PREDICTION OF CRACK INITIATION AND CRACK GROWTH OF THE SPLIT SLEEVE PROCESSED HOLES IN ALUMINUM 2024-T3 USING THE FINITE ELEMENT METHOD

摘要

The split sleeve process is one of the most popular techniques in the fatigue enhancement foraircraft structures and it has been widely used as a means of improving the fatigue strength ofmetallic structures with holes. The split sleeve process produces beneficial compressive residualstresses around the hole, which hinders the growth of a crack from the hole edge to a detectable0.25 mm crack. This paper aims to predict the fatigue crack initiation and crack growth of the splitsleeve processed holes in Al 2024-T3. A three-dimensional finite-element simulation wasconducted for a split-sleeve cold-expansion process in order to determine the residual stress fieldaround an expanded hole. The strain-life analysis was conducted to estimate fatigue crackinitiation/growth cycles and the crack shape for the split sleeve processed holes. Finally, thefatigue-crack propagation was simulated, based on linear elastic fracture mechanics and stressintensity factor determination. The simulation results were compared with experimentalmeasurements of the smallest detectable crack and its propagation in Al 2024-T3. The estimatedcrack growth rate (4.72×10-5 mm/cycles) from the simulation was found to be close to that(1.13×10-4 mm/cycles) from the experiments.