Fiber-Image- Guide Airframe Roughness Profilometer

To address the DARPA need for airframe crack nucleation prediction through surface roughness measurement, Luminit, LLC proposes to develop a new Fiber-Image-Guide Airframe Roughness Profilometer (FIGARP), based on a novel phase resolvable full-field optical coherence tomography (OCT) and a handheld Fiber-Image-Guide (FIG) probe. OCT offers rapid tomographic imaging of strongly scattering materials. The FIG probe offers simultaneous acquisition of a 2D pixel array from a surface without physical contact. The portable FIGARP requires no anti-vibration measures. It can measure the surface topography of a real aircraft in < 0.1 ms, with sub-nanometer depth and sub-micron lateral resolution. The FIGARP will be built with COTS components and packaged in a 19-inch rack-mountable box. Measurement is controlled with user-friendly software on a laptop computer. In Phase I, Luminit will demonstrate the feasibility by studying physics and data-driven models on fatigue crack growth as a function of surface roughness, and developing a proof-of-concept FIGARP for inspecting aircraft Al alloys of varying surface quality. In Phase II, Luminit will develop algorithms and computer programs to simulate and predict crack nucleation as a function of measured surface roughness, and integrate the programs into a commercial FASTRAN software package.