STP72: Stress Concentration and the Fatigue Strength of Engine Components

    Gadd, Charles
    Research Laboratories Division of General Motors Corp., Detroit, Mich.

    Ochiltree, N. A.
    Research Laboratories Division of General Motors Corp., Detroit, Mich.

    Zmuda, Andrew
    Research Laboratories Division of General Motors Corp., Detroit, Mich.

    Pages: 11    Published: Jan 1947


    Abstract

    Estimates either of the relative or of the absolute mechanical strength of machine components must frequently be made by the engineer. Such an estimate will usually involve primarily, a consideration of the geometry of the part, or the manner in which stresses are concentrated as a result of changes in section. The stress analysis must then be placed in terms of fatigue strength through the application of endurance strength data obtained from the literature. A look into the literature, however, leaves one somewhat in doubt as to the validity of any strength estimate whatever, since most fatigue data are from simple beam type specimens which may not take properly into account the numerous pitfalls encountered in attempting to extrapolate to parts of complicated section and in the as-manufactured condition. For this reason the authors have, over the past several years, attempted to compile data for checking the theoretical strength of parts of complicated shape against their actual fatigue strength. In each case, the “theoretical” analysis has been by measurements of maximum local stress at the points of stress concentration, rather than by calculation, using either 1/16 or 1/8-in. extensometers, while the actual fatigue strength has been obtained by testing a sufficient number of factory-made specimens to permit the construction of a complete S-N diagram (1,2).


    Paper ID: STP47670S

    Committee/Subcommittee: E08.03

    DOI: 10.1520/STP47670S


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