Relationship between fatigue life in the creep-fatigue region and stress-strain response

On the basis of mechanical tests and metallographic studies, strain-range partitioned lives were predicted by introducing stress--strain materials parameters into the universal slopes equation. The method was developed by correlating fatigue-damage mechanisms and deformation mechanisms operating at elevated temperatures. Correlation between high-temperature fatigue and stress--strain properties for Ni-base superalloys (e.g. MAR-M200 + Hf, Udimet 700, AF2-1DA) and stainless steel (e.g. 316) substantiated the method. Parameters which must be evaluated for PP- and CC-life are the maximum stress achievable under entirely plastic and creep conditions, respectively, and corresponding inelastic strains, and the elastic modulus. For plasticity/creep interaction conditions (PC and CP) two more pairs of stress--strain parameters must be ascertained. Graphs, Photomicrographs. 16 ref.--AA