In-Process Laser Ultrasonic Inspection of Additive Manufactured (AM) Simulated Aerospace Critical Parts

ABSTRACT: Additive manufacturing (AM) is a very promising technique for rapid, low-cost production of aerospace-related parts directly from a CAD file. AM is especially appealing for complex parts that would be costly or impossible to fabricate by machining or casting. It is also attractive for repairs to existing parts and fabrication of prototype parts. At present there are no reliable, cost-effective process control techniques to minimize defect production and for qualification of finished parts. Studies at several government agencies have noted this gap and urged increased efforts to develop techniques for part qualification. In this project we will demonstrate the feasibility of applying laser ultrasonic testing (LUT) to inspect each deposited layer in real time as it is formed. This in-line inspection qualifies the part layer-by-layer, ensuring finished parts that require no further testing. We will work with Air Force personnel to select or prepare simulated aerospace critical parts for testing. We will then optimize the beam configuration for the best defect sensitivity, and also develop signal processing algorithms to enhance defect detection. We will then test the selected samples and demonstrate the detection of critical defects. In Phase II a prototype in-line inspection system will be developed and tested.; BENEFIT: Additive manufacturing is finding broad applications for the fabrication of high-value, safety-critical components. AM of components for rocket engines and spacecraft thrusters is particularly advanced. NASA is pursuing AM of critical engine components for future heavy-lift space launch systems. Aerojet Rocketdyne is developing a liquid-oxygen/gaseous hydrogen rocket injector assembly built by additive manufacturing. The SuperDraco engines for the SpaceX Dragon V2 manned spacecraft have 3D-printed combustion chambers that enable the engines to produce 100 times the thrust than the Draco engines in current unmanned versions of the Dragon. Aircraft engine suppliers have been investing heavily in capacity for AM parts manufacturing. Key high-value components such as injection nozzles are found multiple times in a turbine engine. The use of AM will reduce engine weight and cost. Components designed with complex cooling channels that were expensive or even impossible to make can now be produced by AM. The introduction of in-line, real-time laser ultrasonic testing to characterize 3D-printed parts supports Executive Order 13329, "Encouraging Innovation in Manufacturing."