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Daytona Beach


Aerospace Engineering

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This research aims to establish the effect of hole cold expansion on fatigue life of pre-cracked material under aggressive environment. A relationship between crack propagation and secondary crack initiation was established for AA2024-T3 cold worked holes subjected to cyclic loads to determine the impact on fatigue life of joints in presence of saline solution. Galvanic corrosion of a steel fastener/aluminum plate assembly was investigated assuming the presence of cracks in the aluminum plates, whose growth will be monitored in-situ with a digital microscope throughout the fatigue process. The cold expansion treatment improved the fatigue life fourfold under a corrosive environment, and 11.3 times in a clean environment when compared to a plain hole. Corrosion revealed the possibility of a location shift in critical stress intensity factor, causing growth of the critical crack happening outside of the region where benefits of cold expansion can be achieved. The benefits of cold work expansion could be applied for pre-cracked materials for an improved inspection interval, but also calls for reevaluation of inspection area to prevent secondary crack initiation that could lead to ultimate failure of the structural component.

Publication Title

AIAA Journal