Implementation of the Kachanov — Rabotnov creep model with damage in ABAQUS UMAT: analysis of stress and damage fields at the crack tip

This study focuses on a finite element analysis of stress, strain, and damage fields near the tip of a central crack in a plate subjected to a tensile load under creep conditions, taking into account the damage accumulation effect. The simulation was performed in Simulia ABAQUS using the UMAT (User Material) procedure, which implements the Bailey-Norton power law constitutive relation and the Kachanov-Rabotnov damage kinetics equation. The results of calculations without damage confirmed compliance with the known Hutchinson-Rice-Rosengren analytical asymptotics for the creep zone and the asymptotics of linear fracture mechanics in the elastic region. It was established that the presence of damage significantly affects the asymptotic behavior in the creep zone near the defect tip. Numerical calculations showed that the continuity parameter exhibits asymptotic behavior. Power-law asymptotics were found for both the stress tensor components and the damage parameter. The result of the study is also the identification of a self-similar structure of the fields of mechanical quantities in the vicinity of the crack tip.