STP404: Random-Loading Fatigue Crack Growth Behavior of Some Aluminum and Titanium Alloys

    Smith, S. H.
    Research engineer, Commercial Product Development—Structures StaffPersonal member ASTM, The Boeing Co., Seattle, Wash.

    Pages: 27    Published: Jan 1966


    Abstract

    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.

    Keywords:

    fatigue crack growth, aluminum alloys, titanium alloys, random loading, sinusoidal loading, power spectrum, fatigue (materials), crack propagation


    Paper ID: STP48341S

    Committee/Subcommittee: E08.06

    DOI: 10.1520/STP48341S


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