Fatigue strength of small-notched specimens under variable amplitude loading within the fatigue limit diagram

Y. Kondo, C. Sakae, Masanobu Kubota, S. Nagamatsu

    Research output: Contribution to journalArticlepeer-review

    2 Citations (Scopus)

    Abstract

    Although the fatigue limit diagram is defined in principle for constant stress amplitude, it is often considered that fatigue failure would not occur, even in varying loading, if applied stresses were kept within the fatigue limit diagram. However, it was shown in the case of small-notched specimens that fatigue failure occurred in some special cases of variable amplitude loading, even when all stress amplitudes were kept within the fatigue limit diagram. The cause of this phenomenon was examined using two-step stress and repeated two-step stress patterns in which the first step stress was chosen to be equal to the fatigue limit with zero mean stress and a mean stress was superposed on the second step stress. A non-propagating crack was formed by the first step stress. This crack functioned as a pre-crack for the second step stress with high mean stress. Consequently, fatigue failure occurred even when all stress amplitudes were kept within the fatigue limit diagram. It was an unexpected fracture caused by the interference effect of a non-propagating crack and a mean stress change.

    Original languageEnglish
    Pages (from-to)301-310
    Number of pages10
    JournalFatigue and Fracture of Engineering Materials and Structures
    Volume30
    Issue number4
    DOIs
    Publication statusPublished - Apr 1 2007

    All Science Journal Classification (ASJC) codes

    • Materials Science(all)
    • Mechanics of Materials
    • Mechanical Engineering

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