This study investigates the dependence of ductile fracture-initiation strain on the Lode angle in aluminum alloy 5083-O to help identify an appropriate phenomenological damage model for crack propagation simulations. Novel rectangular-notched (RN) tensile specimens were used to overcome the coupled variation of stress-state parameters in conventional test matrices. Finite element analysis showed that the RN specimens could vary the normalized Lode angle parameter independently from 0.01 to 0.92 while maintaining the average stress triaxiality in the central fracture-initiation zone at approximately 0.70. Quasi-static tensile tests and corresponding simulations revealed only slight variation in the fracture-initiation strain, with mean values ranging from 0.268 to 0.278 and limited scatter for all specimen configurations, despite a clear morphological transition from equiaxed to elongated dimples. These results indicate weak apparent sensitivity of the fracture-initiation strain of AA5083-O to the Lode angle under the investigated stress states. For engineering prediction of typical Mode I crack propagation in AA5083-O, a conventional triaxiality-dependent fracture model without explicit Lode-angle incorporation thus appears to be a reasonable simplification. • RN specimens varied Lode angle while keeping triaxiality nearly constant. • Fracture strain remained nearly unchanged across four RN geometries. • Fracture morphology changed from equiaxed to elongated dimples.
Li et al. (Fri,) studied this question.