Volume 19, Issue 2 (March 1991)

    Specimen Size Requirements for Fracture Toughness Testing in the Transition Region

    (Received 18 December 1989; accepted 20 July 1990)

    CODEN: JTEOAD

      Format Pages Price  
    PDF 12 $25   ADD TO CART


    Abstract

    The article utilizes plane strain elastic-plastic finite element analysis and a local criterion for cleavage fracture to establish specimen size requirements for the ductile-brittle transition region. Critical J and CTOD values, relative to the small-scale yielding value, were predicted as a function of specimen size, strain hardening exponent, and a/W. These analyses predict an increase in the apparent toughness with decreasing specimen size due to a loss in crack tip constraint; this effect is particularly pronounced in shallow notched specimens and low hardening materials. For deeply notched bend and compact specimens, the following size requirement must be met for critical J values for cleavage to be size independent: b,B,a>200JcσY where b is ligament length, B is thickness, a is crack length, and σγ is flow stress. This criterion is eight times more severe than the size requirements in ASTM E 813-87, but it is less stringent than the requirements of ASTM E 399-83. In order for a CTOD value to be nearly size independent, it must be less than 1/300 times the relevant specimen dimensions.

    The constraint loss in shallow notched specimens is usually far too rapid to obtain J-controlled cleavage fracture, but the analyses presented in this article provide a means for correcting fracture toughness data for constraint loss. Predictions of the effect of a/W on toughness in the transition region agree favorably with experimental data.

    Future work will consider the effects of specimen thickness and ductile tearing on transition region toughness.


    Author Information:

    Anderson, TL
    Assistant Professor, Texas A&M University, College Station, TX

    Dodds, RH
    Professor, University of Illinois, Champaign-Urbana, IL


    Stock #: JTE12544J

    ISSN: 0090-3973

    DOI: 10.1520/JTE12544J

    ASTM International is a member of CrossRef.

    Author
    Title Specimen Size Requirements for Fracture Toughness Testing in the Transition Region
    Symposium , 0000-00-00
    Committee E08