Influence of corrosion fatigue on the stress gradient effect of the aluminium alloy EN AW-6082 T6

This study investigates the influence of corrosion fatigue on the fatigue strength of the aluminium alloy EN AW-6082 T6 with regard to the stress gradient. The experimental design involves varying loading conditions and specimen geometries to facilitate testing under three distinct stress gradients: tension/compression (0 mm-1), rotary bending (0.2 mm-1), notched rotary bending (5.3 mm-1). Reference constant loading tests in air as well as continuously irrigated corrosion fatigue tests in a 5 wt% NaCl-solution are conducted with a constant stress ratio of R =−1. The results reveal a substantial reduction in fatigue strength due to corrosion fatigue across all three stress gradients. The slope of the S-N curves drops by a factor of at least two and no second slope of the S-N curves is found within the tested load cycle range (up to 107). The study demonstrates a significant increase in the support factor for tests conducted in the corrosive environment. This discrepancy becomes more pronounced towards higher stress gradients and lower load cycle numbers. The application of the support factor derived from tests in a non-corrosive atmosphere is shown to be conservative, emphasizing the significance of accounting for corrosion effects in assessing fatigue behaviour.