STP791

    Stress Intensity and Fatigue Crack Growth in a Pressurized, Autofrettaged Thick Cylinder

    Published: Jan 1983


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    Abstract

    Stress-intensity factors are determined using the modified mapping collocation (MMC) method for a single, radial, straight-fronted crack in a thick cylindrical tube that has been subjected to full autofrettage treatment (100 percent overstrain). By superposition of these results and existing solutions, stress-intensity factors are determined for the same geometry with internal pressure and any amount of overstrain from 0 to 100 percent.

    Correction factors for crack shape and nonideal material yielding are determined from various sources for the pressurized, autofrettaged tubes containing semielliptical cracks. These results are employed in the life prediction of pressurized thick tubes with straight-fronted and semicircular cracks, for various amounts of autofrettage. Experimentally determined lifetimes for tubes having 0 and 30 percent nominal overstrain are significantly greater than the predictions for both straight-fronted and semicircular cracks. This is related to multiple initiation and early growth of cracks from the notch.

    Experimentally determined lifetimes for a tube with 60 percent nominal overstrain are somewhat less than predicted. This effect is partially explained by additional experimental work, which shows that the angle of opening of rings cut from autofrettaged tubes is somewhat less than the ideal predictions. The latter effect is attributed to the Bauschinger effect and the associated reduced yield strength in compression during the unloading of tubes during the autofrettage process.

    Keywords:

    crack growth, fatigue cracks, cylinders, fracture (materials), fracture mechanics, residual stress, stress-intensity factor


    Author Information:

    Parker, AP
    Guest scientist, U.S. Army Materials and Mechanics Research Center, Watertown, Mass.

    Underwood, JH
    Research engineer, U.S. Army Research and Development Command, Watervliet, N.Y.

    Throop, JF
    Research engineer, U.S. Army Research and Development Command, Watervliet, N.Y.

    Andrasic, CP
    Research scientist, The Royal Military College of Science, Shrivenham,


    Paper ID: STP37073S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP37073S


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