This study focuses on the evolution, distribution, and growth of multiple-site damage (MSD) in a pristine full-scale fuselage panel, containing a longitudinal lap joint, during accelerated fatigue testing. The five-bay test panel, representative of a generic narrow-body fuselage, was subjected to a programmed constant-amplitude cyclic load spectrum that included underload cycles that were used to mark the fracture surfaces. The resulting underload marker bands were used to reconstruct subsurface crack growth history at the crack initiation sites. In addition, detailed fractographic examinations of the fracture surfaces near 57 of the 64 rivet holes, along the critical rivet row of the lap joint, were conducted. It was determined that subsurface MSD fatigue surfaces were generated throughout the critical rivet row in the lap joint. Their areas, dimensions, and crack front shapes were measured and correlated with an extensive eddy-current database that was generated during the course of this research.
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