The Role of Fretting Fatigue on Aircraft Rivet Hole Cracking.

Abstract : This is the final report on the Federal Aviation Administration (FAA) Grant No. 93-G-068 Program conducted by the Quality and Integrity Design Engineering Center (QIDEC), Department of Mechanical Engineering, University of Utah. The program is entitled The Role of Fretting Corrosion and Fretting Fatigue on Aircraft Rivet Hole Cracking. A lap joint panel removed from an aircraft used in service was investigated for evidence of fretting induced cracking in and adjacent to the rivet holes. Cracks were found in all of the rivet holes that were inspected. A sensitivity study was conducted to determine the effects of fretting on the fatigue lives of 2024-T3 clad sheet aluminum alloy riveted joint specimens prepared with either FV or CE rivets using either C-squeeze riveting or a rivet gun with bucking bar riveting procedures. A method was developed to predict coefficient of friction characteristics within a fretted contact during the nucleation of a crack. A finite element method was used to calculate the state of stress at CE rivet locations where fretting-nucleated cracks were observed. The primary conclusion of this grant program is that fretting in riveted joints is a potentially major cause of crack nucleation in aircraft skin structure.