Fracture Toughness Determined by the Centrally Cracked Brazilian-Disc Test: Some Critical Issues in the Light of an Alternative Analytic Solution

    (Received 30 September 2013; accepted 25 November 2013)

    Published Online: 2014

    CODEN: MPCOAD

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    Abstract

    The centrally cracked Brazilian-disc test is among the configurations proposed for the experimental determination of fracture toughness of brittle rock-like materials. In spite of its wide use and the fact that the test is already standardized by the International Society for Rock Mechanics (ISRM), quite a few issues are still open related especially to the exact expressions of the respective stress intensity factors (SIFs) and the actual shape of the crack during loading. The latter is crucial since for specific crack inclinations, the crack lips are coming in contact and contact stresses appear which alter the boundary conditions, rendering analytic solutions erroneous. In this context, an alternative analytic approach is here introduced assuming that the cracked disc is under uniform pressure along two finite symmetric arcs of its periphery. The main advantage of the present approach is that it provides physically acceptable results independently of whether the crack is under opening- or closing-mode. The results of the analysis are validated against experimental data obtained using the method of Caustics and the Digital Image Correlation (DIC) technique. Based on the analytic solution, some critical practical aspects of the cracked Brazilian-disc test are explored including the influence of the loading type and the length of the loaded arc, the role of the specimen's thickness, the range of crack inclination angles for which generation of contact stress is unavoidable, and the rotation of the crack axis. Moreover, a redefinition of the SIFs in case of Mixed Fundamental problems is proposed. The limitations of the analysis are critically considered and finally some thoughts about the future steps concerning the fracture toughness determination using the cracked Brazilian-disc test are discussed.


    Author Information:

    Kourkoulis, S. K.
    Department of Mechanics, School of Applied Mathematical and Physical Sciences, National Technical Univ. of Athens, Athens,

    Markides, C. F.
    Department of Mechanics, School of Applied Mathematical and Physical Sciences, National Technical Univ. of Athens, Athens,


    Stock #: MPC20130056

    ISSN: 2165-3992

    DOI: 10.1520/MPC20130056

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    Title Fracture Toughness Determined by the Centrally Cracked Brazilian-Disc Test: Some Critical Issues in the Light of an Alternative Analytic Solution
    Symposium , 0000-00-00
    Committee E08