Fracture Analysis in The Boeing Company

Abstract Text: The Fracture Analysis Group in Seattle, Washington analyzes over 150 components returned from service annually to determine the cause of service damage. Largely serving Boeing Commercial Airplanes, a significant fraction of work originates within Commercial Aviation Services, as a part of air-on-ground (AOG) incident recovery and repair services. The group also supports Air Safety Investigations in the event of in- flight mishaps, and analysis of components replaced during airline scheduled maintenance checks. Materials investigated include essentially all alloy classes (magnesium, aluminum, steel, superalloys, titanium, etc.), from the very tiny (electronic components) to the very large (spars, skins and landing gear). Many investigations involve fatigue and/or corrosion damage interrogated by state-of-the-art electron and light microscopic techniques. Microstructures are interpreted to discern metallurgical and service histories and adherence to quality requirements, and fracture surfaces are analyzed to determine fracture mode and initiation sites. Electron microscopy is also utilized to collect data to model fatigue crack growth for cycles-to- initiation analyses. This supports adjustment of service inspection intervals to maintain a safe fleet. All resulting reports are maintained in a Boeing-proprietary, searchable electronic database, and many are shared with respective airline customers. This paper will review the analytical methods utilized by the Fracture Analysis Group, and some recent analyses that are highly interesting and educational. These will include: lower wing skin damage (fatigue), nose gear steering cable (bird strike and wear) and a engine fire switch (manufacturing flaw). These examples illustrate the variety of materials, components and service damage analyzed, and that contribute to the Boeing knowledge base.