In order to discuss the effect of interaction between corrosion fatigue and stress corrosion cracking on the fracture strength of metals, zero to tension low-cycle fatigue tests with a hold time were conducted under a constant tensile stress on notched sheet specimens of aluminium alloy in salt water (3.0% NaCl). The results obtained are summarized as follows:
(1) From the low-cycle corrosion fatigue tests with trapezoidal stress wave, the number of cycles to rupture was found to decrease with increasing stress hold time and was approximately proportional to the cyclic frequency fa.
(2) The tests of alternate loading of stress cycling and holding a constant stress showed that, when the proportion of the number of stress cycles to a period of stress wave form was large, the number of cycles to rupture remarkably decreased as compared with that of corrosion fatigue.
(3) The crack propagation rate, da/dN, was enhanced by the crack growth during the hold time. The crack growth was remarkably affected by the number of stress cycling in one period of stress wave form and was larger than that of stress corrosion cracking.
(4) The effects of the interaction between stress cycling and hold time on crack propagation rate and fracture life were found to change complicatedly with the ratio of the stress cycle time to the hold time in one period of stress wave form.
