SEDL / STP / STP610-EB / STP28669S

Stress-Intensity Dependence of Stress-Corrosion Crack-Growth Rate in 7079-T651 Aluminum

Finnegan, JE
research engineer, Dow Chemical Company, Freeport, Tex.

Hartt, WH
Associate professor of Ocean Engineering, Florida Atlantic University, Boca Raton, Fla.

Pages: 17    Published: Jan 1976

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Abstract

Stress-corrosion cracking experiments have been performed on double-cantilever-beam specimens of 7079-T651 aluminum in 3 percent sodium chloride in distilled water and in seawater. At relatively low-stress intensities (Region I of the crack-growth rate/stress-intensity plot) crack length versus exposure time curves were comprised of steps, plateaus, and straight-line segments. These could not be related to any variations in the stress-intensity parameter; so, where such behavior was encountered, no unique relationship between stress intensity and crack-growth rate was apparent. On the other hand, crack-growth rate did vary inversely with exposure time for the range 25 to 200 h. Such an observation was interpreted to mean that properties of the local environment within a crack control extension rate.