Effect of some factors of programmed loading on the endurance of an aluminum alloy in a corrosive medium

Abstract

1. The initial stress in fatigue tests under varying stress application may have a considerable effect on the endurance of alloy D16T, particularly in air. The application of high initial stresses leads to an increase in endurance, the extent of the increase depending on the character of the load sequence employed. 2. The accumulation of fatigue damage during tests under varying stress application is more intense in corrosive media than in air. 3. When the ratio of the number of cycles at stresses below the corrosion-fatigue limit σ−1 (determined by a standard test for N=2×107) to that at stresses above this limit is 1∶1, the endurance of alloy D16T tested in 3% NaCl solution under varying stress application is not affected by stresses lower than 0.5 σ−1. The 25% reduction in endurance recorded for specimens tested under varying stress application which includes such a low stress level is caused solely by the corrosive action of the medium alternating with the mechanical action of the higher stresses of the program module used. 4. The range of stresses in corrosion-fatigue tests under varying stress application must include stress levels down to σ min pr =0.5–0.6 σ−1. The effect of stresses below this level may be replaced by the action of the corrosive medium alone (without any stress) alternating with test periods under higher stresses.