SYMPOSIA PAPER Published: 01 January 1966

Random-Loading Fatigue Crack Growth Behavior of Some Aluminum and Titanium Alloys


This paper presents the results of an experimental investigation of the fatigue crack growth characteristics of some airframe materials under sinusoidal, narrow-band, and broad-band random loadings. Prerecorded random-time histories, generated by filtering the output of a white-noise generator to produce desired power spectral shapes, were utilized as input loadings to an electrohydraulic fatigue crack growth testing system. Uniform tension-tension loadings were applied to centrally cracked panels, and the fatigue crack growth behavior was observed. Alloys studied include 7075-T6 bare aluminum alloy, 2024-T3 bare aluminum alloy, Ti-8Al-1Mo-1V duplex and mill anneal, and Ti-6Al-4V mill anneal. Fracture-mechanics concepts are applied in correlating and comparing the fatigue crack growth behavior of the alloys. A comparison of sinusoidal- and random-loading behavior, based on the average of the greatest rise or fall in stress intensity between mean-level crossings, shows a faster fatigue crack growth rate for sinusoidal loading at the higher stress-intensity levels and a slower rate at the lower stress-intensity levels.

Author Information

Smith, S., H.
The Boeing Co., Seattle, Wash.
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Developed by Committee: E08
Pages: 74–100
DOI: 10.1520/STP48341S
ISBN-EB: 978-0-8031-6795-7
ISBN-13: 978-0-8031-6627-1