Finite element investigation of fatigue initiation in 1.5 single-shear lap joints with Hi-Lok fasteners including the effect of CIC treatment

This study used Finite Element (FE) modelling to investigate how CIC application changes the expected fatigue initiation behaviour in 1.5 single-shear lap joint samples. The FE models included the Hi-Lok interference fit and clamping force, as well as the frictional differences with and without CIC application. Results from the modelling were processed via various fatigue equivalent cyclic stress or strain methods to estimate the crack initiation location, or “hotspot”, and whether there was likely to be a change in the initiation duration with CIC application. The experimental results showed an eyebrow fretting damage zone above fastener the holes where the majority of fatigue cracks originated (for both the with and without CIC cases). The FE modelling demonstrated that many of the considered hotspot methods were able to correctly predict the eyebrow stress concentration zone. However, not all methods were able to predict whether the initiation duration was likely to increase or decrease with application of CICs. The best method was a fretting based parameter, which correctly predicted the increase in life with CIC application. Overall, this study highlights which fatigue equivalent cyclic stress/strain methods are suitable to account for the effects of CIC application in lap joints. • Finite element modelling of lap joints was used to predict fatigue initiation. • Fatigue equivalent cyclic stress/strain methods were compared against experiments. • Most methods unable to account for corrosion inhibiting compound (CIC) application. • Only a fretting based parameter was able to predict changes with CIC application. • Fatigue crack initiation in lap joints is driven by local stress and fretting work.