Residual life predictions of corroded fuselage lap joints

Abstract

This paper presents the results from a study that was carried out to determine the capability of the Equivalent Initial Flaw Size approach, referred to as Equivalent Corrosion Damage (ECD), to predict the effect that corrosion has on the residual life of fuselage lap joints. Coupons fabricated from pristine and naturally and artificially corroded lap joints were tested to failure to determine the ECD value. The stress distribution at the critical rivet hole was determined by carrying out a finite element analysis. The resulting stress correction curves were used in the afgrow crack growth rate program along with the equivalent ECD radius to predict the residual life of multi-site damage (MSD) specimens that were tested in a previous study. The analytical results were close to the experimental ones, which was not surprising given the assumption behind the ECD concept that corrosion and fatigue act sequentially. The shortcomings of the ECD approach to corrosion fatigue damage assessment and prediction are discussed along with the relationship between ECD and a new holistic approach known as the Discontinuity State Evolution Process.