A ductile fracture model based on continuum thermodynamics and damage

The paper presents an approach to ductile failure modeling derived based on continuum thermodynamics and damage. A continuum damage enhanced formulation of the effective material is used to describe the degradation of the response. From the thermo-mechanically motivated dissipation rate, a novel damage driving energy that involves both stored energy and dissipative contributions due to inelasticity is presented. This damage driving energy is combined with a damage threshold that controls the onset of inelastic damage driving dissipation. The damage evolution law is formulated as a balance of produced dissipation and produced fracture area induced dissipation, involving damage progression velocity and length-scale parameters without any non-local gradient term. As main prototypes for the effective material and damage threshold, the Johnson Cook continuum and failure models are exploited. From the verification examples, satisfactory convergence properties of the model are obtained. The model capabilities to represent real thermodynamic ductile failure processes are demonstrated for a specimen made of a ductile Weldox steel subjected to tensile split-Hopkinson Tension Bar tests. The model is computationally efficient and shows well controlled damage progression in the FE-application.