Corrosion Pit to Crack Transition. Delivery Order 0051: Task 2
Abstract
Corrosion is an economic burden for the United States Air Force (USAF) since repair and maintenance operations undertaken to mitigate its effects on legacy aircraft are typically over-conservative due to the lack of a reliable methodology to predict the future effects of corrosion on structural performance. Therefore, a need exists for the quantitative evaluation of the effects of corrosion on such failure modes as structural fatigue. Quantitative evaluation will enable the safe and economical operations of aircraft. Pitting is among the commonly observed type of corrosion damage in aircraft structures, as the heterogeneous microstructures of high-strength aluminium alloys such as 2024 and 7075, widely used in the construction of legacy aircraft, render them highly susceptible to this type of localized corrosion. Accordingly, quantitative modeling of corrosion damage by pitting and its effects on the fatigue behavior of aluminium alloys has received considerable attention. In this study, the fracture surfaces of broken corrosion fatigue test specimens were examined in detail in a scanning electron microscope (SEM) to develop an understanding of the nature of the transition of the corrosion damage into fatigue cracks. The purpose was to construct a quantitative data set of the corrosion damage metrics for use in developing and validating corrosion fatigue life prediction models. Available aluminum alloy 7075-T6 specimens, which had been subjected to varying levels of pitting corrosion, systematic characterization, and fatigue testing, were used for the fractographic investigation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 2002
- Accession Number
- ADA414049
Entities
People
- Gary E. Weaver
- Krishnan K. Sankaran
Organizations
- Boeing