STP631

    Fracture Analysis Under Large-Scale Plastic Yielding: A Finite Deformation, Embedded Singularity, Elastoplastic Incremental Finite-Element Solution

    Published: Jan 1977


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    Abstract

    The potential of the well-known J-integral as a fracture initiation criterion has been demonstrated in recent experiments by Begley and Landes and others. This paper deals with a numerical procedure for the estimation of J-integral and for arbitrary strain-hardening materials, in general situations of ductile fracture under large-scale yielding conditions. A finite-deformation analysis is employed to study the effects of crack-tip blunting. An incremental “tangent modulus” finite-element method has been used to account for both the geometric nonlinearity and the elastoplastic strain-hardening material behavior. A kinematic hardening law was used to describe the incremental plastic flow. Strain and stress singularities, corresponding to the material model, have been embedded in finite elements near the crack tip. Displacement and traction continuities between these near-tip elements and the surrounding elements have been enforced through the hybrid-displacement, finite-element model. This numerical procedure has been used to solve the case of a three-point bend specimen of Ni-Cr-Mo-V steel for which experimental results are also available. Excellent correlation between the present results and available experimental results has been established for the J versus δ (load-point displacement) relatinships. To characterize the effect of crack-tip blunting, the present example also has been solved using a small-deformation theory, and solutions are compared with those from the present finite-deformation analysis. The implication of the results in predicting crack-growth initiation and its stability in ductile materials is discussed. By using the modified definition of J-integral as valid for finite deformation, it has been found that approximate path independence of J is maintained, accurately, even for a contour closest to the crack tip.

    Keywords:

    crack propagation, fractures (materials), finite-deformation effects, finite-element method, strain hardening


    Author Information:

    Atluri, SN
    Professor, postdoctoral fellow, and graduate student, School of Engineering Science and Mechanics, Georgia Institute of Technology, Atlanta, Ga.

    Nakagaki, M
    Professor, postdoctoral fellow, and graduate student, School of Engineering Science and Mechanics, Georgia Institute of Technology, Atlanta, Ga.

    Chen, W-H
    Professor, postdoctoral fellow, and graduate student, School of Engineering Science and Mechanics, Georgia Institute of Technology, Atlanta, Ga.


    Paper ID: STP35531S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP35531S


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