Fatigue behavior of 2618-T851 aluminum alloy under uniaxial and multiaxial loadings

AA2618 aeronautical aluminum alloy has been largely used in the past, especially in well-known Concorde aircraft, developed during sixties decade. In more recent aircraft, this alloy has been largely replaced by others such as 7075 which present greater fatigue resistance. Forgotten for a time, AA2618 comes back in new aircrafts for structural parts submitted to fatigue loading at high temperature because of only a slight decrease of fatigue resistance of this alloy compared to room temperature fatigue resistance. In this paper, a complete fatigue characterization of 2618-T851 aluminum alloy is presented: fatigue tests under uniaxial tensile or torsion cyclic loadings, with mean tensile or shear stress have been realized; fatigue tests under combined tensile-torsion, in or out-of-phase have also been conducted as well as some combined tensile-torsion-internal pressure fatigue tests. All these tests covered 10(4)-10(7) cycles range. At last, Crossland multiaxial fatigue criterion has been used and extended to median fatigue life domain to analyze these results.