By Cynthia Greenwood
DoD Corrosion Policy and Oversight Office
Two university researchers supported by the DoD Corrosion Policy and Oversight Office’s Technical Corrosion Collaboration (TCC) are advancing the preservation of legacy DoD aircraft and ship platforms with the help of grants from the Air Force Office of Scientific Research (AFOSR) and the Office of Naval Research (ONR).
A 2016 Young Investigator Program award from AFOSR has enabled James Burns, assistant professor at University of Virginia (UVA), to investigate the actual rate of material crack growth on an aircraft in high altitude environments. These rates can be much slower than those generally used in prognosis calculations which are gathered in laboratory environments.
In addition to teaching materials science and engineering at UVA, Burns also oversees the Burns Research Group, whose work spans the intersection of metallurgy, solid mechanics, and chemistry. Burns’ award-winning proposal focused on the fatigue of aerospace aluminum alloys, specifically the effect of high-altitude environments on the dislocation structure evolution during fatigue cracking.
Typically, the Air Force has used laboratory-generated crack growth rates to set aircraft inspection intervals. But if the fatigue cracking that actually occurs on an aircraft takes place more slowly, by several orders of magnitude, than the lab measurements would suggest, it may be possible for the Air Force to change the rates of inspection, Burns explained. “If the Air Force is able to inspect its aircraft less often, it has the potential to both reap significant cost savings, reduce the inspection burden, and increase the availability of weapon systems in the fleet,” Burns said.
Dr. Jenifer Locke, an assistant professor of materials science at The Ohio State University, is working on a systematic study of the effect of sensitization on the corrosion fatigue of aluminum-magnesium alloys used in several naval applications. Her current research is being conducted with the support of a Young Investigator Program award, granted in 2016 by the Office of Naval Research (ONR).
Locke is studying the phenomenon of corrosion fatigue on various corrosion-resistant aluminum-magnesium alloys that are prevalent in structures found on the Navy’s Littoral Combat ship, Joint High Speed Vessel, and Ship-to-Shore Connector platforms.
Locke’s investigation of corrosion fatigue is significant because naval structures experience fatigue loading while they are deployed in a seawater environment. “As such, understanding and quantifying the effect of crack tip corrosion on the incidence of corrosion fatigue affecting sensitized aluminum-magnesium alloys is critical to predicting the performance of these alloys while they are in-service,” Locke explained.
“The goal of this work is to bridge the gap between our basic understanding of the effect of aluminum-magnesium alloy sensitization on inter-granular stress corrosion cracking, which is rather well understood, and corrosion fatigue, where critical and systematic studies are lacking,” Locke explained.
According to the AFOSR guidelines, the Young Investigator Program that is benefiting Burns aims to “foster creative basic research in science and engineering, enhance young investigators’ early career development, and increase opportunities for recipients to recognize the Air Force mission and related challenges in science and engineering.”
The ONR Young Investigator Program that has recognized Locke’s achievements is designed to attract outstanding university faculty members to the Department of the Navy’s research program. Through the program, ONR hopes to support the research of award recipients, while also helping advance their teaching and research careers.