In the trenchesUSAF partners with national labs to improve aircraft component design

Working with national laboratories, universities, and industry, the Air Force is ensuring it stays on the cutting edge of global security by creating a new engineering paradigm to improve the safety and fuel-efficiency of aircraft.

Materials research engineers at the Air Force Research Laboratory (AFRL) have partnered with national laboratories to model defects and study materials at their grain level in an effort to develop and advance the design of systems used by the military personnel, including aircraft.

Traditionally, engineers approach component design in a manner that homogenizes the physical properties of a structure. Significant achievements have been made in the longevity of a component by optimizing this process. Now, engineers are looking deeper to incorporate the materials substructure into the design process.

An Argonne National Laboratory (ANL) release reports that to address the strategic need for microstructure data, a diverse team of scientists and engineers developed a novel capability to nondestructively map the material substructure and grain-level stresses concurrently in three dimensions. The team comprises researchers from the AFRL, the Advanced Photon Source (APS) at the U.S. Department of Energy’s Argonne National Laboratory, the DOE’s Lawrence Livermore National Laboratory, Carnegie Mellon University, and PulseRay.

For the first time, the team has integrated three high-energy synchrotron X-ray techniques during mechanical testing to:

• Quantify the average elastic strain and stress tensor for each grain using far-field High Energy Diffraction Microscopy (HEDM)
• Map the grain shape and local crystallographic orientation within and between grains using near-field HEDM
• Track the formation and spread of voids and cracks using micro-contrast tomography

These one-of-a-kind datasets provide insight into deformation and form an essential basis for the development and validation of modeling tools. Currently, the capability has been applied to nickel and titanium alloys.

Metallic materials, like those found in aircraft, have directional dependent properties. By altering the material processing conditions, the microstructure can be tailored by designers to provide optimized properties for expected stress and temperature environments. Location-specific design has made an entrance into the aviation industry and the Air Force fleet but is currently limited to a small number of components because of the extensive testing program needed. The process works well for incremental changes but limits the development of revolutionary new materials like those used for engine turbine disks, because it would require millions of dollars over a span of decades.

With the development and validation of these new microstructure modeling tools that can predict materials behavior, including variability and uncertainty, engineering design can be revolutionized by unlocking the true potential of the materials’ employed capabilities, safety, and fuel efficiency. The economies of scale for materials affected by these advancements have the potential to save billions.

“Access to this data — nondestructively — during conventional thermo-mechanical testing provides a unique opportunity to go after previously unanswered questions and opens new areas of research,” said Jay Schuren, the principal investigator on the project and a Materials Research Engineer at the Air Force Research Laboratory.

The release notes that the APS provided the team with access to the nation’s only X-ray beamline for non-destructive in situ structural studies of buried interfaces at atomic resolution. The HEXD beamline capitalizes on the penetration power of the APS’s high-energy X-rays and their high-brightness, which enables scientists to examine small areas. This combination is perfect for measuring strains to study the stresses under extreme operating conditions such as thermo-mechanical deformation. By using these unique tools to pinpoint material defects in design and processing, scientists can gain the knowledge needed to create new high-performance materials.

“This type of research shows how government, industry and academia can come together to improve the nation’s security and further energy efficiency,” said Jon Almer, a physicist in the X-ray Science division at Argonne who worked on the research team.

Funding for this research was provided by Department of Defense and university grants. The use of the APS was funded by the Department of Energy.