Volume 2, Issue 6 (June 2005)

    Effect of Shot Peening on Fatigue Crack Growth in 7075-T7351

    (Received 28 May 2004; accepted 17 November 2004)

    Published Online: 2005

    CODEN: JAIOAD

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    Abstract

    The effects of shot peening on fatigue crack growth in 7075-T735 single-edged notch bend (SENB) and three point bend (TPB) specimens are discussed. Fifty-one total fatigue tests were conducted with SENB and TPB specimens, which were machined from an 8.1 mm thick 7075-T7351 aluminum stock plate. All specimens were tested in the as-received or shot peened conditions, with crack perpendicular to the rolling direction, i.e., in the L-T direction. Fatigue tests of SENB specimens were conducted at a constant maximum load, stress ratios of R = 0.1 or 0.8, and to a pre-determined fatigue cycle or to failure. Crack growth rate was determined from the tunneling crack profile or by fractography. Peened surface roughness, subsurface microstructure, and micro-hardness profiles were also examined to evaluate their effect on crack growth rate. The TPB specimens were fatigued to failure at stress ratios of R = 0.1 or 0.8 and a S-N diagram constructed. Both the SENB and the TPB test results showed that severe shot peening (0.016A) slightly increased the fatigue life at low stress ratio of R = 0.1 but was found to be negligible at a high load ratio of R = 0.8. The stress concentration factor due to dimples generated by severe shot peening was estimated to be 1.14 and had negligible effect on the fatigue life. Grain distortion was observed to a depth range of 130–410 µm indicating the depth of the residual compressive stress layer developed for peening intensities of 0.004–0.016A, respectively.


    Author Information:

    Honda, T
    Senior Researcher, National Institute of Industrial Safety, Kiyose, Tokyo,

    Ramulu, M
    Professor, University of Washington, Seattle, WA

    Kobayashi, AS
    Emeritus Professor, University of Washington, Seattle, WA


    Stock #: JAI12569

    ISSN: 1546-962X

    DOI: 10.1520/JAI12569

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    Author
    Title Effect of Shot Peening on Fatigue Crack Growth in 7075-T7351
    Symposium Residual Stress Effects on Fatigue and Fracture Testing and Incorporation of Results into Design, 2004-05-21
    Committee E08