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Predictive Distortion Compensation of Thin-Wall Aerostructures Fabricated Using Directed Energy Deposition

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Conference Abstract: To meet the extreme aero-thermal environments experienced by aircraft, metal alloys are being investigated in conjunction with additive manufacturing to create complex part geometries. Due to schedules and budgets, it is crucial to achieve first-time quality parts. However, the steep thermal gradients experienced during the laser-directed energy deposition (L-DED) process can adversely affect the geometry by inducing distortions through residual stress buildup, which may cause the part to not meet geometric tolerances.
To address those issues, Boeing developed a physics-based process model for L-DED using the inherent strain method. Three Inconel-718 aircraft leading-edge builds were completed each containing one unique component. A dimensional scan of the first component was obtained to develop the process model which was used to evaluate and generate new build concepts that were implemented into the final prediction-based distortion-compensated design.
The model was able to accurately predict the distortions in just three hours on a desktop computer. In addition, the model successfully compensated for predicted distortions by generating an optimized preform geometry that, when accounting for process-induced distortions, produces a part within the as-designed profile tolerances. By utilizing the model, profile conformance was improved by 58% and maximum distortion was reduced by 90%. In summary, the model developed under this project provided accurate and rapid assessments of distortions in large, thin-walled AM builds while also successfully optimizing the design to meet acceptance criteria, thus enabling first-time quality.