Fatigue Crack Closure at Near-Threshold Growth Rates in Steels, Effects of Microstructure, Load Sequence and Environment

    Volume 9, Issue 1 (January 2012)

    ISSN: 1546-962X

    CODEN: JAIOAD

    Published Online: 9 December 2011

    Page Count: 17


    Schaper, Michael K.
    Institute of Materials Science, Univ. of Technology Dresden,

    (Received 11 May 2011; accepted 18 October 2011)

    Abstract

    This paper summarizes long-term research on fatigue crack closure in several labs of the author. Various experimental techniques were used in different combinations. Primarily, a sophisticated dynamic compliance technique based on highly sensitive resonance vibration measurements and crack tip diffracted ultrasonic wave analysis is applied. Whereas the first method reflects the global through thickness behavior, the second method enables spatial resolution, which is achieved with a reduction of sensitivity yet has the advantage that the signal generation is independent on the stress state ahead of the crack tip. The results allow a coherent view into the effects of the stress state, material plasticity, fracture surface roughness, and oxidation tendency on the closure behavior and, therefore, on both the threshold stress intensity and near-threshold crack propagation. Specifically, the different load ratio, load sequence, and the environmental effects on the threshold values of ferritic, martensitic, and austenitic steels are addressed.


    Paper ID: JAI103968

    DOI: 10.1520/JAI103968

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    Author
    Title Fatigue Crack Closure at Near-Threshold Growth Rates in Steels, Effects of Microstructure, Load Sequence and Environment
    Symposium , 0000-00-00
    Committee E08