Lessons Learned in Failure Analysis of Copper Wires for Electrical Aerospace Components

Failure analysis of copper wires in electrical aerospace components present a very different set of challenges when contrasted with structural or hydro-mechanical systems components. Electrical components are often very small and failures may be hidden in coils, windings, and under coatings or lacquers. Identifying the failure location(s) can be difficult and in-service application of electrical current often induces arcing and localized heating that obscures traditional metallographic features at the fracture site essential for determining the failure mode. This paper will follow two interesting examples of such investigations, detailing the investigations and outcomes.  Both parts were made by external suppliers, adding an additional layer of complexity to the investigations and analyses. The first wire failure was from a solenoid valve in hydraulic systems, the second was from a stator motor associated with aerodynamic trim. Corrosion was found in both cases, but was not straightforward as in a structural component. Other mechanical factors from the winding of the coils were found to have effects on the fracture in the solenoid. These investigations have helped our team better understand details unique to these fine wire fractures, the available methods to investigate these details, and highlight ‘tell-tale features’ to look for in future evaluations of electrical components.