New ductile fracture model for fracture prediction ranging from negative to high stress triaxiality

Abstract

In this study, the ductile fracture of the alloy metal is analyzed. First, the key factors affecting the initiation of ductile fracture are investigated. Then, a new uncoupled ductile fracture model is established in the stress space by considering the volume change work and the distortion work simultaneously. The proposed ductile fracture model is not only dependent on stress triaxiality but also dependent on the Lode angle parameter. Subsequently, the proposed ductile fracture model is transformed to the mixed stress-strain space. Experimental tests are adopted to verify the validity of the fracture model. The comparative study with four typical ductile fracture criteria, viz., the pressure modified maximum shear stress criterion (PMMS), the extended Mohr-Coulomb criterion (EMC), the extended Hosford-Coulomb criterion (EHC), and the extended unified strength theory criterion (EUST), indicates that the proposed fracture model predicts the fracture strain with good stability and accuracy in a wide range of stress states, especially in the range of the high stress triaxiality. Finally, the asymmetry of the fracture locus and the realistic stress space are discussed.