Incorporation of Pitting Corrosion Damage into F-111 Fatigue Life Modelling

摘要

In this report, an Equivalent Crack Size (ECS) approach is assessed and implemented for corrosion pittIng in D6ac steel. Relationships between physical corrosion morphology and fatigue life of laboratory coupons were established that allowed corrosion pits to be described as cracks to provide input for durability and damage tolerance analyses. Using the ECS relationship, fatigue lives were accurately predicted in complex coupons tested under spectrum loading. Details are provided on all the corrosion procedures, the developmental testing program, and the validation testing program. So far, the ECS model for corrosion pitting is only valid for areas of the structure that do not experience yielding. Examination of the application of ECS to cases that experience compressive and tensile yield, awaits final development of the appropriate analysis software. The impact of this research on F-ill fleet management can be quite positive by helping avoid unnecessary maintenance and helping to reach a life-of-type goal of 2020.