Statistical Fatigue and Residual Strength Analysis of New/Aging Aircraft Structure

Abstract

The structural integrity of both military and civilian transport aircraft fleets is governed by Department of Defense and Federal Aviation Administration regulations, respectively, dictating use of fracture mechanics techniques to determine the durability and damage tolerance of the aircraft structure. Driven by economic pressures, both fighter and transport aircraft are remaining in service longer than their original design lifetimes. Maintaining mission readiness and ensuring the safety of the flying public is of utmost concern and the responsibility of the aircraft manufacturers, aircraft operators, and airworthiness authorities. In general, a fracture mechanics based crack growth prediction model is just another tool in the designer and maintainer's toolbox to safely and efficiently manufacture and operate the aircraft. Furthermore, state-of-the-art fatigue life prediction algorithms may only consider simple, well-behaved structural cracking problems. Unfortunately, all modern aircraft are complex assemblies with diverse materials and joining methods. As a result, mission planners and combat leaders are forced to maintain the old paradigm of over-conservative fatigue life predictions and find-it and fix-it corrosion control programs. As a result, the main outcome of our Challenge Project is better fleet management through more robust fatigue life predictions in both peace- and war-time