Creep-fatigue crack growth rate assessment using ductility damage model

In this study, we analyzed the behavior of creep damage and fracture resistance parameters in a 3D finite thickness compact specimen by employing damage-evolution equations. A damage model for the fracture process zone is represented using a ductility-based formulation. Following the ductility model, a new multi-axial failure strain condition is derived. Both damage-free and defective creeping solids are analyzed. The variations in the creep damage contour and crack tip governing parameters in terms of the creep In-integral with respect to time, as well as the crack size, are considered using full-field finite element model solutions. Creep-fatigue crack growth rate tests are performed on a specially designed program test cycle. The application of the previously introduced creep stress intensity factor, as a creep-damage-sensitive parameter for creep-fatigue interaction, is discussed.