Overload Effects on Sustained Load Crack Growth at Elevated Temperature.
Abstract
This theses investigates the crack growth behavior of Inconel 718 effected by over-loads at elevated temperature. A cumulative damage model was developed to predict the total time-to-failure. Predictions were noted to improve at higher values of stress intensities. All tests were conducted under sustained loading with isothermal conditions of 650 C. Precracked compact tension specimens were used to establish a data base for baseline and overload conditions. The delay time associated with crack growth retardation was determined by comparing the baseline behavior with the results of the overload specimens. The effects of 20-and 50-percent overloads of 1 minute or 1 hour duration were investigated. The shape of the crack tip plastic zone and, hence, the retardation effect was found to be independent of overload duration. The retardation delay time was found to be dependent upon the overload magnitude and the value of K at which the overload was removed. It was also found that a sudden crack advancement occurred when the overload was applied. The above factors were accounted for in the model development. The model was generally capable of predicting the time-to-failure within about 10 percent of the actual material behavior. Originator supplied keywords: Sustained-load crack growth; Crack growth retardation; Elevated temperature; Nickel-based superalloy; Crack growth model; Overloads; Data reduction; Graphs.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1984
- Accession Number
- ADA153223
Entities
People
- K. E. Harms
Organizations
- Air Force Institute of Technology