Recent developments in fatigue crack growth assessment

This paper examines the fatigue crack growth histories, at low to mid range ΔK’s, for a range of aircraft aluminium alloys, test specimens and service loaded components. It concludes that the crack growth history shows that, as a first approximation, there is a log–linear relationship between the apparent crack length or depth and the life (N), respectively. This leads to the further observation that, for the range of materials and spectra considered here, there is a linear relationship between the crack growth rate and the crack length when plotted on a log–log scale.