Multi-Scale Ultrasonic Evaluation of Cold Spray Additive Manufacturing Repairs

Cold spray additive repair has the potential to revolutionize DoD aircraft maintenance processes.  It enables parts to be repaired with nearly full density and strength so that damaged parts can be reworked, rather than replaced, at a small fraction of the cost.  For use in Critical Safety Items (CSIs), it is essential that non-destructive quality control processes are used to verify no loss in component performance prior to fielding.  Existing quality control processes are limited either to surface defects (e.g., visual inspection, fluorescent dye penetrant), or provide no information on the elastic properties of a repair region.  Here we propose a multi-scale ultrasonic inspection approach that applies electromagnetic acoustic transducers (EMATs) and curvature-matching fixtures to conduct inspections on a range of component geometries.  The Multi-scale Ultrasonic Repair Evaluation (MSURE) system will characterize the elastic properties and defect content in repair regions on complex parts by leveraging both nonlinear (frequency domain) and linear (time domain) ultrasonic metrics.  The system will enable detection of sub-surface microstructural irregularities and bond-line defects that serve as future fatigue crack initiation sites, while retaining the current levels of sensitivity macroscopic defects.