Experimental and FEM analysis of fatigue behavior of impact‑damaged 7075‑T6 aluminum components

• Experiments and FEM for impact damage in 7075-T6 aluminum aerospace components. • Johnson–Cook plasticity and failure laws for stress–strain state after impact. • Fatigue life remains nearly constant across 75–100 m/s impact speeds. • Residual stresses dominate cyclic stress distribution in damaged components. This study investigates the fatigue strength of 7075‑T6 aluminum hourglass specimens subjected to perpendicular impact loading via experimental tests and finite element analysis. In the experimental campaign, a single impact dent was created at the minimum cross‑section of each specimen using steel spheres at nominal speeds of 75, 87.5, and 100 m/s. The damaged specimens were subsequently tested under an identical rotating bending moment amplitude across all impact conditions to assess their fatigue lives. The finite element study was conducted in two phases. In the first phase, the Johnson–Cook plasticity model was adopted to assess the post‑impact stress–strain state, and the Johnson–Cook failure law was included to simulate potential damage during impact. In the second phase, stress evolution during rotating bending was assessed through a sequence of static finite element simulations performed on the impact-damaged specimens, accounting for the residual stresses induced by impact. Experimental results revealed that fatigue life is nearly constant across the tested impact speeds. Finite element analyses supported these observations and demonstrated that residual stresses significantly contribute to the total stress field in the specimens during cyclic loading. This work contributes to the understanding of the fatigue behavior of lightweight components with complex geometries subjected to impact damage.