Effect of stress state on the fracture behavior of Al6061-T6 via combined experimental and numerical approaches

This study presents an experimental and numerical investigation into the influence of stress triaxiality, Lode angle parameter, and ductile fracture behavior in Al 6061-T6 aluminum alloy. To explore negative stress triaxiality conditions, uniaxial tensile and compressive tests were conducted on geometrically tailored specimens, including dumbbell-shaped and rectangular samples with elliptical curved holes. Negative triaxiality values ranging from –0.355 to –0.554 were successfully achieved. A hybrid experimental–numerical approach was adopted to characterize the fracture behavior. In the numerical approach, the Ganjiani fracture model incorporating damage parameters, was implemented in finite element simulations using Abaqus via custom VUHARD and VUSDFLD subroutines. Comparative analysis of experimental and numerical results revealed good agreement in fracture strain predictions. Numerical evaluations indicated that the fracture occurs at the site where maximum plastic strain is observed. The results confirm that stress triaxiality significantly influences ductile fracture, and notably, the variation in fracture strain exhibits different trends under positive and negative triaxiality conditions.