Thresholds for high-cycle fatigue in a turbine engine Ti-6Al-4V alloy
Document Type
Article
Publication Date
1-1-1999
Abstract
The characterization of critical levels of microstructural damage that can lead to fatigue-crack propagation under high-cycle fatigue loading conditions is a major concern for the aircraft industry with respect to the structural integrity of turbine engine components. The extremely high cyclic frequencies characteristic of in-flight loading spectra necessitate that a damage-tolerant design approach be based on a crack-propagation threshold, ΔKTH. The present study identifies a practical lower-bound large-crack threshold under high-cycle fatigue conditions in a Ti-6Al-4V blade alloy (with approx. 60% primary α in a matrix of lamellar α+β). Lower-bound thresholds are measured by modifying standard large-crack propagation tests to simulate small-crack behavior. These techniques include high load-ratio testing under both constant-R and constant-Kmax conditions, performed at cyclic loading frequencies up to 1 kHz and R-ratios up to 0.92. The results of these tests are compared to the near-threshold behavior of naturally-initiated small cracks, and to the crack initiation and early growth behavior of small cracks emanating from sites of simulated foreign object damage.
Publication Title
International Journal of Fatigue
Recommended Citation
Ritchie, R.,
Boyce, B.,
Campbell, J.,
Roder, O.,
Thompson, A.,
&
Milligan, W.
(1999).
Thresholds for high-cycle fatigue in a turbine engine Ti-6Al-4V alloy.
International Journal of Fatigue,
21(7), 653-662.
http://doi.org/10.1016/S0142-1123(99)00024-9
Retrieved from: https://digitalcommons.mtu.edu/michigantech-p/7408