STP700: Fully Plastic Crack Solutions, Estimation Scheme, and Stability Analyses for the Compact Specimen

    Kumar, V
    Mechanical engineers, Corporate Research and Development, General Electric Co., Schenectady, N.Y.

    Shih, CF
    Mechanical engineers, Corporate Research and Development, General Electric Co., Schenectady, N.Y.

    Pages: 33    Published: Jan 1980


    Abstract

    This paper presents the fully plastic solutions for the compact specimen and an estimation scheme that exploits these solutions to generate crack driving force diagrams under contained and large-scale plasticity conditions.

    Plane-strain and plane-stress fully plastic solutions for compact specimens are obtained for a wide range of crack length to width ratios and for hardening exponent n of up to 20. The calculations are based on deformation plasticity theory and use the finite element method for incompressible deformation developed by Needleman and Shih. Relevant crack parameters like the J-integral, crack opening displacement, mouth opening displacement, and load-line displacement are appropriately normalized and tabulated. Simple formulas are given for estimating the relevant crack parameters from contained yielding to fully plastic situations using the elastic and the tabulated fully plastic solutions. The results thus obtained are compared with accurate finite element solutions for stationary and extending cracks based on flow theory of plasticity.

    Crack driving forces in terms of the J-integral and crack opening displacement are computed for A533B compact specimens using the above estimation scheme. Assuming that the conditions for J-controlled growth are satisfied, the load-displacement behavior, stable crack extension, and the point of instability can be determined from the crack driving force diagrams if the material J-resistance curve is known. Comparisons of the predictions with actual test measurements for several different sized compact specimens show good agreement.

    Keywords:

    compact specimen, plane strain, plane stress, fully plastic solutions, elastic-plastic estimation scheme, crack growth, instability, creep crack growth, limit load, J-integral, crack opening displacement, resistance curve, tearing modulus, fractures (materials), crack propagation


    Paper ID: STP36983S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP36983S


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