A thermodynamics-based microdamage model combined with a non-local macro damage regularization for ductile fracture analysis of single crystals

In this study, a microdamage coupled crystal plasticity model, combined with a non-local macro damage regularization for ductile fracture is developed. The governing equations of the slip system considering plasticity, hardening, external structure effects and microdamage are established in the framework of thermodynamics by introducing four groups of conjugate variables. The principle of damage dissipation energy equivalence is then proposed to determine the homogenized macro damage of a material element by incorporating the microdamage of each slip system. This equivalent method provides an approach with physical meaning to correlating macro damage and microdamage. Afterward, a non-local method is introduced to solve the mesh-dependence issue during the fracture process simulations. An explicit algorithm for the proposed non-local damage model is applied, in which only one user subroutine is needed. Numerical tests are conducted on a 1D bar and a 2D notched specimen to investigate the basic features of the model. Furthermore, to validate the applicability of the model for complex problems, crack propagation simulations on 2D compact tensile specimens and ductile failure simulations on a 3D specimen with distributed holes are performed. Comparisons between the calculated results and the experimental data are also provided. The results demonstrate that the proposed model is capable of accurately capturing the ductile fracture behavior of single crystals and offers a robust and efficient tool for simulating complex fracture processes.