Additive Friction Stir Deposition for Large, Efficient Structural Sustainment

The NAVY seeks an improved structural sustainment solution for the production of large aluminum structures such as F/A-18 center barrels, utilizing the additive friction stir deposition (AFSD) technology to produce replacement barrels from custom forgings. Given the necessity for high-quality structural sustainment of large-size and complex geometries of constructed parts, while simultaneously reducing manufacturing and repair time and costs, Global Engineering and Materials, Inc. and collaborators propose several innovative technologies based on our extensive experience and successful results in repairing high-strength aluminum alloys using AFSD to achieve fully dense materials in the as-printed state with equiaxed fine microstructures and the ability to improve mechanical performance. To tailor the process and the resulting microstructure-driven structural performance, the GEM team will extend the process-structure-property-performance (PSPP) modeling capability for AFSD from components to full-scale parts. The resulting digital-twin toolkit, combining simulation-informed AFSD with in-situ data collection, to capture the process-thermo-mechanical response associated with a multi-stage fabrication process including a layer-by-layer deposition, stress relief treatment, machining, and a modified heat treatment. To support GEM’s digital-twin tool for performance-informed tailoring of AFSD, a three-stage approach will be developed and executed to design, fabricate, and test parts at coupon, featured component, and part levels. In-situ property data will be generated using the coupons sliced from AFSD printed walls at two different orientations. The in-situ static and fatigue properties will be used to validate the relation between the process and performance established using the PSPP tool. Process tailoring through rational selection of process parameters, printing strategies, and boundary conditions will be demonstrated using two featured components extracted from a representative center barrel F/A-18. Drawing on the knowledge gained from the AFSD printing and fabrication at the coupon and sub-component levels and synthetic data generated from the validated digital-twin tool, an optimal fabrication strategy along with the rational selection of process parameters will be determined for the construction of two half-scale parts of a representative center barrel. A customized fatigue loading frame will be constructed to evaluate the mechanical performance of the AFSD fabricated representative center barrels and examine the crack initiation and failure mechanisms. The collected data will be compared with the simulation results and the collected literature data on the corresponding parts made by forging.