Fretting fatigue failure of lug-bush connection members under tensile loading

Abstract

© 2019 The Vertical Flight Society. All rights reserved.Lug-bush connection members are used widely in the aerospace industry. Under cyclic loads, these connection members fail due to fretting fatigue. The tensile fatigue loading creates sliding and sticking regions at the lug-bush interface and leads to the fracture of the lug. In this study, four different lug-bush members are investigated. Different surface conditions are observed at the sticking and sliding regions of all members. Black residues are observed only at the sliding regions, which are caused by the relative motion between the contacting lug and bush surfaces. A crack initiated from the sliding region and the lug fractured at this point. The contact surfaces are investigated using a digital microscope and a scanning electron microscope (SEM). Additionally, elemental compositions of the sticking and sliding surfaces are obtained with energy dispersive spectroscopy (EDS) analysis in SEM. The results showed that rubbing of lug-bush surfaces created wear debris at the sliding region, which was corroded and formed a tribolayer containing fine metal particles and oxides. The crack is observed to initiate from this tribolayer. Comparison of the fracture and sticking-sliding region positions indicated that the fracture locations of four different lug-bush members were similar. Shape of the tribolayer of similar lug-bush materials are observed to be different from the shape of dissimilar lug-bush materials. Finite element analysis is done using ABAQUS and sliding region locations are in agreement with the observations