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Effect of specimen thickness of fatigue-crack-growth behavior and fracture toughness of 7075-T6 and 7178-T6 aluminum alloys

Author
Newman, J. C., Jr.
Published
Apr 1, 1973.
Physical Description
1 electronic document
Additional Creators
Hudson, C. M.
Online Version

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Summary
A study was made to determine the effects of specimen thickness on fatigue crack growth and fracture behavior of 7075-T6 and 7178-T6 aluminum alloy sheet and plate. Specimen thicknesses ranged from 5.1 to 12.7 mm (0.20 to 0.50 in.) for 7075-T6 and from 1.3 to 6.4 mm (0.05 to 0.25 in.) for 7178-T6. The stress ratios R used in the crack growth experiments were 0.02 and 0.50. For 7075-T6, specimen thickness had relatively little effect on fatigue-crack growth. However, the fracture toughness of the thickness of the thickest gage of 7075-T6 was about two-thirds of the fracture toughness of the thinner gages of 7075-T6. For 7178-T6, fatigue cracks generally grew somewhat faster in the thicker gages than in the thinnest gage. The fracture toughness of the thickest gage of 7178-T6 was about two-thirds of the fracture toughness of the thinner gages of 7178-T6. Stress intensity methods were used to analyze the experimental results. For a given thickness and value of R, the rate of fatigue crack growth was essentially a single-valued function of the stress intensity range for 7075-T6 and 7178-T6. An empirical equation developed by Forman, Kearney, and Engle fit the 7075-T6 and 7178-T6 crack growth data reasonably well.
Other Subject(s)
Collection
NASA Technical Reports Server (NTRS) Collection.
Note
Document ID: 19730012726.
Accession ID: 73N21453.
L-8731.
NASA-TN-D-7173.
Terms of Use and Reproduction
No Copyright.
View MARC record | catkey: 15749630