Predicting fatigue life of pre-corroded 2024-T3 aluminum from breaking load tests

Characterization of material properties is necessary for design purposes and has been a topic of research for many years. However, there has not been as much success in quantifying the susceptibility of a material to corrosion damage and its subsequent impact on material behavior. To that end, the goal of this investigation was to formulate a cheaper and quicker method for assessing the consequences of corrosion on remaining fatigue life. For this study, breaking load specimens of a single nominal gage (0.063″) of 2024-T3 alloy aluminum from three different manufacturing lots were exposed to three levels of corrosion. Correlations between breaking load results and fatigue life results in the presence of corrosion damage were developed using a fracture mechanics foundation and the observed mechanisms of failure, through the use of effective flaw size conversions. Life predictions using this technique, which is based on breaking load data, were generally shorter than the experimental lives by an average of 20%. The life prediction methodology developed from this investigation is a very valuable tool for assessing material substitution for aircraft designers, alloy differentiation for manufacturers, or inspection intervals and aircraft retirement schedules for aircraft in service.