Investigation of fretting fatigue failure mechanism of lug-bush connection members

Abstract

Lug-bush connection members are widely used in aerospace industry, specifically in the connection of rotor to helicopter main body. Under small amplitude cyclic loadings, a fraction of the contact area experiences relative motion which causes fretting on the contacting surfaces. In this study, failure mechanisms of four different lug-bush members subjected to high cycle tensile fatigue loading are investigated. The contact surfaces are inspected using a digital microscope and a scanning electron microscope (SEM). Different surface regimes are observed at the mating surfaces which are shown to be the results of partial stick and slip of the contacting bodies. Energy dispersive spectroscopy (EDS) analysis in SEM showed that rubbing of lug-bush surfaces created wear debris at the sliding regions which then corroded and formed a tribolayer. A crack is observed to initiate in the vicinity of tribolayer boundary. FEA of these members are carried out using ABAQUS by defining interference and contact to mating surfaces of the lug and bush. The results showed qualitative agreement with the experimental investigations in terms of peak slip locations.