STUDY ON FATIGUE LIFE OF PRE-CORRODED ALUMINUM ALLOY TYPICAL SINGLE BOLTED LAP JOINTS

Corrosion experiment was performed for aviation LY12 aluminum alloy typical single bolted lap joints with imitating service environment of the military airplane. The fatigue life data for both un-corroded and pre-corroded specimens was obtained by fatigue tests. The specimens were torn down and then inspected. The corrosion effect on LY12 aluminum was analyzed. Two predictive models which consider the effect of corrosion for countersunk bolted lap joints are presented to calculate the fatigue life based on fracture mechanics. Results of two predictive models were calculated and analyzed. The results show that the faying surface and region round about bolt were corroded seriously with “pillowing effect” due to the expansion of corrosion products. Results of predictive models agree reasonably with the experiment results, with the maximum relative error being 36.7% for model 1 and 25.7% for model 2. It may be necessary to use different predictive models rather than a single predictive model to predict the fatigue lives. Multiple corrosion site damage in faying surface should be considered when serious corrosion effect on fatigue life of lap joint is investigated.