Fatigue crack growth threshold as a design criterion - statistical scatter and load ratio in the Kitagawa-Takahashi diagram

International Conference on Materials, Processing and Product Engineering 2015

Kolitsch, S.^1,2 ; Gänser, H.-P.^1 ; Maierhofer, J.^1 ; Pippan, R.^2

Materials Center Leoben Forschung GmbH, Roseggerstraße 17, Leoben

A-8700, Austria^1

Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Department of Materials Physics, University of Leoben, Jahnstraße 12, Leoben

A-8700, Austria^2

关键词: Admissible stress;    Crack extension;    Endurance limit;    Engineering applications;    Fatigue specimen;    Resistance curves;    Statistical approach;    Statistical scatter;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/119/1/012015/pdf
DOI  :  10.1088/1757-899X/119/1/012015

来源: IOP

【 摘 要 】

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.