New Techniques for Detecting Early Fatigue Damage Accumulation in Aircraft Structural Components

The remaining safe operational life of flight critical aircraft structural components prior to crack initiation and detection is currently estimated by fatigue and fracture models supplemented by destructive testing. To more accurately assess the remaining life of a structural component prior to the initiation of a detectable crack, a non-destructive inspection process that measures fatigue damage accumulation is required. Induced Positron Analysis (IPA) was investigated and evaluated to determine IPA's capability to measure operationally induced fatigue damage accumulation in thick and multilayer aircraft structural components. Aircraft wing attach fittings (WAFs) made of 7475-T3751 aluminum with varying operational histories were obtained and evaluated using IPA. The purpose was to determine IPA's capabilities for detecting fatigue damage in the WAFs, correlate the damage with the operational usage history, and determine if IPA results were suitable for use in life remaining predictive models. In addition to WAFs, other structural components are being assessed for IPA evaluation. Candidates include landing gear and turbine engine components.