Double cantilever beam specimens of 7079-T651 aluminum were
subjected to low constant stress intensities in a sea water
environment to determine the stress corrosion cracking response.
In addition to a constant stress intensity some specimens
were subjected to controlled, constant potentials. Despite
the fact that all tests were in Region I of the crack growth
rate-stress intensity curve, where the former has been projected
to be very dependent upon the latter, a unique relationship
between stress intensity and crack growth rate was not
always indicated. Therefore, some variable other than stress
intensity is assumed to control crack growth, particularly
for the first several hundred hours of exposure. The observed
behavior is discussed in terms of accepted theories of stress
corrosion cracking in high strength aluminum alloys, including
electrochemical dissolution and hydrogen embrittlement.