Spike Overload and Humidity Effects on Fatigue Crack Delay in Al 7075-T651

O Buck; JD Frandsen; HL Marcus

doi:10.1520/STP33366S

SYMPOSIA PAPER Published: 01 January 1976

STP33366S

Spike Overload and Humidity Effects on Fatigue Crack Delay in Al 7075-T651

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This paper describes experiments on fatigue crack growth, Δa/ΔN, in part-through crack specimens of 7075-T651 aluminum alloy. The effects of dry and humid environment in combination with single-spike overloads on Δa/ΔN, the crack growth delay, N_D, and the “effective” stress intensity range, ΔK_eff, are discussed. Using an acoustic monitoring technique, it was observed that the crack closure not only reflects the influence of the environment, but also of the spike overload on the plastic deformation at the crack tip and therefore on Δa/ΔN. The relationship Δa/ΔN = A (ΔK_eff)ⁿ describes both environmental and spike overload effects, uniquely. Delay is more pronounced in a dry environment and increases strongly with increasing overload ratio.

Author Information

Buck, O

Science Center, Rockwell International, Thousand Oaks, Calif.

Frandsen, JD

Science Center, Rockwell International, Thousand Oaks, Calif.

Marcus, HL

University of Texas, Austin, Tex.

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Details

Developed by Committee: E08

Pages: 101–112

DOI: 10.1520/STP33366S

ISBN-EB: 978-0-8031-4672-3

ISBN-13: 978-0-8031-0344-3

Spike Overload and Humidity Effects on Fatigue Crack Delay in Al 7075-T651

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