Experimentally derived crack growth models for different stress concentration factors

This paper summarises the investigation into a unique set of fatigue crack growth data involving coupons containing three different stress concentration factors (Kt) tested at various stress levels. Crack growth history data were determined through the use of quantitative fractography (QF). These coupons were made of 7050 aluminium alloy, and were tested with the same representative F/A-18 aircraft fatigue usage wing root bending moment spectrum. These data were used in the analysis of fatigue crack growth from the various Kts and also in the development of crack growth models capable of predicting the fatigue crack growth history at one Kt from data obtained at a different Kt. These models were based on the stress dependency of the Paris parameter C.