Modeling the ductile fracture process of void coalescence by void-sheet formation

Ductile fracture of engineering alloys frequently occurs by a mechanism of void coalescence in which void-sheets form between the primary voids. Based on the microstructural features that control failure of HY-100 steel, computational modeling has been performed to examine the deformation localization behavior between primary voids and to predict ductile fracture by the void-sheet coalescence mechanism. Elongated inclusion-initiated voids are simulated as two distinct, hole-like voids on a plane inclined to the stress axis based on the inclined nature of the fracture surface. Consistent with experimental behavior, the micro-mechanical model identifies a strong tendency for strain localization between the voids (and therefore void-sheet failure) but only at a high degree of stress triaxiality. Furthermore, based on the formation of a secondary void population, the analysis also predicts with reasonable accuracy both the magnitude and stress-state dependence of the experimentally determined failure strains.