Calibration of ductile fracture properties of a cast aluminum alloy

To numerically predict crack formation and growth of cast components under accidental loading, it is necessary to characterize fracture properties at the macroscopic level. In this paper, a ductile fracture locus formulated in the space of the effective plastic strain to fracture and the stress triaxiality for a cast aluminum alloy was obtained using a combined experimental–numerical approach. A total of 12 tests were conducted including 6 tensile tests on notched and unnotched round bars and 6 biaxial loading tests on flat butterfly specimens. Corresponding finite element analysis was performed to determine the evolution of stress and strain states. It was found that the material ductility strongly depends on the stress triaxiality for the present cast alloy. The fracture strain is as high as 0.54 when the stress state is predominately compressive. At the same time, the fracture strain drops to a very low value of 0.05 under uniaxial tension. The obtained fracture locus covers a wide range of the stress triaxiality and thus it be applicable to various loading cases. A large spread of fracture data was observed indicating a need of using a probability method to describe the fracture properties of the cast alloy.