The RAE contribution to the first phase of the AGARD corrosion fatigue co-operative testing programme (CFCTP)

Abstract

This Report describes the RAE participation in an AGARD-coordinated corrosion fatigue programme. Fatigue specimens from a single batch of aluminium alloy 7075-T76 have been tested at constant amplitude in air at 2 Hz and in acidified salt fog at 0.5 Hz, using stress maxima of 210 MPa and 144 MPa, and an R ratio (minimum stress/maximum stress) of 0.1. Test conditions were designed to simulate the service conditions of shipborne aircraft deployed in maritime operations. The programme was designed to permit a comparison of results from the participating laboratories. The results from all eight participants formed a statistically valid set of data, and the low inter-Iaboratory variation established confidence in the comparability of results from future test programmes. Exposure to acidified salt solution prior to testing reduced significantly subsequent air and corrosion fatigue lives and the effect of a salt fog environment reduced the fatigue lives significantly compared to those achieved in air. The detrimental effect of corrosive environment during fatigue was more pronounced at the higher stress level.