Notch Fatigue Property of 7050-T7451 Aluminum Alloy under Bending Resonance Environment

Abstract

Based on the electromagnetic shaker table, the resonant fatigue testing system and the corresponding conventional fatigue testing system were designed respectively. The fatigue life (S-N) curves of smooth and notched 7050-T7451 aluminum alloy specimens were measured in the range of 10⁵-10⁷ cycles, and the notch fatigue property of 7050-T7451 aluminum alloy under bending resonance environment was studied. The results indicate that the fracture mechanism under bending resonant fatigue environment is roughly the same as that under bending conventional fatigue loading. All the S-N curves obtained through resonant and conventional fatigue tests show a continuously downward trend, and there are no obvious fatigue limits. Notch fatigue property under bending resonance environment presents “stage characteristics”, which increases first and then decreases with the increase of cycles. There is a critical cycle number N_c at 8×10⁵ cycles, corresponding to the maximum fatigue notch factor K_f-max (or the maximum notch sensitivity factor q_max). There are two critical cycles N₁ and N₂. When N₁<N<N₂, the notch fatigue property of the material and the corresponding structures under resonance environment requires more consideration than conventional fatigue loading.