Analysis on dynamic fracture failure under different stress states for aluminum alloy based on a physical damage model

Aluminum alloys are widely used in engineering applications. Dynamic ductile fracture failure often occurs in engineering structures and can result in economic losses and casualties. Stress states are known to significantly affect the fracture characteristics. It is therefore essential to investigate dynamic fracture characteristics for aluminum alloys under different stress states. In this study, experiments were performed using M-shaped and double-shear specimens with split Hopkinson pressure bar tests. The macroscopic fracture behavior and microscopic void characteristics under different loading rates and stress states were analyzed. "Void evolution band" was proposed to explain the entire process from void evolution to final fracture. To predict the dynamic ductile fracture under different stress states, a physical damage model that considers the dynamic void evolution and stress state effect was introduced. The physical damage model was then embedded into a numerical simulation, and its effectiveness in predicting dynamic ductile fracture was validated by comparing the numerical and experimental results. The dynamic ductile fracture characteristics under different stress states were also investigated in detail using numerical simulations. These results imply that the stress state fundamentally affects the orientation of the final void coalescence, rather than the elongation direction of the ellipsoidal voids, thereby affecting the initiation and propagation of macroscopic fractures. The proposed damage model proved to be more suitable for predicting dynamic fractures under different stress states than other damage models.