Ductile fracture behavior of metallic materials is significantly influenced by the stress states, especially for geometrically complex structures fabricated by laser additive manufacturing (AM) technique. This study proposes a new uncoupled ductile fracture criterion (DFC) that considers void evolution behaviors to predict the ductile fracture of AMed Ti-6Al-4V alloy. The new criterion is derived by synthetically taking into account the effects of stress triaxiality and the Lode parameter on microscopic void evolution behaviors, including void nucleation, growth, and coalescence, which eventually leads to the macroscopic ductile fracture. By comparison with the representative uncoupled ductile fracture criteria, the predictive ability of the proposed criterion for different metallic material is comprehensively discussed through a series of fracture experimental data published in the literature to verify the effectiveness and accuracy of the new criterion. The comparative studies indicate that the new uncoupled ductile fracture criterion can accurately predict fracture strain under different stress states. Particularly, the proposed micromechanism-motivated criterion demonstrates the distinguished effectiveness in predicting ductile fracture under high stress triaxiality compared to other criteria. Furthermore, fracture experiments of additively manufactured titanium alloy were conducted under various stress states to calibrate the material parameters of the proposed criterion. It can be found that the predicted fracture locus of AMed titanium alloy is more dependent on stress state and is generally lower than that of cast titanium alloy produced by traditional processing technology.
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