Microstructural Models to Predict Creep Fatigue Reliability

This paper discusses the simulation of creep fatigue damage incorporating damage mechanisms based on the underlying physics of failure. Computational models are used to predict the material response by explicitly modeling the randomness of the material microstructure, interacting loading, dwell and temperature effects. The variation in the material response is determined using mesomechanical models applied at the grain and sub grain level. The model predictions were compared with smooth specimen laboratory test data for nickel-based alloys from 1200°F to 1350°F. The model does an excellent job of capturing the effect of temperature on the fatigue life of the specimens. Finite element analysis (FEA) was performed for notch specimens. The results of an elastic-plastic analysis and peak dwell creep are taken and used to simulate the load conditions for a notched specimen at various temperatures and different maximum applied stresses. The model correlates very well with the notched specimen test data and captures the variability that would be expected in the test.