Fatigue behavior of an airfoil with tolerable exfoliation cracks induced by dynamic corrosion: Experimental and numerical assessment

•Fluid flow varied the pit morphology and concentration in the dynamic corrosion.•Shallow cracks with a surface open edge were induced in the corroded airfoil.•An allowable flaw size acted only as a stress concentrator.•Cracks in the leading-edge reduced the residual fatigue strength of the AA 2024-T3.•Load increment can increase the crack growth rate six times at the same degradation. Pitting corrosion creates preferential sites for cracks formation by the exfoliation process, which grow due to the continuous action of flight loads, even those of constant amplitude (CA). Whether the find-fix protocol must repair all defects, some may go unnoticed due to their sizes or locations in the aircraft. For this reason, it is necessary to study the fatigue behavior of airfoils with defects (cracks), analyzing their growth rates and the affectation on residual strength. This research work studied experimental and numerically fatigue performance of an airfoil with initial defects caused by dynamic corrosion. Intentionally, single-edge cracks (SECs) formation was induced in three wing skin regions: leading and trailing edges and central zone. The pre-corroded airfoil was subjected to alternate drag and lift forces to assess the crack growth and take validation data as deflection and the load level. The low stress intensity factor (SIF) estimated by means of a 3D finite element (FE) numerical model indicated that cracks did not propagate. Even though the stress level in the crack tip remained under the fatigue limit, giving rise to infinity life, the degraded material residual strength was considerably reduced. Also, the estimations obtained from an FE 1D model considering the damage factor and the mechanical properties loss in the crack region corroborated the infinity life behavior. Numerical and experimental results could determine an allowable flaw size under CA load conditions. However, the load variation play an important role increasing crack growth rate up to six times.