Fatigue behaviour of aluminium alloy in corrosive environment

In this work the effect of fatigue life reduction of 2024 Al alloy for aerospace components due to the corrosive (exfoliation) environment is investigated. Both standard fatigue tests on prior corroded samples and fatigue tests conducted with the samples in corrosive solution are developed in order to define some guidelines for the inclusion of such effect in design and to improve aircraft life management. The effect of corrosion is taken into consideration introducing specific concentration factors into the life estimation relationship. Differences between fatigue in corroded specimens and fatigue in presence of corrosive environment are emphasized. No crack propagation is considered. Two alternative procedures are considered in the analysis: “a-procedure” based on maximum stress calculated on un-corroded sample section; “b-procedure” based on stress calculated on final residual section, including corrosion. Related concentration factors are derived and compared by the experimental results with the aid of an original proposed ”power law” showing a substantial equivalence of the considered procedures both in the case of prior corroded samples and in combined situation. This tendency is consistent with the available data results. The combined effect of fatigue load acting in presence of corrosive environment reveals an important reduction in fatigue life that cannot be determined by means of classical fatigue tests performed on prior corroded samples. Original analytical relations are introduced in order to manage such kind of combined effect revealing consistency of data also if few samples were tested. An extensive experimental investigation is deemed necessary to confirm the presented analytical approach and to improve the capability to predict such phenomenon .