johnson-Cook model and Xu et al.’s model. The ability of the prediction of plastic deformation in Taylor impact test was evaluated for different models. The results show that the new constitutive model is suitable for predicting the impact deformation associated with complex strain rates, temperatures, and stress states.