Effect of pit detail morphology on fatigue characteristics of LD2CS aluminum alloy

Abstract

Abstract LD2CS aluminum alloy is an important structural material for a certain type of aircraft in coastal service. In order to assess the fatigue mechanical properties of LD2CS aluminum alloy materials in the coastal airport environment, accelerated pre-corrosion fatigue test of LD2CS aluminum alloy specimens in the laboratory environment is required. Through the study of the surface morphology of LD2CS aluminum alloy specimen and fatigue fracture observation,it is found that with the increase of the number of year of the equivalent accelerated corrosion in advance, internal corrosion pit morphology is complicated, and the crack initiation corrosion pit roots are often more strident. the root radius depth ratio of corrosion pit η is defined, it is found that after equivalent accelerated pre-corrosion 7 years, when η ∈ (0,0.4], the corrosion pit is easy to become the key pit which could initiate the dominant crack. The equivalent crack for the key pit was quantified by η, and the fatigue life of the equivalent crack was predicted by the Forman formula, which was in good agreement with the life test value of LD2CS aluminum alloy specimen. It shows that the equivalent crack method considering the details of the pit root is of high engineering practical value and can provide more powerful data support for the aircraft damage tolerance analysis.