Fracture prediction in metal forming has captured attention because of its practical importance. Recently, demand for fracture prediction has grown to conduct an effective forming process design using numerical simulation; however, the increasing use of high-strength steels and anisotropic materials prevents accurate simulation in large strains in which fracture tend to occur. In this study, a fracture prediction framework based on the bifurcation theory is constructed. The core is a material model based on stress-rate dependency related with non-associate flow rule. This model is based on non-associated flow rule with arbitrary higher order yield function and plastic potential function for any anisotropic materials. And this formulation is combined with the stress-rate-dependency plastic constitutive equation, which is known as the Ito-Goya plastic constitutive equation, to construct a generalized plastic constitutive model in which non-normality and non-associativity are reasonably included. Then, by adopting the three-dimensional bifurcation theory, more accurate prediction of the initiation of shear band is realized, leading to general and reliable construction of forming limit diagram.
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