Development of Fatigue and Crack Propagation Design and Analysis Methodology in a Corrosive Environment for Typical Mechanically-Fastened Joints. Volume 1. Phase I Documentation.

A corrosion fatigue methodology has been developed for predicting the crack initiation and crack propagation behavior of mechanically-fastened joints. An experimental test program was also conducted using 7075-T7651 aluminum alloy and beta-annealed Ti-6A1-4V alloy to evaluate the effects of environment, test frequency, R-ratio, holding-time, and stress level on corrosion fatigue behavior. Based on this investigation, it was concluded that The reaction between aqueous environments and the 7075-T7651 aluminum alloy appears to be limited. Hence, a special crack propagation model for corrosion fatigue is not required for design A better understanding of the corrosion fatigue behavior of beta-annealed Ti-6A1-4V alloy is needed before a reliable predictive methodology can be developed for mechanically-fastened joints and The corrosion fatigue predictive methodology developed looks promising for constant amplitude applications. Now, the predictive methodology needs to be further developed to account for spectrum loading and variance in the input data base.