Effect of pre-fatigue damage on the residual strength of 2198-T8 aluminum-lithium alloy sheet with holes

The 2198-T8 aluminum-lithium alloy is the advanced aircraft aluminum-lithium alloy used for airframe construction. During the service of the aircraft, the rivet joints of the fuselage skin are vulnerable to fatigue damage, which is accompanied by the formation of fatigue cracks near the rivet holes. The influences of pre-fatigue damage on the residual strength of 2198-T8 aluminum-lithium alloy with rivet holes were studied by combining the digital image correlation (DIC) technique and the micro and macro fracture morphology. The results show that with the increase of the pre-fatigue loading ratio, the residual strength and residual strain of 2198-T8 aluminum-lithium alloy gradually decrease, and when the pre-fatigue loading ratio is greater than 90 %, the attenuation trend is sharply accelerated. The relationship between residual strength and residual strain satisfies the residual strength degradation model, and the formula has a goodness of fit of 0.9878. The fatigue cracks at the hole edge propagate in both vertical and horizontal directions, and the propagation rate increases with the increase of the pre-fatigue loading ratio, and the fatigue striations gradually widen.