Principles of Variable Amplitude Fatigue Design and Testing

    Volume 1, Issue 10 (November 2004)

    ISSN: 1546-962X

    CODEN: JAIOAD

    Published Online: 1 November 2004

    Page Count: 21


    Sonsino, CM
    Professor, Fraunhofer-Institute for Structural Durability (LBF), Darmstadt,

    (Received 16 April 2002; accepted 17 July 2003)

    Abstract

    The proper consideration of variable amplitude loading by utilizing service spectra and appropriate Gassner-lines is essential for the design of light-weight components and structures by allowing loads in significant excess of the Woehler-line (S-N curve). This permits higher stresses than under constant amplitude loading and renders reduced component dimensions. Reliable reconstitution and simulation methods for service load-time histories require not only the rainflow matrices, but also information about the order of the cycles described by Markovian matrices, the power spectral density and, for multiaxial applications, the cross-correlations between the particular load directions as well as the phase relations. A major problem in numerical fatigue life assessment is still the fatigue life calculations for spectrum loading, because of the scattering of the real damage sum D over a wide range, which is not entirely understood. These findings demonstrate the need for experimental spectrum tests, which are indispensable for ensuring the safety of parts. With regard to safety and liability requirements, the failure probability resulting from the probability of occurrence of the spectrum, from the scattering of the fatigue strength and from the failure criterion (technical crack or propagation), must be taken into account.


    Paper ID: JAI19018

    DOI: 10.1520/JAI19018

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    Author
    Title Principles of Variable Amplitude Fatigue Design and Testing
    Symposium Fatigue Testing and Analysis Under Variable Amplitude Loading Conditions, 2002-05-31
    Committee E08