Ductility, Fracture Resistance, and R-Curves

    Published: Jan 1976

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    A method for analytical predictions of the thickness effect on fracture toughness, and of R-curves is presented. It is based on the recent observation that the fracture resistance KR is proportional to the local fracture strain εF,αβ, where α = σ21, and β = σ31 characterize the local stress state. As this stress state varies from the surface, where it is plane stress (α = 0, β = 0.61), to the center, where it approaches plane strain (α = 0.81, β = 0.61) for sufficiently thick specimens, the local fracture resistance varies correspondingly. The model proposed here assumes that the measured fracture resistance represents the average of the local GR values along the crack front. The calculated thickness effect is in excellent agreement with experimental results. From the same model an analytical expression for R-curves is suggested with the additional consideration of the relation between the plastic zone size as a function of crack growth. The preliminary results of the predicted R-curves are in reasonable agreement with the experimental curves.


    crack propagation, ductility, fracture strength, stress analysis, plastic deformation, aluminum, stainless steels

    Author Information:

    Weiss, V
    Professor and research assistant, Syracuse University, Syracuse, N.Y.

    Sengupta, M
    Professor and research assistant, Syracuse University, Syracuse, N.Y.

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP33946S

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