Propagation and non-propagation of small fatigue cracks

ABSTRACT The propagation and non-propagation of small fatigue cracks at the notch root were studied in the first part of the present paper. A resistance-curve method was proposed for predicting the growth threshold of mechanically short cracks on the basis of the experimental results on the development of crack closure. The effects of material, notch geometry, and mean stress on the growth threshold of short cracks and the notch fatigue strength were successfully predicted by the resistance-curve method. In the second part, the propagation behaviour of small fatigue cracks in smooth specimens was examined. A micromechanical model of small crack growth was combined with statistical simulation of crack growth for life prediction. The fatigue failure diagram was constructed to judge the threshold condition for small crack growth.

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