STP536

    Overload Effects on Subcritical Crack Growth in Austenitic Manganese Steel

    Published: Jan 1973


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    Abstract

    Single and intermittently repeated tensile overloads were applied to precracked compact type specimens using austenitic manganese steel which strain hardens under cyclic loading. Delayed crack retardation following overloading was observed macroscopically and verified microscopically with a scanning electron microscope. Crack growth during delayed retardation varied up to 0.10 in. or up to about 30 percent of the overload reversed plane stress plastic zone size and involved up to 6×103 cycles. Total crack retardation life varied from 50–6000 percent. Single tensile overloads, in general, tended to produce the greatest crack growth retardation compared with intermittently repeated tensile overloads. This behavior is best explained by comparing ΔN with ΔNag. The greater the single overload, the larger the crack growth retardation. Likewise, for a given number of cycles between overloads, the greater the overload force, the larger the crack growth retardation. Use of the crack growth equation da/dN=A(ΔK)n for single and periodic intermittent overloads is conjectural since n takes on negative, zero, and positive values, and a substantial percentage of the total life involves negative and zero values of n. Single compressive overloads decreased crack growth life up to 23 percent.

    Keywords:

    fatigue (materials), fracture properties, stresses, strain hardening, overloads, crack propagation, striations, cracks, residual stress, plastic deformation, retarding, steels, mechanical properties


    Author Information:

    Rice, R. C.
    research assistant, University of IowaBattelle Memorial Institute, Columbus, Ohio

    Stephens, R. I.
    Professor, University of Iowa, Iowa City, Iowa


    Paper ID: STP49639S

    Committee/Subcommittee: E08.06

    DOI: 10.1520/STP49639S


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