On the fatigue enhancement of interference fitted stop drilled holes

This article presents a study of the fatigue life enhancement of a through-cracked plate specimen using combined interference fitting and cold expansion of stop-holes. Finite element analysis has been carried out to quantify the effect of combined cold expansion and the use of interference plugs on the growth behaviour of fatigue cracks emanating from stop-holes. It is found that although the use of interference plugs has no discernible effect on the stress/strain distributions under a static remote tension load, it does significantly reduce the magnitude of cyclic strain under fatigue loading. To model the growth behaviour of short cracks re-initiated from the stop-holes, both linear elastic fracture mechanics and elastic-plastic fracture mechanics analyses have been conducted to determine the crack growth driving force. The results show that equivalent stress intensity factors determined from the crack-tip opening displacement are significantly higher than those predicted based on linear elastic fracture mechanics. Finally predictions of fatigue lives are made based on the equivalent stress intensity factors via a fatigue crack growth code (FASTRAN), which appear to correlate well with experimental results. (C) 1999 Elsevier Science Ltd. All rights reserved.