Fatigue life of panels with multiple site damage

Abstract

This article describes research aimed at predicting the fatigue lives of unstiffened aluminum panels that contain multiple site damage (MSD). The initial damage consists of through-the-thickness cracks emanating from a row of holes in the center of a finite width panel. The row of holes is aligned perpendicular to a cyclically applied, constant amplitude, tensile load. A fracture mechanics analysis is employed to predict the growth, interaction, and coalescence of the various cracks that propagate in the panel. A strain-life analysis incorporating Neuber's rule for notches, and Miner's rule for cumulative damage, is also employed to predict crack initiation for holes with no initial cracking. Twelve fatigue tests of 2024T3 aluminum panels with MSD were conducted to evaluate the analysis, and the test results compare favorably with predictions for the fatigue life of these panels. Crack interaction effects in the MSD test specimens are apparent, and are shown to significantly accelerate crack growth rates, particularly during the latter stages of fatigue life.