PHYSICALLY-BASED MODELS FOR PREDICTING FATIGUE LIFE VARIABILITY IN NI-BASED SUPERALLOYS

摘要

Physically-based fatigue models have been developed for treating the variability of fatigue life due to microstructural variations. Both fatigue crack initiation and growth processes have been modeled in terms of the accumulation of dislocations in a material volume representative of the underlying microstructure. The representative material volume is located at the crack tip for crack growth, but is embedded in an optimally oriented grain for crack initiation. Explicit relationships between fatigue resistance and material parameters such as Young's modulus, dislocation barrier spacing, yield strength, and fatigue ductility have been established. Based on these deterministic models, probabilistic models are developed in which the variability of the material parameters is expressed in terms of appropriate dimensionless random variables. The application of the fatigue models to predict fatigue life variability in Ni-based superalloys will be evaluated against experimental data from the literature.