An experimental evaluation of fatigue crack growth

Composite repairs to bridge steels demystified

“…Following the development of composite repair technology it was subsequently found [1,[38][39][40][41] that cracks that grow in operational aircraft and in full scale fatigue tests and cracks growing beneath composite repairs often exhibit a (near) linear relationship between the log of the crack length and the number of cycles 6 which can be expressed in the form, viz:…”

“…Since as per [40,41,43,44,47,48] the value of  is proportional to the cube of the stress the value of after patching ( patch ) is related to its value prior to patching ( unpatched ) and the ratio of the change of stress due to patching, viz:…”

A multi-scale approach to crack growth

“…This expression coincides with that presented in [40,41,43]. More details on this derivation are given in 0.…”

“…It was also revealed 0 that such a crack growth law also corresponds to together with the realisation that "in the threshold regime, there is something missing either in the model…", see 0, led to the conjecture [40,41] that in the low ∆K region, i.e. Paris Region I, the crack growth rate can be expressed in the form:…”

“…The data presented in Fig. 5, along with that presented in [13,40,45] suggests that by using the cubic relationship we can estimate the growth rates at one stress level (σ 2 ) from those of another stress level (σ 1 ) given the initial crack size a 0 for the new crack and the value of λ for the original crack growth, viz:…”