International Journal of Aerospace and Lightweight Structures (IJALS)

Volume 1 Number 1 (2011)

doi: 10.3850/S2010428611000109

Crack Propagation Laws Corresponding to a Generalized El Haddad Equation

M. Ciavarella
Politecnico di Bari, 70125 Bari, Italy


The El Haddad equation permits to deal simply with both short and long cracks, and we have recently suggested a generalization for finite life, defining a “finite life intrinsic crack size”, as a power law of number of cycles to failure. Here, we derive the corresponding crack propagation law, finding that it shows features similar to Paris' law in the limit of long cracks, but shows some dependence of the “equivalent” $C,m$ Paris' material’ “constants” with applied stress range. The increase of crack propagation speed is obtained for short cracks, but additional size effects are derived, which may require quantitative validation, and correspond to the intrinsic difference with respect to the standard Paris' law.

Keywords: Fatigue design, Crack propagation, Critical distance approach.

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