On the prediction of the residual fatigue life of cracked structures repaired by the stop-hole method

The stop-hole method is a simple and economic repair technique widely used to retard or even to stop the propagation of a fatigue crack in structural components that cannot be replaced immediately after the detection of the crack. Its principle is to drill a hole at or close to the crack tip to transform the crack into a notch, reducing in this way its stress concentration effect. The fatigue life increment that can be achieved with this technique can be modeled by assuming that it is equal to the number of cycles required to re-initiate the crack at the resulting notch root, which depends at least on the crack size and on the hole diameter. The aim of the present work is to predict the fatigue crack initiation lives by employing classical εN concepts properly modified by short crack theory to model the stop-hale effect. The comparison among the experimental and the calculation results show that the life increment caused by the stop-holes can be effectively predicted in this way.