Corrosion-Prevention-Compounds (CPC) are commonly used to prevent corrosion in the aircraft industry. The presence of corrosive environment on aircraft structures has detrimental effects on the aircraft components which reduces the fatigue life and may also accelerate the crack growth rate in the structures. This is an experimental study on 2024-T3 aluminum alloy to investigate the effect of fatigue crack growth (life from threshold crack growth to final failure) using CPC on fatigue life. The corrosion fatigue with the presence of water-vapor reduces the total fatigue life. The fatigue life with the CPC treatment is shown to increase the fatigue life due to the protection from the corrosive environment containing water-vapor. Test results are obtained for various stress ratios and frequencies with and without the CPC treatment under constant amplitude fatigue loading in water vapor. The second aspect of this work is to investigate the effect of periodic overloads and the limitation in their spacing cycles on the fatigue life under constant amplitude fatigue loading. The results confirm the earlier work that the fatigue life increases due to the periodic overloads in 2024-T3 aluminum alloy. The interactions between overloads that are controlled by the spacing cycles between overloads are also examined. From scanning electron microscopic work the transition from the ductile to brittle mode is observed clearly in this experimental work.
CONSTANT AMPLITUDE AND POST-OVERLOAD FATIGUE CRACK GROWTH BEHAVIOR IN PM ALUMINUM ALLOY AA 8009