STP868: Effects of Load Gradient on Applicability of a Fatigue Crack Growth Rate-Cyclic J Relation

    Jolles, M
    Head, Fracture Mechanics Section, Naval Research Laboratory, Washington, DC,

    Pages: 11    Published: Jan 1985


    Abstract

    The use of a cyclic J to characterize fatigue crack growth rates for conditions where the assumptions of linear elastic fracture mechanics are violated is addressed. In particular, the effects of the load gradient on the applicability of a cyclic J are examined. Experiments were conducted to quantify fatigue crack growth rates and cyclic J on modified compact tension specimens of A533B steel. Fatigue cycling at constant load amplitude where the cyclic J increases as the crack extends and constant displacement amplitude where the cyclic J decreases as the crack extends were performed. It is found that prior cyclic crack tip history affects the fatigue crack growth rate only as a consequence of influencing the extent of crack closure. Accounting for crack closure by requiring J equal to zero at the crack opening load results in excellent correlation between the fatigue crack growth rate and cyclic J for a wide range of loading conditions.

    Keywords:

    fracture mechanics, elastic-plastic fracture, J, -integral, fatigue crack growth


    Paper ID: STP34264S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP34264S


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