Study on the Fracture Behaviour of 6061 Aluminum Alloy Extruded Tube during Different Stress Conditions

To study the deformation and fracture mechanism of 6061 aluminum alloy extruded pipe after secondary heat treatment under different stress triaxiality, a Johnson-Cook failure model was developed. Through the FEM method and SEM, the fracture mechanism of different types of aluminum alloy tensile specimens was analyzed. The research results show that the Johnson-Cook failure model could better simulate the tensile deformation of 6061 aluminum alloy specimens of different types, the parameters of the Johnson-Cook failure model were finally obtained D-1 = 0.29, D-2 = 1.356, and D-3 = -2.567. With the increase of the stress triaxiality, the fracture strain showed a decreasing trend as a whole, and the fracture mechanism changed from a shear type to a hole aggregation type. The stress triaxiality gradually decreased with the increase of the notch radius/angles of the aluminum alloy notch specimen, and the stress triaxiality at the center of the notch was higher than the stress triaxiality at the root of the notch.