Fatigue Damage in Wood

Christian Odin Clorius, Martin Bo Uhre Pedersen, Preben Hoffmeyer, Lars Damkilde

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    Abstract

    An investigation of fatigue failure in wood subjected to load cycles in compression parallel to grain is presented. Fatigue failure is found to depend both on the total time under load and on the number of cycles.Recent accelerated fatigue research on wood is reviewed, and a discrepancy between failure explanation under fatigue and static load conditions is observed. In the present study small clear specimens of spruce are taken to failure in square wave formed fatigue loading at a stress excitation level corresponding to 80% of the short term strength. Four frequencies ranging from 0.01 Hz to 10 Hz are used. The number of cycles to failure is found to be a poor measure of the fatigue performance of wood. Creep, maximum strain, stiffness and work are monitored throughout the fatigue tests. Accumulated creep is suggested identified with damage and a correlation between stiffness reduction and accumulated creep is observed. A failure model based on the total work during the fatigue life is rejected, and a modified work model based on elastic, viscous and non-recovered viscoelastic work is experimentally supported, and attempted explained at a microstructural level. The outline of a model explaining the interaction of the effect of load duration and the effect of the loading sequences is presented.
    Original languageEnglish
    Title of host publicationProceedings of the 1996 International Conference on Wood Mechanics
    Place of PublicationStuttgart
    PublisherFMPA
    Publication date1996
    Pages243-258
    Publication statusPublished - 1996
    Event1996 International Conference on Wood Mechanics - Stuttgart, Germany
    Duration: 14 May 199616 May 1996

    Conference

    Conference1996 International Conference on Wood Mechanics
    CountryGermany
    CityStuttgart
    Period14/05/199616/05/1996

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