STP945

    An Elastic-Plastic Finite-Element Analysis of the J-Resistance Curve Using a CTOD Criterion

    Published: Jan 1988


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    Abstract

    The tentative test procedure for determining J-R curves (crack-growth resistance curves based on the J-integral) on compact and three-point bend specimens showed a discrepancy between specimen types: the bend specimen gave a higher J-R curve than the compact specimen. The purpose of this paper is to investigate this discrepancy, numerically, by simulating the fracture process on compact and bend specimens using a two-dimensional finite-element analysis and a critical crack-tip opening displacement (CTOD) criterion.

    An elastic-plastic (incremental and small strain) finite-element analysis was used with the critical CTOD criterion to model stable crack growth in compact specimens made of HY-130 steel. A combined analysis between plane-stress and plane-strain conditions was found to simulate the fracture process quite well. In the combined analysis, plane-strain conditions were imposed around the crack tip while plane-stress conditions were imposed elsewhere. The same analysis was then used to predict stable crack growth behavior of bend specimens. J-R curves were then calculated from the numerical results for each specimen type using several different methods. In general, the J-R curves obtained from the bend specimens were higher than those obtained from the compact specimens, especially beyond maximum load. Up to maximum load, however, the modified deformation theory of plasticity J*D and the contour-integral JΓ methods gave essentially the same J-R curves for both specimen types.

    Keywords:

    fracture, cracks, plastic deformation, stress analsis, finite-element method, J-integral, crack-tip opening displacement


    Author Information:

    Newman, JC
    Senior scientist, NASA Langley Research Center, Hampton, VA

    Booth, BC
    Former graduate student, The Johns Hopkins University, Baltimore, MD

    Shivakumar, KN
    Senior scientist, Analytical Services and Materials, Inc., Hampton, VA


    Paper ID: STP23268S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP23268S


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