Citation:
X. Zhang and Z. Wang, Fatigue life improvement in fatigue-aged fastener holes
using the cold expansion technique, International Journal of Fatigue, Volume 25,
Issues 9-11, September-November 2003, Pages 1249-1257.
Abstract:
The use of cold expansion process as a life extension technique on aircraft
structural joints was investigated. The primary focus was an experimental test
programme consisting of open-hole and low-load transfer joint specimens made of
2024-T351 aluminium alloy and pre-fatigued to 25, 50 and 75% of the baseline
fatigue life for plain holes. The FALSTAFF loading spectrum was applied. The
results indicate that significant life improvements can be obtained through cold
expansion applied at all percentages of fatigue life tested in this work with
the optimum stage being around 25% of the baseline life. The major life
extension was obtained through slower crack growth in the short crack stage. The
life improvement factors for the open-hole and joint specimens were comparable
provided that the degree of cold expansion is the same. Crack growth life of the
open-hole specimen was predicted by employing an analytical residual stress
model and the AFGROW computer code. The prediction results showed good agreement
with the experimental results for cold expansion at build cases.
