Abstract
Abstract The fatigue test with the digital image correlation system is applied to 2198-T8 aluminum-lithium alloy sheets with preset cracks and impact dents. The influence of different inserts and impact energies on residual fatigue life and failure behavior is analyzed. The results show that the shape of inserts is the main factor of the residual fatigue life at the same impact energy following the order: U-shaped > hemispherical > conical. Moreover the fatigue life decreases with the increase of impact energy. The hemispherical and U-shaped inserts cause local hardening at low impact energy 5 J, resulting in a maximum increase in fatigue life of 12.09 %. In the initial stages of fatigue failure, high strain areas are always around the preset crack where the propagations initiate. There is a multi-axial loading area around the impact dent in the middle stage. Its fatigue crack propagation mode is type I+III, resulting in a deceleration period.
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