J.M.L. Tan, M.E. Fitzpatrick, L. Edwards

This paper describes work undertaken to predict fatigue crack growth from StressWave? cold-worked holes in aerospace aluminium alloys. The Stress Wave? process is a novel cold working technique capable of generating symmetric residual stress distribution around treated holes. This new technology can potentially provide increased costefficiency and operational flexibility compared to conventional fatigue life enhancement procedures of fastener holes in structures. However, experimental and predictive knowledge of fatigue crack growth at StressWave? cold-worked holes must be firstly obtained if the technique is to be included in damage tolerance of structural design and optimisation, as well as in service maintenance. The residual stress field around a StressWave? cold-worked hole was determined using neutron and X-ray diffraction. A novel Greens function method has been developed to calculate the stress intensity factor for cold expanded hole. The Greens function model is capable of handling arbitrary stress field acting along the crack flanks of single through-thickness flaw emanating from hole. Using the concept of average SIP along the straight-fronted crack, the representative stress intensity factor is obtained by integrating the average surface stress field determined by X-ray diffraction. This SIP solution is then used to describe the fatigue crack growth of through-thickness cracks artificially initiated from the hole edge with residual stress field created by the Stress Wave process. This enabled the fatigue life predictions to be made using AFGROW and two predictions philosophies, based on (i) mean stress, and (ii) crack closure effects. Reasonable agreement was found between these predictions and our laboratory data. Possible further work to improve the accuracy and reliability of the predictions is also discussed.

23rd ICAF Symposium of the international Committee on Aeronautical Fatique, 2005, Hamburg

Conference Poster

englisch

A5, 16 Seiten

DGLR-Bericht, 2005, 2005-03, 23rd ICAF Symposium of the international Committee on Aeronautical Fatique - Proceedings; S.706-721; 2005; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

fatigue life, predictions, greens function, residual stress

Bestellbar

2005