A New Ductile Fracture Criterion for Various Deformation Conditions Based on Microvoid Model

To accurately predict the occurrence of ductile fracture in metal forming processes, the Gurson-Tvergaard (GT) porous material model with optimized adjustment parameters is adopted to analyze the macroscopic stress-strain response, and a practical void nucleation law is proposed with a few material constants for engineering applications. Mechanical and metallographic analyses of uniaxial tension, torsion and upsetting experiments are performed. According to the character of the metal forming processes, the basic mechanisms of ductile fracture are divided into two modes: tension-type mode and shear-type mode. A unified fracture criterion is proposed for wide applicable range, and the comparison of experimental results with numerical analysis results confirms the validity of the newly proposed ductile fracture criterion based on the GT porous material model.