Digital Repository, ICF12, Ottawa 2009

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Some Considerations on the Prediction of Fatigue Crack Growth Retardation in Structural Materials
M. V. Pereira, F.A. Darwish, A. F. Camarão, S. H. Motta

Last modified: 2013-05-06


The purpose of this work is to evaluate the applicability of the Willenborg model
to predicting residual fatigue life extension in an R3 grade structural steel and a
7150 T7 aluminum alloy. Compact tension specimens were subjected to a single
overload during constant amplitude loading and crack propagation rate da/dN
was monitored as a function of the stress intensity factor range ΔK. The size of
the delay zone as well as the number of the delay cycles were predicted by the
model and then compared with the experimental data. Whereas the predicted
delay zone size was found to be in good agreement with the experimental
observations, the application of the model to predict the retardation factor may
lead, depending on the intensity of overloading, to under- or overestimating
crack propagation rate within the delay zone. This, in turn, could result in an
imprecise estimate of the delay cycles number and hence of the residual fatigue

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