Assessing the Loading Rate for a Fracture Toughness Test in the Ductile-to-Brittle Transition Region

    Volume 5, Issue 3 (March 2008)

    ISSN: 1546-962X

    CODEN: JAIOAD

    Published Online: 27 March 2008

    Page Count: 8


    Lucon, Enrico
    SCK•CEN, Institute for Nuclear Material Science, Boeretang 200,

    Scibetta, Marc
    SCK•CEN, Institute for Nuclear Material Science, Boeretang 200,

    (Received 3 October 2007; accepted 18 February 2008)

    Abstract

    For fracture toughness tests in the ductile-to-brittle transition region, ASTM E1921-05 requires specimens to be loaded using a loading rate dK/dt between 0.1 and 2 MPa√m/s during the initial elastic portion. It has been proposed that the standard allow testing at higher loading rates, including precracked Charpy specimens tested on an instrumented pendulum machine (impact toughness tests). The revised standard would require test results (KJc or To) to be reported along with the relevant loading rate, and should therefore provide guidance on how to assess the value of dK/dt in a relatively simple but reliable manner. Various options for measuring the loading rate have been investigated in this paper for several fracture toughness tests performed at different loading rates (quasi-static, dynamic, and impact). For each loading rate, three different toughness levels have been considered: low, medium, and high. Three considerably different materials have been selected: two RPV steels (JRQ, JSPS) and a ferritic/martensitic 9 % chromium steel (EUROFER97). It is found that the preferable option is given by the ratio between KJc and time at the onset of cleavage, whereas the elastic value Kel/tel or the average dK/dt can be used when partial unloadings are performed.


    Paper ID: JAI101467

    DOI: 10.1520/JAI101467

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    Author
    Title Assessing the Loading Rate for a Fracture Toughness Test in the Ductile-to-Brittle Transition Region
    Symposium Seventh International ASTM/ESIS Symposium on Fatigue and Fracture Mechanics (36th ASTM National Symposium on Fatigue and Fracture Mechanics), 2007-11-16
    Committee E08