Three models are evaluated for their capability in modelling short and long crack growth using long crack growth rate data. The models considered are the El Haddad model which a crack size dependent on the threshold stress intensity range is added to the physical crack length, so that ΔK is proportional to {the square root of}(a + a_0) instead of {the square root of}a; the FASTRAN model which adds a plastic zone size dependent fictitious crack size to the physical crack; and the C~* model (Molent, L., R. Jones, S. Barter, and S. Pitt, Int J Fat, 2006. 12: 1759), which is a different representation of the Frost-Dugdale model. The first two models aim to achieve a desirable effect, i.e., increasing the crack growth rate when the crack is short while diminishing the effect when the crack becomes longer. The objective of this paper is to evaluate the capability of these three models, and a combination of the first two models, in treating short and long crack growth in a unified manner, and to illustrate their merits and shortcomings.
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