A numerical study of damage development and creep life in circular notched specimens during creep

In this study, numerical calculations of creep damage development and life behaviour of circular notched specimens have been performed with the Kachanov-Rabotnov damage law. The emphasis was placed on the role of specimen geometry and material ductility. The creep deformation will relax the elastic stress concentrations. The redistribution of the stress concentration depends on the material properties and specimen geometry. 'Brittle' materials will redistribute faster than 'ductile' materials. The creep crack initiation place can be the centre of the specimen (large radius of notches e.g. R = 3 mm in this study) or the tips of the notches (small radius of notches). The characteristics of 'notch strengthening' and 'notch weakening' depend on the notch radius and notch type as well as material properties. For the same notch type, the creep lives decrease with the decreasing of notch radius and the depth of cracks. Generally, the 'V-type' notched specimens have longer lives than 'U-type' notched specimens for the same notch radius. For all specimens studied, the 'ductile' material specimens have longer creep lives than 'brittle' material specimens.