Prediction of Creep Behaviour of 316LN SS Under Uniaxial and Multiaxial Stress State Using Kachanov-Rabotnov Model at 923 K

摘要

Finite element analysis coupled with the continuum damage mechanics-based Kachanov-Rabotnov (KR) model has been carried out to describe the creep deformation and damage behaviour of 316LN austenitic stainless steel (SS) at 923 K under the uniaxial and multiaxial state of stress. Uniaxial creep experimental data have been used to optimize the material parameters of the KR model. The coupled differential equations are numerically integrated by fourth-order Runge-Kutta method in the USERCREEP subroutine and passed on to the Abaqus solver. 316LN SS exhibited notch strengthening effect under the multiaxial state of stress. Detailed analysis showed that stress distribution during creep deformation is localized to notch root due to the high constraint imposed by V-notch geometry. The estimated maximum value of the creep damage variable (omega) suggested that fracture is likely to initiate at the notch root location. Good agreement between experimental and predicted results has been observed for both plain and notch specimens.