Fatigue crack growth threshold as a design criterion - statistical scatter and load ratio in the Kitagawa-Takahashi diagram
Abstract
Cracks in components reduce the endurable stress so that the endurance limit obtained from common smooth fatigue specimens cannot be used anymore as a design criterion. In such cases, the Kitagawa-Takahashi diagram can be used to predict the admissible stress range for infinite life, at a given crack length and stress range. This diagram is constructed for a single load ratio R. However, in typical mechanical engineering applications, the load ratio R varies widely due to the applied load spectra and residual stresses. In the present work an extended Kitagawa-Takahashi diagram accounting for crack length, crack extension and load ratio is constructed. To describe the threshold behaviour of short cracks, a master resistance curve valid for a wide range of steels is developed using a statistical approach.
- Publication:
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Materials Science and Engineering Conference Series
- Pub Date:
- March 2016
- DOI:
- 10.1088/1757-899X/119/1/012015
- Bibcode:
- 2016MS&E..119a2015K