Reducing Uncertainty in Fatigue Life Limits of Turbine Engine Alloys (Preprint)
Abstract
In probabilistic design of materials for fracture-critical components in modern military turbine engines, a typical design target risk (DTR) is 5x10-8 component failures/engine flight hour. This goal highlights the essential role of safety in a design process that simultaneously strives for a balance of performance, efficiency, safety, reliability, and affordability over the entire life cycle of the engine. Historically, to meet safety and reliability requirements, the design and life management approaches for engine materials have involved large experimental programs from which statistically based life limits are derived by extrapolation from mean fatigue behavior. However, we have recently found that the fatigue lifetime under a given test condition often exhibits a bimodal form, and the trends in mean vs. minimum fatigue lifetime typically respond differently to loading and microstructural variables. Under such circumstances, the underlying life-limiting mechanisms appear to follow a probabilistic microstructural hierarchy that is controlled by susceptibility to early damage and growth of small cracks.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 2012
- Accession Number
- ADA567713
Entities
People
- A. H. Rosenberger
- C. J. Szczepanski
- D. J. Buchanan
- J. R. Jira
- James M. Larsen
- M. J. Caton
- P. J. Golden
- R. John
- Sushant K. Jha
Organizations
- Air Force Research Laboratory