A High-Temperature Semi-Coupled Damage Model for 7075 Aluminum Alloy Considering Temperature and Strain Rate Effects

Fracture is a common and fatal defect in the hot stamping of aluminum alloys. Accurate prediction of high-temperature fracture behavior is crucial for forming process planning. However, existing high-temperature fracture criteria suffer from a trade-off between predictive capability and parameter calibration difficulty, which limits their industrial application. This study establishes a high-temperature semi-coupled damage model by incorporating strain rate and temperature terms into a semi-coupled fracture framework and coupling it with a viscoplastic constitutive model. This model maintains the convenience of parameter calibration while describing the nonlinear characteristics of damage evolution using a hyperbolic sine function. The model was applied to the finite element analysis of 7075 aluminum alloy. For hot tensile tests, the simulated load–displacement responses, fracture displacements, and strain fields agree with the experiments, with a maximum load–displacement root mean square error (RMSE) of 0.047 kN and a maximum fracture displacement relative error of 3.141%. For isothermal bulging validation tests, the average relative error for fracture location prediction is 5.10%, and the maximum relative error for normalized thickness is 6.67%. These results demonstrate that within 350–450 °C and 0.001–0.1 s−1, the proposed model accurately predicts the damage initiation, evolution, and fracture behavior.