Master of Science in Mechanical Engineering (MSME)
Corrosion-Prevention Compounds (CPC) are commonly used to prevent corrosion in the aircraft industry. The presence of corrosive environment (salt-fog, water-fog, even dry air) on aircraft structures has detrimental effects on the integrity of aircraft components which reduces the fatigue life and may accelerate the crack growth rate in the structures. This thesis work is aimed at identifying the effect of CPC and corrosion fatigue on the fatigue life of test specimen. This study describes the results of an experimental study on aluminum alloy 2024-T3 with center-crack specimen to investigate the effect of CPC on fatigue life. Generally, these compounds contain a volatile solvent, corrosion inhibitors, and a barrier film such as grease or wax. The mechanism of corrosion fatigue is studied with the application of CPC. 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 (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. Second objective of thesis work is to investigate the effect of periodic overloads on the fatigue life under constant amplitude fatigue loading. The results show 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 and overload ratios are also examined. The maximum interaction to achieve a maximum increase in fatigue life is observed that the best spacing cycle between overloads has been found to be in the range from 400 to 2000 cycles for an overload ratio of 1.7. Micrograph of the failed specimen surface is examined by using Scanning Electron Microscope (SEM) to investigate the failure processes and the formation of crack surface along the crack front in the crack growth surface. It is indicated that two distinct failure modes are found. These are ductile fracture and brittle fracture. The transition from the ductile mode to brittle mode is observed in this thesis work.
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Park, Jin Hee, "Effects of corrosion prevention compounds and overload induced residual stress field on fatigue life in aluminum alloy" (2004). LSU Master's Theses. 554.
Muhammad A. Wahab