STP803V1: Influence of Time-Dependent Plasticity on Elastic-Plastic Fracture Toughness

    Ingham, T
    Senior scientific officer and scientific officer, Risley Nuclear Power Development Laboratories, U.K. Atomic Energy Authority, Risley, Warrington, Cheshire

    Morland, E
    Senior scientific officer and scientific officer, Risley Nuclear Power Development Laboratories, U.K. Atomic Energy Authority, Risley, Warrington, Cheshire

    Pages: 26    Published: Jan 1983


    Abstract

    The paper describes the results of preliminary experiments to examine the effect of time-dependent plasticity on ductile crack growth, resistance to ductile tearing, and instability in laboratory fracture toughness tests. Experiments on a carbon-manganese (C-Mn) steel and two specimens of A533B-1 steel have shown that unstable ductile fractures can be induced at ambient temperature when 20- and 40-mm-thick compact specimens are held at constant loads between the load approximating that for crack initiation and the maximum load attained in a conventional displacement-controlled fracture toughness test; the time to failure after holding at constant load decreases with increasing constant load level and increasing strain rate prior to load-holding. The data suggest that final failure occurs under conditions paralleling “tertiary creep” behavior. Specimens were loaded at typical rates used in “static” fracture toughness testing and at a slower rate where the maximum load condition was reached in approximately 24 h. Crack extension under constant load has been related to J-resistance curves derived from multispecimen displacement-controlled tests.

    The J-resistance curve for C-Mn steel specimens is dependent upon strain rate at rates of loading which are conventionally taken to be representative of “static” conditions. This effect was not observed in tests on A533B-1 steel.

    Keywords:

    constant load, creep, displacement control, ductile, initiation, J, -controlled growth, load-control, plastic collapse, R-curves, strain rate, time dependence, upper shelf, carbon-manganese, A533B-1 steels, elastic-plastic fracture


    Paper ID: STP37325S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP37325S


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