SYMPOSIA PAPER Published: 01 January 1988
STP27236S

Effects of Closure on the Fatigue Crack Growth of Small Surface Cracks in a High-Strength Titanium Alloy

Source

Fatigue crack growth experiments were conducted on surface flaws in a high-strength titanium alloy. Surface crack lengths in the range 50-μm to 8 mm were investigated under both increasing and decreasing ΔK conditions. Crack length and closure loads were determined from load-displacement data obtained with the aid of a laser interferometric displacement gage, which has resolution capability at 0.01 μm. Stress ratios of 0.1, 0.5, and −1.0 and net-section stress levels from 0.2 to 0.9 of yield stress were utilized. The applied stress intensity factor range, ΔK, correlated crack-growth-rate data for R = 0.1 and R = −1, but all R = 0.5 data fell along a separate band. The effective stress intensity factor range ΔKeff determined from closure data, consolidated most of the data into a single band, but some small-crack data fell outside the band. Fracture surface roughness and plasticity were concluded to be the primary features contributing to crack closure.

Author Information

Jira, JR
Materials Laboratory, Air Force Wright Aeronautical Laboratories, AFWAL/MLLN, Wright-Patterson Air Force Base, OH
Weerasooriya, T
University of Dayton Research Institute, Dayton, OH
Nicholas, T
Materials Laboratory, Air Force Wright Aeronautical Laboratories, AFWAL/MLLN, Wright-Patterson Air Force Base, OH
Larsen, JM
Materials Laboratory, Air Force Wright Aeronautical Laboratories, AFWAL/MLLN, Wright-Patterson Air Force Base, OH
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Details
Developed by Committee: E08
Pages: 617–635
DOI: 10.1520/STP27236S
ISBN-EB: 978-0-8031-5052-2
ISBN-13: 978-0-8031-0996-4