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Effectiveness of High Modulus Interference-Fit Bushes for Fatigue Life Extension of Plates with Circular Holes.
DEFENCE SCIENCE AND TECHNOLOGY ORGANIZATION CANBERRA (AUSTRALIA)
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An experimental program has been carried out to examine the influence of bush modulus on the fatigue lives of aluminum alloy specimens with bushed holes of 12 mm diameter. The specimens, with 1 mm or 2 mm thick bushes of 0.5 interference fit and of widely different modulus, were fatigue tested under a representative fighter aircraft loading sequence. The thin-walled bushes were found to extend the fatigue lives of the plates with holes by at least 4.2 times, and the thick walled bushes produced at least a 10.9 times increase in life. The test results also indicated that different failure modes can occur depending on the relative thickness and modulus of the interference-fit bush. Thus, the specimens with the highest bush modulus did not necessarily have the longest lives, even though the stress concentration factor due to remote loading at the hole edge for these specimens was the lowest finite element work was also conducted to determine the stresses and strains in the interference fit bushes for conditions of no-slip and frictionless contact between the bush and plate. High tensile strains were found to occur in the bush at the inner surface.
APPROVED FOR PUBLIC RELEASE