Modified NASGRO equation for physically short cracks

By J. Maierhofer, R. Pippan, H. Gänser. 2014

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Abstract A typical fatigue crack growth curve consists of the threshold region, the Paris region (linear in a logarithmically scaled diagram) and the transition region from the Paris region to unstable crack growth. For cracks exceeding a certain material-dependent length, this curve depends only on the load ratio R and is well described by commonly accepted crack growth models such as the Forman/Mettu (NASGRO) equation. However, cracks below this length typically grow significantly faster due to the absence of crack-closure effects, leading to an additional dependence of the crack growth curve on the crack extension Δ a . In this paper, a simple analytical model for describing the crack growth behavior for any crack length and load ratio R is presented. For the QT steel 25CrMo4, the model is applied to describe the crack growth behavior for different crack length and load ratios between −3 and 0.5.

Subfields: Civil and Structural Engineering, Mechanical Engineering, Mechanics of Materials

View Paper: https://www.semanticscholar.org/paper/ce6438c5e4d7fff1a239209b4af30c1cda3593b4