The extended GTN model for stiffness degradation prediction based on voids evolution mechanism

Considering the evolution of void defects and their influence on the stiffness degradation of ductile metallic materials, this study extends the voids evolution mechanism of the Gurson–Tvergaard–Needleman (GTN) damage model in order to better predict the mechanical behavior of ductile metallic materials under axial tension. The relationship between void defects and the macroscopic equivalent elastic modulus of metallic materials is established based on the theory of asymptotic homogenization, while the equivalent damage factor is calculated using the Lemaitre model. Based on the material stiffness degradation under uniaxial loading and unloading conditions, the constitutive model parameters for Ti-6Al-4V were determined using genetic algorithm. The simulation results show that the maximum relative error of the predicted effective elastic modulus of Ti-6Al-4V after damage based on the extended GTN model is 3.32 %, compared with experimental results. The proposed method can effectively reflect the degradation of material elastic properties due to the evolution of mesoscale void defects under large deformations with high accuracy.