STP678

    KIc and JIc of Westerly Granite—Effects of Thickness and In-Plane Dimensions

    Published: Jan 1979


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    Abstract

    An investigation is described in which tensile properties, fracture toughness, and critical J-integral are measured for Westerly granite, a rock that is used widely in rock mechanics studies. This was primarily a parameter sensitivity study in which the effects of specimen dimensions and testing techniques were assessed. It is hoped that this study will aid in establishing tentative standards and guidelines for fracture toughness testing of rock as well as indicate the feasibility of using a J-integral fracture criterion for this material.

    ASTM standard specimen configurations of the compact and bend types were tested with compact specimens ranging in width from W = 25.4 mm to W = 406.4 mm (0.5T to 8T) and with thickness ranging from 13 to 100 mm. A series of 4T compact specimens were tested to assess the effects of thickness and fatigue precracking.

    Techniques are described that enable several values of KIc, a complete J versus crack growth curve, and a JIc value to be obtained from each sample. Direct-pull tension tests on shaped specimens of Westerly granite are described which indicate a high degree of nonlinear, inelastic behavior. This fact raises questions about the use of linear elastic fracture mechanics, LEFM, but the JIc data presented appear to validate the KIc measurements.

    Keywords:

    fracture properties, fracture (materials), mechanical properties, fracture tests, size effect, fracture toughness, crack propagation, rock mechanics, rock (material)


    Author Information:

    Schmidt, RA
    Member of technical staff and engineering and science assistant, Sandia Laboratories, Albuquerque, N. Mex.

    Lutz, TJ
    Member of technical staff and engineering and science assistant, Sandia Laboratories, Albuquerque, N. Mex.


    Paper ID: STP36635S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP36635S


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