Published online by Cambridge University Press: 28 July 2016
In the past attempts have been made to correlate the estimated load variations which the component will experience during a stipulated lifetime (in hours) with estimations of the fatigue strength (in cycles of loading) for typical structural components, such as wing spar boom joints, riveted joints, and so on. The trend of thinking so far has been that one should design for a certain fatigue life. In this paper it is shown that, even with the most careful attention given to the detail design of aluminium alloy components, it is not possible to attain what has been regarded hitherto as the minimum acceptable fatigue strength for typical structures, i.e. 2 x 106 cycles of 1g±7½ per cent. ultimate strength of the structure, based on present British Civil Airworthiness Requirements (Reserve Factor 1.0). There is no implied criticism of the criterion which is an ideal one, and if structures attained the criterion then the fatigue life would be adequate.