STP745

    Fracture Toughness of Glass Using the Indentation Fracture Technique

    Published: Jan 1981


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    Abstract

    Half-penny shaped cracks called median vents are formed about indentations made with sharp indenters in brittle materials. Two fracture mechanics analyses for the formation of median cracks exist and constitute a basis upon which the fracture toughness (Kc) can be obtained from indentation fracture experiments. However, little attention has been directed toward assessing the applicability of indentation fracture as a method for determining Kc in brittle materials.

    In this paper, such an evaluation of indentation fracture was performed on various glasses. Initially, indenter load-median crack length data were used to establish that the model of Lawn and Fuller described best the indentation fracture data. Their analysis was used to calculate Kc-values, which were compared to Kc-values obtained with conventional fracture mechanics methods. The difference in Kc-values determined by the two methods was ∼30 percent or less for normal glasses (glasses containing network modifier ions), and good reproducibility of indentation fracture Kc-values was found. A qualitative ranking of Kc by these two methods, however, did not agree. An evaluation of Kc by indentation fracture was not possible in anomalous (silica-rich) glasses due to the presence of cone cracks.

    Keywords:

    fracture toughness, indentation fracture, glass, fracture (materials), sharp indenters, crack propagation


    Author Information:

    Smith, SS
    Metallurgical engineer, General Electric Co., Wilmington, N.C.

    Magnusen, P
    Undergraduate research assistant and assistant professor, Michigan Technological University, Houghton, Mich.

    Pletka, BJ
    Undergraduate research assistant and assistant professor, Michigan Technological University, Houghton, Mich.


    Paper ID: STP28296S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP28296S


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