In situ corrosion fatigue life of 2198-T8 Al–Li alloy based on tests and DIC technique

Abstract

Abstract The advanced aluminum–lithium alloy is used in aircrafts fuselage. Based on the combination of fatigue test and digital image correlation technique, the influence of pre-corrosion and in situ corrosion damage on the fatigue performance of 2198-T8 aluminum–lithium alloy was investigated. The integrated evolution process of fatigue crack and strain distribution fields of two types of the damaged sheets were captured and evaluated by the digital image correlation technique. The results reveal a declining tendency of in situ corrosion fatigue life with the rise of solution temperature, as well as the decrease of flow rate. But, at increasing the NaCl concentration, the fatigue life tends to decrease first and then increase. The observed fatigue behavior and related phenomena are directly associated with fracture morphology such as micro-cracks and corrosion pits. The analysis indicates a competition mechanism between fatigue and corrosion, the fatigue damage dominates the failure process under lower NaCl concentration on the contrary to the higher one that the corrosion damage is the dominant factor. Considering the effect of flow rate on the surface adhesion, the crack tends to initiate at the position of low flow rate. The simulation on the flow field presents an attractive similarity with experimental results.