Investigation of ductile rupture in U-notched Al 6061-T6 plates under mixed mode loading

The aim of the present research is to evaluate ductile failure of U-notched components under mixed mode I/II loading conditions. For this purpose, first, several rectangular plates made of the aluminium alloy Al 6061-T6 and weakened by central bean-shaped slit with two U-shaped ends are tested under mixed mode I/II loading conditions, and the load-carrying capacity of the specimens are experimentally measured. Then, using the equivalent material concept, Al 6061-T6, which is a highly ductile material, is equated with a virtual brittle material, and the load-carrying capacity of the same U-notched specimens virtually made of the equivalent material is theoretically predicted by using two well-known stress-based brittle fracture criteria. Finally, the theoretical failure loads of the virtual specimens are compared with the experimental ones of the real Al 6061-T6 specimens. It is revealed that the experimental results could very well be predicted by means of both brittle fracture criteria without conducting time-consuming elastic-plastic analyses.