Microstructural Effects and Fatigue Life Predictions of Notched and Un-notched Ni Base Superalloys at Elevated Temperatures PDF Download

Author: Stephen D. Antolovich
Publisher:
ISBN:
Category :
Languages : en
Pages : 54

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Book Description
The LCF(Low Cycle Fatigue) behavior of Ni base superalloys was studied both for smooth and notched test bars. The primary research material was Rene 80 which finds application in turbine blades used in the temperature range of 650-982 C (1200-1800 F). The smooth bar LCF behavior was studied in the as-heat treated condition and also after exposure for 100h at 982 C, either under a stress of 97 MPa (14 ksi) or OMPa. Test conditions included continuous cycling at different strain rates as well as 90 second hold periods at either maximum or minimum strain. The primary test temperatures were 871 C (1600 F) and 982 C (1800 F). It was found that prior exposure greatly reduces the fatigue life. Since these experiments tend to duplicate actual engine conditions, use of data obtained using as-heat treated specimens may be very non-conservative to predict lives of actual components. The test results correlated very well with a model for LCF which is based on the concept that cracks initiate at a critical combination of oxide depth and stress. The notch LCF problem was also studied. A computer model for calculating local stresses and strains was developed. In addition to the Rene 80 studies, some initial smooth bar LCF studies were carried out using Rene 77.