Evaluation of Methods for the Treatment of Mean Stress Effects on Low-Cycle Fatigue Available to Purchase

Several methods proposed for the treatment of mean stress effects on time-independent low cycle fatigue (LCF) lifetime were critically evaluated using LCF crack initiation data on a number of materials used in gas turbine design. The methods evaluated included Jaske’s equivalent strain (ε_eq) formulation, Manson ’s mean stress correction method and nonlinear Goodman diagram representation of the strain-controlled LCF data. LCF crack initiation data on STA Ti-6-4 (533K), Ti-5522S (783K), IN-706 (866K) and MAR-M246 (1033K) were utilized in the evaluations. The evaluations were carried out in terms of each method’s capability to back-predict the experimetnal data used in its construction. Also considered were the implications associated with the type and the extent of data required for each method.