STP844

    Fatigue Properties of Ceramics with Natural and Controlled Flaws: A Study on Alumina

    Published: Jan 1984


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    Abstract

    A systematic study has been made of the fatigue properties of an as-fired polycrystalline alumina containing either “natural” (sawing damage) or indentation-induced (Vickers) strength-controlling flaws. All fatigue strengths were measured in four-point bending in water. The study is presented in three steps: first, comparative Weibull analyses are made of inert strength data for the two flaw types, both to demonstrate the reduction in scatter that attends the indentation method and to characterize the flaw distributions for the as-sawn surfaces; next, fatigue data are taken on indented surfaces to determine relatively accurate fracture parameters for the alumina and to confirm that constant stressing rate tests can be used as a base for predicting the response in static loading; finally, the results from the two previous, independent steps are combined to generate lifetime responses for the surfaces with natural flaws, and fatigue data taken on such surfaces are used to evaluate these predictions. It is emphasized that residual stresses around the critical flaws (associated either with the preceding contact events responsible for creating the flaws or with extraneous processing, preparation, or service conditions) can play a crucial role in the fracture mechanics. Notwithstanding this complication, the present approach offers a new design philosophy, with the potential for predicting responses relating to flaws generated after, as well as before, any laboratory screening tests.

    Keywords:

    alumina, fatigue, indentation flaw, lifetime prediction, residual stresses, strength testing, structural reliability, brittle materials


    Author Information:

    Gonzalez, AC
    Engineer, guest student, graduate student, physicist, and engineer, Center for Materials Science, National Bureau of Standards, Washington, D.C.,

    Multhopp, H
    Engineer, guest student, graduate student, physicist, and engineer, Center for Materials Science, National Bureau of Standards, Washington, D.C.,

    Cook, RF
    Engineer, guest student, graduate student, physicist, and engineer, Center for Materials Science, National Bureau of Standards, Washington, D.C.,

    Lawn, BR
    Engineer, guest student, graduate student, physicist, and engineer, Center for Materials Science, National Bureau of Standards, Washington, D.C.,

    Freiman, SW
    Engineer, guest student, graduate student, physicist, and engineer, Center for Materials Science, National Bureau of Standards, Washington, D.C.,


    Paper ID: STP35236S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP35236S


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