Low cycle fatigue behaviors of low-velocity-impacted (LVI) aluminum-alloy plate

摘要

In this paper,we will look into the effects of various impact energy levels on the mechanical properties of aluminum alloy plate. Tensile properties and fatigue behaviors of LY12-CZ aluminum alloy sheet subjected to low-velocity-impact (LVI) with various energies have been experimentally investigated. Three levels of LVI damage were introduced in specimens by falling-weight tests. Static strength for the un-impacted and post-impacted specimens were measured respectively;it was showed that the yield strength slightly reduced,but the residual stiffness and ductility properties after LVI are weakened,and failure strain decreased significantly with the increasing LVI energy. The un-impacted and post-impacted specimens were cycled in tension-tension fatigue until failure. The center of impact-crater was found to be a preferred site for crack nucleation and subsequent propagation. The combination of stress concentration and weakened ductility induced from LVI damage could act as a significant limiting factor for component lives. Manson-Coffin model can be used to explain the reduction of low-cycle-fatigue life phenomenologically. Statistical characteristics of the fatigue life for the un-impacted and impacted aluminum alloy sheet were obtained. Comparing with the un-impacted specimens,significant reductions of the spread and the number of cycles to failure were observed in LVI specimens. It can be concluded that the LVI damage accelerated the components' failure under monotonic or cyclic loading conditions.