An Evaluation of Four Current Models to Predict the Creep-Fatigue Interaction in Rene 95
Abstract
Four current models for the creep-fatigue interaction were evaluated for their ability to predict fatigue behavior at 1200 F (650 C) of thermochemically processed Rene 95--an advanced nickel-base superalloy used for turbine disks. These models are the Strainrange-Partitioning Model, the Frequency-Separation Model, the Ostergren Model, and the Damage-Rate Model. A series of strain controlled fatigue tests was conducted to evaluate these models. These tests consisted of continuously cycling tests at two different frequencies, various types of strain-hold tests, and dual-rate continuously cycling tests. These fatigue tests were divided into two groups--baseline tests and verification tests. The baseline tests were used to determine the constants in the models and the correlation ability of the models. The verification tests were used to determine the predictive ability of the models. The best correlation of the baseline tests was to within a scatter band of plus or minus 3.6 and was achieved by the Frequency-Separation Model and the Ostergren Model. The other two models had scatter bands greater than plus or minus 5. The best prediction of the verification tests was to within a factor of plus 5.2 and was achieved by the Ostergren Model. The other models predicted the verification tests from factors of plus or minus 6.1 to plus or minus 18. Each of the models consistently overpredicted or underpredicted the lives of certain types of tests that form the data base. Based upon the results of this study, it was concluded that these models in their present form could not adequately predict the fatigue life of Rene 95 at 1200 F (650 C). (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1979
- Accession Number
- ADA077168
Entities
People
- Henry L. Bernstein