STP821: Threshold-Stress Determination Using Tapered Specimens and Cyclic Stresses

    Fessler, RR
    Department Manager, Transportation and Structures, and Principal Research Scientist, Battelle Columbus Laboratories, Columbus, Ohio

    Barlo, TJ
    Department Manager, Transportation and Structures, and Principal Research Scientist, Battelle Columbus Laboratories, Columbus, Ohio

    Pages: 15    Published: Jan 1984


    Abstract

    Traditional methods of determining the threshold stress for stress-corrosion cracking involve testing a number of specimens that are loaded to various levels of constant initial stress. In research sponsored by the Pipeline Research Committee of the American Gas Association, it was shown that low-frequency, small-amplitude cyclic loads superimposed on a constant load can reduce the threshold stress substantially. Since such loading can occur on real structures, it was felt that the threshold stress should be determined under those more severe and realistic conditions. Furthermore, by using a specimen with a tapered gage section, a range of stresses could be evaluated in a single test, making it possible, in principle, to determine the threshold stress with one or two specimens. Test procedures involving tapered specimens and cyclic loads superimposed upon a constant load are described, and representative data for various line-pipe steels are presented. The test environment consisted of a water solution of sodium carbonate and sodium bicarbonate, and the temperature was controlled at 352 K (175°F). The potential was controlled potentiostatically at the center of the range in which stress-corrosion cracking occurs. Test durations typically were 1 to 2 weeks.

    Keywords:

    stress corrosion, tests, cyclic loads, sodium carbonate, pipelines, steel


    Paper ID: STP34443S

    Committee/Subcommittee: G01.06

    DOI: 10.1520/STP34443S


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