Size and Deformation Limits to Maintain Constraint in KIc and Jc Testing of Bend Specimens

    Published: Jan 1995

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    The ASTM Standard Test Method for Plane-Strain Fracture Toughness of Metallic Materials (E399-90) restricts test specimen dimensions to insure the measurement of highly constrained fracture toughness values (KIc). These requirements insure small-scale yielding (SSY) conditions at fracture, and thereby the validity of linear elastic fracture mechanics.

    Recently, Dodds and Anderson have proposed a less restrictive size requirement for cleavage fracture toughness measured in terms of the J-integral (Jc), as given by a,b,B ≥ 200 Jc0. The size requirement proposed by Dodds and Anderson increases the applicability of fracture toughness experiments by expanding the range of conditions over which fracture toughness data meeting SSY conditions can be reliably measured. This investigation compares the proposed size requirement with that of ASTM Standard Test Method E399 and, by comparison with published experimental data for various alloys, provides validation of the new requirements.


    size requirements, small scale yielding, experimental validation, E-399, fracture toughness

    Author Information:

    Koppenhoefer, KC
    Research Assistant, and Professor, University of Illinois, Urbana, IL

    Kirk, MT
    Edison Welding Institute, Columbus, OH

    Dodds, RH
    Research Assistant, and Professor, University of Illinois, Urbana, IL

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP14646S

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