(natural) environment, and (iv) tensile tests on specimens subjected to corrosion exposure and then to removal of the corrosion-affected surface layer by machining in order to investigate whether the corrosion-induced tensile property degradation is volumetric. For alloy 2024-T3 some specimens were subjected to hard anodizing and sealing prior to corrosion exposure. They were used to derive (i) the reference tensile behavior of uncorroded material subjected to anodizing and sealing and (ii) to evaluate this protective role of the coating when the material is exposed in corrosive environments. Indicated in Tables 9.33-9.36 are also the corrosion tests applied to precorrode the tensile specimens, the specimen direction, as well as the number of tests performed. The tensile tests were performed according to ASTM E8m-94a [63] specification. For the tests a 200 KN Zwick universal testing machine and a servohydraulic MTS 250 KN machine were used. The deformation rate was 10 mm/min.

The fatigue tests performed to obtain S -N curves on as received, on protected, as well as on corroded 2024 alloy are summarized in Table 9.37. The same material fatigue crack growth tests were performed for the R values 0.01, 0.1, 0.5, and 0.7. For each R value two tests were performed on the as-received specimens and two tests on specimens subjected to 36 h exfoliation corrosion exposure prior to fatigue crack growth test. The frequency for all fatigue crack growth tests was constant at 20 Hz. Fatigue crack growth measurements were

TABLE 9.35 Tensile Tests Performed on Alloy 2091-T84
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