An Experimental Investigation of Fretting Fatigue with Spherical Contact in 7075-T6 Aluminum Alloy

Abstract

A new fretting fatigue loading system which facilitates continuous monitoring and control of such parameters as normal and tangential contact loads, and cyclic displacements in addition to the specimen fatigue loading parameters has been designed and built. Systematic and controlled experiments have been carried out with a spherical-tip contact pad fretting against a flat surface. The pad and specimen materials were both 7075-T6 aluminum alloy. For this pad geometry, an analysis of the mechanics of the fretting test has been carried out. In addition, the influence of a number of fretting parameters on the fatigue lifetime has been experimentally investigated. The geometry of fretting scars and the stick-slip annuli has been established for the different contact conditions employed. An approach has been developed to determine the eccentricity produced by the axial load on the stick zone, which correlates very well with the experimental results. Metallographic and fractographic examinations have also been performed on the fretted specimens.