Parametric analysis of the stress-strain and continuity fields at the crack tip under creep regime taking into account the processes of damage accumulation using UMAT

The subject of this study is the analysis of the stress-strain and continuity fields in the proximal nearness of the crack tip, which is in creep regime conditions with due regard for the accumulation of damage. The aim of the work is to conduct computer finite element modeling of uniaxial stretching of a two-dimensional plate with a central crack under creep conditions and to analyze the continuity field around the crack tip. The Bailey–Norton power law of creep is used in numerical modeling. The simulation was performed in the software multifunctional complex SIMULIA Abaqus. The analysis of the circumferential apportionment of stresses, creep deformations and continuity in the direct of the crack tip is carried out.
The power law of creep with the help of the user procedure UMAT (User Material) of the SIMULIA Abaqus package was supplemented by the kinetic equation of damage accumulation of Kachanov–Rabotnov in a related formulation. The UMAT subroutine has many advantages in predicting material damage and allows you to work with materials that are not in the Abaqus materials library. The UMAT subroutine is called at all points of the material calculation and updates the stresses and state variables depending on the solution to their values at the end of the increment. After that, the updated elements of the Jacobi matrix are calculated.
Stress, strain and continuity distributions under creep conditions are gained, considering the damage accumulation of over time. Angular distributions of continuity, stresses and deformations are constructed using the Matplotlib library over time at various distances from the crack tip. The obtained angular distributions of the stress and strain tensor components are compared when modeling without taking into account damage and when taking into account damage accumulation. It is shown that the presence of damage leads to large values of creep deformations and lower stresses.