Fatigue behaviour of aluminium alloy 7075 bolted joints treated with oily film corrosion compounds

The effect of oily film corrosion-prevention compounds on the fatigue behaviour of aluminium alloy 7075-T6 mechanically fastened joints was investigated. Unpainted double-lap joints with a single bolt fastener were tested under constant-amplitude fatigue loading with and without treatment with lubricative corrosion-prevention compound (CPC). Fatigue tests were conducted with different levels of fastener clamping force to determine the variation in fatigue life as a function of the clamping force with and without the CPC. Fractography of the failed specimens indicated that there are two distinct modes of fatigue initiation, one dominated by fretting and the other dominated by bearing at the fastener hole. It was found that in joints with high fastener-clamping force, the application of lubricative corrosion-prevention compounds increases the fatigue life, whereas the use of CPC is detrimental to the life of joints with low fastener-clamping force.