Realistic chemical environments in commercial transport aircraft and their effect on corrosion fatigue crack propagation.

摘要

In order to incorporate corrosion fatigue crack propagation data into damage tolerant analysis, it is necessary to duplicate both the mechanical and the chemical environments that can be expected in service. Some corrosion fatigue crack propagation research has focused on the use of 3.5% NaCl solution. It has been shown that corrosion fatigue crack propagation rates in a simulated environment can vary significantly from those found in 3.5% NaCl.; For this reason, sampling of the chemical species found in commercial aircraft in passenger service has been conducted to determine a representative chemical environment to apply during fatigue crack growth experiments. Aluminum alloys 2024-T351, 2324-T39, 7075-T651, and 7150-T651 were studied using this realistic chemical environment. In addition, experiments were conducted using 3.5% NaCl solution and dry air for reference.; The chemical species present in some commercial transport aircraft are presented as well as the results of the crack propagation studies. These results are contrasted with those found in dry air and 3.5% NaCl to demonstrate the need to incorporate a realistic chemical environment in damage tolerant assessment.; A fractographic study also was conducted to verify that the crack morphology seen in the laboratory simulated environment.