Fatigue crack growth at high R ratio in Ti-6Al-4V at 1.5kHz: The effect of periodic removal of mean stress
The components of gas turbine engines operate at high mean stresses due to the centrifugal loads caused by high rotational speeds. The turbine blades also have vibratory stresses that are superimposed on the mean stresses. Any fatigue problems that are experienced by turbine blades are driven by the vibratory stresses, but fatigue phenomena are also well known to depend strongly on mean stress effects. Here, fatigue cracks were grown under high mean stress at {approx}1.5 kHz at rates of 10{sup {minus}10} to 10{sup {minus}12} m/cycle within the scanning electron microscope in vacuum. Periodically, mean stress was removed, then reapplied, and the effect on subsequent crack growth rate was measured. This process has been called HCF/LCF interaction. Detailed crack tip micromechanics analyses were made of these load interactions. The only HCF/LCF effect detected was less than a factor of ten change in crack growth rate, in agreement with expectations from the micromechanics analysis, and previous experimental results in air.
- Research Organization:
- Southwest Research Inst., San Antonio, TX (US)
- Sponsoring Organization:
- US Department of the Air Force
- OSTI ID:
- 20013310
- Resource Relation:
- Conference: TMS Fall Meeting '98, Symposium on Fatigue Behavior of Titanium Alloys, Chicago, IL (US), 10/11/1998--10/15/1998; Other Information: PBD: 1999; Related Information: In: Fatigue behavior of titanium alloys, by Boyer, R.R.; Eylon, D.; Luetjering, G. [eds.], 382 pages.
- Country of Publication:
- United States
- Language:
- English
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