Analysis of Creep Crack Growth Based on New Multiaxial Ductility Factor and Creep-Damage Model

In this study, the multiaxial ductility factor and creep damage model were analyzed based on the power-law creep grain-boundary cavities growth theory under multiaxial stress states. Theoretical cavities growth rates under multiaxial stress state were discussed and the predicting model of stress-state parameter α was revised by using an empirical fitting expression denoted as αNEW, then a new empirical predicting model of multiaxial ductility factor MDFNew was established which involving multiaxial parameter αNew and uniaxial parameter α0. Besides, a novel creep constitutive model considering the damage parameter was also be established, which could correctly describe the whole period of creep regime, especially the tertiary period. Finally, the damage process was analyzed by using finite element method with this novel creep damage model, and the FE results of the load line displacement and crack growth predictions coincide well with experimental observations.