In order to understand the effect of local aerodynamic intake loads in addition to the regular primary flight loads on fatigue cracking in the F-111 aircraft nacelle former and surrounding intake structure, a numerical procedure has been developed. The cracking is characterised by local cyclic notch plasticity resulting in residual stresses. Previous analysis ignored the effect of the intake loads, and its result did not correlate well with service reported cracking. The stress distribution in the vicinity of the notch was calculated using a nonlinear kinematic hardening cyclic plasticity model and a generalised form of Neuber’s rule. The stress intensity factors were calculated using the Green’s function approach. Numerical results show that the intake loads have two effects; they change the magnitude of the stress, and they cause the mean spectrum stress to be reduced. The overall effect retards the fatigue crack growth. The resulting crack growth prediction including the intake loads and an improved cyclic plasticity model correlates significantly better with in-service data than the previous analysis
