Fatigue Resistance of Al-Cu-Li and Comparison with 7xxx Aerospace Alloys

Assessment of mixed mode loading on macroscopic fatigue crack paths in thick section Al–Cu–Li alloy plate

“…To model the crack path they modified the model due to Pettit et al [61] to include the present combination of K II /K I and K eq.max conditions and generally found good correspondence experimental and predicted crack paths [60]. Also FCG tests on a AA2050-T8 30 mm plate by Danielou and Ehrstrom [11] conducted at a range of K II /K I and K eq.max conditions reveal crack growth angles that are consistent with the functionalities seen in Fig. 7.…”

“…In this study, samples in the S-L orientation were considered, consistent with the crack plane/orientation taken up after crack deflection has occurred in L-S type coupons, as shown in Figures 1 and 2. Mixed mode fatigue testing was carried out in the S-L orientation using 5 mm thick compact shear specimens (CSS) and a special loading fixture (similar to those described in [9,11,52]) that allowed various combinations of normal (mode I) and shear (mode II) crack loading, as shown in Figure 5.…”

“…The lack of a fully verified model for this behaviour hampers efficient design with these materials [11], leading to overly conservative designs, or avoidance of materials exhibiting the strongest orthotropic behaviour.…”

“…Fatigue testing has revealed macroscopic deflections from nominal mode I paths under both cyclic and monotonic loading: this has been seen for both in-plane testing (L-T and T-L type specimen orientations * ) [6], and through-thickness testing (L-S and T-S type specimen orientations) in wrought plate materials [7,11]. The former phenomenon has been linked to the propensity for crystallographic fatigue crack propagation in strongly textured alloys containing a high volume fraction of the shearable precipitates, whilst the latter has been linked to grain boundary failure.…”

Aerospace Applications of Aluminum–Lithium Alloys

“…Over the last decade, several third-generation alloys have been qualified for applications in commercial transport aircraft, notably the Airbus A380, and there are ongoing developments (Figure 15.11; Table 15.7) which have been compiled from several sources (Daniélou et al, 2012;Denzer et al, 2012;Giummarra et al, 2007Giummarra et al, , 2008Karabin et al, 2012;Lequeu, 2008;Lequeu et al, 2007Lequeu et al, , 2010Magnusen et al, 2012;Pacchione and Telgkamp, 2006;Rioja and Liu, 2012;Tchitembo Goma et al, 2012) and Alcoa in-house knowledge. Alloy producers develop basically similar alloys for different product forms and applications.…”